Supercritical Geothermal Cogeneration: Combining Leading-Edge, Highly-Efficient Energy and Materials Technologies in a Load-Following Renewable Power Generation Facility

摘要

Geothermal power must contribute much more to the supply of clean renewable energy. Electricity generated from wind and solar power is intermittent and cannot alone balance the demands of the grid. Geothermal power provides baseload generation. The geothermal industry needs to both improve its return on investment and increase its flexibility in supplying electricity to the grid. A recent development that has great promise occurred last year, when the Iceland Deep Drilling Project successfully drilled a well into a supercritical geothermal reservoir. This breakthrough has the potential to offset the high front-end costs and risks of geothermal power by allowing high enthalpy production from supercritical wells. Such wells are expected to produce an order of magnitude increase in power output relative to conventional, subcritical geothermal systems, as discussed by Elders et al. (this volume). In addition to greater power output, supercritical resources cause dramatic changes in important properties of water. As a result, supercritical geothermal cogeneration (SGC) can produce electricity and create hydrogen with high efficiency and low costs using a flexible and thermally integrated energy plant combining: (1) a Brayton-cycle turbine generator using supercritical CO_2 as its working fluid; (2) electrolysis cells using ceramic proton-conducting membranes; (3) extraction of metals and minerals; and (4) desalination by switchable polarity solvent forward osmosis to supply deionized water required for brine processing, electrolysis and electrical power generation. The results will enable exploitation of new geothermal resources, and provide a flexible source of grid balancing for more rapid increases of intermittent wind and solar power enabling 100% use of renewables for both electric power generation and transportation.