Photovoltaic (PV) cells are devices that convert sunlight to electricity, bypassing thermodynamic cycles and mechanical generators. PV stands for photo (light) and voltaic (electricity), whereby sunlight photons free electrons from common silicon. The phenomenon was first discovered in the 18th century. The photovoltaic cells were developed at Bell Labs in 1950 primarily initially for space applications. The Hubbell telescope utilizes solar panels for its energy requirements.
The US Department of Energy during the Carter administration spent 500 million dollars developing this technology. Costs have dropped since then and currently, solar cells have proved to be cost effective. Other than space satellites, the photovoltaic cells are being used in rural health clinics for refrigeration, water pumps for irrigation and for small scale power generation.
Solar cell are also being used in developing countries. Solar panels can power a 17" b/w TV, a radio or a fan. Some electric lighting systems provide sufficient current for up to 10 hours of lightning each evening. Locally produced car batteries can provide up to 5 nights of energy for a 8 watt DC fluorescent light.
The new Mazda 929, uses solar cells to activate a fan to ventilate the car when the car is idle and parked during a sunny hot day.
The use of silicon crystals in the Photovoltaic cells makes it expensive. First of all, silicon crystals are currently assembled manually. Secondly, silicon purification is difficult and a lot of silicon is wasted. In addition, the operation of silicon cells require a cooling system, because performance degrades at high temperatures. However, it has convinced analysts that solar cells will become a significant source of energy by the end of the century.
Research is underway for new fabrication techniques, like those used for microchips. Alternative materials like cadmium sulfide and gallium arsenide are at an experimental stage. Reduction of cost will depend the economies of scale.
Oil companies for example, are aware of the renewed interest in solar power. They are diversifying their holdings in other forms of energy. Today, the chemical giant Exxon is the second largest producer of solar cells.