Solar Power WNDW（太阳能WNDW）.pdfVIP

7 Solar Power This chapter provides an introduction to the components of a standalone photovoltaic system . The word standalone refers to the fact that the system works without any connection to an established power grid. In this chapter, we will present the basic concepts of the generation and storage of photovol- taic solar energy. We will also provide a method for designing a functional solar system with limited access to information and resources. This chapter only discusses the use of solar energy for the direct production of electricity (photovoltaic solar energy). Solar energy can also be used to heat fluids (thermal solar energy) which can then be used as a heat source or to turn a turbine to generate electricity. Thermal solar energy systems are beyond the scope of this chapter. Solar energy A photovoltaic system is based on the ability of certain materials to convert the radiant energy of the sun into electrical energy. The total amount of solar energy that lights a given area is known as irradiance (G) and it is measured 2 in watts per square meter (W/m ). The instantaneous values are normally averaged over a period of time, so it is common to talk about total irradiance per hour, day or month. Of course, the precise amount of radiation that arrives at the surface of the Earth cannot be predicted with high precision, due to natural weather varia- tions. Therefore it is necessary to work with statistical data based on the so- lar history of a particular place. This data is gathered by a weather station over a long period and is available from a number of sources, as tables or 211 212 Chapter 7: Solar Power databases.