A variable-capacity power system driven by geothermal energy: research methodology and preliminary experimental study

To match for the different temperature of the geothermal resource and strengthen the flexibility of organic Rankine cycle (ORC), this paper proposes a variable capacity power generation superstructure based on Flash and ORC for geothermal energy. A combined Flash-ORC experimental prototype is newly established to investigate its performance on both steady and dynamic conditions in this paper. Pressured hot water is adopted as the extensive worldwide existed hydrothermal geothermal resource, eliminating the influence of the used heat transfer oil on evaporating process. Important variables are investigated including the working fluid mass flow rate, loads quantity and outdoor environment of ORC subsystem in the preliminary experimental study. Firstly, steady experiment indicates that the maximum net power generation of ORC subsystem is 0.74 kW, revealing the existing optimal working fluid mass flow rate of the specific system. Secondly, dynamic on-off investigation of working fluid pump illustrates that ORC system has a certain extent self-adaption capacity and reliability. In addition, power generation increases with the decrease of the loads, and the condensing temperature makes a big influence on system performance when ORC using the cooling tower.