Renewable Energy – Solutions for application in the communal energy infrastructure

GEOTHERMAL ENERGY |
17
Surface ground heat absorbers use the heat stored in the
ground. They require a large area and are, therefore, suitable
for larger, undeveloped plots.
For small plots of land or areas with deeper groundwater veins,
geothermal probes aare advantageous.
Possible applications and benefits for municipalities:
Heat pumps can be used where heating energy is required
and heat is reliably available at a low temperature
level. There, they reduce operating costs and CO 2
emissions attributable to room heating:
• Heating buildings of any size with heat
from the earth
• The combination of heating in winter and cooling in
summer (reversible operation)
• The use of waste heat at a low temperature level, e.g.
from machines or wastewater
Functional principle and design
A heat pump-based heating system consists of three
main parts: With the source system, heat is collected
from the ground or another heat source. The heat pump
raises the temperature to the desired level. The distribution
and storage system ensures that the heat arrives in
the right room at the right time.
In order to use the ground as a heat source, horizontal
(geothermal collector) or vertical (geothermal probes)
pipe systems can be deployed. Water mixed with antifreeze
– brine – flows through these systems. The brine
absorbs the heat from the ground, and the heat pump
renders it usable for people.
the building’s heating system. The vaporous refrigerant
transfers its heat to the heating water. It becomes liquid
again and the cycle can begin anew
The closer the temperature in the building’s floor and in
the heating circuit are to each other, the more heat can
be “pumped” into the building with the same amount of
electricity. It is thus important to combine heat pumps
with, for example, underfloor heating or air heating.
These can achieve a comfortable room temperature in
excess of 20 degrees Celsius with heating circuit temperatures
around 35 degrees Celsius – provided the
building is well-insulated. At temperate latitudes, for
example, it is possible to generate more than four kilowatt
hours of usable heating with one kilowatt hour of
electricity, based on an annual average.
So-called reversible heat pumps are also helpful. They
are used for cooling in summer by pumping heat from
the building into the ground by reversing the process
described above. This also has the advantage that the
ground becomes warmer and the heat pump works
more efficiently in winter. As a general principle, good
planning and the coordination of components are particularly
important for heat pumps.
The brine heats the so-called refrigerant in the heat
pump. This is a liquid that evaporates at very low
temperatures. When turned into steam by the heat of
the brine, the refrigerant flows to a compressor. There,
it is compressed with the use of electrical energy. The
gas heats up under pressure. It then meets the medium
of the distribution circuit in a heat exchanger, the
so-called condenser – usually the water circulating in