Photovoltaic solar

Electricity from the sun

‘Photovoltaic cells’ are used to make electricity from sunlight. They are sometimes called solar cells.

Photovoltaic cells (PV) generate electricity when exposed to sunlight. They were developed for use in space to provide power for satellites. The Russian Sputnik 3 satellite in 1957 was the first to use solar power.

Early solar cells were used to provide power in remote locations where other power (e.g. mains electricity) was not available. Uses included power for remote telephones, water pumps, lighting and small consumer electronics like watches and calculators.

Home solar cells can be used with mains electricity to provide household electricity and pump surplus power back into the electricity grid.

Solar power is also used by electricity generators to produce ‘green’ power.

Electricity from solar power is an environmentally friendly alternative to electricity produced by other sources, such as coal that produce greenhouse gases.

Household solar power

There are three components in a household solar power system:

solar panels:these are flat panels of solar cells usually located on the roof and point towards the sun.

inverter: this converts the DC (direct current)* current from the cells to AC (alternating current)* – the type of current used in homes. Some inverters have a display that shows the householder how much power is being generated from the solar panels.

two-way electricity meter: this allows surplus power from the solar cells to be directed into the electricity grid for other consumers to use. The value of the surplus power is credited to the household electricity account.

How do PV cells work?

It’s all about getting excited by solar energy! The electrons in the solar cells get excited when they are heated by the sun’s radiation. This excitement produces an electrical current. During daylight, even under cloud cover, the solar cells will produce some current. More sun means more current. Without the sun, solar cells cannot produce current, for example at night.

Solar panels are described by their maximum current output under Standard Test Conditions (STC). A typical solar panel of 1.4 metres square will produce 160 watts (W) in full sunshine. Cloudy skies or high air pollution will reduce this output significantly.

What is watt (W)?
A W is a measurement of energy used. Electricity consumption is measured in watt-hours (Wh) and more typically kilowatt-hours (kWh).

A simple example is a 100W light globe. This means it uses 100 joules (J) per second. To power the light for one hour would require 100Wh of electricity or 0.1kWh of electricity.