Thermo-hydraulic simulation of district heating systems

The geothermal energy production is expanding. How can these systems best be integrated into existing structures? To answer this question, a simplified district heating network model was set up and applied as well as validated to an existing 2000 customer district heating network in Bavaria. The network is powered by gas-fired heating and cogeneration plants. A geothermal plant with a significantly lower supply temperature will replace a heating plant. This paper investigates the arising operating conditions due to the replacement. Therefore, profiles of temperature, mass flow and pressure are analyzed. Furthermore, potential damage caused by temperature changes, a reduction in the supply temperature of the cogeneration plant as well as resulting CO2 emissions, primary energy consumption and necessary pumping power are examined. The results show that a geothermal plant with a lower supply temperature can be integrated into an existing district heating network, taking all operational restrictions into account. The resulting electricity demand for pumping in the network is approx. 5% higher than with a gas-fired heating plant. In return, annual savings of e.g. 116,000 tCO(2) as well as about 437 GWh primary energy can be achieved.