Thermodynamic comparison of different types of geothermal power plant systems and case studies in China

One of the greatest problems in using renewable energy sources is the great variability of energy level, both in the short and long term. Geothermal energy, by nature, has high availability because the source is not dependent on weather conditions, so it is among the most stable renewable energy sources. In China, urban populations are provided with their electricity requirements, but rural areas need guaranteed electricity for socio-economic development. Fortunately, mid-low temperature geothermal resources are located proximal to rural areas without access to grid electricity in China. Small-scale geothermal power plants can support electricity demand as well as create employment opportunities for the rural public. Therefore, geothermal energy has the potential to play an important role in the future energy supply of China.Based on mid-low temperature geothermal resource and waste heat resource, the paper introduces the energy efficiency of single-flash and binary cycle geothermal power plant. The result shows that binary cycle plant is favorable for power generation when water temperature is below 130 °C, otherwise, flash steam power plant is a better choice. Furthermore, two project cases were analyzed in the end, focusing on the operating parameters and thermal efficiency. The single-flash and binary cycle geothermal power plants could be improved energy efficiency of low-grade resources and both widely utilized in China.

► Thermodynamic comparison of flash and binary geothermal power plant is conducted.
► Two project cases with operating parameters are given.
► Flash system is better choice when the geofluid temperature is more than 130 °C.
► The lower the resource temperature, the worse the problem for flash technology.