Solar Photovoltaics (PV) uses energy from the sun to create electricity to run appliances and lighting. PV requires only daylight – not direct sunlight – to generate electricity. The PV systems use cells to convert the solar radiation into electricity. The cell consists of one or two layers of a semi conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers, causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity.
HOW IT WORKS
PV systems generate no greenhouse gases, saving approximately 325kg of carbon dioxides emissions per year – adding up to about 8 tonnes over a system’s lifetime – for each kilowatt peak (kWp – PV cells are referred to in terms of the amount of energy they generate in full sunlight). PCV arrays now come in a variety of shapes and colours, ranging from grey ‘solar tiles’ that look like roof tiles, to panels and transparent cells that you can use on conservatories and glass to provide shading as well as electricity. As well as enabling you to generate free electricity they can provide an interesting alternative to conventional roof tiles!
SOLAR PV & YOUR HOME
You can use PV systems for a building with a roof or wall that faces within 90 degrees of south, as long as no other buildings or large trees overshadow it. If the roof surface is in shadow for parts of the day, the output of the system decreases. Solar PV installations should always be carried out by a trained and experienced installer.
RENEWABLE TECHNOLOGY COST & MAINTENANCE
Prices for PV systems vary, depending on the size of the system to be installed, type of PV cell used and the nature of the actual building on which the PV is mounted. The size of the system is dictated by the amount of electricity required. Grid connected systems require very little maintenance, generally limited to ensuring that the panels are kept relatively clean and that shade from trees has not become a problem. The wiring and components of the system should however be checked regularly by a qualified technician. Stand-alone systems, i.e. those not connected to the grid, need maintenance on other system components, such as batteries.
PLANNING CONSIDERATIONS
In England, changes to permitted development rights for domestic renewable technologies mean that most solar PV installations don’t require planning permission, as long as they respect certain size criteria. Exceptions apply for installations on flat roofs, Listed Buildings, and buildings in Conservation Areas and World Heritage Sites. In Wales, Scotland and Northern Ireland, the devolved governments are currently all considering changes to their legislation, to make installations of microgeneration technologies easier. Legislation is expected in all three countries later this year. Until then, householders in Wales, Scotland and Northern Ireland must consult with their local authority regarding planning permission.
© Energy Saving Trust 2008