Conversion Efficiency of Active Energy and Solar Energy Essay -- Solar

Conversion Efficiency of Active Energy and Solar Energy Solar technology already boasts a century of R&D, requires no toxic fuels and relatively little maintenance, is inexhaustible, and, with adequate financial support, is capable of becoming directly competitive with conventional technologies in many locations. These attributes make solar energy one of the most promising sources for many current and future energy needs. As Frank Shuman declared more than 80 years ago, it is "the most rational source of power." The average amount of solar energy arriving on top of the atmosphere is 1,330 watts per square meter. The amount reaching the earth’s surface is 10,000 times more than all commercial energy used annually. Until recently, this energy source has been too diffused and low intensity to capitalize for electricity. Solar energy is a renewable resource and is converted to electrical energy in two ways - using photovoltaic materials which generate an electrical potential when exposed to light or using a thermal process that uses the energy from the sun to heat a working fluid in an electricity generating cycle. Another way of looking at it is as passive and active solar energy. Now you might be wondering what is meant by active and passive, isn’t all transformation of energy active? Passive solar energy relates to systems that are relating to solar radiation and angles to define solar positions which work with heating and cooling systems. To generate the higher temperatures necessary to make steam to generate electricity, the sunlight must be concentrated. Solar thermal technology often uses reflectors, in the form of parabolic concentrators or flat mirrors, to focus the sun's rays onto a water-filled pipe, known as 'abso... ...veloped thin film technology is hydrogenated amorphous silicon. This is the material normally used in consumer applications, although it is used, but less frequently, in power modules. The efficiency of commercial amorphous silicon modules has improved from around 3.5 % in the early 1980's to over 7% currently. The most efficient modules are made with multiple layers of photovoltaic material, for instance three layer amorphous silicon modules with germanium added to two of the layers (a-Si/a-SiGe/a-SiGe) which have a record cell efficiency of 13.5 %. Other types of thin films can be made using polycrystalline silicon, cadmium telluride (CdTe), and copper indium gallium diselenide (CIGS). Today's solar panels are made with silicon. The silicon usually has impurities, which limits its efficiency. Purifying a chemical is too expensive. For that reason, smaller is better.