Ammerland
The plans for a single family home for four persons with a living space of approximately 300 sqm in Ammerland, on the east side of lake Starnberger See (municipality of Münsing) included the use of an earth-coupled heat pump to supply heat for the home. The heating load calculation for the heating of the building, the hot water and the swimming pool showed a total demand of 19 kilowatts.
A brief investigation of the local geological-hydrogeological situation showed that in this case geothermal ground loops would be the most suitable source of geothermal energy.
The principle of the geothermal ground loops is fairly simple. In this project, double-U-tubes made of especially dense polyethylene (HDPE) were inserted into the boreholes in a standard installation and the space between the borehole wall and the loop bundle was grouted with a clay-cement-suspension, which provides a good heat exchange with the surrounding rock. The heat from the borehole wall (source temperature approximately 5 to maximally 14 °C) is transmitted to the refrigerant (ethylene glycol) that circulates in the loop pipes and is increased to approximately 35 °C with an electrical compression heat pump and transferred into the heating system. After the refrigerant, which is liquid in the well, has undergone evaporation, compression, liquefaction and expansion while passing through the compression heat pump, it flows back with a reduced temperature to the geothermal ground loops, is reheated and runs through the whole primary circuit again.
The geological conditions regarding ground water protection were favorable in the present case, since the existence of a second ground water story, which has to be protected in general, would mean that drilling operations are only allowed down to the first story. In the area of the building site no ground water was expected at the planned borehole depths, which was subsequently confirmed by the drillings.
Because of the local hydrogeological situation it was even possible to place the geothermal loops deeper than 100 m. Three loops were installed at depths to 125 m. Through this design the heat pump can be supplied with enough geothermal energy for the heat load mentioned above.
During this project, ERDWERK dimensioned the geothermal loops, conducted the geological-technical and water- and mining-law related planning, as well as the site supervision.
On March 10, 2009, the drilling and installation operations were completed and the heat pump system has been running smoothly ever since.
