Environmental Engineering Reference
If a heat pump is to be installed in a water conservation area, no groundwater is
allowed to be drawn. Approval for the use of a deep-ground probe to utilize the heat
from the ground is only given in special cases as the brine could contaminate the
groundwater if there is a leak. In Switzerland, for example, there are ground probes
in water conservation areas where carbon dioxide (R744) replaces the brine.
Using ambient air as a heat source is the simplest and most cost-effective approach.
This is not even a problem in water protection areas. No approvals are necessary to
install and operate air/water or air/air heat pumps in these areas. All these heat
pumps basically need are two openings in a house wall through which the ambient
air can be fed to the heat pump (Figure 11.5). Condensation forms if the outside
air is very cold and should drain off in a controlled way. Heat pumps can also
easily be installed outdoors. Air/water heat pumps function at ambient temperatures
as low as
20 °C. A supplementary electric heater helps to ensure that necessary
heating requirements are covered when temperatures are particularly extreme. A
small buffer storage unit can optimize the operating times of a heat pump. The
disadvantage of using ambient air is that the annual performance coeffi cients are
relatively poor. Compared to other heat sources, it necessitates a higher use of
Figure 11.5 A heat-pump system. Source: BBT Thermotechnik GmbH.
Brine/water heat pumps, in other words heat pumps that extract heat from the
ground, are the types that use the least amount of energy. Either ground collectors
or ground probes are used to extract the heat. A ground collector usually comprises
a set of plastic pipes that are laid in a snakelike pattern in the soil (see Figure 11.2).
The optimal depth for the pipes is 1.2 to 1.5 m, and the gap between pipes should
be about 80 cm.