Use Case 5: Holzkirchen, Germany

  • Use Case Area of Application: The use case will apply the RESTORE concept to a DHC network (local utility of Holzkirchen) with Geothermal Technology.
  • Expected goals to be achieved: Maximization of the geothermal heat exploitation and optimum WEH utilization for highly efficient seasonal storage of heat.

Use Case Description

Geothermie Holzkirchen GmbH is a wholly owned subsidiary of the local utility of Holzkirchen, a town located in the south of Munich, Germany. The existing conditions for developing geothermal energy are particularly favourable in the southern German Molasse basin, as there is particularly hot water at the appropriate depth (500 meters). Heat can be used as direct supply to district heating and, from a temperature of around 120 degrees Celsius, electricity production is possible. It is estimated that in the long term up to 80 percent of Holzkirchen's district heating network demand can be covered with geothermal energy equivalent to around 10,000 tons of climate-damaging carbon dioxide avoided every year.

The Holzkirchen community works have provided the market with water and energy for more than a century. Since 1894 the company has developed into a modern, medium-sized service provider company. It has successfully faced numerous challenges, the growing population, technical progress and economic necessities. Since 1985, the business areas have expanded by supplying the community with natural gas and in 1992 with district heating.

An ORC from Turboden is already installed on site to exploit geothermal hot water during the summer from a temperature of 140°C, producing a power output of 2.8 MWel. Differently from the conventional geothermal steam turbines, the ORC process uses low-to-high enthalpy geothermal fluid to preheat and vaporize a suitable organic working fluid within a closed loop:

  • The organic fluid vapor rotates the turbine, which is coupled to the electric generator.
  • The exhaust vapor flows through the regenerator and condenser, which is cooled by air or water.
  • The organic working fluid is then pumped again, thus completing the closed-cycle operation.

In such way the ORC turbine is not in contact with the geothermal fluid, which remains enclosed in the heat exchangers, allowing a full reinjection of all the brine and steam condensate with zero emissions to the ambient. In order to increase the geothermal heat exploitation Turboden will study a large HP in order to achieve higher flexibility in terms of heat and power production as well as increased geothermal utilisation. The energy contained in a shallow aquifer at low temperature can be used to feed a LHP and supply heat to a district energy network at higher temperature

uc5 holzkirchen geothermal plant
Geothermie Holzkirchen GmbH plant overview