Solar Energy
Solar Energy in Britain
Solar energy is not likely to be the first form of renewable energy one would consider installing in the British Isles. With our rain, moody skies and large coast line, the likes of tidal, wave and wind appear the more logical considerations for sustainable sources of energy. Yet solar energy can very readily be used in the UK, for water heating as well as electricity, depending on the hardware. It offers both the home-owner and business-owner an opportunity to cut their carbon contributions and dependance upon fossil fuels.
Solar requires a considerable financial investment at the beginning. Yet this can be offset by grants and will also be recovered through lower energy bills in the years to come. The average household in the UK has the ability to save about 50% of the cost of providing hot water for their home though solar energy and small businesses, like a B&B or a small hotel have the ability to generate even more savings on energy costs. Through generating solar electricity, a home or business can be completely removed from the grid or even contribute sustainable energy to the grid, depending on the needs of the residence and size of system installed.
With all technologies and home improvements, one should not only consider the economic costs but the environmental costs as well. Solar power is known for its ability to cut carbon emissions used in water heating and electricity production. And while a sustainable form of energy, the manufacturing processes of the hardwarevrequire energy and natural resources themselves to be produced. Where these come from, how theyare produced and their costs to the plant are all wise question to ask when considering not just solar, but any home improvement.
This article will give a basic overview of the technologies available for both solar thermal and electricity generation, and where the information is available the energy pay-back and possible environmental costs of both kinds of technology.
Solar Water Heating
One way of using solar energy is for hot water by concentrating sunlight into useful heat in the form of hot water. Just like water from aa gas boiler, the water can then be used not only to heat a building but also for hot water from the taps. Such systems are often referred to as Active Solar Heating, Solar Thermal, Solar Hot Water or Solar Water Heating.
HOW DOES IT WORK?
A solar water heating system for a home or small building will have three main components: Solar panels, a hot water cylinder and a plumbing system.
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The system can work through the use of a pump or through natural convection forces in order to circulate hot water. Water is heated in the solar panels and then circulated into the system with a constant flow of cold water entering the panels and leaving them warm to return to the water cylinder and possibly boiler.
In areas that are likely to freeze, closed-loop systems have been used which keep an antifreeze and water mixture within the solar panels. The pipes containing the antifreeze-water mixture never mix with water for human use. Water held in a tank is heated through a heat exchange from the pipes. There now another option to using the antifreeze available on the market from UK company. It works with the freezing of the pipes in cold weather rather than trying to prevent it. (see SolarTwin http://www.solartwin.com/).
Currently on the market, there are three forms of solar panels that can be
used to heat water for homes (and other types of buildings):
• evacuated tubes
• selective panels
• non-selective panels
Evacuated tube panels are made of twin glass tubes that have a vacuum between
them. These panels tend to be smaller but are more costly. Selective panels
have a surface which is not only good at absorbing energy, but does not radiate
a great deal of energy back into the atmosphere so making them more efficient
than the non-selective.
THE COSTS
There are three types of costs that are worth considering. While financial costs are an obvious consideration, energy and other environmental costs are also good to keep in mind - for environmental debt is equally important.
According to Solar PV (a DTI funded programme managed by the Ehergy Savings Trust), a solar water heating system for an existing home will cost in the range of £2,500 to £4000 and less than this for a new build. DIY installation can cost between £500 to £1500, but will take longer to install and requires you have a certain number of skills applicable to installing the system. Other factors that can also vary the cost are roof type, existing hot water system, and your geographic location.
There are grants available to offset these cost (some up to 50%) and the size and availability of these grants can depend on where you live. (For more information on them as well as grants for PV, please see LINKS at the end of the article.) In addition, some banks may offer special loans for installing solar systems.
With concerns to maintenance, solar hot water systems require very little input and most come with a 10 year guarentee. According to Energy Savings Trust, the house holder should annually check on the system and a “more detailed check every 3-5 years” by your system supplier.
The energy and environmental costs are sometimes harder to calculate and put into useful terms. But there are some points to keep in mind and companies out there who are trying to make a difference in how their solar technology in produced - from using only power from small hydro schemes to green office polices.
At one time, early in the development of solar panels, it took more energy to produce the panel than the energy panel would ever be able to supply in its lifetime. Why would this be important? Unless stated in a company’s policy, it is highly likely that the energy used to create the solar water heating system was generated by coal or another fossil fuel - a nonrewable, green-house gas contributing, source of energy. If a solar water heating system is not going to provide a number of years above its own energy-manufaturing (and greenhouse gas) costs, its production and use are difficult to warrent. Fortunately, this is no longer the case. According to the Scottish Renewables Inititive, solar water heating systems now produce the energy equivilent to its production energy input in 3 years time. There are also companies that will only order in their raw materials that are processed with renewable energy - for example Solar Twin will only use aluminium from manufactured using small hydro power.
In addition to energy, there are other environmental concerns - heavy metals, systems that use toxins like antifreeze and freight miles. All of these will depend on what company as well as system you chose, therefore such details are a bit to indepth for the range of this article. But this is where you, as the consumer needs to ask questions and make sure companies know what you want and why. Asking questions and being conscious of your choices is one of the most important things we can do as consumers.
Photovoltaics : Solar Electricity
The other means of using solar energy is Photovoltaics (or PV) which produce electricity through semiconductor cells when daylight falls upon them. (But they do not require direct sunlight to work.) A very common use of PV cells are on battery-free calculators or outdoor garden lights. You may also see them in cities to power street lamps or paid parking machines.
HOW DOES IT WORK?
To convert solar energy into electricity, the PV Cell will have one or two layers of a semiconductor, the commonest being silicon. When light hits the cell, a field of electricty is created within the layers causing the electricity to flow. The greater the intensity of the light, the greated the flow across the layers and so the more electricity generated. But such a system still does not require direct sunlight to work. Once eletricity is generated, it can go to power anything in your house or be stored in batteries for later use.
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The size of PV system you would need to install depends completely on what you wish to power and the type of PV cell you wish to use. Currently, there are three main types: Monocrystalline, Polycrystalline and Thin Film.
•Monocrystalline is a very thin slice of a single crystal of silicon.
Normally, it has an efficiency of 15%.
•Polycrystalline is a very thin slice of silicon cut from a block of
crystals. Its efficiency is a bit lower, at 13%.
•A thin film is a very thin layer of semiconductor atoms deposited on
a glass or metal base with a efficiency of about half of the monocrystalline,
at 7%.
In addition, PV tiles can come in a variety of styles, colours and shapes,
from looking like roof tiles.
THE COSTS
Again, when considering PV, one needs to look at the financial, energy and environmental costs.
Financially, PV systems are much more expensive than solar hot water, but also have a greater number and larger payments of grants set aside for them. Prices will vary due to size of the system (which will be completely dictated by to how much power is needed from the system), the type of PV cell used and the building in which the cells are to be attached to. A typical installation, according to the Energy Savings Trust, will have about 1.5 - 2 kwp and cost between £7,500 and £14,000. In addition, integrated roof systems and tiling (rather than panels) are even more costly - but can be worth looking into if you are already having to replace part or all of your roof or working in a new build situation.
Maintenance comes down to making sure panels are kept fairly free of debris and managing shade from any trees growing nearby. The electronics of the system should be checked regularly by someone qualified to do so. The frequency of this will depend on your system and is best advised by the manufacturers.
The energy and environmental costs also need to be considered. The energy payback for a PV system is a bit longer than a solar hot water system - around a 4-5 year average - but this can vary widely depending on the construction materials, manufacturing processes as well as the amount of sunlight the system recieves. PV is mainly made of silicon, which in itself, is pretty inert yet requires high energy costs to produce the high grade silicon crystals. Silicon for PV cells is usually sourced from scrap left over by the computer industry. Other environmental concerns are difficult to pinpoint at the time of writing, outside the varibles of energy payback. Little seems to be written on the environmental life cycles of the eletronics at this time. (But the author is always happy to be enlightened if she missed information out there!)
Wrapping it up
Even in the midsts of our clouds and rain, solar energy has something to offer those of us in the British Isles seeking a sustainable source of energy. Hopefully this article has given a basic introduction to how this can happen and questions to ask.
There are high initial financial investments but grants and energy savings can help to off-set these. Additionally, both solar thermal and photovoltaic cells have environmental costs - yet they can and do offer a viable alternative to fossil fuels. This article ends with a list of links for you to find more information and an open invitation to others experiences and thoughts on solar.
Please feel free to write me at TDNSolar [at] oakandapple [dot] com.
Have you installed solar?
Want to share your experiences with others who might be considering their options? Drop me a note! TDNSolar [at] oakandapple [dot] com
LINKS
Energy Savings Trust
This organization “provide[s] independent evidence-based policy analysis
around the areas of energy efficiency small-scale renewables and clean low
carbon transport, covering both the UK and Europe.” Has information
on both Solar thermal and PV, grants and home energy audits.
http://www.est.org.uk/
HI-energy - Renewable Energy in the UK
Thanks to its geography and abundance of renewable and alternative energy
sources, the Highlands and Islands of Scotland are poised to become the Green
powerhouse of the UK.
http://www.hi-energy.org.uk/
Solar Trade Association
The trade association for solar thermal. His a wide range of infomation and
case studies.
http://www.greenenergy.org.uk/sta/
PV-UK
The trade association for the PV industry. Will provide information and installers.
http://www.pv-uk.org.uk/
Solar Twin
UK based company that sells a solar thermal system that does not require antifreeze.
http://www.solartwin.com/
These are just a few links - if you have found others you feel should be here, feel free to contact me.
Susan
November 2004
TDNSolar [at] oakandapple [dot] com