The Reduced Pumping Power Requirements from Increasing the Injection Well Fluid Density

摘要

The reduction of parasitic loads is a key component to the operational efficiency of geothermal power plants, which include reductions in pump power requirements. Variations in fluid density, as seen in CO_2-based geothermal plants have resulted in the elimination of pumping requirements, known as a thermosiphon; this effect, while less pronounced, is also found in traditional brine geothermal systems. Therefore, we find the reductions in pumping power requirements for traditional 20 wt% NaCl brine and CO_2 geothermal power systems by increasing the injection fluid density. For a reduction in temperature of 1°C at a 15°C surface condition, a traditional brine system was found to require up to 2kWe less pumping power. A CO_2 system in the same condition was found to require up to 42 kWe less power. When the density of the injected brine was increased by increasing the salinity of the injected fluid to 21 wt% NaCl, the injection pumping requirement decreased as much as 45 kWe. Both distillation and reverse osmosis processes were simulated to increase the salinity while producing 7 kg s~(-1) fresh water. The pumping power reduction does not account for the increased energy cost of salination; however, this may still be economical in locations of water scarcity.