OFF-GRID SOLAR MADE EASY

For tiny houses, motorhomes and vans

Christopher Johnson

Copyright © 2020 Christopher Johnson

All rights reserved

Independently published

ISBN: 9798646280665

This book is for someone who believed in me.

TABLE OF CONTENTS

PART 1: INTRODUCTION TO SOLAR ENERGY AND ELECTRICITY

Introduction

Why solar?

Strenghts of solar systems

Weaknesses of solar systems

Type of solar systems

Grid-connected solar system

Hybrid solar system

Off-grid solar system

Why off-grid solar?

Advantages of an off-grid solar system for homes

Advantages of an off-grid solar system for RVs

Electricity for beginners

Electrical energy

Electrical circuit

Passive and active devices

Passive device (charging)

Active device (power supply)

Direct current and alternating current

Measuring electricity

Volts

Amperes

Amp-hours

Watts

Watt-hours and Kilowatt-hours

Watt peak rating

Resistance

The relationship between volts, amps, ohms and watts

Series and parallel connections

PART 2: COMPONENTS SELECTION

Basic components of a grid-independent solar system

Solar panels

Batteries

Solar charge controller

Inverter

Fuses

Wires

Plugs and sockets

Solar panels selection

Rigid vs. Flexible solar panels

Solar panels voltage

Solar panel cells type

Amorphous solar panels

Polycrystalline solar panels

Monocrystalline solar panels

Hybrid solar panels

Which solar panel technology is best?

What to look for when buying a cheap solar panel

Buy bigger than you think you’ll need

Make sure the product is under warranty

Make sure that the solar panel uses tempered glass

Things to consider when buying second-hand solar PV panels

Battery selection

AGM and Lithium batteries

Battery capacity

Depth of discharge (DoD)

Calculating how long a battery pack will last

Days of autonomy (DoA)

Things to consider when buying used batteries

Charge controller selection

Voltage

Current capacity

Maximum Power Point Tracking

Earth fault protection

Emergency power supply

Multiple controls

Inverter selection

Battery bank voltage

Rated capacity

Waveform

Installation options and operating environment

Earth fault protection

Wires selection

Wires thickness

Wires length

Fuses selection

How to choose the fuse between charge controller and battery

How to choose the fuse between solar panels and charge controller

How to choose the fuse between inverter and battery

Low voltage devices selection

Lighting

Refrigeration

Microwave ovens

Televisions, DVDs, computer game consoles and music

Music systems

Dishwashers, washing machines and tumble dryers

Air conditioners

PART 3: BASIC CONNECTIONS AND CONFIGURATIONS

Sizing your off-grid solar system

Determine your energy requirements in watts per hour.

Determine the peak hours of the sun available per day

Take in account some losses

Determine the number of panels required.

Determine the size of your battery

Consider the ambient temperature

Oversize your battery

Optimize your electricity needs and usage

Connecting things together

Connecting solar panel together

Connecting batteries together

Solar System configurations

Very small off-grid solar system configuration

Small off-grid solar system configuration

Medium off-grid solar system configuration

Large off-grid solar system configuration

PART 4: SOLAR SYSTEM INSTALLATION

Tools needed to assemble your solar system

Digital multimeter (DMM)

Gloves

First aid kit

Chemical cleaning kit

Other useful tools

Safety first

Consideration of the public

Working at height

Handling

Working with Batteries

Grounding Your electrical system

Solar panels installation

Preparing Your site

Testing Your solar panels

Testing a solar panel with a multimeter

Cleaning the panels

Mounting and connections

Solar panel mountings

Panel tilt angle

Calculating the Optimal solar panel Angle

Adjustable angle solar panel mounting bracket

Shading

Final cabling

Inserting the Batteries

Before Installation

Positioning the Batteries

Ventilation

Access

Insulation

Connections

Installing the solar controller and the inverter

Programming your solar controller

Testing your system

Charging your batteries

Connecting your devices

Maintenance tips for your solar modules

Make sure the solar panels are not in the shade

Clean the solar panels

Check the panels from time to time

Record and analyse performance

PART 1

INTRODUCTION TO SOLAR ENERGY AND ELECTRICITY

INTRODUCTION

Off-grid or autonomous solar systems are the best choice - sometimes the only choice - for remote locations where access to the supply network is restricted or impossible.

They are also widely used in areas where access to the power grid is expensive or where there is a constant risk of power outages.

Also, off-grid solar systems are installed on recreational vehicles (RVs) such as motorhome and caravans, that require an independent power supply solution. Considering that solar charging systems are not standard equipment on most RVs if you have decided to take this path, Do It Yourself is the only possible option.

If you've begun researching solar electrical systems for RVs or tiny homes, you may have quickly become overwhelmed (I know I did). For people choosing van-life or small home life with little experience in solar technology, installing a solar module and knowing the right components may seem particularly daunting.

You will probably find someone who will tell you that it is straightforward to install an off-grid solar system… "just follow my guide," and it's true: there are a lot of guides out there. Unfortunately, very often, these guides are incredibly technical and complicated to understand if you do not have an electronic engineering degree.

Solar is an investment, there is little to do. Thinking of getting real benefits by spending a hundred dollars is pure fantasy.

A solar system could have a good return on an investment after a few years, but this only happens if the system has been carefully planned from the beginning. For this reason, if you are going to install a solar electrical system yourself, don't be a dummy: be sure that you are getting accurate and understandable information!

I'm not an electronic engineer, but I have had a lot of experience with solar systems.  I, therefore, thought of writing a book to help people who know nothing about electricity, batteries, series, and parallel circuits to build their stand-alone solar system by themselves without too much effort.

In this book, you will not find difficult concepts, but a lot of practical information that will allow you to start realizing your project immediately.

If you want to understand how solar power works and you are planning to install your own stand-alone solar system, this book has everything you need to know. You will find how to get all the components of your solar system separately and assemble them all by yourself.  You will learn the basic formulas you can't live without when building a solar system.

You will discover all you need to know about batteries, solar panels, inverters, charge controllers, generators, cables, devices, and many other things. Finally, You will find some DIY solar system wiring diagrams you can use as a guide to putting together your DIY solar panel system.

The book is divided into four sections. The first one contains all the basic concepts needed to understand solar energy and electricity. The second part contains everything you need to know about choosing the components of your solar system. The third section explains how to connect the batteries and panels together. In this part, I will also provide you with some typical solar system configurations, along with some original cost estimates.

You will have the opportunity of choosing the configuration you prefer based on your energy needs and then using the wiring diagrams provided as a guide to putting together your solar panel system. In the final part, You'll find a step by step guide on how to build your off-grid solar system.

At the end of this book, you can consider installing solar panels as a relatively straightforward process, with the possibility of having a little fun. What is more: once you've done it successfully, it's almost like learning to ride a bike - you'll never have to forget or learn the process again!

WHY SOLAR?

Solar energy is the most important source of energy on Earth. From the beginning, the power of light has promoted the development of life for our planet, for the plants that feed higher organisms, and ultimately for humanity. Much of our common energy source on Earth, biomass, is created by using solar energy to promote photosynthesis and capture carbon dioxide. For the production of atmospheric and organic compounds. As a result, the material contains both biomass and fossil fuels that are currently growing on Earth. These are old biomass debris and fuel that have been buried in the Earth over time. These are presently burned to generate electricity and release trapped carbon. Sulphur dioxide returns to the atmosphere. From an energy source perspective, solar energy is even more critical. Sunlight is a heat source that powers the Earth's weather system. It produces evaporation and precipitation of water responsible for hydropower. The Sun also provides most of the energy that powers the Earth's wind power.

Solar energy is responsible for all of these available forms of energy.

Sunlight can also be used directly for power generation. There are two ways to do this. The conceptually most straightforward method is to use the thermal energy contained in solar radiation as a heat source and collect sunlight to store heat so that it can be used to drive heat engines such as steam and gas turbines. This type of power generation has a long history, and today, solar thermal power plants are built in many parts of the world.

The second wisest way to use solar energy to generate electricity is with solar cells. The latter is a solid-state device that is closely related to transistors or microchips, capable of absorbing sunlight and converting the absorbed light energy into electrical energy. Solar cells use sunlight as an energy source to generate direct current. Solar cells use a different portion of the solar spectrum than solar power plants and rely on higher energy and shorter-wavelength radiation. In contrast, solar thermal systems use longer and shorter infrared and near-infrared light.

Individual solar cells typically only generate tiny amounts of electrical energy. These cells (connected to one another) form a solar module, which is also referred to as a photovoltaic module (PV module). The term solar panel is a colloquial term for the module (PV module).

A PV module is an assembly of solar cells mounted on a frame for installation. A collection of PV modules is called a PV panel, and the system of panels is an array. The photovoltaic system arrangement provides solar power to electrical equipment.

There are several reasons to consider installing a solar power system:

- When no other power source is available or when the cost of installing conventional electrical energy is too high.

- When other power sources are not reliable. For example, if blackouts are a problem and a solar system as Cost-effective eventuality.

- When a solar system is the most convenient and safest option. For instance, installing low-voltage solar lighting in a garden or providing indoor lighting in a remote location. You can become completely self-sufficient with your own electrical energy. After installation, solar energy offers practically free electricity without harming the environment.

Before installing a solar system, there are some pros and cons which should be kept in mind:

STRENGHTS OF SOLAR SYSTEMS

- Solar energy is environmentally friendly and does not generate greenhouse gases after installation.

- Declining dependence on foreign oil and fossil fuels.

- Renewable clean energy, available 24 hours a day, even on cloudy days, produces some power.

- Solar panels have a lifespan of over 30 years, requiring almost no maintenance, so after some years, there is also a Return On Investment (ROI).

- Ability to live without a grid if all the electricity generated is sufficient for the house/building.

- It can be installed virtually anywhere.

- Safer than traditional electricity.

- The efficiency of solar cells is continuously improving. Modern solar panels look better and are more versatile than previous models.

- Federal grants, tax breaks, and discount programs contribute to acquisition costs.

WEAKNESSES OF SOLAR SYSTEMS

- The high acquisition cost of materials and installation and long ROI (even if I have to say that reduction of solar costs over the past ten years makes solar costs more feasible every day).

- It needs a lot of space as efficiency is not 100%.

- A large battery bank is required due to the lack of solar energy at night.

- Devices operated directly on Direct Current are expensive.

- Cloudy days do not produce much energy.

- Some people do not like the aesthetic appearance of solar panels.

TYPE OF SOLAR SYSTEMS

There are three main types of residential photovoltaic systems. These three significant types differ in their close relationship to traditional energy supply infrastructures, which are referred to as networks. Each class has advantages and disadvantages.

It is not possible to say which is the best system. If you have to choose, however, you can try to understand which system is the most suitable for your needs.

GRID-CONNECTED SOLAR SYSTEM

The grid-connected PV system is directly connected to the house and the traditional power grid. The grid-connected system enables homeowners to draw electricity either from the electrical house system or from the grid. The switch between the housing system and the network is seamless.

The main advantage of this type of system is that Its production can be reconciled with the electricity needs of the house. If the grid-connected system produces more electricity than the home consumes, the excess power can be repurchased to the utility company in a so-called grid meter. If the system does not produce enough power, the house can draw electricity from the grid.

Grid-connected systems are the cheapest solar systems for private households because they only need a few components.

HYBRID SOLAR SYSTEM

Hybrid solar systems generate power in the same way as a standard grid-connected solar system but use unique hybrid inverters and batteries to store energy for later use. This ability to save energy enables most hybrid systems to also operate as a backup power supply during a blackout, similar to a UPS system [1] .

The hybrid solar system is also connected to the conventional power grid. Still, with the additional emergency power supply, the system can balance production and demand and protect against power outages.

Solar electric system production depends on the available sunlight. With a lot of sunlight, production can exceed demand. When production exceeds demand, excess electricity charges the battery and stores energy. When the system produces less power than is needed at home, the battery can make up for the shortage.

The hybrid solar system is also connected to the commercial power grid. This enables homeowners to get electricity from the network in times of excessive demand and to sell it to the grid when production is excessive.

Hybrid solar systems offer greater flexibility but are not without drawbacks. Charging and discharging batteries reduce overall system efficiency, and these systems are more expensive to design and install because they are more complex than a grid-connected solar system.

OFF-GRID SOLAR SYSTEM

The off-grid photovoltaic is a practically autonomous system.  It produces energy to power only the users to which it is directly connected and is almost always combined with accumulation batteries. The batteries store the surplus energy produced during the hours of sunshine to make it available in the various times of the day.

Off-grid living systems are entirely decoupled from conventional power grids. Without a connection to a supply network, batteries are essential to compensate for periods of overproduction and excessive demands.

A generator is usually added to the system to avoid a power failure if the photovoltaic system is underproducing and the battery is discharged. Generators are used as a power source in times of sustained underproduction or unusual demand.

WHY OFF-GRID SOLAR?

Among the solar systems described in the previous paragraphs, the most widely used are those connected to the grid.

Compared to a grid-tied system, a stand-alone solar system could be more expensive, and its installation can be intimidating.

Why then would anyone choose this system? There are many advantages both for those who want to install this kind of solar system in a house and for those who want to install it on an RV.

ADVANTAGES OF AN OFF-GRID SOLAR SYSTEM FOR HOMES

Until recently, those who wanted to have a residential photovoltaic system had no other choice than to connect to the national electricity grid. With the on-grid solar system, an exchange contract must be concluded with the power line operator. This mechanism provides that the part of the energy produced by the photovoltaic system, but not immediately used in the home (i.e., not self-consumed), is fed into the network, counted, and paid to the owner of the photovoltaic system that produced it.

However, people who use this system quickly realize that the price paid by the operator to purchase the excess of energy is far less than what the operator himself sells it to users when they need it, that is, in the evening or in periods of insufficient solar radiation.

The consequence of this is that the return on investment time is extended, and the potential of the home solar system is not fully exploited.

Off-grid solar systems are the only ones that actually make total energy independence from the operator possible. These systems can quickly satisfy the consumption of a family.

There is nothing to fear. The energy produced by photovoltaic panels is, first of all, used to satisfy the energy consumption absorbed by the house at a given time.

The extra electricity produced during the daytime is stored in the battery for later use in the evening or in times of weak irradiation.

The system could also be connected to a generator, which is activated only in case of need or emergency.

But then are there only advantages? No, there is a small cost to pay for this type of system, even if all in all it is not very relevant: the energy that should be produced in excess by the photovoltaic system, remains unused. Beyond this small limitation of the system, however, there are numerous and significant advantages:

- No supply contract and no agreement must be activated with the operator of the power line. This saves all the costs for requesting a quote and for the connection. You are not going to pay the professionals who have to carry out the paperwork. Consequently, you will not even pay all the fixed costs that we are sadly used to finding in the bill every time.

- The second advantage is time savings due to bureaucratic simplicity. The rules from one country to another may be different. Still, if the system is not to be built in a historical center or in an area subject to particular constraints, often the only fulfillment is a communication to the Municipality.

- The third and most important advantage is that any future changes to be made to the system (expansion, replacement of modules or batteries or moving to other places) will be completely free. There will be no need to ask anyone for permission or authorizations.

- The fourth advantage is that a totally autonomous photovoltaic system can be installed in remote or isolated areas not reached by the traditional electricity grid.

- A further significant advantage is that a totally autonomous photovoltaic system can also be installed on a tiny house on wheels, a motorhome, a van, or a boat.

ADVANTAGES OF AN OFF-GRID SOLAR SYSTEM FOR RVS

Recreational vehicles are the best thing that ever happened to guys who like camping. More especially people who enjoy going to parks and station for some time and want to feel like they are still at home.

This comfort will, however, not be there if you do not have a reliable, steady supply of power with you. Most campsites have electrical hookups available, but what about those times when you’re camping away from one, or you’re in a campground where all the connections are taken?

There are two main power options you’ll come across: generator power and solar power. Generators have been a dependable source of energy for a very long time, but in recent years with developing technology and improved access, the solar power camp has grown.

There are many benefits of having solar on your RV:

- You will be able to search for more remote places with incredible views, privacy and therefore take better advantage of nature. There is an abundance of free camping options available on public land; you can spend whole seasons moving from one part to another, and, thanks to solar, you can have invaluable experiences almost free.

- Many campsites have developed parking areas that do not offer electrical connections. Staying in these areas means spending less. Moreover these regions are often even better than those connected to the electricity grid.

- If you have a mechanical failure while on the road in some remote corner of the planet, the solar energy you will have can make waiting less stressful.

- The solar system can be designed to perfectly adapt to your needs. As we will see later in this book, it is possible to choose between different configurations, from the smallest to the largest. I know that money is a sticking point for a lot of people, but with the ever-changing and improving solar products now offered, it doesn’t have to be anymore. There are options for all budgets. Depending on your energy needs, solar setups can be inexpensive and readily available on websites such as Amazon and eBay.

Last but not least, solar is more sustainable and better for the environment. The sunlight is there, and using it does absolutely no damage to the environment, so why not to take advantage?

ELECTRICITY FOR BEGINNERS

Before understanding how an off-grid solar system is made and how it should be installed, it is good to understand some critical concepts concerning electricity.

For this reason, this part of the book will provide you with some basics that you cannot ignore if you intend to build a solar electrical system.

First of all, we will try to understand the fundamentals of an electrical circuit and the meaning of the primary electrical units.

ELECTRICAL ENERGY

The concept of energy can be defined in many ways. In general, we mean the capacity to do a work or apply a force to move an object along a given distance. The word "electricity" is sometimes used to indicate "electrical energy," which is a particular form of energy resulting from the flow of electric charge.

ELECTRICAL CIRCUIT

An electric circuit is like a pathway made of wires that electrons can flow through. A battery or other power source gives the energy (voltage) that makes the electrons to move. When the electrons get to a device like a light bulb, your computer, or a refrigerator, they give it the power to make it work.

The word “circuit” sounds like a “circle,” and a circuit needs to be circular to work. The wires have to go from the power source to the device and back again so that the electrons can go out and come back.

Many circuits have a switch so that they can be turned on and off. When the switch is off, it makes a gap in the circuit, and the electrons are not able to flow around. When the switch is turned on, it closes the gap, and the electricity is ready to move and make the device to work.

Electrical energy is usually generated by a generator, but can also be supplied by a power source such as a battery.

PASSIVE AND ACTIVE DEVICES

Electrical energy is converted into other forms of energy when electrical charges move through electrical circuits. From a performance perspective, electrical circuit components can be divided into two categories:

PASSIVE DEVICE (CHARGING)

When the charge moves from a higher voltage to a lower voltage due to a potential difference, i. e. when a conventional current (positive charge) flows from the positive (+) connection to the negative (-) connection, the device charges. The job is done. The potential energy of the charge due to the voltage difference at the terminals is converted into kinetic energy within the device. These devices are called passive components or loads. They "consume" electricity from the circuit and turn it into other forms of energy, such as mechanical work, heat, and light. Examples are electrical devices such as light bulbs, electric motors, and electrical heaters. In Alternate Current (AC) circuits, the voltage direction is periodically reversed, but current always flows from the high potential side to the low potential side.

ACTIVE DEVICE (POWER SUPPLY)

When the charge moves through the device (positive charge moves from the negative to the positive connection) by an "external force," the load and mechanical energy are processed. Other types of energy are used to convert chemical energy into potential energy. The device in which this occurs is called the active equipment or power supply, generator and battery, etc. Some tools are either sources or loads, depending on voltage and current. For example, a rechargeable battery acts as a power source when powering a circuit. However, as a load when connected to a battery charger and charged.

DIRECT CURRENT AND ALTERNATING CURRENT

Electricity flows in two ways: either in an alternating current (AC) or in a direct current (DC). As we have seen before, electricity or "current" is nothing but the movement of electrons through a conductor, like a wire. The difference between AC and DC is in the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction, or "forward." In AC, electrons keep switching directions, sometimes going "forward" and then going "backward."

An alternating current (AC) is an electrical current that alternates its direction within a circuit over time.

Now it is important to note that our home runs on AC, while solar panels produce DC. So, to use DC power in the house, it must pass through a device called an inverter to change the power from DC to AC.  We will talk more about inverters later in this book.

MEASURING ELECTRICITY

There are many units of measurement for electricity, but to build your photovoltaic system, you just need to know the primary metrics. The three most basic units in electricity are voltage (V), current (I,) and resistance (R). Voltage is measured in volts, the current is measured in amps, and resistance is measured in ohms. To better understand these concepts, we can think of electricity as water flowing through a pipe. The voltage is equivalent to the water force, the current is equal to the flow rate, and the resistance is like the pipe size.

Let’s try to understand better in the following paragraphs what these measures are for.

VOLTS

Voltage is the pressure from a circuit's power supply that pushes charged electrons (current) through a conductive loop and enables operations such as illuminating light. That means voltage = pressure, measured in volts (V) [2] .

For example, a household AA alkaline battery supplies 1.5 V. A typical household socket (in USA) supplies 120 V. The higher the voltage in the circuit, the more electrons can be "pressed" during operation.

The voltage/potential difference can be compared with the water stored in the tank. When the height of the water into the tank gets higher the water gives a shock when the valve is opened up, causing water (e.g., electrons) to flow.

When assembling a solar system, it is important to consider the voltages of the components. For example, a 12-volt battery will only be able to power a component that has the same number of volts. The volts are therefore used to understand if the system components are compatible with each other.

AMPERES

Electric current is the speed at which electrons pass points in a complete circuit.

Ampere (AM-per) is an international unit for current measurement. It describes the number of electrons (sometimes called "charges") that flow through points in a circuit over time.

An ampere current means that one coulomb [3] of electrons (6.24 billion electrons) passes a point in the circuit in one second. The calculation is similar to measuring the water flow.

When designing your solar system, it is crucial that you know the amperage of your components because it determines the thickness of the wires you need to use.

In addition to the volt rating, some components of the solar system also report an ampere rating. This index tells you how much energy you can produce or consume at any given time. The larger the amperage, the thicker the wires should be.

AMP-HOURS

Another critical unit of measure that you need to know is amper-hour, which is a measure of charge or current flow over time. To be more specific, ampere-hour or amp-hour (Ah) is the quantity of electricity that flows in one hour through a conductor carrying a current of 1 ampere. One ampere-hour is equivalent to 3600 coulombs. Milliamp hours (mAh) that are frequently seen are 1/1000 of an ampere-hour (3.6 coulombs).

From our point of view, an ampere-hour is an essential unit of measure to consider because it is used to measure the amount of energy a battery can store. In fact, battery capacity is specified either in kilowatt-hours, or amp-hours. To know the exact size of a battery, however, you must also take into account the volts. Batteries are typically wired for either 12 volts, 24 volts or 48 volts depending on the size of the solar system. The higher the number of volts with which the battery is used, the lower is its capacity in ampere-hour. For instance, a lead-acid battery of 24 kWh is equal to:

- 2,000 amp-hours at 12 volts;

- 1,000 amp-hours at 24 volts;

- 500 amp-hours at 48 volts;

WATTS

An essential aspect of any electrical or electronic circuit is the power (P) associated with it. In terms of an electric circuit, electrical power [4] is measured in Watts (W). Back to our analogy, if we think of electricity as water flowing through a pipe, the Watts is the power the water could provide (like to a mill wheel). The Watt is a measure of how much energy is released each second.

Wattage is an important factor to consider when comparing solar panel options. You may hear your solar installer say, “it’s a 255 -Watt panel” or “the panel I am recommending has a wattage of 300”. Solar panel wattage represents a solar panel’s theoretical power production under ideal sunlight and temperature conditions.

In an electrical system, wattage is equal to the voltage multiplied by the amperes. For example, if the current is 3 amps (3A) and the voltage is 110V, you multiply 3 by 110 to get 330W (watts).

Most home solar panels on the market today have power output ratings ranging from 250 to 400 watts.

WATT-HOURS AND KILOWATT-HOURS

It is handy to know how much electricity a device consumes typically or generates over an hour. In electrical systems, it is measured in watt-hours (Wh) and kilowatt-hours (kWh).

The watt-hour is a unit of energy equivalent to one watt (1 W) of power expended for one hour (1 h) of time. The watt-hour is not a standard unit in any formal system, but it is commonly used in electrical applications. It is equal to 3,600 joules [5] .

While the watt is the SI unit of power, electrical power consumption is usually measured in kilowatt-hours for a household. A kilowatt-hour is a unit of energy equal to outputting one thousand watts for one hour. It is equivalent to 3,600,000 joules. The kWh is the unit of measurement for a residential power bill, and we usually use kilowatt hours for personal energy use.

WATT PEAK RATING

In the field of solar energy, it is sometimes preferable to use the watt peak rating (Wp) instead of watt-hours. Now I will try to better explain this concept: a solar panel that can generate 50 Watts of electricity per hour has an energy generation potential of 50 Wh, that is 50 W per one hour time. However, because solar power generation is so variable based on temperature, weather conditions, time of day, etc. it may happen that the solar panel does not always generate that amount of Watt-hour.

For this reason, a new number is now often explicitly displayed for solar systems: Watt peak rating (Wp). A peak wattage shows how much electricity a solar panel can produce at its peak power (under full solar radiation). It was introduced to emphasize the fact that the amount of energy that a solar panel can produce is variable and reminds consumers that a 50-watt solar panel will not produce 50 watt-hours of power every hour of the day.

RESISTANCE

Resistance is a measure of strength opposing to the flow of current in a circuit.

Resistance is measured in ohms and is represented by the Greek letter omega (Ω). Ohm is named after Georg Simon Ohm (1784-1854), a German physicist who investigated the relationship between voltage, current, and resistance. The wording of Ohm's law comes from him.

All materials resist certain current flows. These fall into one of two categories:

• Conductor: A material that has little resistance and allows electrons to move easily. Examples: silver, copper, gold, aluminum.

• Insulator: A material that has a high resistance and limits the flow of electrons. Examples: rubber, paper, glass, wood, plastic.

Resistance measurements are usually made to indicate the state of a component or circuit.

• With the same voltage, the higher the resistance, the lower the current. At unusually high values, one of the possible effects is damage to the conductor due to burning or corrosion. Overheating is often a resistance-related problem because all conductors give off a certain amount of heat.

• The lower the resistance, the more current will flow. Possible causes: Insulation damaged by moisture or overheating.

Many components, such as heating elements and resistors, have fixed resistance values. These values are often printed on the component nameplate or manual for reference.

If the tolerance is displayed, the measured resistance value must be within the specified resistance range. Significant changes in fixed-resistance usually indicate a problem.

"Resistance" may sound negative, but it can be used in favor of electricity.

Example: The current flowing through a small circuit of a toaster must be sufficiently hard to generate the heat that burns the bread. Old-style bulbs energize filaments that are thin enough to produce light.

Resistance cannot be measured in an operating circuit. Accordingly, troubleshooting technicians often determine resistance by taking voltage and current measurements and applying Ohm's Law: V = I x R.

THE RELATIONSHIP BETWEEN VOLTS, AMPS, OHMS AND WATTS

According to Ohm's Law, the current flowing through a conductor between two points is directly proportional to the voltage between the two locations. With the introduction of the constant proportionality resistance, we achieve the usual mathematical formula that describes this relationship:

I = V / R

where I is the current through the conductor in amperes, V is the voltage measured on the conductor in volts, and R is the resistance of the conductor in ohms. In particular, Ohm's Law states that the R is constant regardless of the current. Ohm's law is an empirical relationship that accurately represents the conductivity of most conductive materials over many orders of magnitude of the current.

Given the Ohm's law, if you know volt and current, you can calculate the resistance:

R= V / I

If you know volt and resistance you can calculate current:

I= V /R

If You know the power [6] and current you can also calculate voltage:

V= P / I

Example: A 48-watt motor with one current of 4 amps runs at 12 volts (in fact 48/4= 12).

If You know voltage and power you can calculate current:

I = P / V

Example: A 48-watt motor with a 12-volt supply requires a current of 4 amps (in fact 48/12 = 4).

SERIES AND PARALLEL CONNECTIONS

Components of an electrical circuit can be connected in series, parallel, or series-parallel.

With simple series circuits, all components are connected end-to-end to form only one path for the current to flow through the circuit:

With simple parallel circuits, all components are connected between the same two sets of electrically common points, creating multiple paths for the current to flow from one end of the battery to the other:

With each of these two basic circuit configurations, we have specific

sets of rules describing voltage, current, and resistance relationship.

Series Circuits:

- Voltage drops add to equal total voltage.

- All components share the same (equal) current.

- Resistances add to equal total resistance.

Parallel Circuits:

- All components share the same (equal) voltage.

- Branch currents add to equal total current.

- Resistances diminish to equal total resistance.

However, there are also some circuits where components are series-connected in some parts and parallel in others, these circuits are called series-parallel.

Because these circuits are a combination of both series and parallel, we cannot apply the rules for voltage, current, and resistance like we could when the circuits were one way or the other. Instead, we will have to identify which parts of that circuit are series and which parts are parallel, then selectively apply series and parallel rules as necessary to determine what is happening.

We will return to discuss this topic later in this book.

PART 2

COMPONENTS SELECTION

BASIC COMPONENTS OF A GRID-INDEPENDENT SOLAR SYSTEM

Few components are needed to build a stand-alone solar system. In this chapter, I will briefly explain what they are and what they are for. Next, we will see how to choose the most suitable components for your needs.

Basically, in a grid-independent solar system, there are few main components:

Solar panels

Batteries

Charge controller

Inverter

Wires and fuses

Plugs and sockets

In addition to these, you may also have to take additional parts like:

Solar panel roof mounting rack (optional)

Adjustable tilt mount (optional)

Circuit fuse block + bus bar (optional)

Battery terminal connectors

Battery monitor (optional)

Electrical wire crimp connector

Solar panel extension cable (optional)

Finally, when you install the system, you should take out a few items from your toolboxes such as copper wire, circuit breaker, meter, fuse and MC4 connector.

The following diagram shows an off-grid solar system in which there are all the components listed above.

SOLAR PANELS

Solar panels convert sunlight into direct current and are the basic building blocks of the solar system.

The term solar panel is a colloquial term used for the module (PV module).

A PV module is an assembly of solar cells mounted on a frame. Solar cells use sunlight as an energy source to generate direct current. A collection of PV modules is called a PV panel, and the system of panels is an array. The photovoltaic system arrangement provides solar power to electrical equipment.

As we will see later, there are different types of solar panels to choose from and different ways to connect them together.

BATTERIES

The solar panel supplies energy, in the form of direct current, only when it is sunny.

Under certain conditions, however, the system could not supply energy, for example at night, in cloudy weather or when the photovoltaic system is disconnected for repair and maintenance work.

The above problems can be solved by storing solar energy with one or more batteries during the day and using it as you wish.

In an off-grid solar system, batteries provide a constant source of stable, reliable energy.  They are used to store energy and supply it to the system when needed.

As we will see later, there are different types of batteries to choose from and different ways to connect them together.

SOLAR CHARGE CONTROLLER

A solar charge controller is a device that is placed between a solar panel and a battery. It regulates the voltage and the current of your solar modules. It is used to maintain the correct charging voltage on the batteries. When the input voltage of the solar panel rises, the charge controller regulates the charging of the batteries and thus prevents overcharging.

Many solar controllers also have an LCD status screen where you can check the current battery level and see how much electricity the solar system is generating.

Another essential function of a solar controller is to manage the charge in each battery and to ensure that each battery is properly charged. As the batteries age, the charge on each battery begins to vary. This means that some batteries are charged and discharged at different speeds. If it remains over time, the overall battery life will deteriorate. Intelligent solar controllers can cope with these fluctuations by balancing the charged batteries. Most controls require you to manually activate a scale as part of a routine inspection.

The solar power systems normally use 12-volt batteries. However, solar modules can supply much more voltage than is required to charge the batteries. By substantially converting the excess voltage to current, the charging voltage can be maintained at an optimal level while reducing the time necessary to fully charge the batteries. This enables the solar system to work optimally at all times.

INVERTER

Solar panels receive the sun's rays and convert them into direct current (DC). Direct current is useful, but most household appliances (refrigerators, hairdryers, vacuum cleaners, washing machines) run on AC power. If we want to connect these devices to our system, we need something that transforms direct current into alternating current. This is the inverter.

As for solar panels and batteries, there are different types of inverters. I will try to explain later how to choose one that is suitable for your needs.

FUSES

Fuses are a crucial part of any electrical system. A fuse is essentially just a thin piece of wire that will break when the current running through it is higher than the limit the cable can handle. This makes them a fantastic protection against surges and short circuits, that if uninterrupted would damage your appliances and drain your batteries to empty.

WIRES

It's easy to miss, but wires play an essential role in a successful solar power system. There are three different wire sets that you have to take into account:

- solar array cables

- battery cables

- device cables

For all wires, make sure you always use cables that can handle the maximum amount of current (amps) you want to work with. Be aware that you may want to upgrade your system at a later date, and use a higher amperage cable than you actually need to make future expansion as easy as possible.

PLUGS AND SOCKETS

For 12-volt or 24-volt circuits with a current of fewer than 30 amperes, you can use the same standard switches and light sockets as for regular household power supply. However, you must not use the usual household plugs and sockets to connect low-voltage devices to your low-voltage circuit. If you do so, you run the risk of accidentally connecting your low-voltage devices to a high-voltage circuit, which can have catastrophic consequences. Instead, you can choose to use non-standard plugs and sockets or the same 12-volt plugs and sockets that are used in caravans and boats. These low voltage sockets do not have to have a separate grounding cable, as the negative wire should always be grounded in a DC circuit system.

SOLAR PANELS SELECTION

The number and type of solar modules required to generate enough solar energy to support your electricity consumption plays an essential role in the design, dimensioning, operating voltage and costs of your photovoltaic system.

There are a lot of decisions to make when you install solar panels on a tiny house or RV. Some of the most basic are: what size solar panels to buy?  Is it better to go with flexible solar panels or aluminium framed rigid panels?  The solar cells should be monocrystalline or polycrystalline? Is it better to install nominal 12 volt or 24-volt panels?

Rigid vs. Flexible solar panels

Solar panels can be rigid or flexible. Rigid panels are built with an aluminium frame surrounding tempered glass that covers the solar cells. They are tried and true, and no one will look at you sideways if you choose to go this route. These are the main strengths of rigid panels:

- They are the industry standard, have been around for decades.

- They can stand up to all kinds of weather.

- They can be installed in super sturdy brackets which can be angled to maximize solar gain throughout the year.

- They are cheaper than flexible panels.

Rigid panels also have weaknesses:

- They are relatively heavy. For a traditional house, this weight may be irrelevant, but for a home on wheels or a van, it is an element to be carefully considered.

- The installation requires to make holes in the roof. There is no problem with this for houses. For those who have a van, however, the idea of making holes in the roof is not always welcome.

Flexible solar panels are more manageable and lightweight options. Flexible panels are flat cells that are moulded with a layer of protective plastic on top.

Flexible solar panels have several advantages over rigid panels:

- They are a little lighter than framed solar panels (they provide the same power as rigid panels, and weigh less than a quarter).

- You can glue them onto an RV roof using Dicor Lap Sealant, or something similar. This saves you from the complexity of drilling holes into a perfectly watertight roof and risking creating leaks. This is especially helpful with a fibreglass roof. It takes just a few minutes with a caulk gun to attach these panels to the RV roof.

- Another nice feature is that they can adapt to almost any curved surface because they don’t have a frame and can bend to follow the contour of the roof, making them ideal for non-traditional RV shapes.

On the other hand:

- flexible solar panels are less efficient than rigid aluminium framed solar panels, which means you may want to get a few more total watts of solar panels than you would if you were buying framed panels.

- The price is almost twice that of traditional panels.

- Bendable panels also can’t be installed on tilting brackets. So, again, buying more total watts may be the best solution.

- Flexible solar panels are not as rugged as rigid aluminium framed solar panels built with tempered glass. Overhanging branches can scratch them.

- Flexible solar panels are sold with a much shorter warranty than rigid solar panels. Whereas many solar panel manufacturers warranty their tempered glass aluminium framed rigid solar panels for 25 or 30 years, bendable solar panel manufacturers generally warranty their panels for 5 years or less.

Once again, there is no absolute best solution. The choice depends on your particular needs.

SOLAR PANELS VOLTAGE

- Solar panels are constructed internally with DC wiring, and they are sized to work on 12- or 24-volt circuits. So, they are commonly referred to as 12- or 24-volt solar panels.

- Smaller solar panels (both physically and in terms of watts) are typically nominal 12-volt panels while larger panels generally are 24 volts. Solar panels under about 150 watts in size are usually 12-volt panels.  Solar panels over about 150 watts are traditionally 24-volt panels. 12-volt solar panels are also cheaper than 24-volt panels.

How to choose between a 12V and 24V solar panel? A 12V solar panel is generally suitable for small residences or projects of more modest size in contrast to a 24V solar panel. Other than this basic thumb rule, there are different technicalities to consider when deciding between the two.  The choice of the rating of a solar panel depends on:

- The rating of the battery used. Generally, a 12V solar panel should be paired with a 12V battery, and a 24V solar panel should be used with a 24V Battery [7] .

- The rating of the inverter used. Like the battery, the solar panel should also be compatible with the inverter. For example, a 12V solar panel should be paired with a 12V inverter, and a 24V solar panel should be used with a 24V inverter. Inverters are available in different ratings like 12V, 24V, 48V, etc.

- The rating of the charge controller. If a 12V battery and a 12V inverter are there, a 12V charge controller should be used. Similarly, for 24V. One important thing to keep in mind here is that the solar panel’s rating should not be higher than that of the charge controllers. For instance, a 9 Ampere solar panel cannot be paired with a 6 Ampere charge controller.

SOLAR PANEL CELLS TYPE

There are three different technologies used for producing solar panels. Each has its own set of benefits and disadvantages. For the purpose of this handbook, I am ignoring the expensive solar cells used on satellites and in research laboratories and focusing on the photovoltaic panels that are available commercially at a reasonable cost today.

AMORPHOUS SOLAR PANELS

The cheapest solar technology is amorphous solar panels, also known as thin-film solar panels.

These panels have had a bad reputation in the past, with poor product reliability and questionable lifespan. This has often been down to the chemistries used in older designs of panels breaking down under extremes of temperature over a period of a few years, or the poor quality of materials used in the production of cheap panels. Thankfully, this technology has matured significantly over the past few years, and amorphous solar is now regarded as being highly reliable, with some significant benefits over traditional solar panels. Big-name manufacturers such as Sanyo and Sharp now manufacture high-quality amorphous solar panels, along with some exceptionally good specialist manufacturers such as Solar Frontier and Uni-Solar. Some manufacturers now even offer a ten- or twenty-year warranty on their amorphous panels.

On paper, amorphous solar panels are the least-efficient panels available, typically converting around 6–8% of the available sunlight to electricity. This means that you need twice as much space available for installing amorphous solar panels compared to crystalline panels. However, amorphous panels are good at generating power even on overcast and extremely dull days. In general, they are also far better in extreme temperature conditions, with significantly less power loss at higher temperatures than other solar panel technologies.

Unlike other solar panel technologies, amorphous solar panels provide excellent performance even when partially shaded. Whilst a best-case scenario is to eliminate shading whenever and wherever possible, amorphous panels continue to operate at a high level of efficiency even if part of the array is in the shade.

Amorphous panels can also be manufactured into a shape or mounted on a curved surface. They can be made to be hard-wearing enough to be fitted onto surfaces that can be walked on.

A few solar manufacturers have started manufacturing amorphous solar roof tiles (or shingles) so that new-build houses can incorporate solar into the structure of the roof. This combination makes amorphous panels suitable for integration into consumer products such as mobile phones and laptop computers, and for mobile products such as the roof of an RV or caravan, where the manufacturer has no control over where the products are placed or how they are used.

Amorphous panels are the cheapest panels to manufacture, and a number of manufacturers are now screen-printing low-cost amorphous solar films. Between 2008 and 2013, amorphous solar panel costs dropped by around 30% each year. Whilst the prices are dropping more slowly now, the success of amorphous solar panels has been a big factor in driving down the costs of the entire solar industry.

Because of their lower efficiency, an amorphous solar panel has to be much larger than the equivalent polycrystalline solar panel. As a result, amorphous solar panels can only be used either where there is no size restriction on the solar array or where the overall power requirement is very low. In terms of environmental impact, amorphous panels tend to have a much lower carbon footprint at point of production, compared to other solar panels. A typical carbon payback for an amorphous solar panel would be in the region of 12–30 months.

Most amorphous solar panels have comparatively low power outputs. These panels can work well for smaller installations of up to around 300-watt outputs, but not so well for larger installations where larger numbers of panels will be required, and the additional expense in mounting and wiring these additional panels starts to outweigh their cost advantage. Consequently, amorphous solar panels are often more suited to original equipment manufacturer (OEM) applications, as an energy source built into a manufactured product, or for large-scale commercial installations where the panels are incorporated into the structure of a roof-space on a new building. Some of the most exciting advances in solar technologies over the past three years have come from amorphous technology. Products as diverse as mobile phones, laptop computers, clothing, and roofing materials have all had amorphous solar panels built into them. An exciting technology, amorphous solar is going to get better and better over the coming years.

POLYCRYSTALLINE SOLAR PANELS

Polycrystalline solar panels are made from multiple solar cells, each made from wafers of silicon crystals. They are far more efficient than amorphous solar panels in direct sunlight, with efficiency levels of 12–16%. Consequently, polycrystalline solar panels are often around one-third of the physical size of an equivalent amorphous panel, which can make them easier to fit in many installations.

Polycrystalline solar panels often come with a 25-year performance warranty and a life expectancy of far longer. Commercial solar panels only became available in the mid-1970s, and many of these panels are still perfectly functional and in use to this day.

The manufacturing process for polycrystalline solar panels is complicated. As a result, polycrystalline solar panels are expensive to purchase, often costing 20–30% more than amorphous solar panels.

The environmental impact of production is also higher than amorphous panels, with a typical carbon payback of 2–5 years.

Prices for polycrystalline solar panels are dropping, thanks to both the increase in manufacturing capacity over the past few years and the increasing popularity for larger screen televisions, which use the same specification glass.

Between 2007 and 2014, prices dropped by around 25-30% per year. In 2015 and 2016, prices dropped a further 10-15%. Most industry experts agree that prices have now bottomed out and are likely to remain at their current levels for the next years.

MONOCRYSTALLINE SOLAR PANELS

Monocrystalline solar panels are made from multiple smaller solar cells, each made from a single wafer of silicon crystal. These are amongst the most efficient solar panels available today, with efficiency levels of 15–19%.

Monocrystalline solar panels have the same characteristics as polycrystalline solar panels. Because of their efficiency they are the smallest solar panels (per watt) available. Monocrystalline solar panels are the most expensive solar panels to manufacture and, therefore, to buy. However, the prices are still competitive, typically costing around 10% more than the equivalent polycrystalline solar panels.

HYBRID SOLAR PANELS

They combine monocrystalline solar cells and amorphous thin-film between each monocrystalline cell. This provides the benefits of the efficiencies of monocrystalline and the benefits of improved shade and high-temperature performance from the amorphous technology. Hybrid panels provide efficiency levels of between 18—22% in optimum conditions but really benefit from sub-optimal conditions where the real-world performance can be 10-20% better than other solar panels. The downside is the price. Price-wise, hybrid solar panels are expensive, around twice the price of monocrystalline panels. Unless space is at such a premium that the price difference can be justified, hybrid solar panels are usually ruled out on economic grounds.

WHICH SOLAR PANEL TECHNOLOGY IS BEST?

For most applications, polycrystalline panels offer the best solution, with reasonable value for money and a compact size. Amorphous panels can be a good choice for smaller installations where space is not an issue. They are usually not practical for generating more than a few hundred watts of power because of their overall size unless you have an extremely large area that you can cover with solar panels.

Not all solar panels are created equal, and it is worth buying a quality branded product over an unbranded one. Cheaper, unbranded solar panels may not live up to your expectations, especially when collecting energy on cloudy days. If you are spending a lot of money buying a solar energy system that needs to last many years, it is advisable to purchase from a known brand such as Eco Future, Kyocera, Panasonic, Hyundai, Mitsubishi, Solar Frontier or Sharp. My personal recommendation is Eco Future monocrystalline solar panels or Solar Frontier amorphous panels. I have found these to be particularly good.

WHAT TO LOOK FOR WHEN BUYING A CHEAP SOLAR PANEL

As I said, branded products are always the safest and the ones I recommend for those who want to make an investment that lasts over time. Anyway, not all solar energy systems have to last ten or twenty years. If you are looking for a small, cheap system to provide power to an RV or caravan, or your requirements are modest, such as installing a light in a shed, buying a cheap solar panel may well be the right option for you.

The quality of the cheaper solar panels has improved significantly over the past few years. Six or seven years ago, buying a cheap, unbranded Chinese-made product was a recipe for disaster. Many of the panels were poorly assembled, allowing water to seep through the frames and damaging the solar cells. A lot of them used plate glass, often a thin, low-grade glass that becomes clouded over time and is easily chipped or broken.

The cells used by these manufacturers were often sub-standard reject cells and often degraded very quickly. Thankfully, most of these problems are now resolved, and if you buy a cheap solar panel on eBay, you are likely to have a good product that will reliably generate power for five to ten years, and in all probability, a lot longer.

If you are buying a solar panel from a manufacturer you have never heard of, here is a checklist of things to look for:

BUY BIGGER THAN YOU THINK YOU’LL NEED

If you are buying a very cheap solar panel, you are likely to be saving as much as 50% of the price when compared to buying a branded product. However, expect it to degrade slightly more quickly than a branded unit, and do not expect it to be quite so efficient. To counter this, buy a solar panel with a higher watt rating (often shown as a watt peak, or Wp, rating) than you actually need, or buy additional solar panels if you are purchasing an entire array. Aim for 15% more power than you would otherwise have bought. You will still save a lot of money, but you will have an extra bit of assurance that the system will be up to the task.

MAKE SURE THE PRODUCT IS UNDER WARRANTY

With cheap solar panels, you’re not going to get a five, ten- or twenty-years warranty, but you should still expect a one- or two-years warranty with any solar panel you buy. Check to see what the warranty offers. You are looking for a warranty that guarantees a minimum output under controlled conditions. The standard across the industry is to guarantee 80% of the quoted output under controlled conditions. If you have a warranty claim, also check to see how you can claim on that warranty. Shipping a broken solar panel halfway around the world and paying for return carriage is likely to cost as much as buying a new solar panel.

MAKE SURE THAT THE SOLAR PANEL USES TEMPERED GLASS

If you are buying a solar panel that is going to be fitted to a moving vehicle, or if you are buying a physically large solar panel, make sure that the solar panel uses tempered glass. Tempered, or toughened, glass is around eight times stronger than plate glass. This makes it far more robust. If your glass is chipped on your solar panel, you will immediately see a significant drop in power output. If water gets into the solar panel itself, it can create a short circuit and becomes a fire hazard. Water and electricity do not mix. It is worth noting that some amorphous solar panels cannot use tempered glass because of the way the thin film is applied to the glass. Some manufacturers reduce this problem by using a thicker plate glass. It is also worth investing in solar panels that use self-cleaning glass. Self-cleaning glass means that the panels are washed every time it rains. This ensures your panels remain clean and therefore more efficient in every day conditions.

THINGS TO CONSIDER WHEN BUYING SECOND-HAND SOLAR PV PANELS

From time to time, secondhand solar panels appear for sale. They appear on eBay or are sold by solar equipment suppliers or building salvage yards. So long as they come from a reputable brand, second-hand solar panels can be an excellent value for money, and even old panels that are 25–30 years old may still give many more years of useful service. Although good quality solar panels should provide at least 25 years service, nobody knows how much longer they will last.

The first commercially available solar panels (which are now almost forty years old) are still working extremely well, typically operating at around 70% of their original capacity. There are, however, a few points to look out for if you are considering buying secondhand solar PV panels: never buy worn solar PV panels unseen.

Take a multi-meter with you and test them outside to make sure you are getting a reasonable voltage and wattage reading. Check the panels and reject any with chipped or broken glass.

Also, reject any panels where the solar cells themselves are peeling away from the glass or have condensation between the glass and the solar cell. The efficiency of older solar PV panels is significantly lower than new groups. 30 years ago, the most efficient solar panels were only around 5–6% efficient, compared to 13–24% efficiency levels today. 10–15 years ago, most solar panels were about 10–12% efficient. Consequently, a solar PV panel from the early 1980s is likely to be three times the size and weight of an equivalent modern crystalline group. These secondhand panels will not have any of the safety certification ratings that you get with new solar panels. This may cause issues with building regulations or building insurance if you are installing these onto a building as part of a new solar installation.

BATTERY SELECTION

When you build a solar system, you have so many battery options that you might be confused: lithium batteries, AGM batteries, flooded lead-acid batteries, sealed lead-acid batteries, gel batteries, etc.

There are also other parameters to consider like the depth of discharge, the battery lifespan and the holdover. Let's clarify these things in the following paragraphs.

AGM AND LITHIUM BATTERIES

For the purposes of this book, I don't think it's useful to talk to you about every type of battery on the market. Instead, I recommend that you consider only two main battery options: lithium and AGM. Each has its strengths and weaknesses.

- AGM batteries have a reasonable price point, resist vibration and can handle higher charge/discharge rates. They have a shorter lifespan and require regular maintenance to keep them running correctly.

- Lithium batteries perform efficiently and very well across the board, they are maintenance-free and have a longer lifespan to match their higher price tag. When requiring a fast charge or using a generator, they come into their own, saving fuel, time and money. On the other hand, Lithium batteries are much more expensive and can stop working below zero degrees Celsius.

Below is a comparison chart to help You decide:

To summarise, there is no best off-grid battery overall.

Each application is different from the overall power required each day, the frequency of charging, the capacity of batteries required, weight, budget considerations, etc.

All the attributes must be considered to create the best battery for solar off-grid applications.

In most cases, in homes and off-grid systems where generators are used to recharge regularly, lithium batteries are worth the extra investment. With cells of this size, the cost is not far from a high-quality AGM battery. With huge generator run time savings, it will pay back very quickly.

In less regularly used systems (could include holiday lets, weekend homes and non-permanent residences) where solar can recharge the battery, AGM would be a good option as they have a superior recharge rate and restore time.

BATTERY CAPACITY

The capacity of a battery to store direct current (as we have already said) is measured in ampere-hours (ampere-hours, Ah) and shows how much current can be provided for a certain number of hours. A battery of 100 Ah of capacity can provide either 100 A within 1 hour or 10 A within 10 hours. The optimal charge/discharge current for a battery of 100Ah of size should be 10 A. Such a battery can deliver such a charge/discharge current for 10 hours. An important factor affecting capacity is storage temperature. The lower the temperature, the less size provided. After DC electricity is stored in a battery, it can later be rendered as DC voltage.

The higher the capacity, the longer the rated voltage delivery. After a while, a battery is no longer able to deliver the rated voltage. At this point, the battery is said to be in a state of ‘discharge.’ The battery needs to be recharged to provide the stated energy.

Important! The shorter the discharge/charge period, the shorter the battery life. As a rule of thumb, for optimal battery life, the charge/discharge current should not exceed 1/10 of its capacity. This means that for a battery of capacity 55 Ah, the charging current should not exceed 5.5 amps.

In a PV system, the battery bank is recharged by the PV array.

Batteries used in PV systems are rechargeable. Each battery has a certain life duration, which means that it cannot be discharged and recharged an unlimited number of times.

DEPTH OF DISCHARGE (DOD)

Batteries don't last forever, and at some point, in the life of your solar power system, you need to replace them. Of course, we want a battery system that lasts as long as possible, so we have to find out about the lifespan of the batteries we use. There are two ways to measure the life of a battery, both of which say something different about it. The service life is expressed as the number of cycles up to a certain depth of discharge. The lifespan of the Float Service indicates how many years the battery will last if it is stored, regularly charged, but never used.

Each time you discharge and recharge a battery, turn that it off and on again. After a few cycles, the chemistry in the battery begins to break down, and finally, the battery needs to be replaced. The lifespan shows how many cycles the batteries last before they need to be replaced. Lifespan is given up to a "depth of discharge" (DOD), and manufacturers typically provide a graph or table that shows the lifespan of the cycle versus depth of discharge.

Typical cycle life numbers may look like this:

- 20% DOD 1600 cycles

- 40% DOD 1200 cycles

- 50% DOD 1000 cycles

- 80% DOD 350 cycles

As you can see, the battery lasts a lot longer if you keep it at its depth of discharge low. For this reason, it can often be better to specify a larger battery or a series of batteries than a smaller set of batteries. Most experts recommend that you insert enough batteries to ensure that your system does not normally discharge your batteries beyond 50% of their capacity. The second advantage of a larger battery bank is that it allows you to handle your electricity consumption more flexibly. If you need to use more electricity for a few days than you originally planned, you know that you can do it without running out of energy.

CALCULATING HOW LONG A BATTERY PACK WILL LAST

Calculating the life of a battery for your application is not rocket science. It is impossible to predict the number of discharges, as this depends on the conditions under which the batteries are maintained and how you will use the system for years. Still, it can pretty well predict how long the batteries will last. This calculation can help you determine the type and size of batteries to use. First, write down your daily energy needs. In our vacation home, we see a daily power requirement of 695 watt-hours. Then consider the remnant. In this case, we would like to supply electricity for five days. If we multiply 695 watt-hours per day by five days, we will get a storage requirement of 3,475 watt-hours of energy.

Batteries are specified in amp-hours rather than watt-hours. To convert watt-hours to amp-hours, we divide the number of watt-hours by the battery voltage. If we plan to run our system at 12 volts, we divide 3,475 by 12 to get 290 amps per hour at 12 volts.

If we want to operate our system at 24 volts by connecting two batteries in series, we divide 3,475 by 24 to get 145 amps per hour at 24 volts. We do not want to completely discharge our batteries as this will damage them. So, we have to look at our life cycle to see how many cycles we want.

We then use this to determine the capacity of the required batteries. In spring, summer, and fall, we expect the solar power system to fully charge batteries every day - batteries are unlikely to discharge more than 10-20%. However, in the winter months, the batteries can be exhausted for several days before the solar modules can recharge them. Therefore, for four months a year, we have to adopt the worst-case scenario, in which the batteries are discharged to a depth of 80% for five days and then charged by the solar panel system. With batteries, we can do this 350 times before the end of their useful life. Three hundred and fifty cycles multiplied by five days = 1,750 days = 58 months.

Since this scenario only occurs in the four months from November to February, these batteries last approximately 14 and a half years before they reach the end of their useful life. Actually, the battery lifespan (i.e. the maximum lifespan) for batteries is likely to be around ten years, meaning they fail for this application before they reach their lifespan. Based on our energy needs of 145 amps per hour at 24 volts and a maximum discharge of 80%, we can calculate that we need a battery capacity of 145 ÷ 0.8 = 181.25 amps per hour at 24 volts.

DAYS OF AUTONOMY (DOA)

When thinking about batteries, you need to consider how long you want your system to work while the solar array is not charging at all. This period is called a holdover.

The days of autonomy or DoA is the number of days a battery can support a load, without any need to be recharged by the PV array. DoA depends on whether a solar panel system will use a generator or not.

If you do not live in the Arctic or Antarctic circles (both of which provide excellent solar energy during summer), there is no day without sun. You get a charge from your solar system even in the deepest winter. It can happen that the solar panel system does not supply all the energy you need. It is therefore important to consider how many days the batteries should be able to supply electricity if the solar power system does not generate all the energy you need.

The typical value of DoA is 2-3 days for hybrid off-grid systems and 3-7 days for stand-alone (photovoltaic-only) systems.

Of course, the longer the days of autonomy, the more expensive the battery will be.

THINGS TO CONSIDER WHEN BUYING USED BATTERIES

If you are on a tight budget and your electricity requirements are not high, used batteries could be a good way to save money.

Used batteries are often available as ex-UPS batteries (UPS = Uninterruptible Power Supplies) or as batteries for electric vehicles. Although these batteries do not have the lifespan of new batteries, they can be extremely cheap to buy and are often sold at their scrap value.

When considering used batteries there are few things to care about:

- Do not combine different brands and models of batteries. Use the same brand and model of battery throughout your battery bank.

- Do not use a mix of new and used batteries. This is a false economy because the life of your original batteries may be affected by the older ones.

- Try to find out how many cycles the used battery had and how deeply it was discharged. Many UPS batteries have rarely been clocked and rarely discharged during their lifetime.

- When buying batteries for electric vehicles, remember that they had a very heavy lifespan under heavy loads. However, ex electric vehicle batteries can still provide good service for low demand applications: if your total load is less than 1 kW, these batteries can offer good service.

- If possible, try testing used batteries before you buy them. Make sure they are fully charged, and then use a battery charge tester to see how they work. If your used batteries have not been deeply clocked many times, they are unlikely to have a very long lifespan when you first receive them. To wake them up, connect a solar controller or an inverter to them and insert a low-power device into the battery to discharge them to a state of charge of around 20%. Then recharge the battery with a trickle charge and repeat the process. After three deep cycles, you have regained much of the capacity of your used batteries. If you use old batteries, expect them to provide half of their stated capacity. So, if they are advertised as 100-amp hour batteries, assume that you can only use 50 amp-hours. Assume only a third of the capacity for batteries for electric vehicles. Chances are they will give you much more, but it is better to be satisfied with the performance of your used batteries than to be disappointed because they are not as good as new ones.

CHARGE CONTROLLER SELECTION

As we have seen in previous chapters, the solar charge controller takes care of the batteries and prevents them from either being overcharged by the solar system or being overcharged by the devices that run from the batteries.

Choosing the most suitable charge controller is easy and requires consideration of a few things:

VOLTAGE

Choose a charge controller that is compatible with the system voltage. The standard configurations are 12, 24, and 48 volts. If you connect your batteries to 24 volts, you need a charge controller with a nominal voltage of 24 volts.

Some controls are voltage specific, which means that the voltage cannot be changed or replaced. Other, more sophisticated controls have an automatic voltage detection function that allows them to be used with different voltage settings.

CURRENT CAPACITY

Select a charge controller that can process the maximum output current of the solar panel (or solar array). The maximum possible flow that a PV module can generate is the "short-circuit current", which is indicated on the label or on the panel datasheet.

It is recommended that you also enter a safety factor for individual events. For example, a solar panel with 7.89 amps could produce an additional 25% on a sunny day with a very light snow cover (extra light reflected by snow). This results in a maximum possible of 9.86 amps (7.89 x 1.25 = 9.86 amps). In this case, a 10-amp charge controller is recommended.

If you're looking at solar controllers, it's worth buying one with a higher amperage than you actually need. This gives you additional flexibility to add other loads or modules to your solar array in the future without incurring the additional cost of replacing your solar controller.

MAXIMUM POWER POINT TRACKING

More expensive solar controllers have a technology called Maximum Power Point Tracking (MPPT). An MPPT controller adjusts the voltage received by the solar array to provide the optimum energy for charging the batteries without any apparent loss of wattage due to the voltage conversion. If you have an MPPT controller, you can capture about 20% more power from the solar array compared to a more straightforward controller. If you have less than 120 W solar panels, it may be cheaper to buy additional solar panels than to spend the extra money on an MPPT controller. However, prices continue to drop, and if you have a choice, a controller with maximum credit tracking is a worthwhile investment.

EARTH FAULT PROTECTION

Many solar controllers have earth fault protection. In the event of a short circuit from the solar system, a residual current circuit breaker (RCD) interrupts the current flow between the solar system and the control system, thereby avoiding the risk of damage to the control system or the solar panel system. In the United States and Canada, RCDs are also known as Ground Fault Interrupters (GFIs).

For solar panel systems with an output of more than 100 watts and for all systems installed on a building, you must integrate a separate RCD / GFI into your system if no earth fault protection is integrated into your controller.

EMERGENCY POWER SUPPLY

Some controls have an additional useful function: the possibility of starting an emergency power generator if the batteries are too weak and the solar panel system does not supply enough power to handle the load. This can be a useful feature for locations where the system should never fail, or to handle unexpected additional charges. While this doesn't seem so environmentally friendly, there are now many generators available that run on biodiesel or bioethanol. Alternatively, you can use an environmentally friendly fuel cell system instead of a generator. These usually run with bio methanol or zinc and only release water and oxygen.

MULTIPLE CONTROLS

Sometimes, it is desirable to have multiple controls in your solar system. For example, you may want to install solar panels in different locations or in different directions, or you may have mismatched solar panels that you want to use. If you need multiple controllers, only one needs to have fancy features like battery balancing. The other controls can be much simpler controllers that just provide additional charging for the batteries and turn off when the batteries are fully charged.

INVERTER SELECTION

For many solar applications, an inverter is required to switch the voltage from alternating current to direct current.

Please note that only off-grid inverters should be used in an off-grid system.

An inverter for stand-alone systems is a different device than a grid-shaped solar inverter. With a grid-connected inverter, your electricity is fed into the grid and must work in conjunction with the network. The inverter is connected directly to your solar modules and switches off when the solar modules no longer produce enough energy. With an independent system, your electricity is wholly disconnected from the mains. The inverter is connected to your battery bank and switches off when the battery bank is almost empty. There are few things to consider when buying an inverter:

BATTERY BANK VOLTAGE

Different inverters require different input voltages. The smallest inverters with an output of up to 3 kW are available for 12-volt systems. Larger inverters tend to require higher voltages.

RATED CAPACITY

The nominal power is the maximum continuous power that the inverter can supply to all loads in the system. You can calculate this by adding the power of all devices that are turned on at the same time. It is worth adding an error rate to this number. Inverters don't spend their maximum continuous return for long. Most inverters have peak and constant power. This maximum performance enables additional loads to be applied for short periods. This is useful for some electrical devices that consume another electric shock when switched on for the first time (e.g. cooling apparatus). Usually, a higher nominal power than you really need. Inverters can get very hot if they approach their maximum load for a long time. Many experts recommend buying an inverter with a continuous output that is at least a third higher than planned.

WAVEFORM

The waveform refers to the quality of the AC signal that an inverter provides. The cheaper inverters often provide a modified sine wave signal (sometimes advertised as a near sine wave). The most expensive inverters deliver a pure sine wave signal. Modified sine wave inverters are generally considerably cheaper and also have a higher maximum output. However, some devices may not work properly with a modified sine wave inverter. Some power supplies, such as those used for notebooks and portable televisions, may not work at all, while some music systems produce a hum when operating with a modified sine wave inverter. These errors are corrected with a pure sine wave inverter that generates alternating current with a waveform that is identical to the standard household power supply provided by the network.

INSTALLATION OPTIONS AND OPERATING ENVIRONMENT

Small inverters with a continuous output of less than 3 kW are light units and are often simply placed on a shelf or desk. Medium-sized inverters are usually heavy units that must be securely mounted on a wall. Larger inverters with an output of 10 kW or more may need to be screwed to a floor. All inverters generate a significant amount of heat, especially if they run close to their nominal power, and require good airflow around the device. Most off-grid inverters are designed for indoor installation. Outdoor inverters are available but expensive and possibly difficult to obtain.  Inverter installed outdoors should be sealed against the ingress of dust and water with a degree of protection of at least IP64. Overheating inverters are the main reason for a solar system failure. When an inverter gets hotter, it delivers less electricity. If the temperature continues to rise, they will eventually be turned off to avoid permanent damage. When choosing an inverter, check its operating temperatures and consider how you can ensure that your system stays within these limits. Inverters should always be in a well-ventilated area outside of the blanket and with space around each side, the top, and bottom. They cannot be built into a sealed cabinet. Some inverters have an external heat sink or temperature-controlled fans to keep the inverter fresh. If your inverter generates more than 500 watts of power, it will likely make very little noise. This is usually a continuous low-level hum. This is generally only noticeable when the surroundings are calm.

For this reason, inverters are generally not installed in the living area of a house or office environment. Instead, fix your inverter in a garage or on an outside wall of your building. Large inverters are quite loud and make life quite uncomfortable, even when they are mounted on an outer wall or on the wall of a garage. This is very rare but is most likely when you want to install your inverter on a solid concrete wall. The solution is to dampen the mounting between the inverter and the wall or floor on which the inverter is mounted. There is a handy product called Green Glue that is manufactured by the Green Glue Company (www.GreenGlueCompany.com) and is used between the wall and the inverter. If it is compressed when the inverter is mounted again, the adhesive spreads and forms a soundproofing barrier, which is particularly useful in suppressing low-resonance vibrations.

EARTH FAULT PROTECTION

Most inverters now have earth fault protection. All inverters must always be grounded. If the grid inverter you selected does not contain earth fault protection, you must integrate it into your system using a residual current device (RCD). RCDs are known in the United States and Canada as Ground Fault Interrupters.

WIRES SELECTION

The thickness of the wire you use is crucial for minimizing line losses. Line losses occur due to the internal resistance of the wire used. The higher the current, the higher the line losses and the thicker the cable required. Wire thickness is measured in cross-sectional diameter or American Wire Gauge.

Choosing the right wire sizes in your PV system is essential for both performance and safety reasons. If the wires are undersized, there will be a significant voltage drop in the cables resulting in excess power loss. Besides, a tiny wire may heat up to the point in which a fire may result.

Just like water flowing in a pipe, the thicker the wire is - the easier it will be for larger electrical currents to flow in it. Therefore, short wires with large wire cross-sectional area have a small electrical resistance that will result in a low voltage drop. Long cables with a small cross-sectional area have a significant resistance that results in a large voltage drop along the wire.

WIRES THICKNESS

Copper wires are sized using the gauge scale: American Wire Gauge (AWG). The lower the gauge number, the less resistance the cable has, and therefore, the higher the current it can handle safely.

Commercial solar PV panels over 50 watts or so use 10-gauge (AWG) wires. This allows up to 30 amps of current to flow from a single group. If multiple panels are combined in parallel, then a three to eight AWG “combiner” wire set is generally needed to safely transfer the power to a charge controller.

The wires from the charge controller to the battery bank can generally be the same or larger gauge than the main set from the PV array. The exception (B*) is when the Charge Controller is of the type that can operate a 12 or 24-volt battery bank even when the PV array is operating at higher voltages, such as 48 V and larger. These Charge Controllers have large transformers that lower the energy but, in the process, they increase the current going to the battery bank. Refer to the installation material for the charge controller you have chosen when selecting the correct wire size to use.

The wires between batteries in a battery bank tend to be the largest in the system since they are used in conjunction with a power inverter that can, at times, demand more current than that the PV system can supply on its own. These same wires will also have to be simultaneously used for charging and for power inversion.. A typical battery bank wire size is 1/0 or “one-ought.”

WIRES LENGTH

The length of the cables is also important. An excessively long cable can lead to power losses, so you need to choose the right length. The rule of thumb is to have no more than 4% loss in a complete run of the cable. If you still aren't sure whether or not a given wire will be adequate, you can test it out. Take the wire to the desired length and connect to your batteries and lights/appliance. Measure the voltage at the battery and again at the appliance end. Any drop over the distance is caused by internal resistance in the wire. If the reduction is significant (higher than 4%), consider thicker wire.

FUSES SELECTION

The best way to add protection to your solar panel system is by using fuses or circuit breakers. Fuses and circuit breakers are used to protect the wiring from getting too hot and also protect all devices connected in the system from catching fire or getting damaged if a short circuit occurs. They are not necessary for the system to run correctly, but it is always recommended to use fuses or circuit breakers for safety purposes.

There are three different locations that we recommend for installing fuses or breakers. First, between the charge controller and battery bank, second, between the charge controller and solar panels, and third would be between the battery bank and inverter.

HOW TO CHOOSE THE FUSE BETWEEN CHARGE CONTROLLER AND BATTERY

To determine the fuse size needed between the charge controller and battery bank, you simply match the amperage rating on the charge controller. For instance, if you have one 40 amp charge controllers, I would recommend using a 40 amp fuse.

HOW TO CHOOSE THE FUSE BETWEEN SOLAR PANELS AND CHARGE CONTROLLER

The second fuse between your solar panels and the charge controller is a little bit different to figure out. The size of this fuse is dependent on how many solar panels you have and how they are connected (series, parallel, or series/parallel). If the panels are connected in series, the voltage of each group is added, but the amperage stays the same. For example, if you have four 100 W panels connected in series, each producing 20 volts and 5 amps, the total output would be 80 volts and 5 amps. We then take the total amperage and multiply it by a safety factor of 25% (5A x 1.25), giving us the fuse rating of 6.25 A or 10 A if we round up. If you have a parallel connection, where the amperage of the panels is added up, but the voltage stays the same, you would have to add up the amperage of each panel, and then we add a 25% industry rule to figure out the fuse size. For example, if you had four 100W panels hooked in a parallel connection, each panel produces about 5 amps, so we would use this equation (4 * 5 * 1.25) = 28.75 amps, so in this instance, I would recommend a 30 amp fuse.

HOW TO CHOOSE THE FUSE BETWEEN INVERTER AND BATTERY

The last fuse that I recommend in the system would be between your inverter and the battery bank. The fuse size is usually stated in the manual, and most inverters already have built-in fuses/breakers.

The rule of thumb that we use here would be “Continuous Watts / Battery Voltage times 1.25, for example, a typical 1000 W 12 V inverter draws up around 83 continuous amps, and we would add the 25% safety factor which comes out to 105 amps, so we would recommend a 150 A fuse.

LOW VOLTAGE DEVICES SELECTION

Most off-grid systems are based around 12 V or 24 V solar panels. This is because 12 V and 24 V are standard off-grid electrical voltage. As we have already said, when you have an inverter, you can use the same appliances that you would typically power from your household mains. However, it can sometimes be more convenient (due to low power consumption) to get devices that are already designed to be used in a 12 V or 24 V system.

There is a lot of technology and equipment available inexpensively, particularly for 12 V systems. For instance, all appliances that plug into a car cigarette lighter sockets can be used directly in your 12 V system. These include but are not limited to: lights, mobile phone chargers, laptop chargers, kettles, cookers, fridges, TVs, DVD players, projectors.

Many low voltage devices can be switched between 12 and 24 volts. Compared to devices that are operated with mains voltages, low voltage devices are usually more expensive. However, this is not always the case, and with careful shopping, items such as televisions, DVD players, radios, and laptops do not have to cost more than standard versions.

LIGHTING

The 12-volt and 24-volt lighting are often chosen for off-grid solar power systems due to the lower power consumption of the low-voltage lighting. You can buy energy-saving low-voltage lamps and light strips, both of which offer the same quality of light as conventional lighting.

Light bulbs are also available in low voltage forms, and although they are not very energy efficient, they offer excellent light quality. You can buy a lot of 12-volt lighting in regular hardware stores. Many kitchen and bathroom lights operate on low voltage and work just as well with a 12-volt battery as with the 12-volt AC transformers. Diachronic floodlights, halogen spotlights, strip lamps, and LED lights are often operated with 12 volts, which gives you an excellent choice. Buying these products at a hardware store and not from a specialized solar provider can also save a significant amount of money

REFRIGERATION

There is a good selection of refrigerators and freezers that can operate with 12 volt and 24-volt power supplies. Some refrigerators are served with both low-voltage DC voltage and AC voltage; others can also be operated with a bottled gas supply. Unlike most other devices you use, refrigerators need to keep running. This means that although energy consumption can be quite low, overall energy consumption is comparatively high. There are three types of low voltage refrigerators. Absorption refrigerators are commonly used in caravans and can often use 12-volt mains and bottled gas to power the fridge. These are very efficient when operated on gas, but the efficiency, when operated at lower voltages, varies significantly for different models. Peltier effect coolers are not independent refrigerators. These are portable coolers, as are often sold in auto parts stores and are powered by the 12-volt accessory socket in the car. While these are cheap, most of them are not very efficient. Avoid using these devices for solar applications. Compressor refrigerators use the same technology as household refrigerators. They are the most efficient for low voltage operation. They are more expensive than other types, but their efficiency is significantly better. Many models now use less than 5 watts of electricity per hour.

You can use a standard household refrigerator for your running solar system at mains voltages. However, they are usually not as efficient as a functional 12-volt / 24-volt compressor refrigerator. Household refrigerators also tend to have a very high starting current, which can lead to problems with inverters. Several manufacturers are now producing refrigerators that have been specially developed for operation with solar energy. Companies like Waeco, Sundanzer, and Shoreline manufacture a range of refrigerators and freezers that are suitable for home, medical, and business use. If you want to use a regular household refrigerator, contact the supplier of your inverter to ensure that the inverter is suitable. Many refrigerators have a very high starting current, and you may need to buy a larger inverter to handle this demand.

MICROWAVE OVENS

Standard household microwave ovens use much more electricity than their nominal power since their official symbolic power is the output power and not the input power. The input power can be found on the power label on the back of the device, or you can measure it with a wattmeter. As a rule, the input power of a microwave oven is 50% higher than the nominal power. Low voltage microwave ovens are available, which are often sold for use in caravans and recreational vehicles (mobile homes). They are usually slightly smaller than standard household microwaves and have a lower nominal output, which increases cooking times, but they are much more energy efficient.

TELEVISIONS, DVDS, COMPUTER GAME CONSOLES AND MUSIC

Flat-screen LCD TVs and DVD players for 12-volt or 24-volt operation are available in boats, camping and leisure shops. These are usually quite expensive and often cost up to 50% more than comparable household TVs and DVD players. However, many household LCD televisions (with screens up to 24 inches) and DVD players often have external power supplies, and many of them are designed for a 12-volt input. You can identify suitable models during some examinations in your local electronics store. If you want to use one of these regulators, you should buy a 12-volt power regulator to connect the TV to your battery. Battery voltages can vary between 11.6 volts and 13.6 volts. This is fine for most devices that are designed for 12-volt electrical systems but can damage more sensitive instruments. Power regulators fix the voltage to precisely 12 volts and thus ensure that this device cannot be harmed by small voltage fluctuations. With many power regulators, you can also operate 12-volt devices via a 24-volt circuit and they are much more efficient than conventional transformers. With the power controllers, you can also switch from one voltage to another low voltage if required. For example, the Sony PlayStation 3 game console uses 8.5 volts, and with a suitable power regulator, you can supply one very effectively with 12-volt batteries.

Power regulators can both increase and decrease voltages. A suitable power regulator can switch the voltage from a solar battery bank to an output voltage between 1½ volts and 40 volts depending on the specification of the regulator. This means that many normal household items with external power supplies such as smaller TVs, laptops, DVD players, music systems and computer games, to name but a few can be connected directly to your solar system.

MUSIC SYSTEMS

Like TVs and DVD players, many music systems have an external power supply, and a power regulator can be used to power a music system instead of the external power supply. Alternatively, you can build your own music system with components in the car. This can be very effective in terms of both sound quality and price, with the added benefit that you can hide the speakers in the ceiling. Using a music system with an inverter with a modified sine wave can be problematic. Music systems that are designed for operation with mains voltages are expected to work with a pure sine wave system and can hum when using a modified sine wave inverter.

DISHWASHERS, WASHING MACHINES AND TUMBLE DRYERS

Dishwashers, washing machines, and tumble dryers are usually very power-hungry.

There are small washing machines, double tubs, and cold air dryers that run on low voltage, but these are really only suitable for small amounts of washing. They can be excellent for one person in a holiday home or in a small house but are not ideal for weekly washing for a family of four. If you have to operate a washing machine with a solar system, you need an inverter to run it. The amount of energy that washing machines actually use varies from model to model. An energy-efficient model may only have 1,100 watts, while an older model could have almost three times that amount. The same applies to dishwashers. Energy-efficient models may only need 500 watts, while earlier models may need less than 2,500 watts. If you have to operate a dishwasher, you must use an inverter. Tumble dryers are incredibly energy consuming and should be avoided if possible. Most of them need between 2,000 and 3,000 watts of power and run for at least one hour per drying cycle.

AIR CONDITIONERS

In recent years, several manufacturers have launched solar-powered air conditioning and air-cooling systems. The air conditioning system was traditionally very power-hungry. For this reason, solar-powered air conditioning was prohibitive because a sizeable solar system was only required to operate the compressors. In response, manufacturers have developed more efficient air conditioning systems that are designed to work with direct current. Companies such as Solar AC, Securus, Sun source, Sedna Aire, Hitachi, and LG supply air conditioning systems that are designed for operation with solar energy. Other manufacturers have developed evaporative air coolers that consume a fraction of the performance of an air conditioning system. Although these air coolers do not offer the "instant chill" factor of a full air conditioning system, they can provide a very comfortable living and working environment at constant sunshine at a fraction of the cost of a whole air conditioning system.

PART 3

BASIC CONNECTIONS AND CONFIGURATIONS

SIZING YOUR OFF-GRID SOLAR SYSTEM

The exact dimensioning of your solar system is not as difficult as you might think. The process involves a series of steps:

1. Determine the actual electric consumption of your home.

2. Estimate the hours of sun available per day.

3. Determine the number of panels required.

4. Calculate the battery size.

Therefore, knowing how many solar panels you need depends on many factors, mostly on the actual energy consumption of your home and the number of hours of sun available per day.

Determine your energy requirements in watts per hour.

Since independent systems are not connected to the grid, the PV system must be able to cover all of your daily energy needs.  This means that before designing your solar system, you need to know precisely how much energy you will need.

The size of the photovoltaic system required varies from house to house (and from RV to RV) because the energy consumption of each home and the energy efficiency are different. However, determining the optimal number of panels and the overall performance of your solar system requires knowledge of your household use and some simple calculations.

To determine output of a photovoltaic solar system, which is required for the power supply of a house or camper, the electrical energy requirement in watts per hour should first be assessed. To determine the electricity needs of your home, you first need to do some homework.

How do you calculate daily electricity consumption?

To calculate daily electricity consumption, you need to perform a load analysis in Wh (or kWh). It is imperative to carry out a load analysis because PV systems should not be too large (= waste of time and money) or too small (= system not used).

To calculate the total daily average load, you need to determine the amount of energy (in kWh) consumed by all AC loads. Therefore, you need to know the rated power of all loads, the daily usage time, and the number of days the device is used weekly.

Each individual's electricity consumption is different. You will find the nominal power of your device on the label. So, if you list and add the devices, lamps, and TVs with their hourly power requirements in terms of their power, you can easily find the total watt-hours a day your house uses, and you can even find out where you are wasting energy.

If only the amperes are specified, the current must be multiplied by the voltage. The energy required (for all devices) is obtained by multiplying the number of hours that the device is switched on.

You can use the list of devices and energy consumption to determine which device uses the most energy.

This is an example of an estimate of a household's average daily performance goal.

The final nominal output of the solar system can then be calculated based on the part of the house's electricity consumption that is to be supplied by the system. For example, a system that must deliver 100% solar power could be maybe twice the size of a system that provides only 50% of home consumption. Then we can see that a photovoltaic system can be dimensioned so that it supplies either part or all of the electricity consumption of your home. The only limitation is the physical size and cost.

DETERMINE THE PEAK HOURS OF THE SUN AVAILABLE PER DAY

First of all, you need to know that photovoltaic solar modules are available in various voltage and power sizes. In general, solar modules are classified according to their nominal output power, which is defined in watts. For example, 10 watts peak power or 200 watts peak power. This standard power is the amount of energy that a single solar panel can possibly produce in a peak hour of bright sunlight.

When the sun is most intense, usually at noon on a clear day, it produces the equivalent of around 1000 watts per m^2 of solar radiation directly on the earth's surface. An hour of maximum or 100% sunshine received by a solar panel corresponds to an equivalent full hour of sun. If a solar panel has a nominal power of 100 Wp (peak watt), for example, it delivers 100 W peak power at the brightest point of the day.

Obviously, during the day we're going to have a variant amount of sunshine, typically in the morning in the early hours between 8 and 9 the sun's irradiance is about half of what it would be at midday, so we need to look back at some historical data for the area that we live in to find out how many average daily sunshine hours we can expect.

If the average peak hours of sunshine for a given location is given as 4.5 hours, this means that a 100-watt solar panel could deliver 450-watt hours (4.5 hours x 100 Wp) of peak energy during the day.

TAKE IN ACCOUNT SOME LOSSES

So,  450-watt hours could be the total amount of energy that we can expect to generate during one day with our 100 WP panel. However, we won't be able to use all of that power because there are some losses to take into account: we could have some dirt on the surface of our solar panels; there'll be voltage drops on the cables, between the panel and the charge controller, and there's also some inefficiencies in the way the charge controller works and how it regulates the power from the solar panel to charge the batteries.  So, if we take all of those things into account, we can expect some system losses of about 30%.

So, if we take our total power of 450 hours minus 30% system losses, we come out with a net value of 315-watt hours, and this is the value that we can actually use.

DETERMINE THE NUMBER OF PANELS REQUIRED.

Now is time to estimate the size of your solar array.

Based on the calculations made in the first example, we have established that we need 1646 Wh per day to supply power to our house or RV.

We subsequently saw that, in the area in which we live, a 100 Wp solar panel supplies about 315 Wh per day.

Consequently, to produce the necessary energy, we need 1646 Wh/315 Wh = 5,22 100 Wp panels.  Anyway, it is always better to add some extra power, to keep us safe from any unexpected climate changes. It follows that for our system of 1646 Wh per day we can use six 100-watt panels.

DETERMINE THE SIZE OF YOUR BATTERY

Now you know how many solar panels you need, but you can't use the power directly from your solar panels: you also need a battery, and you have to determine how big it must be. So, let's look at the calculation to size a battery suitable for this 6 x 100-watt panels system.

The batteries run on a 12-volt system, so we take our total generated power of 1646 watt-hours divided by 12 volts, and that gives us 137.2-amp-hours. Now we cannot take this parameter as it is taking a 137.2-Ah battery because we cannot think of completely discharging our battery.

Lead-acid batteries don't like to be discharged entirely. At best, you don't want to go any further than 50% discharge.

AGM batteries can go up to 80% discharge but the deep you discharged a battery the less average cycles you're going to get out of it, so it's far better to keep the depth of discharge to a minimum and then you'll get a much longer life out of your battery.

So, in this example, I'm going to use a 50% depth of discharge: I take the 137.2-Ah divided by 0.5 because we can only use half of the battery.  In other words, the battery effectively needs to be twice the size = 137.2-Ah/0.5 = 274.33-Ah.

CONSIDER THE AMBIENT TEMPERATURE

One more thing to take into consideration is the ambient temperature that the battery is going to be stored.

Batteries are sensitive to temperature extremes, and you cannot take as much energy out of a cold battery as a warm one. While sizing the battery, the ambient temperature multiplier (as shown in Table) should be considered to take care of the battery capacity.

We can see here in this table that at 10 degrees C there is a multiplying factor of 1.11 so, we take our 247.33-amp-hours multiplied by 1.11, and we get 274,53, and that would be the battery energy required for one day.

OVERSIZE YOUR BATTERY

Now, if we really want to make sure we never run out of energy, we can make a final calculation step. This step is optional and should only be done if you think you can stay in the dark (without sun) for a few days.

Let's suppose, for instance, that you don't have any sunshine for a couple of days, due to a really cloudy weather and you cannot recharge the batteries.

If you want to have a couple of days autonomy on the batteries, you simply have to oversize the batteries again so that you can have a couple of days of spare capacity.

In our example, we'll take the 274,53-Ah multiplied by two days, and we get a total battery capacity of 549-Ah.

OPTIMIZE YOUR ELECTRICITY NEEDS AND USAGE

As we have seen in the previous paragraphs, there are many calculations to be done to determine the optimal size of your solar system.  However, there is still one last critical consideration to be made regarding the optimization of electricity usage.

In a standalone system, you should aim to save more energy than anything else. The ability of a photovoltaic solar system to generate free electrical power is not unlimited. It is limited by the number of hours the sun shines per day and the physical area available for installing the solar modules. Accidentally turning on a light bulb during the day can easily consume and waste unnecessary amounts of energy, regardless of whether it is free or not. Saving and reducing your home's energy needs by using energy-efficient light bulbs and devices not only saves money on reduced bills, but it can also reduce the final size and cost of installing your new solar array system.

Solar panels and arrays are designed to deliver a certain amount of energy. If the house exceeds the planned limits, this extra energy must come from somewhere, either from an emergency generator or storage batteries. An energy-efficient home reduces the number of solar modules required, which makes the installation of the system cheaper and less complicated and reduces the payback period. Reducing your consumption for a day to install a small solar system is not the right approach. It is a long-term challenge to reduce your home's electricity consumption and it demands as much as possible if you want to live "off-grid."

So, think about how you can reduce consumption or consider possible alternatives.

Here are some starting points for improving the energy efficiency of your home:

- Add or replace insulation.

- Replace high-energy appliances with more efficient versions.

- Replace air conditioning with ceiling fans.

- Improve the lighting switching to LED or CFL bulbs.

- Replace old kitchen equipment (refrigerators and ovens) investing in the most efficient models.

- Install double-pane insulated windows.

- Install a programmable thermostat.

CONNECTING THINGS TOGETHER

At this point in our book, the practical part begins. Before talking about how to install the solar system, however, we need to clarify an essential aspect regarding connections. The solar system, as you have seen, is made up of several components. These components must be connected together. At the beginning of this book, I have already explained to you the difference between series and parallel connections. In this part, I want to show you how and why you should connect your solar panels and batteries in series or in parallel.

CONNECTING SOLAR PANEL TOGETHER

When connecting multiple solar panels in the off-grid system, you have a few options: parallel, series, or a combination of the two.

To make a parallel connection, you have to connect all the positive terminals of all the solar panels together, and all the negative terminals of all the panels together.

When solar panels are connected in parallel, it is the current that adds up, so amperage is the sum of the amps of each group, while the voltage remains constant.

E.g., if you had 3 solar panels in parallel and each was rated at 12 volts and 3,5 amps, the entire array would be 12 volts at 10,5 amps.

To make a series connection, you have to connect the positive terminal of the first solar panel to the negative terminal of the next one.

When solar panels are connected in series, the voltages (volts) add up, so the total voltage is the sum of the volts of each group. The total current adjusts to that of the module that generates less current (in theory, it remains constant).

E.g., if you had 3 solar panels in a series and each was rated at 12 volts and 3,5 amps, the entire array would be 36 volts at 3,5 amps.

Sometimes panels can be connected in series, and then series can be connected to each other in parallel. In this case, there is a series-parallel connection.

The total current of the photovoltaic system is given by the sum of the output current from each series group.

The total voltage of the photovoltaic system is that equivalent to the voltage generated by a single series group.

Eg. If you had 3 series group in parallel and each was rated at 36 volts and 10,5 amps, the entire array would be 36 volts at 31,5 amps.

Whatever the connection you are going to use, the total nominal power of the photovoltaic system is equal to the sum of the nominal power of each individual module. So, if you put three 100-watt panels together, you will have a 300-watt solar system. If you put nine panels of the same power together, you will have a 900-watt solar system.

This rule is valid only if the panels connected are of the same type and power rating.

In general, you should never connect different panels (even if this is possible) because mixing different panels, whether connected in series or in parallel, always reduces the installed wattage.

Both in series and parallel connection, plugging a panel of a lower power rating to the array drags the whole output power down. The lower the rating, the higher the loss of solar-generated power [8] .

Therefore, if you want to get the maximum power from your solar array, you should only connect similar panels.

CONNECTING BATTERIES TOGETHER

The batteries, as well as the solar panels, can be connected in series or in parallel. The result of joining two or more batteries together is called “battery bank.” What does this accomplish? Well, by connecting batteries, you can increase the voltage, amperage, or both.

To be more specific: a series connection is used to increase the voltage. A parallel connection is used to maintain the same tension but increase the capacity. In some cases, it is possible to use a mixed series-parallel link.

To connect batteries in a series, use a jumper wire to connect the negative terminal of the first battery to the positive terminal of the second battery. Use another set of cables to connect the open positive and negative terminals to your application.

When connecting batteries: never cross the remaining open positive and open negative terminals with each other, as this will short circuit the cells and cause damage or injury.

For series-connected batteries, the total voltage is the sum of the individual battery voltages, while the full capacity is the nominal capacity of a single battery.

Important! If you connect batteries with different capacities in series, the total size corresponds to the lowest capacity in the chain. Here is an example:

To join batteries in parallel, use a jumper wire to connect both the positive terminals and another jumper wire to connect both the negative terminals of both batteries to each other. Negative to negative and positive to positive. You can connect your load to one of the batteries, and it will drain both equally. However, the preferred method for keeping the batteries equalized is to connect to the positive at one end of the battery pack, and the negative at the other end of the pack.

For batteries connected in parallel, the total capacity is a sum of the individual capacities of the connected batteries, while the voltage is the nominal voltage of a single battery:

It is also possible to connect batteries in series and parallel configuration. This may sound confusing, but we will explain below. This is the way you can increase your voltage output and Amp/Hour rating. To do this successfully, you need at least 4 batteries.

In theory, you can connect as many batteries together as you want. But when you start to construct a tangled mess of batteries and cables, it can be very confusing, and confusion can be dangerous. Keep in mind the requirements for your application, and stick to them.

Avoid using two different types of batteries in the same system. You need to use the same battery specification and size for your battery bank. Mixing battery capacities and types results in some batteries never being fully charged and some batteries being discharged more than they should be. As a result, mixing battery capacities and types can significantly shorten the life of the entire battery.

Always remember to be safe and keep track of your connections. If it helps, make a diagram of your battery banks before attempting to construct them.

SOLAR SYSTEM CONFIGURATIONS

If you have read this far, you will have understood how to choose the components of your solar system, and you can calculate how much energy you need. You also know how to connect the parts together.

At the end of the day, your individual power needs will ultimately determine the size, cost, and components you’ll need. Obviously, no one configuration fits all solution. Based on the power required, there are a few different ways to arrange panels, batteries, and connectors. For sure, you have already made your own idea of what you need. Maybe you previously imagined what your solar system will look like: how many, and which components there will be, and how they will be connected to each other.

Anyway, to simplify your work, in this part of the book, I want to give you typical solar system configurations along with some original cost estimates. As You will see, the cost of a permanently installed off-grid solar system can run from $1,500 for a basic system up to $15,000 or more for a high-end system to run a residential refrigerator or air conditioner.

You can choose the configuration you prefer based on your energy needs and then use the wiring diagrams below as a guide to putting together your solar panel system.

VERY SMALL OFF-GRID SOLAR SYSTEM CONFIGURATION

A 100-watt solar system is really very small. You cannot think of supplying energy to an entire house or RV with this configuration. However, there are many things that this configuration might be useful for.  For instance, you can run a laptop, or you can power some led lights for a good part of the day. You can run an LCD TV for a few hours or a microwave oven (which consumes a lot of energy) for some minutes.

To configure a system like this, you will need a 100-watt solar panel (rigid or flexible), a battery with a capacity between 50 Ah (lithium) and 75 Ah (AGM), a 300 W pure sine wave inverter and a 10 amp MPPT Charge Controller.  You will also need many additional parts such as solar panel roof mounting z-rack (optional), 6 circuit fuse block with bus bar, battery terminal connectors, battery monitor (optional), electrical wire crimp connector, solar panel extension cable, wires, and fuses.

This is quite a cheap option because the cost of all components could easily stay under $1,500.

I advise you to buy all the components separately so that you can choose the best ones. Alternatively, you may want to purchase a pre-configured solar panel kit. Solar kits usually come with solar panels, a charge controller, and z-brackets for mounting. Again though, you will likely need to purchase a battery, inverter, fuses, and wires separately.

This type of configuration is certainly not the best, but if your budget is limited, but it can be a way to start getting closer to the world of solar energy.

SMALL OFF-GRID SOLAR SYSTEM CONFIGURATION

A 200-watt system is still small, but even twice the size described above. With this type of power available, we can power the same appliances as the previous system, but for longer.

To configure a system like this, you will need two 100-watt solar panels (rigid or flexible) connected together in series, a battery with a capacity between 100 Ah (lithium option) and 200 Ah (AGM), a 600-1000 W pure sine wave inverter, a 20 amp MPPT Charge Controller.  You will also need the same additional and optional parts listed in the previous system.

The cost of components could vary from $1,500 to $3,000.

Again, as in all the configurations that follow, you may find it easier to purchase a pre-packaged kit.

MEDIUM OFF-GRID SOLAR SYSTEM CONFIGURATION

If You like to go a little bit bigger, you can opt for a 400-watt system.

To configure a system like this, you will need four 100-watt solar panels (rigid or flexible) connected together in series, two batteries wired in parallel with a capacity between 100 ah (lithium) and 200 Ah (AGM), a 1000-1500 W pure sine wave inverter, a 30-50 amp MPPT Charge Controller.

You will also need the same additional and optional parts listed in the previous system.

This type of configuration is perhaps the most common for RVs because it allows you to have enough energy. The total cost can vary between $4,000 to $6,000. This is higher than that of the previous solutions, but it is still quite affordable.

This setup can power small electronics plus periodic use of a microwave oven, coffee maker, hairdryer, electric blanket, but it cannot power devices that must be switched on 24 hours a day such as a residential refrigerator.

LARGE OFF-GRID SOLAR SYSTEM CONFIGURATION

All the configurations described in the previous paragraphs allow you to have energy when you are not connected to the grid and can be installed on an RV for the temporary use of some devices. However, none of the previous configurations could allow you to be completely independent. Therefore, if you do not have the possibility of also being connected to the grid, you should draw the other energy you need from other sources such as a generator.

For Tiny homes and RV owners who need a continuous source of energy and want to be completely self-sufficient, a more extensive system is recommended.

To run a residential refrigerator 24 hours a day or an air conditioner from time to time, you will need at least an 800-watt system with functional battery capacity.

To configure a system like this, you will need four 200-watt solar panels (rigid or flexible) connected together in series, four AGM batteries wired in series with a capacity of 400 Ah (AGM), a 1000-1500 W pure sine wave inverter, a 40 amp MPPT Charge Controller.  You will also need the same additional and optional parts listed in the previous system.

The total cost can vary between $10,000 to $18,000. This is a significant investment, and you may wonder if it is worth the expense. Again, the answer depends only on you and the use you intend to make of solar. If you don't have other solutions, because, for example, your home is in an isolated place, the answer is definitely yes. If, on the other hand, you are thinking about solar for an RV, then I suggest you start with something smaller and less expensive. Over time you will become better aware of what you need and, if necessary, you can upgrade your system by adding panels or batteries.

PART 4

SOLAR SYSTEM INSTALLATION

TOOLS NEEDED TO ASSEMBLE YOUR SOLAR SYSTEM

Congratulations on getting this far. If you really do, you now have a garage or garden shed full of solar panels, batteries, cables, and so on. The planning phase is over, and the fun begins. Before you pick up and drill your screwdriver, all you have to do is clear a few household items.

In addition to your reliable DIY tools, you need a digital multimeter to test your installation in different phases and some sets of gloves.

DIGITAL MULTIMETER (DMM)

A digital multimeter or DMM is one of the most useful items of test equipment to diagnose electrical or electronic problems. It’s a measuring device that takes analog information and uses an analog to digital converter to convert it into a digital signal which reads out on display.

You can use a digital multimeter for measuring AC voltage, DC voltage, current (both AC current and DC current), Resistance, Temperature, and some other things.

Obviously, the quantity of functions present depends on the model. There are models for all budgets on the market, and even the cheapest ones can be handy.

GLOVES

You need two different sets of gloves to install your solar system.

A collection of chemical gloves for moving batteries and a set of electrical protective gloves for wiring your solar system. When choosing suitable chemical gloves for working with batteries, keep the following in mind: the gloves must be quite durable because lifting and moving cells put a lot of strain on the gloves.  A good grip is essential.  Buy a glove with medium or long cuff length, to protect both hands and forearms.

The gloves should be made of a suitable material to protect against battery acid. The Health and Safety Executive website recommends that 0.4 mm neoprene gloves provide adequate protection during a full shift. If you splash your gloves while working with batteries, wash or replace them immediately to prevent acid from spreading to other parts of the body.

Electrically insulated protective gloves offer protection when working with high voltages. This is of crucial importance when working with high-voltage solar systems and is recommended for all installations.

Electrically insulated gloves have different ratings to provide protection at different voltages: Class 00 gloves offer protection for up to 500 volts, Class 0 gloves provide protection for up to 1,000 volts, Class 1 gloves offer protection for up to 7,500 volts, Class 2 gloves offer protection for up to 17,000 volts, Class 3 gloves provide protection for up to 26,500 volts. Gloves of class 00 or 0 are best suited for most solar systems. Remember that the open-circuit voltage of a solar array can be more than twice the nominal voltage of the solar array:  twenty solar modules connected in series may only have a nominal voltage of 240 volts, but the open-circuit voltage can be over 500 Volt. Like chemical gloves, choose gloves with a medium or long cuff length to protect both your hands and your forearms. If your electrically insulated gloves are spattered with battery acid, immediately remove and put them back on. All electrically insulated gloves should be visually inspected before use and checked for cracks and holes. Class 1-3 gloves must undergo a complete electrical test every six months.

FIRST AID KIT

You need a good first aid kit, including some items that you would not usually have in a standard first aid kit. In particular, you need an eye rinse and a washing set or gel that can be applied to the skin when in contact with battery acid.

CHEMICAL CLEANING KIT

You work with lead-acid batteries that contain chemicals that are hazardous to health. You will need the following: a chemical cleaning kit that is suitable for cleaning battery acids in the event of a spill; a stock of durable polyethylene bags; a good supply of rags / disposable wipes to wipe up spilled batteries. Chemical cleaning kits and chemical first aid kits are available from most battery wholesalers and industrial tool suppliers. They only cost a few dollars. You probably won't need them, but if nothing else, they'll buy you rest.

OTHER USEFUL TOOLS

You should use electrically insulated screwdrivers while wiring the solar array. A test light circuit tester can be helpful. There are a few little things you should also have:

- Cable ties are handy for keeping cables in place. They can keep the cable routing clean and are often suitable for both temporary and permanent use.

- A water and dirt repellent glass polish or wax for cleaning solar panels.

- Vaseline is used on electrical connections of solar panels and batteries to seal them from moisture and ensure a good connection.

SAFETY FIRST

There are a few safety points to consider before installing your solar system. Some of them may not be relevant to you, but read them all first to be sure. Remember that you are working with electricity, hazardous chemicals, and heavy but fragile items. It is better to be on the safe side.

CONSIDERATION OF THE PUBLIC

If you work in an area to which the public has access, you should use barriers or fences and signs to cordon off the area. Clear detour signs should explain an alternative route. In this scenario, I would recommend hiring a professional team of builders to do the installation work on your behalf. You will already understand the impact of working in a public area and the relevant health and safety regulations. Even if you don't have to consider the general public, you should still consider the people around you. Children love to participate in such projects, and there can really be some safety issues. Keep children out of the way and don't let anyone nearby know that you are working with high voltages and keep away.

WORKING AT HEIGHT

It is very likely that you are working at height and may be crawling on sloping roofs. Make sure that you use suitable climbing equipment (ladders, crawler boards, seat belts, scaffolding). You can rent everything you don't have at reasonable prices. If you are concerned about working at great heights, or if you are outside of your area of competence at any time, keep in mind that hiring a professional is no shame. A professional building contractor can mount a solar system on a roof in 2 to 3 hours. This is usually less than half the time that an amateur handyman takes.

HANDLING

Batteries, large inverters, and solar systems can be challenging to handle. Solar panels themselves are not heavy, but when several of them are mounted on a frame and then raised, they are heavy, bulky, and fragile. Most of these devices are moved and installed by at least two people. More people can be useful when positioning a solar system.

WORKING WITH BATTERIES

Lead-acid batteries are heavy and, in some cases, weigh as much as an adult. Use suitable hoists to move them and take care of your back. Heavier batteries often have tires in a top case. To lift a battery, I usually use a piece of rope threaded through these tires to create a handle. This means that I can carry a battery close to the floor and reduce the need to bend down to lift it. Lead-acid batteries contain acid. If the batteries are not gel batteries, the acid is in liquid form. It is incredibly caustic and extremely harmful to health. Splashes of liquid from the batteries can cause severe burns and must be remedied immediately. Pay attention to safety when working with lead-acid batteries:

- always wear protective clothing, including overalls, eye protection (either safety glasses or full-face protection), and protective gloves.

- I would also advise you to wear steel-toed shoes.

- Always keep the batteries upright. Do not drop batteries. If you do this, there is a good chance that the battery has been damaged. In the worst case, the housing may have cracks or breaks.

- If you drop a battery, immediately place it in an overflow tray (a high-performance deep greenhouse irrigation tray can be used if necessary) and check for damage and leaks.

- If the battery is damaged, both the battery and the overflow compartment must be in sealed polyethylene bags, double-packed and labeled as hazardous waste.

- If a battery is spilled, wipe up the spill immediately with a rag or disposable wipe. Put these rags in a plastic bag, seal them, and mark them as hazardous waste.

- If spilled material from a battery comes into contact with clothing, remove the garment immediately and dispose of it in plastic bags.

- If spilled material from a battery comes into contact with the eyes, repeatedly wash with eye rinse and seek urgent medical attention.

- If spilled material from a battery comes into contact with the skin, wash off immediately with water, an anti-acid wash, cream, or an Apply gel to stop burning and then get urgent medical attention.

- If you have battery acid in your mouth, wash your mouth with milk.

- Do not swallow the milk. Spit it out. Then urgently seek medical help.

- Do not smoke near batteries and make sure that the area where you keep the cells is ventilated. Avoid arcing or short circuits on the battery terminals.

- Batteries can deliver enormous amounts of current very quickly. If you short a battery with a wrench, the wrench is likely to be scorching hot within a few seconds and can easily lead to fire or explosion.

- Remove any worn rings, bracelets or watches and keep tools at a safe distance from batteries.

GROUNDING YOUR ELECTRICAL SYSTEM

A solar energy system should do so always be grounded. This means that wire is laid from a negative pole to an earth rod, which is rammed into the ground. A grounding rod is a 1 m metal post, typically made of copper. They are available from all electrical wholesalers and construction traders. Ground connections prevent static electricity from building up and can prevent contact with high voltages if the circuit is damaged.

When connecting a solar array to a house, you should always connect a ground connection from the solar array itself. While it is optional in other cases, it is always a good idea to ground from a solar array where the array can generate more than 200 watts. You must also ground the battery bank as it can deliver very high currents. If you use both AC and DC electronics in your system, you must always have a separate ground for each of them.

SOLAR PANELS INSTALLATION

PREPARING YOUR SITE

As mentioned in the previous chapter, you may need to understand the basics of mounting a solar array on a ground pole or reinforcing one. Consider existing roof construction when installing your solar array on a roof. If you install your batteries in an area where there is no suitable earth, you should install a grounding rod (grounding rod) as close as possible to the batteries.

TESTING YOUR SOLAR PANELS

Now, the fun begins. First, unpack your solar PV modules and perform a visual inspection to ensure that they are not damaged in any way. Broken or cracked glass can significantly affect the performance of the solar modules. They should, therefore, be replaced if there is visible damage to the module. Damage to the frame is not such a problem as long as the damage does not allow water to enter the panel and does not prevent the solar panel from being securely mounted in position. Then check the voltage on the control panel with your multimeter.

TESTING A SOLAR PANEL WITH A MULTIMETER

Learning the use of a multimeter is not excessively difficult, but it is still a sophisticated tool that needs a period of study and a lot of practice before being used at its best.

In this volume, we do not have enough space to provide a full guide to the use of the digital multimeter. Nevertheless, we can try to make a simple example.

Let's suppose you want to test a 100-watt panel to make sure it is working correctly.

The first thing you would like to test is the solar panel voltage output. To do this, put your solar panel in direct sunlight, set your multi-meter to the "volts" setting, and touch the multimeter's (red) positive lead to your solar panel's positive wire.

Then touch the multimeter's (black) negative lead to your solar panel's negative wire.

The volt reading on your multi-meter could be around (or just under) 17 volts.

The second thing you would like to do is to test solar panel amperage output. Put your solar panel in direct sunlight, set your multi-meter to the "amps" setting, and touch the multimeter's (red) positive lead to your solar panel's positive wire.

Then touch the multimeter's (black) negative lead to your solar panel's negative wire.

The amp reading on your multi-meter could be close to (or just under) 5.9 amps.

That's all there is to test solar panels and making sure they work right!

After doing your solar panel testing, you should find that the solar panel output is about 17 volts and 5.9 amps.

Whenever you have these two values, you can figure out the wattage by multiplying them together because you already know that volts x amps = watts, so:

17 Volts x 5.9 Amps = 100,3 Watts

The test, in this example, has been successful. In reality, when you perform a test on a solar panel, you may get very different results from those expected due to lower measurements of amps or volts. When your measurements don't meet expectations, it could mean that there is a problem with your solar panel. In these cases, it is advisable to go back and check all the connections of your solar cells and all your stringers or check for cracks in the solar cells themselves. If everything is in order, you can repeat the test a second and a third time. Keep in mind that weather conditions can affect the result, so it is advisable to carry out tests even on different days. If, after repeating the test several times, you still do not get the desired result then the panel may be defective and must be replaced.

CLEANING THE PANELS

It is a good idea to first clean the glass on the front of the panels with water and dirt repellent glass polish or wax. These glass polishes ensure that rain and dirt do not stick to the glass, which reduces the performance of your solar system. They are available in every hardware store and in many supermarkets and car accessories stores.

MOUNTING AND CONNECTIONS

Some solar mounting kits mounted on the roof are designed so that they can be mounted on your roof before installing the solar modules. In others, the solar modules are designed to be mounted on the mounting kits before they are installed on the roof. In the case of a system mounted on a pole, you normally first set up your pole and then mount the solar panels as soon as the pole is in position. A floor-based mounting system is the easiest to install because there is no heavy lifting.

As a rule, assemble and wire the solar modules at the same time. If you increase the voltage of your system by connecting the panels in series, first wire the required number of panels in series (i.e., sets with two panels for 24 volts, sets with four panels for 48 volts). If you have connected your panels in series, test them with your multimeter and set a voltage setting to check whether you have the expected voltage (20 volts plus for a 12-volt system, 40 volts plus for a 24-volt system and 80 volts plus for a 48-volt system). Be careful when making these measurements as 40 volts or more can cause a nasty shock under the wrong circumstances.

When you have properly wired each series, make the parallel connections, and test the entire array with your multimeter that is set to the appropriate voltage setting. If you have panels with different capacities, treat the different panel sets as separate arrays. Do not wire boards with different capacities in series or in parallel. Instead, connect the arrays on the controller to one another.

After the test is complete, make sure the array is safe so that no one receives an electrical shock from the system. To do this, connect the positive and negative cables of the solar array to short-circuit the array. This will not damage the array and could prevent an evil shock.

SOLAR PANEL MOUNTINGS

You can choose to fabricate your own mountings for your solar panels if you are planning a stand-alone system, but it is far more common to purchase the mountings at the same time as purchasing your solar panels. The main options for solar panel mountings are roof mounting, frame mounting, or pole mounting.

Typically, up to 40 Wp capacity panels often incorporate plastic frames with holes for bolting the panels to a frame. Most solar panels, however, are designed to be clamped to a frame. The frame is typically made up of two mounting rails. Clamps are used to mount the solar panels to the rails. The rails, in turn, are either mounted onto a roof structure using roof hooks, or form part of a larger frame structure for ground mounting or for mounting on a pole.

If you are mounting a solar system on the roof, you usually have to attach a rail or a mounting on the roof before you install the solar system. Once that's done, it's time to customize the array yourself. Make sure that enough people are available to lift the array onto the roof without twisting or bending it. Personally, I would always leave this job to professional builders, but the best way seems to have two ladders and two people lifting the array between them, one on each ladder or scaffolding.

PANEL TILT ANGLE

When You are mounting the solar system on the roof, you also have to consider the tilt angle of the panels.

Solar panels or photovoltaic modules are more efficient if they are perpendicular to the sun's rays.

How to calculate the Solar Panel Angle of your solar system?

The solar panel angle of your solar system is different depending on which part of the world you are.

Solar panels give the highest energy output when they are directly facing the sun.

The sun moves across the sky and will be low or high, depending on the time of the day and the season. For that reason, the ideal angle is never fixed.

To get the most sun reaching the panel throughout the day, you need to determine what direction the panels should face and calculate an optimal tilt angle. This will depend on:

- Where you live.

- What time of the year you need the most solar energy.

CALCULATING THE OPTIMAL SOLAR PANEL ANGLE

As a rule of thumb, solar panels should be more vertical during winter to gain most of the low winter sun, and more tilted during summer to maximize the output.

Here a simple method for calculating approximate solar panel angle according to your latitude.

The default setting is a tilt angle that corresponds to the latitude of the station plus 15 degrees in winter or minus 15 degrees in summer. This usually maximizes annual energy production.

For instance, if your latitude is 34°, the optimum tilt angle for your solar panels during winter will be 34 + 15 = 49°.

The summer optimum tilt angle, on the other hand, will be 34 – 15 = 19°.

ADJUSTABLE ANGLE SOLAR PANEL MOUNTING BRACKET

If you are an RV owner, maybe you want to tilt solar panels on the roof of your RV.  You can secure them with some aluminum angle and a couple of aluminum braces, and then you can drill a series of holes into that angle, which corresponds to the angles for summer, winter, autumn, and spring.  So, You can change the angle during the year to maximize the most you can get out of your solar panels.

Obviously, with this arrangement, you cannot lift the panels if the weather conditions are poor or when you are traveling. If it's very high winds, you need to leave them flat on the roof. Still, if it's beautiful and sunny and calm conditions, you can elevate your panels and maximize the amount of solar energy that you can generate.

SHADING

Solar panels produce the most of solar energy during the day. However, shading can have a massive impact on the performance of solar PV modules. A common misunderstanding is that partial shading does not affect the performance of solar panels. In fact, photovoltaic solar modules consist of a series of cells that are connected to each other in a series connection. This significantly reduces the performance of the solar module, even when the smallest section of the solar module is in the shade.

Another possible problem with partial shading is overheating. Due to partial shading, part of the solar module generates less energy than the other part without shading. Since the power generated in the shaded and unshaded parts is different, this leads to overheating, which in turn reduces the overall power of the solar module.

Placing the solar module shadow-free is the best way to avoid loss of performance. However, this is not always possible.

FINAL CABLING

As soon as your solar panel system is in position, lay the cable down where the solar controller is to be installed. For safety reasons, make sure that the cables to the solar panel system are preserved to be short-circuited while you are doing this. If you are installing a DC circuit breaker and a residual current device (referred to as an earth leakage breaker in North America), install them between the solar array and the controller. Once you have the cables in place, disconnect the positive and negative cables and check with a meter that you have the expected voltage values. Then short the cables again until you are ready to install the solar controller.

INSERTING THE BATTERIES

BEFORE INSTALLATION

Before you insert the batteries, you may need to refresh them before using them for the first time. You can do this in two ways. You can charge the batteries with a battery charger or install the system and then let the solar modules fully charge them for about a day before you start up the rest of the system. Put a sticker with an installation date on each battery. This will be useful for maintenance and troubleshooting in the coming years.

POSITIONING THE BATTERIES

The batteries must be positioned so that they stand upright, cannot fall over, and are not close to public, children, or other sources of ignition. Batteries should not be placed directly on a concrete floor for insulation and heating purposes. During the winter months, a concrete slab can get extremely cold, and its cooling effect can adversely affect the batteries. I prefer to mount batteries on a wooden floor or shelf.

VENTILATION

If there is little or no ventilation in the area where the batteries are located, this must be done before inserting the batteries. When batteries release hydrogen, which is lighter than air, the gas rises. The ventilation should be designed so that the hydrogen is released from the battery area when rising.

ACCESS

It is important that the battery area is easily accessible, not only for inserting the batteries (bearing in mind that the batteries themselves are heavy) but also for routine checking of the batteries.

INSULATION

As already mentioned, you should insulate your batteries if you install them in an area that can get very cold or very hot. Styrofoam or bubble wrap with the back of the film can be used under and around the sides of the batteries to keep them isolated. Do not insulate the top as this prevents proper ventilation and can cause short circuits in the batteries if the insulation material you are using is conductive.

CONNECTIONS

Once the batteries are inserted, wire the connecting cables between the batteries to form a complete battery bank. Always use the correct connections for the batteries used and make sure that the cables provide a good connection. You should use battery connection cables that are professionally manufactured for your batteries. Use petroleum jelly around the brackets to protect them from moisture and ensure a good connection. Next, ground the negative pole. If the ground is not yet available, install a grounding rod as close as possible to the batteries. Now check the outputs on both ends of the batteries with a multimeter to make sure you get the correct voltage. A fully charged battery should have a voltage of approximately 13-14 volts per battery.

INSTALLING THE SOLAR CONTROLLER AND THE INVERTER

The next step is to install the solar controller and the inverter if you are using one. Mount them close to the batteries. Ideally, they should be mounted within one meter (3 feet) to keep the cable runs as short as possible. Most solar controllers have a small LCD and a number of buttons for configuring the controller.

Make sure that the solar controller is easily accessible, and you can read the display. Some solar regulators that work with multiple voltages have a switch to adjust the voltage that you are working with. Others recognize it automatically. In any case, check your documentation to ensure that you install the solar controller according to the manufacturer's instructions.

If you need to adjust the voltage manually, make sure you do it now, not when you've wired your system. Inverters can get very hot during use, and adequate ventilation should be provided. They are usually mounted vertically on a wall to ensure natural ventilation. The installation guide that comes with your inverter brands tells you what is required. Some inverters require an earth connection in addition to the negative pole of the battery. If this is the case, connect a 2.5 mm² green-yellow grounding cable from the inverter to your grounding rod. If you are installing a DC isolator switch between the solar modules and your control units, connect it first and make sure that it is switched off.

After you have installed the controller and the inverter, connect the negative cables to the battery and make sure that you connect the cables with the correct polarity. Then disconnect the positive and negative cables from the solar array and connect the negative cable from the solar array to the solar controller.

Make sure again that the cable is connected with the correct polarity. Now check the wiring. Make sure that you have connected the cables to the correct places. Make sure that you have connected your minus cable from your solar array to the minus solar input connection of your solar controller. Then check whether you have connected your negative cable from your battery to the negative pole of the battery of your solar controller and your inverter. Only then should you wire up your positive connections.

Start with the battery connection. If you plan to install a fuse and a DC disconnect switch in this cable, make sure that your fuse and switch work for both the solar controller and the inverter (if you use one). First, connect the inverter and the end of the solar controller and check whether the wiring is both optically and visually correct by checking the voltages with a voltmeter before joining the battery bank.

Finally, connect the positive connection from your solar array to the solar controller. At this point, your solar controller should turn on, and you should start reading charging information from the screen.

PROGRAMMING YOUR SOLAR CONTROLLER

The type of your solar controller determines what you need to configure. You may not need to configure anything at all. However, in both cases, you should review the documentation that came with the solar controller to determine what to do. As a general rule, you should tell your solar controller what type of battery you are using. You may also need to inform your solar controller of the maximum and minimum voltage levels to indicate when the batteries are fully charged or discharged. You must obtain this information from your battery supplier.

TESTING YOUR SYSTEM

You can test your solar controller by checking the positive and negative connections on the output connections of the controller with your multimeter. Switch the multimeter to DC voltage and make sure that the solar controller supplies the correct voltage. If you have an inverter, plug a simple device like a table lamp into the power outlet and check if it works. If your inverter is not working, switch it off and check the connections to the battery. If everything is OK, check it again with another device.

CHARGING YOUR BATTERIES

If you have not refreshed your batteries before inserting them, switch off your inverter and let your system stand for at least 24 hours to charge the batteries well.

CONNECTING YOUR DEVICES

Once you have started up your solar power plant and fully charged your batteries, it is time to connect your devices. When wiring a house with low voltage equipment, you should follow the same guidelines as to when installing power circuits. For small voltage applications, your installation does not need to be tested by a qualified electrician, but many people choose to make sure that it doesn't break down. The most significant difference between AC wiring and DC wiring is that you don't need a separate grounding with DC electrics, since the negative connection is grounded both on the battery and, if you use one, on the distribution panel. If you use 12-volt or 24-volt low-voltage circuits, you can use the same distribution boards, switches, and lights as in a mains-operated house.

Do not use the same sockets for low-voltage devices as for mains-operated devices. If you do this, you run the risk of connecting low-voltage devices directly to a high-voltage outlet, which can have catastrophic consequences.

Congratulations. You have a working solar power station!

MAINTENANCE TIPS FOR YOUR SOLAR MODULES

Effective maintenance of solar modules can help increase their performance and durability. But that can be difficult. Solar panels are designed for long operating times and are fully automated. As a result, it is not easy to identify a problem with solar panels.

Here are some expert tips for effective maintenance of solar modules.

MAKE SURE THE SOLAR PANELS ARE NOT IN THE SHADE

It is always good to check your solar panels every few weeks. The panels could be exposed to some shade due to a growing branch or nearby construction. This could reduce the productivity of the solar module and also damage it in the long term. If possible, cut the branch to reduce shadow, or contact an expert if you need to move the panels to a different location. Even if 1/4 of the panel is shaded, you will not only lose 1/4 of the output for that panel, but you will probably also lose more than half of the output.

CLEAN THE SOLAR PANELS

Solar panels are usually self-cleaning. But depending on where you live and the weather, many factors such as dust, building materials, and bird droppings can build up over time. This can lead to a reduction in the electricity generated. While the panels need to be cleaned regularly in some places, cleaning may need to be done less frequently in other places. Try not to scratch the glass as this can damage the solar panel. If the solar modules are cleaned regularly, the cleaning effort is less. Running on the hose can also do the job.

However, if there is dirt or dust on the panels, they should be cleaned with a soft cloth. Any type of soap or material that could damage the panels should be avoided.

CHECK THE PANELS FROM TIME TO TIME

Solar modules do not have to be examined in detail regularly. However, it is recommended to check for wear or electrical failure from time to time. Reading the manual and understanding how to spot an error can save your money in the future. Example: a periodic check of the inverter screen can show if the system works correctly. If you notice anything unusual, call the experts. After all, most solar modules carry a long-term warranty then, do not worry.

RECORD AND ANALYSE PERFORMANCE

If you want to analyze how effective solar panels are, you must first measure and record the power every day. If the weather changes dramatically and sunlight decreases, write it down along with the readings for those particular days. In this way, a good evaluation of the effectiveness of the solar modules is obtained. There are also many monitoring applications and systems that can help with analysis and slow downtime.

[1] An uninterruptible power supply or uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails.

[2] The term refers to Alessandro Volta (1745-1827), an Italian physicist who invented the Voltaic Stack, the pioneer of current home batteries. In the early days of electricity, the voltage was known as electromotive force (EMF). Therefore, in formulas such as Ohm's Law, the voltage is represented by the symbol E.

[3] The coulomb (symbolized C) is the standard unit of electric charge in the International System of Units (SI). The coulomb is defined as the quantity of electricity transported in one second by a current of one ampere.

[4] To be more specific, Electrical power is the rate, per unit time, at which electrical energy is transferred by an electric circuit.

[5] The joule is a derived unit of energy in the International System of Units.It is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of the force's motion through a distance of one metre (1 newton metre or N⋅m).

[6] We have already said that electrical power (P) is measured in Watts (W) and that wattage is equal to the voltage multiplied by the amperes.  For instance, a 12-volt circuit with a current of 4 amperes corresponds to an output of 48 watts (12 x 4 = 48).

[7] An important point to be noted here is that a 24V rating battery is not available in the market, but you can create one by joining two 12V batteries in a series connection.

[8] This, however, is much more crucial for panels connected in parallel.

Table of Contents

Table of Contents

PART 1

Introduction

Why solar?

Strenghts of solar systems

Weaknesses of solar systems

Type of solar systems

Grid-connected solar system

Hybrid solar system

Off-grid solar system

Why off-grid solar?

Advantages of an off-grid solar system for homes

Advantages of an off-grid solar system for RVs

Electricity for beginners

Electrical energy

Electrical circuit

Passive and active devices

Passive device (charging)

Active device (power supply)

Direct current and alternating current

Measuring electricity

Volts

Amperes

Amp-hours

Watts

Watt-hours and Kilowatt-hours

Watt peak rating

Resistance

The relationship between volts, amps, ohms and watts

Series and parallel connections

PART 2

Basic components of a grid-independent solar system

Solar panels

Batteries

Solar charge controller

Inverter

Fuses

Wires

Plugs and sockets

Solar panels selection

Solar panels voltage

Solar panel cells type

Amorphous solar panels

Polycrystalline solar panels

Monocrystalline solar panels

Hybrid solar panels

Which solar panel technology is best?

What to look for when buying a cheap solar panel

Buy bigger than you think you’ll need

Make sure the product is under warranty

Make sure that the solar panel uses tempered glass

Things to consider when buying second-hand solar PV panels

Battery selection

AGM and Lithium batteries

Battery capacity

Depth of discharge (DoD)

Calculating how long a battery pack will last

Days of autonomy (DoA)

Things to consider when buying used batteries

Charge controller selection

Voltage

Current capacity

Maximum Power Point Tracking

Earth fault protection

Emergency power supply

Multiple controls

Inverter selection

Battery bank voltage

Rated capacity

Waveform

Installation options and operating environment

Earth fault protection

Wires selection

Wires thickness

Wires length

Fuses selection

How to choose the fuse between charge controller and battery

How to choose the fuse between solar panels and charge controller

How to choose the fuse between inverter and battery

Low voltage devices selection

Lighting

Refrigeration

Microwave ovens

Televisions, DVDs, computer game consoles and music

Music systems

Dishwashers, washing machines and tumble dryers

Air conditioners

PART 3

Sizing your off-grid solar system

Determine the peak hours of the sun available per day

Take in account some losses

Determine the number of panels required.

Determine the size of your battery

Consider the ambient temperature

Oversize your battery

Optimize your electricity needs and usage

Connecting things together

Connecting solar panel together

Connecting batteries together

Solar System configurations

Very small off-grid solar system configuration

Small off-grid solar system configuration

Medium off-grid solar system configuration

Large off-grid solar system configuration

PART 4

Tools needed to assemble your solar system

Digital multimeter (DMM)

Gloves

First aid kit

Chemical cleaning kit

Other useful tools

Safety first

Consideration of the public

Working at height

Handling

Working with Batteries

Grounding Your electrical system

Solar panels installation

Preparing Your site

Testing Your solar panels

Testing a solar panel with a multimeter

Cleaning the panels

Mounting and connections

Solar panel mountings

Panel tilt angle

Calculating the Optimal solar panel Angle

Adjustable angle solar panel mounting bracket

Shading

Final cabling

Inserting the Batteries

Before Installation

Positioning the Batteries

Ventilation

Access

Insulation

Connections

Installing the solar controller and the inverter

Programming your solar controller

Testing your system

Charging your batteries

Connecting your devices

Maintenance tips for your solar modules

Make sure the solar panels are not in the shade

Clean the solar panels

Check the panels from time to time

Record and analyse performance