A new hydraulic concept for geothermal heating plants to achieve maximum geothermal contribution

Abstract

The analysis of selected projects within the South East Bavarian region has shown different optimization potentials. One of these optimization potentials is called displacement of geothermal energy. The phenomenon of the displacement of geothermal energy occurs when the heat supply to the district heating network exceeds the maximum geothermal heat load. In this situation, the common hydraulic design of geothermal heating plants prevents the optimal use of the geothermal potential. Caused by the control system, changes of the flow rate in the plant result in a reduced flow rate to the geothermal heat exchanger. This leads to significant reduction of the geothermal performance (up to 20 %). The increased contribution of the supplementary heating system in a one year cycle was determined with 12 – 20 %.
Current hydraulic concepts for geothermal heating plants have been derivated from the experience gained from the operation of biomass heating plants. Yet, the sensibility of geothermal heat exchangers to changes of the flow rate differs substantially from conventional heating appliances like wood-fired boilers. As a consequence it is necessary to develop new hydraulic solutions for geothermal heating plants with particular consideration of the requirements of the geothermal heat source.
In this paper we present a new hydraulic concept for geothermal heating plants by which the optimal operation of the district heating network with controlled supply temperatures, flexible and independent operation of the heat generators as well as efficient storing of geothermal energy is achieved. The comparison of the new hydraulic concept with common hydraulic concepts shows that it is possible to charge the heat storage faster and simultaneously reach higher temperatures in the storage. Thereby, significant improvements on the energy performance of geothermal heating plants can be expected.