The Low Carbon Partnership

How solar PV works

Photovoltaic or PV cells are semiconductor devices that convert sunlight directly into electricity. A typical cell comprises a wafer of silicon which is manufactured with a "p-n junction" within it. This junction is the boundary between "n-type" silicon on one side of the wafer (silicon with an excess of free electrons) and "p-type" on the other (silicon with a defecit of free electrons). The energy in light frees electrons within the silicon cell - these are captured by the electric field of the p-n junction. Metal contats on the front and the rear of the cell are used to draw off the electric current produced by this flow of electrons.

Photovoltaic or PV modules typically consist of a number of interconnected PV cells encapsulated between a sheet of glass and a backing sheet. This laminate is often mounted within a rigid aluminium frame, but can also be manufactured in a wide range of other configurations to create modules that suit many different applications - e.g. solar roof tiles.

In grid-connected installations the electricity generated is fed into the mains electricity network via an inverter and monitoring system to supply power to electrical 'loads', e.g. lights, appliances.

The inverter converts the DC/direct current electricity generated by a PV cell to AC/alternating current for safe connection to the mains. The monitor records how much electricity is being generated in kilowatts (kW).

A grid-connected system might also incorporate an export meter to measure the amount of electricity fed back to the Grid when it is in excess of on-site demand. This energy can be sold to the mains electricity provider.

In off-grid systems the electricity is stored in batteries.

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