PASSIVE SOLAR POWER: This is the simplest method of harvesting the sun's energy and relies on absorbing warmth through windows and walls, and hanging on to it.

The choice of materials and building design are critical and are often used in reverse to prevent buildings overheating.

SOLAR THERMAL

This is a method of heating water for taps and heating systems via panels, usually on roofs.

These panels run the water in pipes through the panels or run antifreeze and have a heat exchanger to heat the water.

In summer, it can supply all the hot water used in a home. In colder times, other methods are needed to supplement the system. Overall, solar thermal can provide about half the hot water used in a home.

SOLAR GENERATED ELECTRICITY

In photovoltaic cells, layers of semiconductor materials produce a small electric current when heated by the sun.

This current is small, but many cells together can produce a workable amount of electricity, which can be stored in batteries. A typical system would provide about a third of a family's annual electricity.

Published: 11/05/2004