Direct heat utilization of geothermal resources

Abstract

Direct utilization of geothermal energy consists of various forms for heating and cooling instead of converting the energy for electric power generation. The major areas of direct utilization are (1) swimming, bathing and balneology, (2) space heating and cooling including district heating, (3) agriculture applications, (4) aquaculture applications, (5) industrial processes, and (6) heat pumps. Major direct utilization projects exploiting geothermal energy exist in about 38 countries, and the estimated installed thermal power is almost 9,000 MWt utilizing 37,000 kg/s of fluid. The world-wide thermal energy used is estimated to be at least 108,100 TJ/yr (30,000 GWh/yr) - saving 3.65 million TOE/yr. The majority of this energy use is for space heating (33%), and swimming and bathing (19%). In the USA the installed thermal power is 1874 MWt, and the annual energy use is 13,890 TJ (3,860 GWh). The majority of the use (59 %) is for heat pumps (both ground coupled and water source), with space heating, bathing and swimming, and fish and animal farming each supplying about 10%.