For 8.7 seconds, Endurance Energy’s underwater geothermal prototype generated more electricity than it needed to operate. The US company says the median surplus during that brief run was about 2 kilowatts, with a peak of 16.5 kilowatts. It’s a small engineering win, not proof that this works as a power source: the drilled well couldn’t supply enough water, and equipment failures cut the test short.
The experiment took place at Axial Seamount, an underwater volcano roughly 480 kilometers off Oregon’s coast. About 1,500 meters below the ocean’s surface, natural vents release water heated by molten rock beneath the seabed. Endurance Energy’s engineers set out to turn that heat into electricity using the same basic principle as established geothermal power plants on land, according to Science Alert’s report.
Getting enough hot water to the generator proved harder than finding heat. To supply the prototype, named Adélie, the team first drilled a well 16 meters beneath the ocean floor and installed a pipe. Water flowing through it reached 260 degrees Celsius, but there wasn’t enough flow to drive the generator.
The engineers then connected Adélie to a nearby natural vent that supplied enough water at a suitable temperature. During the September 27 test, the water was approximately 281 degrees Celsius, and the system’s turbine spun at around 26,000 revolutions per minute.
That setup produced the brief net-positive run. An onboard battery-protection system then stopped the experiment, and a pump’s power cable failed during an attempt to restart it. The test showed that the prototype could briefly generate more power than it needed to run, but it didn’t establish sustained operation.
Endurance Energy’s Adélie prototype. Photo: Endurance Energy.
The reported electricity balance also has limits. It didn’t include the energy required for drilling, transport and installation. Nor has the system shown that it can run reliably for months or years.
Endurance Energy is already developing Gentoo, a 100-kilowatt test generator designed for longer runs and higher output. Its longer-term goal is to supply consumers on land. The company is developing its first commercial project in the Pacific nation of Tonga, where the electricity grid relies heavily on imported diesel. Under its plans, initial power generation could begin in 2027.
Technical reliability isn’t the only unresolved issue. Seafloor hydrothermal vents support unusual microorganisms and the communities of other organisms that depend on them. Any move toward longer-term operation will also require careful study of how extracting heat and installing equipment affects those ecosystems.
