Photovoltaic (PV) cells use light to generate electricity rather than heat. There are a number of PV panel technologies, including polycrystalline, monocrystalline and thin-film. A PV cell consists of two or more thin layers of semi-conducting material, most commonly silicon. When the silicon is exposed to light, electrical charges are generated and this can be conducted by metal contacts as direct current (DC).
Solar PV cells can be arranged in panels on a building’s roof or walls, and can often directly feed electricity into the building. South facing locations are best for roof applications and between south east and south west for vertical situations. It is also important to reduce any possible shadowing from trees or surrounding buildings as this will affect output. Planning permission is not usually required unless buildings are listed or in a conservation area.
Groups of solar PV cells can be added together to provide increasing levels of power and can either be connected to the local electricity grid or stand alone units. PV systems produce no greenhouse gases and each kWp can save approximately 455kg of carbon dioxide emissions per year, adding up to about 11 tonnes over a system's lifetime which is estimated to be around 30 years. PV heating systems are significantly more expensive than solar heating systems, but they do have the advantage that there are no moving parts so are simpler and more reliable to maintain and waterproof PV panels can be incorporated into a roof as part of the structure.
PV HEATING SYSTEMS ARE SIGNIFICANTLY MORE EXPENSIVE THAN SOLAR HEATING SYSTEMS, BUT THEY DO HAVE THE ADVANTAGE THAT THERE ARE NO MOVING PARTS SO ARE SIMPLER AND MORE RELIABLE TO MAINTAIN
A typical domestic 1 kilowatt (1kW) system will cover about 10 square metres, and produce about 750kWh (units of electricity) over a year, mostly during the summer. With costs ranging between £5- 10,000 payback is between 15 to 20 years however grants are available providing 40-50% of the cost.
The government does support photovoltaic applications but costs for builders and developers may be prohibitive unless using the technology on multiple buildings in one project. If grants are sought only certified installers can be employed.
