Heating houses by sunlight
The technology of photovoltaic cells
Dr Roaf's solar house uses two key methods of harnessing the sun's energy:
Photovoltaic cells were discovered in 1839, when a French scientist noticed that shining light onto one side of a simple battery cell increased the amount of current generated.
Today, PV cells are made from silicon and are used to produce electricity directly from the sun's energy. A typical cell is about 12.5cm across and will produce about 1 watt of electricity in bright sunlight. About 30 of these cells are usually linked together into a module that produces 12 volts of direct current electricity. Any number of modules can be connected to produce the voltage required. The power can also be transformed to change it into an alternating current.
The electricity produced by PV cells can either be:
- used directly, for example to drive machinery
- stored in a battery for later use, as with many lighting systems.
Although PV cells are an expensive way to produce electricity, costs are coming down all the time and cells last for at least 20 years.
Facts about PV cells
When is it appropriate to use PV cells?