Solar energy is becoming a very “fashionable” addition to any Self Build and many Renovation projects across the UK, and is fast becoming one of the subjects I am asked about most frequently by people who are planning a new project.

It’s not a difficult or complicated subject to learn about, and whether or not you use it will often not just be solely dependant on how much energy it generates, but rather a mixture of that and the fact that if you do use it, then you are "doing your bit" for the planet. 

Its one of those subjects which different people see very differently. Some will tell you it's just a fad, and that, although in many of the hotter countries around the world, its a great idea, in the UK its a waste of time and money. Others will tell you that its about time we forget about the cash in our pockets and start to think about the bigger picture.

Personally, I think that if you can make use of something thats going to give you free energy for possibly the lifetime of your property, which will not need a lot of looking after, which, in time will most likely pay for itself, -and its something which you can afford, and which is not extortionately expensive, then I'd probably say it's a pretty good idea.

What I would say though (just as I do in many other sections of this guide), is that it is very important that you do your homework before you make any decisions to use it or not, - and if you do use it, make sure you find out which system is going to be most suitable:

a) For your individual project
b) For your geographical location
c) For your pocket

I’ll just run through the basics so you know where to start, and have a good idea of what questions you need to ask of suppliers and installers.

There are really three main ways to benefit from the energy we receive from the sun:

1) Solar water heating

2) Photovoltaic systems

3) Passive solar energy

All three systems work best when they “point” in the right direction! – The right direction in the UK is facing South East to South West. 

Where you are using any form of “solar collectors” these are best set at an angle of 30% to the horizontal and you should make sure that they are not “overshadowed” by other buildings or trees. (If you are using them on low angle / flat roofs, you will probably need to set them on a  frame in order to achieve the 30 degree angle).

 

This system basically consists of a “heat collector” which is normally situated on your roof. This can be either:

A Flat Plate Collector:

These are made up of a flat sheet of metal (normally painted black to absorb heat) or glass, with pipe work (usually copper) fitted behind, all set in an insulated box, through which water is pumped. In the UK the average panel size is around 3m sq to 4m sq, linking to a storage tank of around 150Litres to 200Litres. The water absorbs the heat generated from the sun hitting the flat plate and passes into your hot water cylinder where it heats up the water for your use (in the same way as an immersion heater works). Its a very simple process which should need very little looking after over the years.

 

Evacuated tube: Similar in operation to the flat plate collector, but made up of glass tubes with a vacuum inside. The area needed is less than you will need to give the same performance as the flat plate system (probably 2 m sq evacuated tube, compared to 3 – 4m sq. flat plate). Heat is transferred, via the pipe work, into the building where it releases its energy into your domestic water system.

If the vacuum tubes are damaged at all they could be more problematic to get to and replace than in 20 - 30 years time the particular tube that you need is not made or is difficult to locate (which may not only make it more expensive, but leave you without the power generating facility whilst you sort the problem out).
 

Solar water heating via either of these methods is probably the cheapest option for Self builders or DIY’ers. – If you are going to install it yourself it could cost as little as £500, but probably more like £1000 - £1500 for a system that will provide a significant amount of hot water. – A professionally installed system could cost around £5000, but as solar systems become more popular and more contractors start to appear, prices should become more competitive.

Photovoltaic cells (otherwise known as “solar electric” cells) do not use the water or vacuum system, instead, they use the suns energy to directly produce electricity for your usage. The system usually goes onto the roof in the same manner as the water heating system, but you will need a larger area (around 10m sq – 15 ms sq) to generate the same omount fo energy "like for like".  – Again, it is important that the roof area where the cells are located is not shadowed by trees or other buildings.

The actual units which contain the “cells” that make up this system can be less “obtrusive” than the flat plat or evacuated tube, can often be the size and shape of a roof tile and can come in various colours, - so can become almost invisible on the roof. There are even systems which are transparent and you can use on a conservatory roof.

The cost to buy and install one of these systems will normally be considerably higher than for the water or vacuum system (with estimates of around £8,000 -£20,000 being about the range at the time of writing), however, as with the water and vacuum system, these prices should fall, and it is worth “shopping round”.

The energy generated can be stored in batteries for use at any time for your domestic energy requirements, so  it is not so dependant on the sun actually shining. - In theory you could have as many batteries as you want to store the power generated to see you over periods of low generation.

This system also has an advantage over the hot water system in that you can actually use it to make money (this needs to be counterbalanced by the higher initial cost).

The way it works is that you agree to sell energy to a supplier at an agreed rate. Your system will be fitted with an "outgoing" meter (as opposed to the incoming meter we are all familair with), and the amount of power you feed into the grid will be "bought" from you by the supplier.

There are different schemes available allowing you to sell your excess energy to the National grid. These are:

1) Export Tariff, - which will earn you money as you sell your excess power (whatever you have left over after you have used all you need)directly to the network. This will often be the best option if you only use a small amount of power yourselves. This will usually be the best option if you use most of the energy and only have a small surplus to sell

2) Generation tariff, - Where you are actually paid for all the power you generate, even if you use some of it yourselves.

3) Set Price Tariff, - where you are paid an amount based on the generating capacity of the installation.

If you get the tariff rates from the suppliers who are going to buy the energy, you can compare the likely incomes from each one before you make any decisions as to which would be the best to go on. If your circumstances change, you can simply alter "tariff plans".

There is also a thing called “A Renewables Obligation Certificate”. – the energy generating companies have been set targets for providing renewable energy by the government. - If they don't reach those targets they have to pay a fine. -  They will buy these certifictaes from you to add towards their target figure for the amount of renwable energy they have contributed to the grid. – You can get further information on these certificates at http://www.ofgem.gov.uk/

 

This is the cheapest option of the lot! – It basically involves designing and positioning property to make the most of the suns energy.

The way your main windows face, the size of the windows, the type of glass, the construction materials used in the walls, floors, roof etc all come into play, when you are designing for passive solar heating. - In other words, rather than  by mechanical means, you simply give it the best chance it can have of doing normal job of warming things up, and then you make sure you keep the benefits created, for as long as possible!

For passive solar heating, the insulation values of the property as a whole, as well as the orientation of the building, are very important. 

Its quite a simple equation if you think about it -If you don’t need to heat a property because it keeps all its heat generated each day by the sun, then running costs will go down, so will your carbon footprint and your CO2 emissions. - The house in the picture is a good example of a house which is well located to take advatage of the passive design principal. - The sun is shining directly on to the face of the building. there are 8 window openings to transfer the heat into the building efficiently and the trees which could cause shadows are all on the opposite side of the house from where the sun shines during its strongest "heat generating" hours.

You will be able to pick up “pointers” throughout this guide which will help you to design the house for maximum heat retention, and you designer should be able to advise you on the best orientation of the property so that it makes best use of the available sunlight.

Just using passive solar design, together with a good level of draughtproofing can reduce your heating bills by 40% - at very little cost. - Add this up over the same time period that you would expect a solar heating sytem to work, and you may well find that by using passive heating, you may actually be better off than if you pay out for a system.

If that's the case, then using both systems together should give you a pretty good package!

 

DIY installation of these systems is quite possible. You can buy full DIY kits giving you everything you need (ask some of the suppliers listed in our directory if they supply the “full installation kits”). It propably would not be good idea for someone who has no idea of plumbing or electrical installation to take this on as a "first project", but if you have a reasonable level of DIy knowledge, then it should not be too difficult. - You will need to think about scaffolding around the working area for safety (which again you can possibly do yourself (2 people) by hiring the “quick form” type system made of light alloys) Just make sure you follow all health and safety procedures if you do decide to have a go at the scaffolding.

Alternatively, you can get the system professionally installed. – It is not usually a major construction exercise, and can be done in a couple of days. – Installation will normally be more straightforward on a new build than it is on a renovation because you will usually design the new building specifically to receive the system. – If you are renovating or converting, you may find that one system has installation advantages over the other (e.g. a system which only requires “wiring” rather than plumbing may be quicker and cheaper to install on some renovation or conversion projects).

The capacity / output of Solar energy systems are measured in “kilowatt – hours”

1 Kilowatt – hour (kwh) is the amount electricity it takes to light a 100 watt light bulb for 10 hours or a 1000 watt fire for 1 hour.

Using these figures should help you make a bit of sense of the technical figures you will see on all the advertising and technical information.

Before you seriously consider any form of solar heating / energy system, as I said earlier, you should make sure you do plenty of research.

If your house is not orientated correctly (i.e. if the roof is not facing the right direction), and if you don’t have anywhere else within your garden to position the panels facing so they face south east to south west at a 30% pitch, then your ability to generate energy could be severely restricted and the whole thing could be a complete waste of money.

If you can't get the system facing the right way on your roof, is there anywhere else in the garden where it would be safe and where it could face in the optimum direction? - Will you be best paying the extra for the photovaoltaic system so you can sell some of the energy back into the grid? How much hassle will it be to install? What is the maximum and minimum outpout you can expect from it in a year?

Before you make any decisions, talk to at least a couple of installers about your own situation, your location, and what they think would be the best system for your project (and why). – Get a compass and work out the direction your roof faces. – Ask the installers how much energy you could expect to generate and how much the system will cost to install. – If the figures don’t make “financial” sense, then at least you have the choice of going ahead with it anyway so that you are “doing your bit” for the environment.

You will probably be reading this hoping that I tell you how much energy a system is going to generate for you, and how much you will save, or make by selling the energy into the grid. – Unfortunately that is not possible.

Anyone who tells you, without doing some research into your particular house design, orientation and location, that a particular system could be expected to generate “X” amount of energy each year, and that it will cost “£Y”, should not be given too much attention. - there are too many "ifs" and "buts" which come together to create the whole equation, to be able to make sweeping claims like that

The way it has to work is that you need to find out which way your roof is facing, and work out the angle of the pitch. The geographical location will have an influence (a property in the highlands of Scotland would be not be expected to produce the same amount of energy each year, as one in the South East of England.

Once you have all the correctly calculated "energy generation" predictions, prepared by a competant person and you do some calculations of your own, you may find that one type of system is better suited to your location than another, and will provide more energy “per £ spent” than another type of system. 

A system which costs 4 times as much to install but generates only 20% more energy (or income from selling it to the grid) than another system would not be a good investment.