Direct heat utilization of geothermal resources

Geothermal energy research and development

Direct uses of geothermal energy 1995

Early humans probably used geothermal water that occurred in natural pools and hot springs for cooking, bathing and to keep warm. We have archeological evidence that the Indians of the Americas occupied sites around these geothermal resources for over 10,000 years to recuperated from battle and take refuge. Many of their oral legends describe these places and other volcanic phenomena. Recorded history shows uses by Romans, Japanese, Turks, Icelanders, Central Europeans and the Maori of New Zealand for bathing, cooking and space heating. Baths in the Roman Empire, the middle kingdom of the Chinese, and the Turkish baths of the Ottomans were some of the early uses of balneology; where, body health, hygiene and discussions were the social custom of the day. This custom has been extended to geothermal spas in Japan, Germany, Iceland, countries of the former Austro-Hungarian empire, the Americas and New Zealand.

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World status of geothermal energy use overview 1995-1999

Direct or nonelectric utilization of geothermal energy refers to the immediate use of the heat energy rather than to its conversion to some other form such as electrical energy. The primary forms of direct heat use are for swimming, bathing, and balneology (therapeutic use); space heating and cooling, including district heating; agriculture (mainly greenhouse heating and some animal husbandry), aquaculture (mainly fish pond and raceway heating), and industrial processes; and heat pumps (for both heating and cooling). In general, the geothermal fluid temperatures required for direct heat use are lower than those for economic electric power generation.

Geothermal Direct Use

District heating is the largest sector of geothermal energy direct use in the world. It holds great promise for further development, especially when operated in conjunction with district cooling. At the end of 1984, the installed thermal power of all direct use projects in the world was about 7072 MW and the associated flow rate, 57,803 kg/s. The thermal energy used was found to be 23,957 GWh, in most instances above a reference temperature of 35 to 40C. The amount of oil saved by geothermal energy direct uses worldwide was estimated to be about 2.8 million tons per year.

J.S. Gudmundsson

Papers

Direct uses of geothermal energy in 1984