Breakthroughs in Solar Power Technologies

Throughout history, mankind has been using the natural energy of the sun, known as solar energy to meet his energy needs. Solar power involves using these emissions of heat and light by the sun to produce electrical or thermal energy. The sun, the most inexhaustible, renewable source of energy known, reaches the Earth's surface to provide 10,000 times more energy than we consume. Numerous devices for collecting solar energy and converting it into electricity have been developed throughout the years, and solar energy is now being used in a variety of ways.

While solar energy has been available to mankind since prehistoric times, we have not always been able to use it as effectively as other sources due to a lack of technology. Solar energy may be used for simple purposes, like drying clothes, cooking, heating swimming pools and buildings, or for more complex tasks like powering telecommunication towers, solar cars, and satellites through solar power technologies which can be divided into mainly two groups; solar thermal technologies and photovoltaics. The latter convert sunlight directly into electricity while solar thermal technologies use solar energy to convert light to heat to electrical energy. Solar thermal technologies being developed include concentrating solar power systems, flat plate solar collectors, and passive solar heating.

Concentrating solar power technologies generate electricity with heat through collectors. Concentrating solar collectors typically use reflective materials such as mirrors or lenses to concentrate the sun's energy to provide heat energy which is then converted into electricity. This can be done in three ways. The first method is the parabolic trough systems which use curved mirrors to concentrate the sun's heat onto a tube which contains a fluid, usually oil. The hot oil then boils water to produce steam which is used to generate electricity. Alternatively, mirrors in the shape of a dish can be also used to concentrate the sun's heat onto a receiver. The latter transfers the solar energy to a heat engine, converting the heat into mechanical energy which drives a generator to produce electricity. This method is called the dish/engine system. A third method of concentrating the sun's energy is through the use of power towers which provide a centralized power supply with the ability to store energy. These systems use a large array of mirrors, called heliostats. These heliostats concentrate the heat onto a receiver on top of the towers. The receiver contains a fluid that once heated can be used to produce steam which then turns a turbine to produce electricity.

A second type of thermal technology makes use of a flat-plate collector, a large and flat box usually found on a roof, to heat water using the sun's energy. Inside the boxes are dark colored metal plates that absorb heat, heating the liquid that flows through tubes inside the collectors. This system is typically used to provide households with hot water or to heat swimming pools. The other solar thermal technology is the simplest of the three. Passive solar heating, used to heat and cool homes, includes design features like large south-facing windows and building materials that absorb and slowly release the sun's heat. Passive solar heating can be used to significantly reduce heating bills and can also be used to cool a building through natural ventilation without any mechanical means. The simplest and most common of the passive solar technologies is referred to as direct solar gain.

The second group of solar power technologies are much more efficient than the solar thermal methods. Photovoltaics, "photo" meaning light and "voltaic" meaning electricity, is one of the fastest growing solar energy technologies. Photovoltaic devices, or solar cells, use semiconductor material to directly convert sunlight into electricity. Solar cells, primarily made of silicon, absorb sunlight which contains photons, the energy by-products of the nuclear reaction in the sun. The photons release electrons that are captured in the form of an electric current which is used as electricity. This is also known as the photoelectric effect.

Photovoltaics cells contain no moving parts, are nearly maintenance-free and have a working life of 20 - 30 years. They can be combined into modules called arrays, and the number of arrays used determines the amount of electricity produced. Photovoltaics are now being used worldwide to provide power for everything