Endurance Energy successfully tested its 3-ton Adélie underwater geothermal power plant near the Axial Seamount in the Pacific Ocean. The 100 kW unit was deployed at a depth of 1,524 meters, utilizing hydrothermal fluid from the seabed to drive a turbine and generator.
During the September tests, the turbine reached 26,000 rpm, generating 60 Wh of electricity. For 8.7 seconds, the system achieved a positive energy balance with a peak net output of 16.5 kW before software protection protocols triggered an automatic shutdown due to sensor and cable issues.
The company plans to test an upgraded version named Gentoo in the winter of 2026–2027. Endurance Energy is also developing a 2 MW commercial generator for a project near Tonga, scheduled for 2027, which may involve deploying up to six container-sized units.
While the technology demonstrates technical feasibility, its economic viability remains unproven. Experts suggest that underwater geothermal systems may face significantly higher construction and maintenance costs compared to land-based alternatives.
