Endurance Energy completes first underwater geothermal power test

Seattle-based startup Endurance Energy has completed a world-first end-to-end demonstration of geothermal power generation near an underwater volcano. The test, known as Adélie, took place at the Axial Seamount, located approximately 300 miles off the coast of Oregon at a depth of about 1,500 meters.

During the three-week trial, the team successfully drilled the world’s first subsea geothermal well, measuring hydrothermal fluids at approximately 260°C. While the initial well did not provide sufficient flow to drive a 100 kW system, the team relocated equipment to a natural hydrothermal vent with temperatures around 281°C. This allowed the system to achieve a net positive power output for 8.7 seconds, reaching a peak net power of 16.5 kW.

The demonstration faced several engineering hurdles, including insufficient fluid flow from the shallow well and interruptions caused by battery module and cable issues. Despite these challenges, the company successfully utilized a subsea fiber-optic network for real-time remote control from Seattle. Endurance Energy plans to conduct further trials between 2026 and 2027, aiming to provide renewable energy alternatives for Pacific Island nations.