Photovoltaics Explained

'Photovoltaic' is a marriage of two words: 'photo', meaning light, and 'voltaic', meaning electricity. Photovoltaic technology, the term used to describe the hardware that converts solar energy into usable power, generates electricity from light.

At the heart of photovoltaic (PV) technology is a semi-conductor material which can be adapted to release electrons, the negatively charged particles that form the basis of electricity. The most common semi-conductor material used in photovoltaic cells is silicon, an element most commonly found in sand. There is no limitation to its availability as a raw material; silicon is the second most abundant material in the earth's mass.

All PV cells have two layers of semi-conductors, one positively charged and one negatively charged. When light shines on the semi-conductor, the electric field across the junction between these two layers causes electricity to flow, generating DC (direct current). The greater the intensity of the light, the greater the flow of electricity.

A photovoltaic system therefore does not need bright sunlight in order to operate. It can also generate electricity on cloudy days. Due to the reflection of sunlight, days with slight cloud can even result in higher energy yields than days with a completely cloudless sky.

1 PV aray	4 Import / Export meter
2 PV array combiner / junction box	5 Connection to the grid
3 Grid-tied inverter	6 Load

Shown on the left is a typical configuration of a roof mounted domestic solar power system.

There are however many different configurations possible including ground mounting, or flat roofs or on the side of buildings.

Many major manufacturers now produce solar panels and grid connection inverters in many different shapes and sizes, including some which are made as roof tiles and others as glass.

For further information on the solar photovoltaic technology and market, download Solar Generation a combined Greenpeace and EPIA document or view the EPIA's short video, 8 Minutes from the Sun.