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Photovoltaic - 'Photo' meaning light and 'voltaic' meaning electricity. At the heart of photovoltaic 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-conducting material, 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, and can generate electricity even on cloudy days. Due to the reflection of sunlight, days with slight cloud can result in higher energy yields than days with a competely cloudless sky.
A typical grid connected roof mounted system (see diagram) consists of a number of components which are scalable and highly versatile, enabling them to be used for a variety of applications, from small domestic properties to large installations. The light that hits the array is converted into clean electricity, and as there are no moving parts, this is done silently.
The electricity the array creates is direct current (DC) which needs to be converted into alternating current (AC) so it can be used in the building. This is performed by the inverter. The AC electricity then passes via the generation meter (this measures how much electricity has been created by the array) and on to the consumer unit where it can be fed into the property for use, or exported back to the mains grid via the electricity meter.
