Coso

Executive Overview

The Coso closed-loop geothermal project is a 1.2 MW demonstration of GreenFire Energy's GreenLoop technology, deployed in 2019 at an inactive well in the Coso geothermal field in Inyo County, California — one of the largest geothermal fields in the United States, with approximately 140 MW of installed capacity. Construction was completed on April 16, 2019, and active flow testing began in May 2019, making it the world's first field-scale demonstration of a closed-loop geothermal power system. The project was funded by a major grant from the California Energy Commission, with additional funding from Shell GameChanger, the Electric Power Research Institute (EPRI), and J-POWER, and was conducted in partnership with Coso Operating Company and the U.S. Navy.

How It Works & Differentiation

GreenFire's GreenLoop system inserts a downbore tube-in-tube heat exchanger (1,083 feet in depth at Coso) into an existing well, circulating a working fluid — water or supercritical CO₂ — in a sealed loop that absorbs heat from the geothermal formation without requiring direct contact with reservoir fluids or natural permeability. Testing at Coso evaluated both water and sCO₂ as working fluids across multiple flow conditions: water achieved a maximum net electric power of approximately 1.2 MW; sCO₂ delivered roughly 10% of that output due to lower achievable flow rates in thermosiphon mode. The closed-loop design eliminates the need for subsurface permeability, produces no greenhouse gas emissions or induced seismicity, and can revive idle or underperforming wells — over 20% of geothermal wells fail commercially over time — extending field productive life at low incremental cost.

Commercialization & Traction

The Coso demonstration successfully validated GreenFire's process models against field results to within 5% accuracy, establishing a credible technical foundation for commercial deployment. A final report was delivered to the California Energy Commission and project participants, fulfilling the funded scope. The project demonstrates applicability to two distinct use cases: retrofitting non-producing wells in existing hydrothermal fields, and potential greenfield deployment in hot dry rock formations where conventional geothermal is not viable. Modelling of a full-scale system at Coso using a 1,000-metre downbore heat exchanger projects 104 kW of net output using sCO₂ in thermosiphon mode, with significantly higher potential when pumped water is used.

Scalability & Strategic Context

The CEC-backed analysis of closed-loop intensive development at Coso suggests a potential of 1–2 GWe from the existing field — roughly 10 times current output — before approaching thermal interference limits at well spacings below 80 metres. At deeper deployment depths targeting 500–800°C rock temperatures (5–8 km), modelled theoretical output at Coso alone reaches 19–39 GWe, though commercial extraction at those depths remains beyond current drilling economics. The California Public Utilities Commission's 2030 target of an additional 2,500 MW of geothermal capacity, combined with the state's requirement for firm zero-carbon resources, positions closed-loop technology as a potential contributor to closing that gap, particularly where conventional hydrothermal development is constrained by geology or permitting.