A Feasibility Study on Hybrid Solar-Geothermal Power Generation

Abstract

A major problem faced by many stand-alone geothermal power plants, particularly in arid regions such as Australia, is the adverse effects of the diurnal temperature change on the operation of air-cooled condensers which typically leads to the fluctuation in the power output. These adverse effects could extend from days to seasons, with the worst scenario taking place in summer time during afternoons. The motivation behind the present study is to introduce a direct/indirect solar heating system to moderate the impact of diurnal temperature change and where possible boost the power output. The ultimate goal is to explore the potential benefits from the synergies between the solar and geothermal energy sources. For this purpose two hybrid solar-geothermal power plant concepts based on the Organic Rankine Cycle (ORC) were analysed. Detailed simulations of hourly ambient temperature and hourly solar irradiance were carried out. Two different alignments for solar parabolic trough systems were examined and the influence of weather conditions on the relevant hybrid plants were analysed. In addition, the hour-by-hour performances of the hybrid plants under various operating conditions were evaluated. The results showed that by combining the solar heating system, a typical ORC type geothermal plant can achieve a stable and improved performance. Furthermore, up to 29% increase in the net electrical power output and 16.6% increase in the thermal efficiency can be realised by hybridising solar and geothermal energy during the peak demand.