| Abstract |
Compared to the traditional Enhanced Geothermal Systems (EGS), the Pressure Geothermal Systems (PGS) reduce the water circulation impedance through the subsurface system. In PGS, the pressure-propped fractures are used to keep flow impedance low and have subsurface above the fracture opening pressure at all times, which improves the hydro-mechanical performance of the geothermal system. However, high differential pressure re-injection pump is required in such a PGS, which adds a significant parasitic load and reduces efficiency and net power output from the geothermal power plant. To remedy this issue, this paper presents a novel pressure recovery system using Rotary Pressure Exchanger (RPX) to recover up to 95% of the pressure energy from PGS well and utilize it to pressurize the brine going into the re-injection well. RPX has a high speed axially ducted rotor that receives the low pressure, low temperature re-injection fluid and the high pressure, high temperature fluid from the production well. As the duct rotates, it is alternately exposed to the low and high pressure RPX ports, and through a direct fluid-to-fluid contact pressure exchange, the pressure energy from production fluid is transferred to the reinjection fluid. This pressure recovery significantly reduces the high pressure reinjection pump work and associated parasitic losses of the geothermal power plant. This paper presents a novel pressure recovery system design for a PGS geothermal power plant utilizing RPX. Fundamental physical mechanisms governing RPX are outlined. The performance characteristics and efficiency improvement of RPX integrated PGS binary power plant are quantified. |