Hybridizing Solar Heat with a Geothermal Binary Power Plant Using a Solar Steam Topping Turbine

Solar-thermal hybridization is a way to boost power generation of geothermal power plants, especially when the geothermal resource cannot supply the design flow or temperature. A new process using a high-pressure steam topping turbine can almost double the conversion rate of solar energy to power compared to the common practice of solar brine heating, and thus improve economic viability. This study looked at one such plant. Output from a geo-solar hybrid is typically increased both from the additional solar energy and from restoring turbine design-point efficiency. In this new process, a third effect occurs: the addition of a solar topping cycle increases the geothermal energy extracted from the brine. Process flow diagrams, off-design results, and economic results are presented. Three representative geothermal locations in the U.S. are evaluated, as are the effects of thermal storage, solar field sizing, and tax incentives.