Page 189 - Low Temperature Energy Systems with Applications of Renewable Energy

Heating with geothermal systems 5

5.1 Geothermal direct heat usage: International
experience

Direct heat applications of geothermal energy can be found anywhere in the world, unlike
electric power generation which is limited to moderate-to-high temperature resources.

There is a wide spectrum of uses from geofluid temperatures as low as 25e30 C(aqua-

culture) and as high as 180e190 C (absorption refrigeration). The range of applications
as a function of temperature is shown in Fig. 5.1 which is taken from Ref. [1] and based on
the Lindal diagram. Heat pumps are included since earth-coupled heat pump systems can
be used for both heating and cooling anywhere in the world.
The latest information on worldwide geothermal direct usage was presented at the
2015 quinquennial congress of the geothermal industry [2]. The following discussion
is based on that work. Geothermal direct heat usage has been growing steadily over
the last two decades. Starting from 1995, the installed thermal capacity has increased
by a factor of 7.8 as of 2015, while the heat utilization has increased by a factor of
5.3; see Fig. 5.2.
By far the most popular application is geothermal (or earth-coupled) heat pumps.
The top five countries in terms of heat pump installed capacity are the United States,

Fig. 5.1 Geothermal direct heat applications as a function of temperature, after [1].

Low-Temperature Energy Systems with Applications of Renewable Energy
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