The Solar Electricity Handbook is a straightforward and practical guide to designing, installing and using solar electric panels.
Assuming no previous knowledge of solar electric systems, the book explains how solar photovoltaic panels work, how they can be used and explains the steps you need to take to successfully design and install a solar photovoltaic system from scratch.
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Solar electricity is a wonderful concept - take free power from the sun and use it to power electrical equipment. No ongoing electricity bills, no reliance on an electrical socket - 'free' energy that doesn't harm the planet.
Of course, the reality is a little different from that. Yet generating electricity from sunlight alone is a powerful resource with applications and benefits throughout the world.
But how does it work? What is it suitable for? What are the limitations? How much does it cost? How do I install it? This solar book is an internet-linked book that answers all these questions and shows you how you can use the power of the sun to generate electricity yourself.
The web site that accompanies the Solar Electricity Handbook includes online solar calculators and tools to simply your solar photovoltaic design, ensuring building your photovoltaic system is as straightforward and successful as possible.
Now is the time to get on board with this exciting technology. Whether you simply want to learn the basics of how solar electricity works or if you are planning to install your own solar photovoltaic system, then this solar book will provide you with everything you need to know.
93 million miles from Earth, our Sun is 333,000 times the size of our planet. It has a diameter of 865,000 miles, a surface temperature of 5,600°c and a core temperature of 15,000,000°c.
Directly or indirectly, our sun provides all the power we need to exist and supports all life forms. The sun drives our climate and our weather. Without it our world would be a frozen wasteland of ice-covered rock.
Solar electricity is a wonderful concept – taking power from the sun and using it to power electrical equipment is a terrific idea. No ongoing electricity bills, no reliance on an electrical socket – ‘free’ energy that doesn’t harm the planet!
Of course, the reality is a little different from that. Yet generating electricity from sunlight alone is a powerful resource with applications and benefits throughout the world.
But how does it work? What is it suitable for? What are the limitations? How much does it cost? How do I install it? This book answers all these questions and shows you how you can use the power of the sun to generate electricity yourself.
Along the way I will also expose a few myths and show where solar power may only be part of the solution – and although undoubtedly there are some significant environmental benefits of solar electricity, I will also be talking about where its environmental credentials have been oversold.
If you simply want to gain an understanding about how solar electricity works then this handbook will provide you with everything you need to know.
If you are planning to install your own solar electric system, this handbook is a comprehensive source of information which will help you understand solar electric power and a practical guide to projects you can undertake yourself.
If you are planning your own solar installation, it will help if you have some basic DIY skills. Whilst I also include a chapter that explains the basics of electricity, a familiarity with wiring is also of benefit – and essential if you are planning a larger project such as powering a house with solar power.
I will keep the descriptions as straightforward as possible. There is some maths and science which is essential to allow you to plan a solar electric installation, but none of it is complex, and there are plenty of short cuts which I’ll cover which are invaluable in keeping things simple.
The book includes a number of example projects that are useful to show how solar electricity can be used. These range from the very straightforward – providing electrical light for an allotment shed or garage, to fitting a solar panel to the roof of a caravan or boat, through to installing photovoltaic solar panels to a house.
I also show some rather more unusual examples, such as discussing the possibilities for solar electric motorbikes and cars – showing what can be achieved using solar electricity alone with a little ingenuity and determination.
Throughout the book, I have used one main example throughout – providing solar electricity for a holiday home which does not have access to mains electricity. I’ve created this example to show the issues and pitfalls that you may encounter along the way. It is based on real life issues and practical experience.
There is a web site that accompanies this book, with lots of useful and up to the minute information, lists of suppliers and on-line solar energy calculators that will simplify the cost analysis and design processes.
The web site is at http://www.solarelectricityhandbook.com.
Solar electricity and solar heating
Solar electricity is produced from sunlight shining on photovoltaic solar panels. This is different to solar hot water or solar heating systems where the power of the sun is used to heat water or air.
Solar heating systems are beyond the remit of this book. That said, there is some useful information on surveying and positioning your solar panels later on that is relevant to both solar electricity and solar heating systems.
If you are planning to use solar power to generate heat, solar heating systems are far more efficient than solar electricity, requiring far smaller panels to generate the same amount of energy.
Solar electricity is often referred to as photovoltaic solar, or PV solar. This describes the way that electricity is generated in a solar panel.
For the purposes of this book whenever I refer to ‘solar panels’ I am talking about photovoltaic solar panels for generating electricity and not solar heating systems.
The principles of solar electricity
A solar panel generates electricity using the ‘photovoltaic effect’. Here is a brief description of how this works.
Solar cells are made from semi-conducting materials such as silicon. Layers of silicon with different impurities are manufactured and laid on top of each other. These impurities create silicon layers with different levels of electrons.
When combined with sunlight, the photons from the light are absorbed by the silicon. This causes some of the electrons to ‘jump’ from one layer to another. An electrical circuit is made as the electrons move from one layer to another, creating an electrical current.
The more photons (i.e. the greater intensity of light) that are absorbed by the solar cell, the greater the current generated.
Solar cells generate most of their electricity from direct sunlight. They can also generate electricity on cloudy days – and some systems can even generate very small amounts of electricity on bright moonlit nights.
Individual solar cells typically only generate tiny amounts of electrical energy. To make useful amounts of electricity, these cells are connected together to make a solar module, otherwise known as a solar panel or, to be more precise, a photovoltaic module.
Understanding the Terminology
In this book, I use various terms such as ‘solar electricity’, ‘solar energy’ and ‘solar power’. Here is what I mean when I’m talking about these terms:
Solar Power is a general term for generating power – whether heat or electricity – from the power of the sun.
Solar Energy is refers to the amount of energy generated from solar power, whether electrical or in heat.
Solar Electricity refers to generating electrical power using solar ‘photovoltaic’ panels.
Solar Heating refers to generating hot water or warm air using solar heating panels or ground-source heat pumps.
Setting expectations for solar electricity
If you are new to these concepts here are some of the things you can achieve with solar electricity.
Solar power is a useful way of generating modest amounts of electricity, so long as there is a good amount of sunlight available and your location is free from obstacles such as trees and other buildings that will shade the solar panel from the sun.
Solar electric experts will tell you that solar is normally only cost effective where there is no other source of electricity available.
Whilst that is often the case, there are plenty exceptions to this rule where solar electricity can indeed be extremely practical – and can often save you money over the more traditional alternatives:
• Where you need to put a light or a power source somewhere where it is tricky to get mains electricity – such as in the garden, or in a shed or remote garage.
• Where you need continuous power that will work even in the case of a power cut.
• Where you need a more mobile power source that you can carry with you – such as for camping, on a building site or for outdoor DIY
The amount of energy you need to generate has a direct bearing on the size and cost of a solar electric system: the more electricity you need the more difficult and more expensive your system will become.
If your requirements for solar electricity are to run a few lights, power some relatively low power electrical equipment such as a laptop computer, a small TV, a compact fridge and a few other small bits and pieces, then if you have a suitable location you can achieve what you want with solar.
On the other hand, if you want to run high power equipment such as fan heaters, washing machines and power tools, you’re going to find a solar system is not going to achieve what you need for a cost-effective price.
As I mentioned earlier, solar electricity is not well suited to generating heat: heating rooms, cooking and heating water all take up significant amounts of energy: using electricity to generate this heat is extremely inefficient. Instead of using solar electricity to generate heat, you should consider a solar hot water heating system and heating and cooking with gas or solid fuels.
Although it is theoretically possible to power the average family home purely on solar electricity without making any cuts in your current electricity consumption, practically there are some issues with doing this:
• The costs involved in generating large amounts of electricity with solar power are very high.
• The average family home probably does not have enough roof-space available in order to fit all the solar electric panels that would be required.
Most households are very inefficient with their electrical usage. Spending some time first identifying where electricity is wasted and eliminating this waste is an absolutely necessity if you want to implement solar electricity.
If you are considering running your home on solar and make solar your only source of power, you will need to make some major economies on power requirements to make such a system a practical option. If you are prepared to do this, solar electricity for your home may become a practical option for you.
Providing electricity for a holiday home, however, is well within the capabilities of a solar electric system, so long as heating and cooking are catered for using gas or solid-fuels and the site is in a sunny position with little or no shade. In this scenario, a solar electric system may be more cost effective than installing mains electricity if the house is ‘off-grid’ and is situated away from mains electricity.
If your requirements are more modest – providing light for a lock-up garage for instance – there are off-the-shelf packages available to allow you to do this for very reasonable amounts of money: around £130-150 ($180-$220) will provide you with a lighting system for a shed or small garage, whilst £200 ($300) will provide you with a system big enough for lighting a large stables or workshop.
This is far cheaper than installing mains electricity into a building, which can run to thousands of pounds even when a local supply is available just outside the door.
Low cost solar panels are also ideal for charging up batteries in caravans, recreational vehicles or on boats, ensuring that the batteries get a trickle charge between trips and keeping the batteries in tip-top condition whilst the caravan or boat is not in use.
Why choose a solar electric system?
There are a number of reasons why you may wish to consider installing a solar electric system:
• Where there is no other source of electrical power available, or where the cost of installing mains electrical power is too high.
• Where other sources of electrical power are not reliable – i.e. when power cuts are an issue and a solar system can act as a cost effective contingency.
• When a solar electric system is the most convenient and safest option – installing low voltage solar lighting in a garden, for instance.
• You can become entirely self sufficient with your own electrical power.
• Once installed, solar power provides virtually free power without damaging the environment.
Cost justifying solar
Calculating the true cost of installing a solar electric system depends on various factors:
• The power of the sun
• Where you are based
• How much energy you need to generate
• How good your site is for capturing sunlight.
Compared to other power sources, solar electric systems typically have a comparatively high capital cost, but a low ongoing maintenance cost.
To create a comparison with alternative power sources, you will often need to calculate a payback of costs over a period of a few years in order to justify the cost of a solar electric system.
On all but the most simplest of installations, you will need to carry out a survey on your site and carry out some of the design work before you can ascertain the total cost of installing a photovoltaic system.
Don’t panic – this isn’t as frightening as it sounds. It isn’t difficult and it is covered in detail in later chapters.
We can then use this figure to put together a cost justification on your project that can then be compared to the alternatives.
Solar power and wind power
Wind turbines can be a good alternative to solar power, but probably achieve their best when implemented together with a solar system: a small wind turbine can generate electricity in a breeze even when the sun is not shining.
Small wind turbines do have disadvantages however, and are very site specific. Compared to large wind turbines used by the power companies, small wind turbines are not particularly efficient and need to be situated in an area of above average wind in order to generate reasonable amounts of power.
If you live on a windswept farm or close to the coast, a wind turbine can work well. If you live in a built up area or close to trees or main roads you will find a wind turbine unsuitable for your needs.
If you are planning to install a small wind turbine in combination with a solar electric system, a smaller wind turbine that generates a few watts of power at lower wind speeds is usually better than a large wind turbine that generates lots of power at high wind speeds.
Fuel cells can be a good way to supplement solar energy – especially for solar electric projects that require additional power in winter months, when solar energy is at a premium.
A fuel cell works like a generator. It uses a fuel mixture – typically methanol, hydrogen or zinc – to create electricity.
Unlike a generator, a fuel cell creates energy through chemical reaction rather than through burning fuel in a mechanical engine. This chemical reaction is far more carbon efficient than a generator.
Fuel cells are extremely quiet – many are virtually silent – and produce water as their only emission. This makes them suitable for indoor use with little or no ventilation.
Grid-tied solar electric systems
Grid-tied solar electric systems are solar electric systems connected directly into the national grid.
During the day, when the sun is shining, instead of storing the electricity, excess electricity is sold to the national grid and used elsewhere. During the evening and night, when the solar panels are not providing sufficient power, electricity is bought in from the national grid as required.
Grid-tied solar electric systems effectively create a micro-power station and electricity can be used by other people as well as yourself. Owners of grid-tied solar electric systems get paid for each kilowatt of power they sell to the national grid.
Because a grid-tied solar electric system becomes part of the national grid, the system will switch off in the event of a power cut. It does this to stop any electricity flowing back into the grid – which could be fatal for engineers working on repairing the fault.
Solar electricity and the environment
Once installed, a solar electric system is a low carbon electricity generator: the sunlight is free and the system maintenance is extremely low.
It is true to say that solar electric system that runs as a complete ‘stand alone’ system can reduce our carbon footprint.
Grid tied solar systems are slightly different in their environmental benefit. Many people have installed grid tied solar systems as a way of reducing their carbon footprint.
Enthusiasts of grid tied solar systems claim this is a good way to reduce your own personal carbon footprint. This argument is flawed by the way power is generated on the national grid.
Electricity power stations tend to generate a fairly uniform amount of electricity throughout the day, no matter what demands are made on the national grid for power. Power demands increase gradually throughout the day, but then rise dramatically during the evening – most particularly between 7pm and 10pm. After midnight, demand for electricity drops dramatically.
All the time, the power stations are generating more or less the same amounts of electricity. Excess capacity is wasted rather than stored, which is why there are very cheap rates available for off-peak electricity whilst peak electricity prices continue to rise.
A grid tied solar system provides electricity for the national grid at a time when there is excess power available on the national grid. In effect this means that any excess power is wasted simply because the overall electricity supply during the day outstrips the demand for that electricity.
During the evening, when most households are consuming electricity, a solar electric system tends to be producing little or no electricity (depending on the time of year) which means a house with a grid tie solar system is not reducing the demand on the national grid during its peak times.
Therefore, although a grid tied solar system theoretically reduces the carbon footprint of an individual or a family, the amount of carbon actually produced by the national grid is not reduced, as the system does not reduce the peak demand for such electricity.
As a consequence, any argument for saying that a grid tied solar system is environmentally friendly is at best questionable and at worse factually incorrect.
Grid tied systems don’t even have the benefit of providing you with power in the case of a power cut. If there is a power cut, the grid tie switches off your solar electric system completely until the fault is resolved.
If you are wishing to use solar electricity in your home as a way of making a genuine reduction to carbon emissions, you need to design a system that will reduce your peak demand for electricity from the national grid.
• Solar electricity can be a great source of power where your power requirements are modest, there is no other source of electricity easily available and you have a good amount of sunshine available.
• Solar electricity is not the same as solar heating.
• Solar electricity absorbs photons from sunlight to generate electricity. Electricity can still be generated on cloudy days and on bright moonlit nights.
• Solar electricity is unlikely to generate enough electricity to power the average family home, unless major economies in the household power requirements are made first.
• The environmental benefit of grid tied solar systems where the building is already connected to the national grid is questionable.
• Larger solar electric systems have a comparatively high capital cost, but the ongoing maintenance costs are very low.
• Smaller solar electric system can actually be extremely cost effective to buy and install, even when compared to mains electricity.
• Solar electricity can be much cheaper than connecting a remote building to mains electricity.