Environmental Engineering Reference
In-Depth Information
energy, the release of harmful substances into the air as well as all other effects
related to the utilisation of fossil fuel energy are reduced in proportion to the geo-
thermal share. The additional energy required for circulation of the heat transfer
medium, and for running the heat pump operation, also has to be considered. But
in general the environmental impact is lower compared to the environmental ef-
fects connected with the direct use of fossil fuel energy.
Theoretically, during normal operation of the deep well environmental effects
are only likely due to the operation of the well. Moreover, as deep wells are gen-
erally well sealed against the surrounding rocks (i.e. closed system), the different
aquifer zones are hydraulically separated from one another; therefore environ-
mental risks are particularly low.
Water, at the most enriched with anticorrosive agents, is commonly applied as
a heat transfer medium within such deep wells. Environmental risks of polluting
the underground by a glycol enhanced heat carrier, as could be the case when
exploiting shallow geothermal resources, are therefore not given.
Additionally, there is neither the risk of any geomechanical impact, or modifi-
cations of stress
as for hydro-geothermal utilisation, as there are no substances
removed from the underground (i.e. closed system).
Further environmental effects at the plant site are related to the use of the heat
pump, which are also particularly low during normal operation, provided that the
corresponding guidelines are observed.
Hence, all in all the effects of useful energy provision by deep wells on humans
and nature are particularly low; generally they are lower than those of fossil fuel-
fired plants (also with regard to landscape and space consumption).
Malfunction.
In case of malfunctions, environmental effects may arise from dete-
rioration of pipelines and a subsequent hydraulic short-circuit of different aquifers
or the penetration of harmful substances.
Further environmental risks may result from fires or explosions of the heat
pump with regard to the toxicity of the heat transfer medium. However, if the
relevant standards and safety regulations are observed, these kinds of malfunc-
tions are very unlikely to occur.
Demolition.
Regarding environmental effects at the end of operation, the same as
for geothermal exploitation by means of wells near the surface applies. Potential
environmental risks are mainly related to proper completion of the well and
proper disposal of the heat pump.
10.3 Geothermal power generation
Geothermal power production has a relatively long history. Just 38 years after the
invention of the electric power generator by Werner von Siemens and 22 years
after the start of the first power station by Thomas A. Edison in New York in
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