Only 60 degrees Celcius is required to provide a building with heating and hot tap water. The underground contains tremendous CO2 neutral energy resources at 70 degrees Celcius or more, making it a renewable energy source worth considering.

Feasibility of geothermal energy

Geothermal energy may be an obvious solution in some countries, e.g. in countries with warm springs like Iceland where the geothermal energy is used for power production and for heating almost all buildings.

In other countries, the hot water resources are not so easily accessible as they may be several kilometres below the surface. In this case, geothermal energy can only be explored at large scale and at considerable cost. The following needs to be considered when exploring this zero carbon solution:

It is very expensive to drill several kilometres into the underground and to establish the necessary facilities. Therefore the plant should always be in a certain scale and with a long utilization period, e.g. as base load in a large district heating system.
There is always a risk that the well will be dry due to low permeability, therefore detailed seismic investigations are important before a decision to proceed is made.
The salinity is very high. Therefore special precautions should be taken in relation to the heat exchangers.
The geothermal water can be utilized more efficiently with low temperature heating, e.g. in buildings using floor heating, and with a heat pump.