The Photovoltaic Effect
Modern solar-energy electricity generation is based on the photovoltaic effect, which was discovered by the French physicist Alexander Edmond Bequerel in the 19th century. However, it was not until the 20th century that it could be explained by physicists, such as Albert Einstein.
Using solar modules, the photovoltaic effect converts light into electrical energy.
Photovoltaic is the transformation of light energy into electrical energy using solar cells. Solar cells are made of the semiconductor silicon that is treated in a special way so it can conduct electricity when exposed to light. There are various types of solar cells, monocrystalline, polycrystalline and amorphous. These types of solar cells differ in efficiency and production cost.
Monocrystalline cells are made from silicon crystals and are round, square or octagon shaped. Depending on their shape they are dark blue, black or grey. Their efficiency ranges from 15 to 18 per cent. This is the highest efficiency available today, but production costs are relatively high.
Polycrystalline or multicrystalline cells consist of silicon blocks that are cut into small pieces. The surface of these cells looks like a frosted window. The shape is square, the colour of these cells ranges from blue to silver-grey. Their efficiency is 13 to 15 per cent with a service life of approximately 30 years.
Thin-layer solar cells
Thin-layer cells are approximately 100 times thinner than monocrystalline and polycrystalline cells. This makes them very light and flexible and easy to apply to flexible materials. The cells are reddish-brown, dark green or black. Their efficiency varies greatly, between 6 and 20 per cent, depending on the material used. So-called “CIS solar cells” can reach an efficiency of 20 per cent in test situations. The energy and material needed to produce thin- layer cells is quite low, but the service life is shorter than that of silicon cells.
In addition “gallium arsenide (GaAs) solar cells” are currently being developed. They are expensive but very efficient and durable. Another type of solar cells in development are “organic solar cells”. However these are not yet suitable for mass production due to their short service life.
From solar cells to photovoltaic system
To get sufficient power, solar cells are consolidated into modules which are combined into photovoltaic panels. To feed the electricity generated into the electrical grid the energy must first be transformed into alternating current by an “inverter”.