Using Geothermal Energy to Preheat Feedwater in a Traditional Steam Power Plant

Abstract

What would happen if geothermal energy was used to preheat the feedwater for a traditional steam power plant? In an effort to determine the most effective way to use geothermal energy this is a left field, yet enticing, idea. Would this produce more ‘extra’ power than a geothermal plant on its own? Would there be sufficient benefit to interest traditional power generators? We investigated retro-fitting two different geothermal preheating options to the 500MW natural-gas-burning, supercritical steam power plant from the Public Service Company of Oklahoma, Riverside Station Unit #1 (PSORSU1). By keeping the feedwater flowrate constant and retro-fitting geothermal preheating, PSORSU1 is able to produce extra power. Our preferred geothermal preheat options produces between 65-135% more power than an Organic Rankine Cycle (ORC), with the variation depending primarily on resource temperature. Given sufficient geothermal resource flowrate and temperature, both geothermal preheat options trialed here, are capable of increasing the power output of PSORSU1 by upto 6.5%.