Closed-Loop Geothermal Demonstration Project, Confirming Models for Large-Scale, Closed-Loop Geothermal Projects in California

The project team investigated using a closed-loop heat extraction technology to unlock the vast geothermal regions of California that cannot be accessed by conventional hydrothermal systems due to insufficient water and subsurface permeability. The project team installed and measured the performance of a downbore heat exchanger in a field-scale closed-loop geothermal power system. Water and supercritical carbon dioxide were circulated in the system as alternatives for transporting heat to the surface where power generation was simulated.
The team conducted onsite testing in May and December 2019 using Well 34-A20 in Coso (Inyo County, California). Construction included the insertion of 1,083 feet of vacuum-insulated tubing inside a liner that was plugged at the bottom to form the downbore heat exchanger.