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Solar  
Photovoltaics

The sunís energy can be converted directly into electricity using photovoltaic cells. PV cells can be used for applications as small as watches and calculators, to large grid-connected arrays of panels. The great attraction of PV technology is that it delivers electricity at the point of use, for example panels can be integrated into buildings to supply the buildings themselves.

In areas where grid connection or other forms of generation are too expensive or not feasible, PV can be very cost-effective. This may be in remote locations, but could also be in a city centre where grid connection may be impractical. For example it can be cheaper to power parking meters with solar energy than with power from the grid.

PV materials are usually solid-state semiconductors. various forms are used:-
  • mono-crystalline silicon (crystalline)
  • Poly-crystalline silicon (crystalline)
  • amorphous silicon (thin film)
  • cadmium telluride (thin film).

Active solar thermal

Active solar heating systems convert solar radiation into heat which can be used directly. In the UK uses are primarily domestic water heating and other low temperature heating applications such as swimming pools. In hotter climates a wider range of applications is possible, including electricity generation.

Domestic water heating schemes consist of solar collectors, (usually) a preheat tank, pump, control unit, connecting pipes, the normal hot water tank, and backup heat source such as gas or electric immersion heater. The collectors are mounted on the roof and heat the water tank via a fluid circulated between the collectors and the tank. The overall area of the panels is typically 3-4 square metres.

A plane inclined at about 30 degrees, facing due south ranges from around 900 KWh/m2 per year in the North of Scotland to around 1,2500 kWh/m2 in the South Wet of England.

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