How Solar Photovoltaic (PV) Works
The "photovoltaic effect" is the basic physical process through which a PV cell converts sunlight into electricity. Sunlight is composed of photons, or particles of solar energy. When a photon is absorbed by a PV cell the energy of the photon is transferred to an electron in an atom of the cell (a semi conductor). With its newfound energy the electron is able to escape from its normal position associated with that atom to become part of the current in an electrical circuit.
PV cells are grouped into modules and encapsulated between a sheet of glass and a backing material (also often glass) within a frame. Modules are connected together (into an 'array') to provide the voltage and DC current levels required to meet a particular load.
Within PV systems for homes, the electricity produced by the PV array is converted from DC to AC and is connected with the home's mains electricity system.
Once installed on a roof the PV system generates clean electricity whenever there is daylight and feeds it into the building’s electricity supply to power lights and appliances. It does not have to be direct sunlight, although the more intense the light, the higher the electrical power produced at any time. The building remains connected to the national grid, and when more electricity is generated than is being used, the excess flows into the grid. When the PV system is not generating enough electricity – like at night time, electricity is drawn from the grid as normal.
PV systems are unique in that they can be mounted on buildings to produce electricity at the point of demand without any adverse environmental effects - no noise, no moving parts, no exhaust gases and no dangerous by-products.
Apart from reducing carbon emissions and electricity costs, our experience shows that installing a PV system has a wider effect on electricity usage in the building. As occupants are able to monitor what their solar electric systems produce, they normally find they start using less electricity because of their new awareness of the resources that they are using.
