In our daily life we all need to consume energy. That consumption, however, has globally highlighted such conventional energy-related issues as global warming caused by the greenhouse effect due to exhaust gases including carbon dioxide, and the run out of fossil fuels. The clean energy approach has attracted particular attention as one viable method of solving these issues. Therefore, many countries around the world are discussing the adoption of the clean energy systems and promoting those systems by the feed-in-tariff, the RPS approach, or both. The clean energy systems have been employed in many countries. The photovoltaic system is considered to play a leading role among the clean energies.

The photovoltaic system is a device to convert the energy of sunlight into electricity. The energy from sunlight is inexhaustible and there is no fear that the energy could run out . In addition, photovoltaic systems are effective to reduce the greenhouse-gas emissions, since it produces no toxic materials such as exhaust gases from plant operation. While various types of photovoltaic systems are now on sales, crystalline silicon solar systems occupy the lion's share of such systems currently available.

At present, the crystalline silicon photovoltaic system cell leads the market. The system's cell is composed of two thin plates, n-type and p-type semiconductor. When the sunlight hits the surface of the cell, voltage is generated between these different types of semiconductors then an electric current is produced.

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