Geothermal Power Station with Supercritical Organic Cycle

Abstract

Geothermal water at moderate temperatures can be used for the supplying or co-supplying of a thermal plant or a power plant. In the latter case, Organic Rankine Cycle (ORC) plants operating with subcritical parameters are usually applied. The alternative to such a design is the ORC power plant operating with supercritical parameters supplied by moderate temperature geothermal water.

A schematic of such installation is presented here with a description of its operation and the algorithm of calculations of a supercritical power plant. An analysis of the influence of a kind of working fluid on the effectiveness of operation of a plant was carried out. In this analysis, geothermal water temperatures varying in the range Tg1=95-120°C and a constant flow rate of 15 kg/s were assumed. Results of calculations have shown that the highest values of efficiency and power were used in the case where propylene was a working fluid. A comparison of a supercritical cycle power plant and an appropriate subcritical ORC power plant was attempted under the assumption of comparable conditions of supply and removal of heat to and from the system. The obtained results enabled the unanimous conclusion that the application of supercritical conditions in low-temperature ORC installations of geothermal plants allows significantly higher values of both efficiency and power to be achieved.