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Endurance Energy says its Adélie test unit generated about 60 watt-hours of electricity from heat at a natural hydrothermal vent off Oregon on Sept. 27, 2026. The turbine ran for about 29 seconds, and the company plans another test this winter after redesigning components; commercial viability remains unproven.
Endurance Energy says its Adélie test unit generated about 60 watt-hours of electricity from a natural hydrothermal vent on the seafloor off Oregon on Sept. 27, a brief demonstration of a technology the startup hopes could eventually supply power from underwater volcanic heat. The turbine ran for about 29 seconds, and the test did not establish that the system can operate reliably or at commercial scale.
The Seattle-based company conducted the test during a three-week expedition in September aboard the research vessel Ocean Guardian. Its equipment was deployed roughly one mile below the Pacific’s surface, near Axial Seamount, an active submarine volcano about 300 miles west of Oregon. Endurance announced the results on Monday, according to Canary Media’s report.
Endurance first drilled a relatively shallow well into a vent field, using a modified geotechnical drill. The company said that well did not produce power, so the team moved Adélie to a nearby natural vent. A remotely operated submarine connected the three-ton system to the site. Its organic Rankine cycle used heat from mineral-rich water to drive a turbine.
For nearly nine seconds of the run, the system produced more power than it consumed, with surplus electricity going to its battery backup, the company said. The demonstration stopped after the battery’s overcurrent protection activated; a power cable failed soon afterward, ending the dive. Endurance received temperature and flow data and controlled the unit remotely from Seattle through an existing fiber-optic cable network.
A Brief Test, Not a Power Plant
The test offers a technical milestone for a young company attempting to use geothermal heat in a difficult offshore setting. It showed that Adélie could be connected to a natural vent and generate electricity, but the short run and equipment failures leave major questions about durability, output and cost. The result is evidence of a demonstration, not proof of a dependable electricity source.
Endurance says it is pursuing a continuous, low-carbon power source and has raised $63 million. It is also working with Tonga on a proposed two-megawatt project intended to reduce the island nation’s reliance on imported diesel. The test does not show that such a project is technically or economically ready to build.
Geologist Emily Pope, a senior fellow at the Center for Climate and Energy Solutions, told Canary Media that subsea projects face the expense and complexity of operating in corrosive, high-pressure seawater, as well as the challenge of transmitting electricity to customers. She also questioned whether remote islands would need the approach when solar power and batteries may be less expensive. Those concerns place the next engineering tests alongside an unresolved question about where offshore geothermal could make economic sense.
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Why Endurance Went Offshore
Most next-generation geothermal efforts focus on land, where developers seek to reach underground heat with improved drilling and power systems. Endurance founder and CEO Andrew Redd has argued that spreading tectonic plates and volcanic regions offshore offer a different resource. The company, launched in January 2025, says it is designing equipment from scratch to withstand deep-sea pressure and corrosive conditions, including through extensive use of titanium.
Earlier offshore geothermal work has largely been research. Canary Media reported that Chinese scientists generated a few watts of sustained power at a hydrothermal vent in 2016. A government-backed project in southwest Iceland drilled near the Mid-Atlantic Ridge but faced engineering problems from corrosive seawater. Endurance says its ambition is to operate at a larger scale, though the Adélie test’s brief output remains far short of a commercial demonstration.
Axial Seamount is a site of ongoing oceanographic research by the University of Washington and the National Science Foundation’s Ocean Observatories Initiative. Redd told Canary Media that the area’s research infrastructure and environmental monitoring made it a practical place to conduct the trial. The source report does not describe the test as a sale of electricity or as a connection to a customer grid.
“We follow the adage ‘make it exist, then make it good.’ Adélie made it exist, and now we know it’s possible.”
— Andrew Redd, Endurance Energy founder and CEO
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Output, Reliability and Cost Remain Open
The demonstration does not establish how long Adélie can run under normal operating conditions, how much electricity a larger system could produce, or whether it could keep generating through repeated deployments. The company reported about 60 watt-hours over about 29 seconds; the source gives no basis for treating that short test as a measure of sustained output or commercial capacity.
It is also unclear what caused the battery protection to activate, why the cable failed, or how extensive the planned redesign will be. Endurance has not provided a confirmed cost per unit of electricity or shown that its proposed system can compete with other energy options. The technical and financial status of the proposed Tonga project, including its construction schedule and funding, was not detailed in the report.
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A Winter Retest Will Test Endurance
Endurance plans to refurbish Adélie and deploy it again this winter, aiming for higher output and a longer operating period, Redd told Canary Media. That test should indicate whether the company has addressed the problems that cut short the September run, although no detailed test date, target duration or power-output goal was given in the report.
The startup is also developing a larger system that Redd said might begin generating electricity in 2027. That remains a company projection, not a confirmed operating date. Further tests would need to show sustained generation, reliable subsea connections and a credible path to commercial costs before offshore geothermal’s potential can be judged.
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Key Questions
How much electricity did the seafloor system generate?
Endurance Energy said Adélie generated about 60 watt-hours over roughly 29 seconds at a natural hydrothermal vent on Sept. 27, 2026. For nearly nine seconds, the company said output exceeded the system’s own operating needs.
Where did Endurance conduct the test?
The test took place near Axial Seamount, an active submarine volcano about 300 miles west of Oregon. The unit was deployed roughly one mile beneath the Pacific Ocean’s surface.
Did the test prove offshore geothermal is commercially viable?
No. It was a short demonstration, and the company reported that battery protection activated and a power cable failed. The test did not establish long-term reliability, commercial-scale output or competitive costs.
What caused the demonstration to end?
Endurance said the battery’s overcurrent protection activated, and a power cable failed soon afterward. The source report does not explain the underlying causes or detail the fixes planned.
What happens next for Adélie?
Endurance plans to refurbish the unit and deploy it again this winter, seeking a longer run and higher power output. The company has not disclosed a specific test date or performance target in the source report.
Source: rss
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