Nearly a mile beneath the Pacific Ocean, roughly 300 miles off the Oregon coast, a 3-ton power plant sitting atop an active underwater volcano generated more electricity than it consumed for 8.7 seconds last month. The company behind it, Seattle-based Endurance Energy, says the brief run marks the first time anyone has drilled a subsea geothermal well and used it to produce net-positive power on the seafloor.
Endurance announced the milestone in a release this week, saying its Adélie power plant reached a median net output of about 2 kilowatts and peaked at 16.5 kilowatts during the test at Axial Seamount, according to a company announcement distributed via PR Newswire. The three-week test involved landing the plant on the seafloor and operating it in real time from Seattle over subsea fiber, the announcement states. Endurance founder and CEO Andrew Redd said the company put a power plant on an active underwater volcano and generated power, describing the end-to-end test as a way to see what works at depth, what needs improvement, and how to build the next system for sustained commercial generation.
The test, completed on September 27, combined drilling a well, deploying the seafloor plant, generating electricity, and communicating with the system from shore — all in one continuous operation, per Interesting Engineering’s account. Engineers used a robotic drilling machine resting on the seabed to bore into the volcano’s caldera roughly 5,000 feet below the ocean surface, boring two closely spaced holes that both reached hydrothermal fluid before installing steel pipe casing, cement, and a valve to control the hot-fluid flow.
A Well Too Tight to Run the Plant
The newly drilled well reached 52 feet below the seabed and, after cementing, flowed hot fluid at roughly 500°F, or 260°C — but it proved too restrictive to actually power the plant, according to the PR Newswire announcement. Instead, Endurance connected its system to a nearby, already-existing hydrothermal vent, which discharged water at 281°C and spun the plant’s turbine at 26,000 rpm, more than 430 revolutions per second, per Interesting Engineering’s reporting…