A new hybrid model of geothermal-solar power generation system has been investigated in this study with particular reference to the utilization of Hot Dry Rock (HDR) geothermal energy which usually associated with the application of enhanced geothermal system (EGS) technology. But long-term extraction of geofluid from the HDR could cause a considerable thermal energy depletion near the production zone, resulting in a decrease of the geofluid temperature. The hybrid system presented here is aimed at using solar energy to avoid continuously extracting too much geofluid in order to mitigate the thermal depletion circumstances. This hybrid system is designed as a power cycle with two interactive heat sources (geothermal and solar energy), which could generate the rated power of 1MW all the time by letting the two heat sources (two vaporizers) operation in different ways. The numerical simulation and optimization of different operation strategies under different solar conditions have been carried out. Organic Rankine cycle (ORC) is used for power generation. The total power output is controlled by adjusting the order in which the working fluid flows through the two vaporizers. The heating system in parallel mode as well as in series mode have been investigated. Results shows that, in the subcritical cycle scenario, the two vaporizers in series (with geothermal heating first) has a better performance. Whereas, in the transcritical cycle scenario, the two vaporizers in parallel has a better performance.
Keywords Geothermal-solar hybrid system, Enhanced geothermal system (EGS), Organic Rankine cycle (ORC), Optimum operation mode