Hybridizing a geothermal power plant with concentrating solar power and thermal storage to increase power generation and dispatchability. (15th October 2018) - McTigue, Joshua D.
Highlights: The power output of a geothermal plant is increased by 2 MWe (9%) by using solar heat. The hybrid plant's solar thermal energy to electricity conversion efficiency is 24%. The hybrid plant cost (LCOE) is 25–50% lower than a PV array with battery storage. The cost is up to 15% lower than a concentrating solar plant with thermal storage. Over-sizing the solar field and using storage improve flexibility and reduce cost. Abstract: Geothermal power plants often deploy less than their full power capacity due to declining geothermal resources. Integrating heat from a concentrating solar power (CSP) collector field increases the power output at low cost. This article considers five methods of solar heat addition in a double-flash geothermal plant. The most promising solution converts solar heat into electrical work with an efficiency of 24.3%. The economic feasibility and optimal sizing of the solar field and thermal stores are evaluated. A hybrid plant that increases power generation from 22 to 24 MWe has a Levelized Cost of Electricity (LCOE) of 0.07 ± 0.01 $/kWhe . Adding three hours of storage increases the LCOE to 0.08 ± 0.01 $/kWhe . Photovoltaic systems are considered to be a low-cost renewable technology, but an equivalent photovoltaic system with battery storage costs 0.15 ± 0.07 $/kWhe due to the high cost and replacement rate of batteries compared to thermal storage. The hybrid plant also has a lower LCOE than a conventional CSP plant. If the dispatchability that thermal storage provides is rewarded with higher electricity prices, calculations indicate storage becomes an attractive investment when discharged power receives 1.75 times the typical price of electricity.