Kalina power plant part load modeling: Comparison of different approaches to model part load behavior and validation on real operating data

Geothermal energy can play a vital role in the mitigation of climate change due to its CO2-neutral, renewable and non-fluctuating character. Because of the expensive preparation of the geothermal wells, the thermal water should be utilized with the highest efficiency. Therefore, the wells are often exploited in combined heat and power concepts. Consequently, the power plant operates in part load most of the time. However, this high portion of part load operation is often not fully considered in the design stage of the plant, due to a lack of suitable simulation models. Therefore, the purpose of this paper is to compare several approaches to simulate the part load behavior of the geothermal Kalina power plant in Unterhaching (Germany) and to validate them with operational data. Simulation approaches to calculate the isentropic efficiency of the turbine and the heat transfer coefficients of the heat exchangers are studied and compared on component level. An investigation of different combinations of these component models then follows. The results show that a detailed correlation to model the isentropic efficiency of the turbine is necessary to achieve sufficient accuracy. Furthermore, modeling plate heat exchangers with a power law approach for the heat transfer coefficient appears promising.