Năng lượng địa nhiệt bao gồm cả việc sử dụng trực tiếp của năng lượng địa nhiệt cho các quá trình không gian, sưởi ấm, làm nóng nước và công nghiệp, được phổ biến hơn, và thế hệ của điện địa nhiệt, hiếm. | Chapter 6 Geothermal energy U. Aswathanarayana INTRODUCTION Geothermal energy covers both the direct use of geothermal power for space heating water heating and industrial processes which are more common and the generation of geothermal electricity which are rarer. Geothermal electricity plants of more than 100 MW installed capacity are listed below country-wise MW installed capacity in 2000 USA - 2 228 Philippines - 1 909 Italy - 785 Mexico - 755 Indonesia - 590 Japan - 547 New Zealand - 437 Iceland - 170 El Salvador - 161 Costa Rica -143. The total capacity of geothermal power plants in the world is 10 GW in 2007 generating 56TWh yr of electricity. Geothermal energy has several advantages i It is non-polluting and has no carbon footprint ii It is of large magnitude - the heat stored in the earth is estimated to be about 5 billion EJ which is 100 000 times more than the world s annual energy use iii It is available all the year round and production costs are low. There are however some drawbacks i Air pollution may sometimes be caused by H2S CO2 NH3 Rn etc. gases vented into the air ii Low magnitude earthquakes may be triggered and land subsidences may take place due to changes in the reservoir pressure iii The overall efficiency of geothermal power production 15 is less than half of the coal-fired plants iv Drilling costs are high USD 150 000-250 000 per well . Compared with wind electricity and solar PV electricity which are intermittent geothermal electricity can be generated round the clock and could therefore serve as baseload electricity. This factor is reflected in the capacity factor which is defined as the actual plant output as a percentage of the maximum output of the plant operated at full capacity. Geothermal plants have a capacity factor of 90 compared to 25 to 30 in the case of wind electricity. 46 Green Energy Technology Economics and Policy Aswathanarayana 1985 p. 159-162 summarized the geological and economic aspects of geothermal energy. The
