Page 238 - Low Temperature Energy Systems with Applications of Renewable Energy

Geothermal energy in combined 6
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heat and power systems

6.1 Introduction to geothermal CHP systems

Geothermal combined heat and power (CHP) systems are a means to capture the avail-
able energy in a geothermal resource in a highly efficient manner. The Second Law of
thermodynamics and considerations of exergy provide a road map for efficient energy
usage. In processes involving heat transfer, high efficiency is attained by closely
matching the geothermal fluid with the working fluid that provides the heating. In
some cases, the geofluid may be used directly as the heating fluid, but often a second-
ary working fluid is the ultimate heat carrier in the heated space. In this section we
consider the basic configurations and basic thermodynamics of CHP systems.
There are ample opportunities for combined geothermal power and heating
applications, as can be seen from Fig. 6.1 which shows only a few of the many possibil-

ities. Typically power generation requires geofluids at temperatures greater than 100 C.
Discharge geofluid temperatures can be matched to a variety of direct heat applications, as
is evident from the figure. Under certain circumstances, the geofluid may be used alone,
straight from the source, to supply heat to a consumer needing thermal energy.

Fig. 6.1 Selected heating applications that may be combined with geothermal power plants.

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Written by Ronald DiPippo.
Low-Temperature Energy Systems with Applications of Renewable Energy
https://doi.org/10.1016/B978-0-12-816249-1.00006-6
Copyright © 2020 Elsevier Inc. All rights reserved.