Seattle-based Endurance Energy says it has completed the first subsea geothermal power demonstration, generating net-positive electricity for less than 10 seconds from a hydrothermal vent at Axial Seamount, an active underwater volcano off the Oregon coast. The September test deployed the 3-ton Adélie plant at about 5,000 feet deep. Both Ars Technica and Canary Media report that the turbine spun at roughly 26,000 rpm and produced 60 watt-hours of electricity, with about 8.7 to 9 seconds of net-positive output before a battery overcurrent protection triggered a shutdown. A subsequent cable failure ended the run.
The two outlets agree on the core facts but differ in emphasis. Ars Technica details the engineering challenges: the initial drilled well, only 52 feet deep and 2 inches wide, could not deliver enough hydrothermal fluid, so the team moved Adélie to a natural vent. Endurance plans deeper wells—its lander drill can reach about 260 feet—and must prove the approach is cost-effective. Stanford professor Roland Horne told Ars that subsea geothermal is "probably technically feasible, but it would undoubtedly be more expensive than to do it on land."
Canary Media adds business context that Ars does not: Endurance has raised $63 million and is partnering with Tonga on a planned 2-megawatt project to reduce diesel imports. However, geologist Emily Pope of the Center for Climate and Energy Solutions told Canary that the economics are doubtful, noting that remote islands could more easily adopt solar and batteries. "It is adding so much technological challenge to an energy production technology, without there being a really significant demand for it," she said.
Both sources characterize the test as a "proof point" rather than a commercial breakthrough. Endurance says it is rearchitecting components and plans to redeploy a refurbished Adélie this winter, with a commercial-scale system possibly generating electricity in 2027. The company's CEO, Andrew Redd, a former SpaceX engineer, framed the milestone as "make it exist, then make it good."