Geothermals, an abbreviation of geothermal resources, often refer to thermal resources in the interior of the earth which can be utilized economically by mankind. Geothermal resources available for direct use only occur in areas of strong modern volcanic activities and tectonic movements, where heat is enriched in the earth's interior. Geothermal resources, in a broad sense, include: all products of the geothermal process, that is, natural steam, hot water and geothermal brine; secondary steam, hot water, geotheram brine arising from the water, gas and other fluids artificially introduced into geothermal reservoirs; and byproducts brought out by the above mentioned products(mineral materials with comparatively high value). At present time five types of geothermal resources have been identified: steam-dominant type; liquid water-dominant type; geopressured type; hot dry rock type and magmatic type. The first two types , called "hydrothermal type", are the major geothermal resources that have been developed and used in China and abroad , while the latter two types, generally called"hot dry rock type", are not commonly developed now.
Geothermal resources are an integrant of mineral energy resources and have extensive usage both as energy and water resources. Their usage is determined by the temperature of the geothermal water. High temperature geothermal resources(t>150 ¡æ )are mainly used for electricity generation; moderate temperature geothermal resources (90<t<150 ¡æ)are used for industry, heat drying, heating and power generation and low temperature geothermal resources (25<t<90¡æ)for heating, medical treatment, bathing, greenhouse, aquiculture, irrigation and soil heating.
China is one of the earliest countries with a history of several thousand years in the world in using geothermal resources . According to the written records, the Huaqing Pool in Xi'an, Shaanxi Province began to be exploited as early as in the Western Zhou Period(c. 11th century-770 B.C.). In the following dynasties, more hot springs were built into pools for bathing and medical treatment.
Planned exploration and exploitation of geothermal resources in China started after the founding of the People's Republic of China in 1949 and has undergone 3 phases. Detail... |
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