SOLAR ENERGY
Introduction
The Sun radiates enormous amounts of energy to the Earth due to its surface temperature of 6,000°C.
In the UK we receive vast amounts of solar energy with the average amount of energy received in a year being as much as 60% of that received on the equator. This radiation is similar to the output of 1,000 power stations.
Today there are a range of high quality products, which enable us to use the Sun's energy very effectively in the UK.
Using the Sun's energy reduces our consumption of conventional fuel and helps to reduce the emission of harmful greenhouse gases.
There are three main ways in which solar energy is used:
Passive solar design uses the form and fabric of a building to capture energy from the sun and so reduce the building's needs for artificial light and heat. Architects are using these principles in many new domestic and commercial buildings.
Solar thermal energy employs solar collectors (often on a south-facing roof) to capture and store the sun's heat via water storage systems and use the heat primarily for water heating.
Photovoltaic cells (PVs) involve the direct conversion of light energy from the sun into electricity by means of specially prepared semi-conductors. Solar photovoltaic cells are arranged in panels that can be located on roofs or external walls of buildings. These solar panels often feed the electricity generated directly into the building for use as lighting or power. While the technology has been successfully employed in special applications (e.g. on satellites or remote installations) it is still too expensive for everyday use, but the cost of energy from photovoltaic cells has come down dramatically over the last few years, and continues to do so.
Solar thermal energy
Solar thermal systems can cover a large part of the needed energy to heat potable water. In the summer the heating remains off: The solar heating system delivers enough heat for bathing, showering and washing machines from May to August. Throughout the remainder of the year the energy demand for warm water remains about the same. Even small solar thermal heaters reach efficiencies from 50 % to 65 %.
During cooler months solar rays can also be efficiently used to cover a considerable part of the heating demand, which in the spring and autumn turns out to be relatively low. This is made possible by solar heating systems that can both heat potable water and support other heating needs. Low energy or passive buildings are especially qualified for solar heating support, as well as heating systems with low flow temperatures (maximum flow temp. 70ºC, maximum return flow 40ºC). Heating systems with high lay out design temperatures reduce solar yield less than expected, as proved in tests. For this reason combination systems are also of interest for the renovation of existing buildings, especially if they can be combined with boilers without seriously reducing their efficiency.
Exactly how combination systems must be designed is being investigated by work groups from the International Energy Agency (IEA), ensuring that solar circulation, space heating circulation, secondary heating, and storage tank all function together optimally. The IEA's work groups are developing storage tank parameters and testing methods to lay the groundwork for international standardization. A study of some system concepts delivered some surprising results: Solar combination systems reduce the total energy needs of a modern single-family home by about 20 - 30 %, dependent on the corresponding construction design, yet independent of which concept planners and building owners decide on. The system's output depends much more on its design and the quality of its components. The most important aspects concerning storage tanks are their optimal size and the high transfer performance of the heat exchanger.
Photovoltaics
The photovoltaic (PV) process converts sunlight - the most abundant energy source on the planet - directly into electricity. PV equipment has no moving parts and as a result requires minimal maintenance. It generates electricity without producing emissions of greenhouse or any other gases, and its operation is virtually silent.
A PV cell consists of two or more thin layers of semiconducting material, most commonly silicon. When the silicon is exposed to light, electrical charges are generated and this can be conducted away by metal contacts as direct current (DC). The electrical output from a single cell is small, so multiple cells are connected together and encapsulated (usually behind glass) to form a module (sometimes referred to as a "panel").
The PV panel is the principle building block of a PV system and any number of panels can be connected together to give the desired electrical output. This modular structure is a considerable advantage of the PV system, where further panels can be added to an existing system as required.
Solar clubs
What is the Solar Club?
The Solar Club is a not-for-profit community initiative for householders, designed to make solar water heating cheaper and easier to install.
How does it work?
The Solar Club operates by training members to install professional solar water heating systems as DIY projects. The training course lasts one day and covers the theory, practice and health and safety aspects of installing a solar hot water system.
What are the benefits?
Installing and using a solar system can be a lot of fun. Not only will you be helping to reduce your fuel bills, but you will also be helping to reduce green house gas emissions, which contribute towards global warming.
By doing the work yourself and adding in Solar Club discounts the cost of installation can be reduced to between one-half and two-thirds of the cost of a commercial system. The Solar Club is run as a 'not-for-profit' scheme. This means it takes no commission on sales, and discounts are passed directly to the members. The Solar Club can also provide you with tools and equipment for loan during the installation of your system.
Do I need to be a DIY expert to install a solar system?
No. Providing you are reasonably competent at DIY and attend a training course, the installation should be straightforward. Many Solar Club members have no experience of plumbing before installing their solar system. Once you have attended a training course, the Solar Club will be on hand to provide technical support if you need assistance.
For those people you prefer not to undertake the installation themselves, membership allows training for you own chosen installer (although of course costs of installation with then become a consideration).
How much will I save?
A solar water heating system can save up to 50% of the energy required to heat your hot water during a twelve-month period. The exact amount of money you save will depend on how you heat your hot water.
A solar system installed through the Solar Club will cost in the range of £1500 to £2500, depending on the type and size of the system you install. There is a one-off membership fee of £95 + VAT to join the Solar Club, which off-sets the cost of training materials and running the Solar Club.
How can I find out more?
CSE also acts as co-ordinator for the National Network of Solar Clubs.
The National Network of Solar Clubs
18 Solar Clubs exist across the country, based on the methodology developed through the pilots pioneered in Bristol and Leicester.
New Solar Clubs are at liberty to develop their own approach to suit their location and specific requirements and different options for maintaining longer term funding are being tested.
As the co-ordinator of the National Network, CSE has a vision to see the network expanded to support householders across the UK. CSE recognises that to achieve this, expand the products on offer (possibly to cover photo-voltaics) and to provide effective support to individual clubs, further funding is required. A range of potential funders are currently being approached.
To find out more about the national network contact Mark Letcher, on 0117 929 9404 or e-mail mark@cse.org.uk.
Further Information
For further information on Solar Energy:
Photovoltaics www.PV-UK.org.uk
Solar Trade association http://www.greenenergy.org.uk/sta
Centre for Alternative Technology Solar Electric course www.cat.org.uk
Centre for Alternative Technology Solar water heating course www.cat.org.uk
