Which element converts solar energy into electricity

Big Bang 7, textbook

48 RG 7.1 G 7.2 Radiation budget of the earth Solar constant, initial value 1367W / m 2 Earth's atmosphere reduces the value through scattering and absorption (–27%) 1000W / m 2 clouds reduce the value (-50%) 500W / m 2 Sun only shines on average 12 hours (-50%) 250W / m 2 sun does not shine vertically (-50%) 125W / m 2 efficiency of a solar cell (-80%) 25W / m 2 Tab. 32.3: Estimation of how the radiation power of the sun changes of the earth and what remains on average in our latitudes on the ground. Fig. 32.20: The map shows the local solar radiation on the earth's surface (mean 1991–93). To cover the current global energy demand with solar power, the darkly marked circular areas, which must have a diameter of 240 km (see Fig. 32.27, p. 50), would be sufficient. How much radiation power ultimately arrives on the ground depends on various factors (Tab. 32.3). In Austria it is on average around 1/10 of the solar constant. But that's still a lot, namely about 125W / m 2. The closer you get to the equator, the steeper the sun's rays and the greater the net yield (Fig. 32.20). Solar systems This is the general term for systems that convert solar energy into other forms of energy. thermal solar systems They convert solar energy into heat. They are also often briefly called solar systems, which can lead to confusion. Solar panels These are the core pieces of solar thermal systems. They convert solar radiation into heat. thermal solar power plants They first convert solar energy into heat and then into electricity. Photovoltaic systems They convert solar energy directly into electricity. Solar cells These are semiconductor elements that convert sunlight into electricity. They are part of photovoltaic systems. Tab. 32.4: Common expressions in connection with solar energy Facilities that convert solar energy into another form of energy are generally called solar systems (Tab. 32.4). Depending on whether heat or electricity is generated, special terms are used. Thermal solar systems, for example, convert solar energy into heat. Often, however, the addition “thermal” is omitted and they are simply called solar systems, which can lead to confusion. Info: Solar collectors Thermal solar systems are used to heat water, ie for the bathroom and central heating. What the sun cannot do, for example because of bad weather, is done by a conventional boiler (see Fig. 32.21). This form of environmentally friendly energy supply is now very widespread in Austria, thank goodness. In 2018 solar collectors The core of a thermal solar system is the solar collector (Fig. 32.21). This essentially consists of a black absorber with an integrated pipe coil. When the sun is shining, the absorber and thus the water flowing through it become hot (Fig. 32.21 a). It's exactly the same effect as if you leave a dark garden hose in the sun (F17), only more professional. When the absorber is heated, light is converted into infrared radiation. A glass plate throws the majority of it back into the collector (b) and thus increases the efficiency. This is typically 60 to 75%. That is very efficient! A particularly simple method is used when heating swimming pools. Black plastic hoses are used that are joined together to form mats, i.e. just one absorber, so to speak (Fig. 32.22). This allows you to increase the water temperature by around 5 ° C - and it's completely free! i Fig. 32.21: Schematic structure of a thermal solar system (a) and a solar collector in cross section (b) Fig. 32.22: Principle of a swimming pool absorber Only e for testing purposes - property of the publisher öbv

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