Space Conditioning

Space conditioning includes both heating and cool­ing. Space heating with geothermal energy has widespread application, especially on an individual basis. Buildings heated from individual wells are popular in Klamath Falls, Oregon; Reno, Nevada; and Taupo and Rotorua, New Zealand. Absorption space cooling with geothermal energy has not been popular because of the high temperature require­ments and low efficiency. Geothermal heat pumps (groundwater and ground coupled) have become popular in the United States, Sweden, and Switzer­land for both heating and cooling.

An example of the use of space heating and cooling with low – to moderate-temperature geothermal en­ergy is the Oregon Institute of Technology in Klamath Falls, Oregon (Fig. 4). Here, 11 buildings (approxi­mately 62,000 m2 of floor space) are heated with water from three wells at 89°C. Up to 62 liters/s of fluid can be provided to the campus, with the average heat utilization rate more than 0.53 MWt and the peak at 5.6 MWt. In addition, a 541-kW (154 tons) chiller requiring up to 38 liters/s of geothermal fluid produces 23 liters/s of chilled fluid at 7°C to meet the campus cooling base load (recently decommissioned).

1.2 District Heating

District heating originates from a central location and supplies hot water or steam through a network of pipes to individual dwellings or blocks of buildings. The heat is used for space heating and cooling,
domestic water heating, and industrial process heat. A geothermal well field is the primary source of heat; however, depending on the temperature, the district may be a hybrid system, which would include fossil fuel and/or heat pump peaking.

Geothermal district heating systems are in opera­tion in at least 12 countries, including Iceland, France, Poland, Hungary, Turkey, Japan, and the United States. The Warm Springs Avenue project in Boise, Idaho, dating back to 1892 and originally heating more than 400 homes, is the earliest formal project in the United States. The Reykjavik, Iceland, district heating system (Fig. 5) is probably the most famous. This system supplies heat for approximately 160,000 people. The installed capacity of 830 MWt is designed to meet the heating load to approximately — 10°C; during colder periods, the increased load is met by large storage tanks and an oil-fired booster station.

In France, production wells in sedimentary basins provide direct heat to more than 500,000 people from 61 projects (200,000 housing units). These wells provide 40-100° C water from depths of 1500­2000 m. In the Paris basin, a doublet system (one production and one injection well) provides 70°C water, with the peak load met by heat pumps and conventional fossil fuel burners (Fig. 6).

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