Solar PV

A solar electric system captures the bountiful energy of the sun, and makes that energy available around the clock. A solar panel, made up of photovoltaic (PV) cells, transforms light photons into electricity. That electricity is then stored in a large battery for use whenever it is needed. The simplicity of solar power systems ensures that they will be extremely reliable and low maintenance.

How PV Cells Function?

PV cells are made up of at least two layers of semiconductor material. One layer has a positive charge, the other a negative charge. When sunlight enters the cell, some of the photons from the sunlight are absorbed by the semiconductor material, freeing electrons from the cell's negative layer to flow through an external circuit and back into the positive layer. This flow of electrons produces an electric current.

To increase power output, several individual PV cells are wired together and sealed in a weather proof housing referred to as a module, or solar panel. Modules are then wired together in a PV array to achieve the desired voltage and current.

A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). Solar cells are used to power many kinds of equipment, including satellites, calculators, remote radiotelephones, and advertising signs.

Most often, many cells are linked together to form a solar panel with increased voltage and/or current. Solar cells produce direct current (DC) which can be used directly, stored in a battery or converted from DC to AC to directly power common household devices or to feed into the utility grid. This DC to AC conversion is done by means of an inverter. Since the solar cell, grid feeding and anti-islanding requires special handling, so called Photovoltaic Inverters are used.

Solar Cells Types:

The simplest type of solar cell is a silicon diode, but research is continuing into more exotic materials (see below) with greater efficiencies. Modern solar cells are encapsulated in glass-fronted plastic sheets. They have design lifetimes that exceed forty years. Sunlight provides about 1 kilowatt per square meter at the Earth's surface, and most solar cells are between 8 and 12 percent efficient. In desert areas, they can operate for an average of 6 hours per day when mounted in nonrotating brackets.

Solar panels come in four varieties:

Most common are rigid monocrystalline and polycrystalline silicon sheets.

Monocrystalline silicon provides the highest efficiency of all four types but is also the most expensive.

Polycrystalline silicon is lower cost but lower in efficiency.

Also available are amorphous silicon solar cells which can be applied to a variety of substrates including flexible ones, like metal foil or plastic foil.

The main advantage of amorphous silicon solar cells is that they should eventually be able to be processed at a much lower cost than crystalline solar cells.

Nanocrystalline silicon has also been used, in the same processing systems as for amorphous silicon, and it shows slightly higher efficiency due to the increased absorption in the longer wavelengths.

Experimental non-silicon solar panels are made of carbon nanotubes embedded in plastic. These have only one-tenth the efficiency of silicon panels but could be manufactured in ordinary factories, not clean rooms which should lower the cost.

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