Geothermal resource of the hydrothermal type is expected to make the full use of the geothermal energy, and more net power is also expected to output for the organic Rankine cycle (ORC) based geo-plant. However, the two aspects often conflict with each other. Moreover, the available temperature range of the geothermal resource has a close relationship with its temperature level. The aim of this paper is to illustrate the corresponding relationship between the temperature level and the available temperature range of the geothermal resource with two different cycle configurations (ORC and Series Double-stage ORC (SDORC)) based on energy, exergy, and entropy analyses, thereby efficiently utilizing the valuable geothermal resource. The results show that the inlet temperature of the heat source has a decisive effect on the system performance. At a fixed inlet temperature of the heat source, there exists an optimal available temperature range to maximize the system performance. Moreover, the cycle configuration is also important for the geothermal power generation. Compared with the ORC, the SDORC can enhance the available temperature range to take the full advantage of geothermal resource. Comprehensively, the SDORC is more competitive than ORC and can be adopted in engineering applications.
Keywords Series Double-stage organic Rankine cycle (SDORC), compound objective function, available temperature difference of the heat source, inlet temperature of the heat source