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18ГЕОТЕРМАЛЬНАЯ ЭНЕРГЕТИКА
GEOTHERMAL ENERGY
Статья поступила в редакцию 17.04.11. Ред. рег. № 987 The article has entered in publishing office 17.04.11. Ed. reg. No. 987
УДК 504.05
ГЕОТЕРМАЛЬНЫЕ ЭЛЕКТРОСТАНЦИИ И ЭКОЛОГИЧЕСКИЕ ПОСЛЕДСТВИЯ ИХ ЭКСПЛУАТАЦИИ
С.М. Говорушко
Тихоокеанский институт географии ДВО РАН 690041 Владивосток, ул. Радио, д. 7 Тел./факс: 8(4232)311653, e-mail: sgovor@tig.dvo.ru
Заключение совета рецензентов: 27.04.11 Заключение совета экспертов: 28.04.11 Принято к публикации: 30.04.11
Рассмотрены типы источников геотермальной энергии и основные сферы ее применения. Сделан обзор развития геотермальной энергетики в мире и России в частности. Показаны принципы работы основных типов геотермальных электростанций. Проведен анализ их воздействия на различные компоненты и параметры окружающей среды (атмосфера, геологическая среда, поверхностные и подземные воды, животный мир, отчуждение земель, шумовое загрязнение).
Ключевые слова: геотермальные электростанции, магма, экологические последствия, геотермальный сухой пар, геотермальные ресурсы, парогидротермы.
GEOTHERMAL POWER PLANTS AND ENVIRONMENTAL CONSEQUENCES OF THEIR USE
S.M. Govorushko
Pacific Geographical Institute FEB RAS 7 Radio str., Vladivostok, 690041, Russia Tel./fax: 8(4232)311653, e-mail: sgovor@tig.dvo.ru
Referred: 27.04.11 Expertise: 28.04.11 Accepted: 30.04.11
The types of geothermal energy sources and the main spheres of its application are described. A review of the development of geothermal energetics in the world and Russia in particular is given. The principles of operation of the main types of geothermal power plants are shown. The analysis of their impact on various environmental components and parameters (atmospheric air, geologic environment, surface water and groundwater, wildlife, condemnation of land, noise pollution) is realized.
Keywords: geothermal power plants, magma, environmental consequences, geothermal resources, steam-hydrotherms, geothermal dry steam.
Global use of geothermal energy
A geothermal power plant is a power station that converts the heat in the Earth into electric power. The virtue of geothermal power plants is their independence from atmospheric conditions associated with things such as the weather and the seasons.
The first large-scale geothermal electricity-generating plant opened at Larderello, Italy, in 1904, and it continues to operate successfully [1]. The second
geothermal power station was built in the 1950s at Wairakei, New Zealand, followed by The Geysers in California (U.S.) in the 1960s [2].
At present, geothermal resources have been identified in some 90 countries (Fig. 1), and there are quantified records of geothermal utilization in 72 countries. Electricity is produced from geothermal energy in 24 countries. A total of 56,786 gigawatt-hours of electricity was obtained from geothermal energy in 2005, accounting for 0.3% of worldwide electricity consumption [3].
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The five countries that led in geothermal electricity production (gigawatt-hours per year) late in 2005 were (1) the United States, 17,917; (2) the Philippines, 9,253; (3) Mexico, 6,282; (4) Indonesia, 6,085; and (5) Italy, 5,340. The global installed capacity was 10 gigawatts in 2007 [4]. Data on electrical power (in megawatts) in different countries are shown in Table.
Данные по номинальной электрической мощности в различных странах мира Data on electrical power (in megawatts) in different countries
Country Installed geothermal electric capacity [5, 6], MW Percentage of national production, %
2007 2010
USA 2687 3086 0.3%
Philippines 1969.7 1904 27%
Indonesia 992 1197 3.7%
Mexico 953 958 3%
Italy 810.5 843
New Zealand 471.6 628 10%
Iceland 421.2 575 30%
Japan 535.2 536 0.1%
El Salvador 204.2 204 14%
Kenya 128.8 167 11.2%
Costa Rica 162.5 166 14%
Nicaragua 87.4 88 10%
Russia 79 82
Turkey 38 82
Papua-New Guinea 56 56
Guatemala 53 52
Portugal 23 29
China 27.8 24
France 14.7 16
Ethiopia 7.3 7.3
Germany 8.4 6.6
Austria 1.1 1.4
Australia 0.2 1.1
Thailand 0.3 0.3
TOTAL 9,731.9 10,709.7
The sequence of operations of a geothermal power plant is as follows. Water is pumped through wells deep in the Earth where the rocks are very hot. Infiltrating into the rock joints and cavities, water gets warm with steam formation and rises back through the other, parallel wells. Thereafter, the hot water is delivered immediately to the power plant, where its
International Scientific Journal for Alternative Energy and Ecology № 5 (97) 2011
© Scientific Technical Centre «TATA», 2011
С.М. Говорушко. Геотермальные электростанции и экологические последствия их эксплуатации
energy is transformed into electric power through the use of one or more turbines and generators.
The other variant uses water heated to high temperatures as a result of natural processes. This water is pumped out of the Earth's interior or, due to high pressure, it rises by itself through drilled holes to the power plant.
Types of geothermal power plants
At present, three types of geothermal power plants are used: (1) power plants operated on superheated steam (geothermal steam is directly used for rotation of turbines [dry steam]); (2) power plants operated on steam-hydrotherms (hot, deep water under high pressure is pumped into reservoirs at reduced pressure; the steam that is formed rotates a turbine [flash steam]); and (3) plants with a binary cycle (moderately hot water comes into contact with a second additional liquid having a lower boiling point; the heat of the geothermal water evaporates the second liquid, and the resulting vapours drive the turbines) [1].
Environmental consequences of geothermal power engeneering
Geothermal power stations have major adverse effects on the following environmental components [7, 8]: (1) atmosphere; (2) geological environment; (3) surface and underground waters; (4) animal world; (5) condemnation of land; and (6) noise pollution.
The major contaminants of the atmospheric air are hydrogen sulphide, carbon dioxide, methane, ammonia, hydrogen, nitrogen, mercury vapour, radium, and radon [9]. These pollutants contribute to global warming and acid rain, and produce noxious smells if released. The emissions of hydrogen sulphide are the most hazardous.
Existing geothermal electric power plants emit an average of 122 kilograms of carbon dioxide per megawatt-hour of electricity [3]. It is believed that the atmospheric contamination per gigawatt-hour of electricity is small as compared with that for coal-fired power plants (Fig. 2). The power plants using binary cycles do not contaminate the atmosphere [10].
The effects on the geological environment are expressed as an increase in seismicity and subsidence of the Earth surface. A project in Basel, Switzerland, was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter scale occurred over the first 6 days of water injection [11]. An increase in seismicity was also recorded after three geothermal power plants were put into operation in Kamchatka (Russia) [12].
The construction of geothermal power plants can adversely affect land stability. Subsidence has occurred in the Wairakei field in New Zealand [13] and in Staufen, southern Germany [14].
Surface waters are polluted when waste waters are discharged. The most toxic pollutants are arsenic, boron, and hydrogen sulphide, elements and compounds that frequently are present in poisonous concentrations in geothermal waters. Other elements and chemicals that may be present in harmful concentrations include aluminium, fluorine, ammonia, salts at high concentrations, and various heavy metals.
High concentrations of heavy metals are associated with high-temperature brines such as those at the Salton Sea in California and on the island of Nisyros, Greece. High bromine and arsenic concentrations are found in many geothermal systems associated with andesitic volcanism. Examples include Mount Apo in the Philippines and Achuapan in El Salvador. Boron-rich geothermal waters form upon reaction with marine sediments, such as at Ngwaha in New Zealand [10].
Consumption of water by geothermal power plants is insignificant. They use 20 litres of fresh water per megawatt-hour versus over 1,000 litres per megawatt-hour for nuclear, coal, or black oil plants [13]. Cases are known of contamination of underground water as a result of leakages in reservoirs and pipelines [15].
The effects on the animal world are demonstrated in inhabitants of surface waters. For example, the geothermal heat carrier used in the New Zealand geothermal power plant Wairakei is discharged to the river of the same name. Concentrations of a number of heavy metals (e.g., mercury) in trout muscular tissue exceed many times the norm [16].
Рис. 2. Геотермальная электростанция в Исландии. Фото: Gretar Ivarsson, 6 октября 2006 г. Fig. 2. The Nesjavellir Geothermal Power Plant in Iceland. Photo credit: Gretar Ivarsson, 6 October 2006
Рис. 3. Геотермальная электростанция на Филиппинах.
Фото: Mike Gonzalez, 17 июня 2006 г. Fig. 3. The Palinpinon Geothermal power plant in Valencia, Negros Oriental, Philippines, is shown here. Photo credit: Mike Gonzalez, 17 June 2006
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The condemnation of land for utilizing geothermal power is minor (Fig. 3). A geothermal facility uses 404 square metres of land per gigawatt-hour, while a coal facility uses 3,632 square metres per gigawatt-hour [1]. The noise impact is also minor. At the well drilling stage, it does not exceed 54 decibels, while in the course of operation, noise levels are only 15-28 decibels [1].
References
1. Kagel A., Bates D., Gawell K. A. Guide to Geothermal Energy and the Environment. 2007. 75 pp. // Geothermal Energy Association. www.geo-energy.org.
2. http://en.wikipedia.org/wiki/Geothermal_electricity.
3. http://en.wikipedia.org/wiki/Geothermal_power.
4. Fridleifsson I.B., Bertani R., Huenges E., Lund J.W., Ragnarsson A., Rybach L. The possible role and contribution of geothermal energy to the mitigation of climate change // Proceedings of IPCC Scoping Meeting on Renewable Energy Sources, Luebeck, Germany, 2008. P. 59-80.
5. Bertani R. World Geothermal Generation in 2007 // Geo-Heat Centre Quarterly Bulletin. 2007. Vol. 28, Is. 3. P. 8-19.
6. http://en.wikipedia.org/wiki/Geothermal_energy.
7. Kubo B.M. Environmental management at Olkaria geothermal project, Kenya // Proceedings of International Geothermal Conference, Reykjavik, Sept. 2003. P. 72-79.
8. Arnorsson S. Environmental impact of geothermal energy utilization // Energy, Waste, and the Environment: a Geochemical Perspective. Special Publications of the Geological Society of London. 2004. Vol. 236. P. 297-326.
9. Gupta G.K., Aggarwal R.K. The environmental impact on development of geothermal resources and its management // Geol. Surv. India. 2001. Vol. 65, Is. 1. P. 37-40.
10. Arnorsson S. Environmental impact of geothermal energy utilization. Reykjavik: University of Iceland, 2005.
11. Deichmann N., Mai M., Bethmann F. et al. Seismicity Induced by Water Injection for Geothermal Reservoir Stimulation 5 km Below the City of Basel, Switzerland // Abstracts of Fall Meeting of American Geophysical Union, 2007. P. 73-74.
12. Chebrov V.N., Kugayenko Yu.A. Seismicity in the operated hydrothermal deposits of Kamchatka // Geothermal and mineral resources of the modern volcanism areas. Petropavlovsk-Kamchatsky, 2005. P. 419-427.
13. Lund J.W. Characteristics, development and utilization of geothermal resources // Geo-Heat Centre Quarterly Bulletin. 2007. Vol. 28, Is. 2. P. 1-9.
14. Waffel M. Buildings Crack Up as Black Forest Town Subsides. 2008. http://www.spiegel.de/international/zeitgeist/0,1518,541 296,00.html.
15. Birkle P., Merkel B. Environmental impact by spill of geothermal fluids at the geothermal field of Los Azufres, Michoacan, Mexico // Water, Air, and Soil Pollution. 2000. Vol. 124, Is. 3-4. P. 371-400.
16. Tomarov G.V. Environmental problems of construction and operation of geothermal power plants // Izvestiya Akademii promyshlennoi ekologii. 1997. No. 4. P. 20-24.
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© Scientific Technical Centre «TATA», 2011
