Geothermal Energy (English) - Referat
Geothermal energy is the heat from the upper crust of our earth. It can be used directly for heating and cooling with a heat pump.
-In combination with heat pumps geothermal energy is used for heating and cooling houses as well as for heating of water.
-Geothermal energy can also be used for producing electricity or as a cogeneration of heat and power.
-It can be used for heating in industrial, private or agricultural purposes and also for desalination of seawater.
-It’s sustainable and non-polluting.
Geothermal energy is an important kind of renewable energy. Coming from the inner earth, it can be used efficiently and economically for heating buildings with a geothermal heating system. The costs are lower than those of gas or oil heating. It’s quite expensive (15000-20000€ installation costs), but the environmental sustainability can be seen as a good reason to invest in a geothermal heating system. There is no exhaust gas pollution. There is n difference in heating power between geothermal and other heating systems.
The sun’s energy is already stored in a depth of about 1,20-1,50 meters in the earth, but and even at low temperatures geothermal heating can produce enough heat. Especially in the winter there’s a large difference between the soil and the air. It’s because in the depth of only 40m there is a constant temperature of around 10° almost everywhere, and only one kilometer deeper it’s 35.40°. Even if the soil cools down, it is still warm enough for this heating system. At -20° air temperature you can still heat a house to up to 25° with this system.
In Germany the first geothermal heating system was built up in 1969. At the end of 2007 there were already 200000 of them. Half of them only were installed in the last two years (2006/2007).
The geothermal heating system works with pipes, which are laid below the earth beside the building, so there has to be enough untilled (unbebaut) land there. Through a tube in the ground a 6° cold cooling liquid is conducted (leiten) into the soil. It is heated up by the constantly warm earth and is brought back into the heat pump in the cellar of the house. The evaporator (Verdampfer) in the pump extracts the heat from the sole and the liquid evaporates, so the tube is brought back into the ground again. The liquid’s vapor is compressed and the temperature rises. In the condenser (Verflüssiger) the vapor heats the water, cools down and condenses. With an underfloor heating the heat is spread in the building. The heating water cools down and runs back into the heat pump. An expansion valve (Entspannungsventil) reduces the pressure of the cooling liquid, so it cools down and can take up heat from the tube again and the cycle starts from the beginning again.
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