In-reservoir Energy Storage and Flexible Geothermal Operating Strategies: Technology Validation, Market Value-potential, and Grid-scale Modeling and Optimization

In a grid with increasingly high solar penetration, recent market forces have eroded the value of producing electricity during the day. From 2015 to 2017, the value of electricity produced at 1 pm fell by half—from $28 to $14/MWh—while the value of 8pm electricity skyrocketed—from $43 to $60/MWh (EIA, 2017). And with nearly 7000 MW of solar expected to be installed by 2030, this problem isn’t going away anytime soon (CPUC, 2019). The California example is illustrative, and as solar has become the largest source of new capacity in many markets, this challenge is set to become widespread across the US (EIA, 2019). The Fervo Energy geothermal system design leverages the recent technological advances that drove the revolution in unconventional oil and gas development, including horizontal drilling, zonal isolation tools, and advanced downhole fiber optic measurement techniques. This design consists of horizontal well pairs that are stimulated with multistage hydraulic treatments to enable effective water circulation and heat mining efficiency between wells. As opposed to conventional geothermal systems, our design results in a tightly controlled connection between the wells, which enables novel operating strategies. By controlling both the injection pressure and production backpressure, the parasitic load and power generation profiles can be managed to effectively shift electricity production to achieve high-efficiency in-reservoir energy storage. Our work in Phase 1 will be along three main tracks: 1) Demonstrating in-reservoir energy storage and flexible geothermal performance characteristics of Fervo Energy geothermal systems. 2) Quantifying the value-potential of geothermal energy – Customer discovery and origination. 3) Evaluating geothermal energy’s role in evolving markets – Grid-scale modeling and optimization.