Integrated assessment of geothermal energy reservoir and organic Rankine cycle systems

This paper presents an integrated assessment of a geothermal power plant, including the degradation of the geothermal reservoir properties over time, and the performance of organic Rankine cycle system. Furthermore, a method to determine the techno-economically optimum design power output for a given geothermal reservoir, resulting in the minimum levelized cost of energy is proposed. The open-source code “Geothermal Reinjection Lifetime Prediction Model” was used to forecast the performance of a geothermal reservoir over time, considering both the reservoir characteristics and operational parameters. Two scenarios were analyzed for the techno-economic assessment: (i) no degradation of geothermal reservoir properties over time, and (ii) degradation of geothermal reservoir properties. Historical data for a geothermal heat source from the literature was also analyzed for both scenarios. The results indicate that the levelized cost of electricity for the scenario with geothermal reservoir degradation is about 18 % higher than that of the no degradation scenario for one heat source profile, and about 46 % higher for the other heat source profile. For the presented case studies, the techno-economically optimum design power output for the organic Rankine cycle system is achieved in design condition at year-11 for one heat source profile and year-5 for another. A reduction in geothermal well system cost causes the design year corresponding to the techno-economically optimal power output to shift slightly later in the plant’s operational timeline.