What is photovoltaic energy?
‘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.
Generating energy through solar PV is quite different from how a solar thermal system works, where the sun’s rays are used to generate heat, usually for hot water in a house, swimming pool etc.
The advantages of PV technology:
✜ The fuel is free.
✜ There are no moving parts to wear out, break down or replace.
✜ Only minimal maintenance is required to keep the system running.
✜ The systems are modular and can be quickly installed anywhere.
✜ It produces no noise, harmful emissions or polluting gases.
PV technology
The most important parts of a PV system are the cells which form the basic building blocks of the unit, collecting the sun’s light, the modules which bring together large numbers of cells into a unit, and, in some situations, the inverters used to convert the electricity generated into a form suitable for everyday use.
PV cells and modules
PV cells are generally made either from crystalline silicon, sliced from ingots or castings or from grown ribbons, or thin film, deposited in thin layers on a low-cost backing. Most cell production (90% in 2007) has so far involved the former, whilst future plans have a strong focus on the latter. Thin film technology based on silicon and other materials is expected to gain a much larger share of the PV market. This technology offers several advantages, such as low material consumption, low weight and a smooth appearance.

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