PV technology was first applied in space, by providing electricity to satellites.

Anyone who has used a modern mathematical calculator can grasp the concept of photovoltaic (PV). It is simply the process of converting energy from the Sun into electricity that can power everything from household appliances, lights, sprinkler systems and water pumps to large-scale communications, industrial and military equipment.

In precisely the same way as the small solar cells on hand-held calculators eliminate the need for batteries, PV can provide the world with a clean, reliable source of electricity and reduce our reliance on ever-depleting fossil fuels.

The PV technology of the 21st Century makes it possible. It employs layers of micro-fine crystalline silicon to convert ordinary sunlight into small electrical charges. This process is then multiplied thousands of times over to create modules and systems that can generate enough electricity to power entire towns.

It's important to note that PV is different from the 'passive' solar thermal energy used for heating or in hot water production. A single PV cell consists of two or more thin layers of semi-conducting material, most commonly crystalline silicon. When the silicon is exposed to light, small electrical charges are generated and conducted away by metal contacts as direct current (DC).  

In order to maximise energy collection and conversion, single cells are connected together and housed in a module. These modules are the building blocks of PV systems and are, in turn, connected together to generate usable volumes of electricity. In some instances, an inverter is also used to convert low voltage DC into higher voltage AC power.

Types of PV Cells

There are essentially two types of crystalline silicon PV cells:

Monocrystalline Cells - These are made using cells cut from a single cylindrical crystal of silicon. While monocrystalline cells offer the highest efficiency (approximately 18% conversion of incident sunlight), their complex manufacturing process makes them slightly more expensive.   

Polycrystalline Cells - These are made by cutting micro-fine wafers from ingots of molten and recrystallised silicon. Polycrystalline cells are cheaper to produce, but there is a slight compromise on efficiency (approximately 14% conversion of incident sunlight).

PV technology was first applied in space, by providing electricity to satellites. Today, PV systems can be used to power just about anything on Earth. PV systems operate in two basic forms.

Grid Connect PV Systems - These systems are connected to a broader solar electricity network. During the day, the solar electricity generated by the system is either used immediately or sold off to electricity supply companies. In the evening, when the system is unable to supply immediate power, electricity can be bought back from the network.

Stand-Alone PV Systems - These systems are used in isolation of solar electricity grids, and may be used to power radio repeater stations, telephone booths and street lighting. There is also a growing market for mobile PV in the boat and caravan leisure market. Stand-alone PV systems also provide invaluable and affordable electricity in the developing world, where conventional electricity grids are unreliable or non-existent.