Solar generated electricity is created by the technology of photovoltaics (PV) – solid state semi-conductors that convert light into electricity. When light (a photon) is incident on a PV cell it gives energy to an electron. The electron moves away from the cell into an electrical circuit. The electricity created is direct current (DC). This can either be used to charge batteries or power DC devices, however in the UK it would normally be converted to alternating current (AC) via an inverter to meet the electrical demands of the site and tied into the grid.
Systems are easily retro-fitted or incorporated into new and existing roofs, facades and glazing, the technology being extremely versatile. The panels themselves when arranged and connected together form an array with electrical generating capacity measured in kilowatts peak (kWp, – a rating calculated using a defined theoretical set of conditions rather than maximum or typical output).
Solar PV panels are available in a variety of different forms including; mono-crystalline poly-crystalline thin film and hybrid. Mono-crystalline and hybrid panels are the most efficient at turning daylight into energy, but it may be easier to install thin film panels in the form of solar roof tiles rather than fitting a standard roof and then retrofitting panels. This is, however, more costly and whilst solar roof tiles come in a variety of different physical sizes and capacities, they do not currently vary much from a grey/blue/black colour.
The key locational requirements for a PV array are to avoid shading and to face within 45° of south, although they will work at a reduced efficiency facing east/west. A tilt of between 30- 45° is also preferable, but not essential. Solar PV material can also be integrated into flexible flat roof membrane materials.