Seafloor test unit makes power for nearly 30 seconds off Oregon

For nearly 30 seconds, a machine about a mile under the Pacific made electricity from the heat of an underwater volcano. That is the result Endurance Energy announced on Monday, after deploying its Adélie test unit during a three-week demonstration in September off the coast of Oregon. The Seattle startup's founder, Andrew Redd, a former SpaceX engineer, calls it a first step: 'Adélie made it exist, and now we know it's possible.'

The drilling came first. From the research vessel Ocean Guardian, the team remotely drilled a relatively shallow well into a vent field at the base of the Axial Seamount, an active submarine volcano about 300 miles west of Oregon. The drill is a modified geotechnical model that offshore oil and gas developers normally use to extract core samples of rock. A submarine robot then connected the Adélie unit to the well, which carries hot, mineral-rich seawater up from the seafloor. The 3-ton system uses an organic Rankine cycle, the same kind of loop found in many land-based geothermal plants, which transfers heat from the fluid to spin a turbine and generate electricity.

Redd's bet is that the offshore route is worth the difficulty. Most geothermal developers focus on land. He sees the most promise in volcanically active zones where tectonic plates spread apart, and says Endurance is designing its technology 'from scratch' to survive the pressure and corrosion of the deep sea. Earlier offshore efforts were far smaller: the Chinese team's few watts in 2016, and the Icelandic well that ran into corrosive seawater. The company has raised $63 million from venture capital firms.

Not everyone is convinced. Emily Pope, a geologist at the Center for Climate and Energy Solutions, calls the approach 'eyebrow-raising.' She sees a real scientific interest but doubts the economics: operating in harsh, salty water is costly and complex, and the power would travel long distances to reach customers. Remote islands look like ideal candidates, yet they could more easily adopt cheaper solar power and batteries. In her words, the subsea pursuit adds 'so much technological challenge' without 'a really significant demand for it.'

What would change if the system works is a question for Tonga first. Endurance is partnering with the island nation on a 2-megawatt project meant to cut its reliance on imported diesel, and the Oregon test is a first milestone for that plan. But the system must first keep running for more than half a minute. The sources do not give a timetable for the Tonga project, so for now the gain is a proof of concept: the seafloor can host a geothermal unit that ran for nearly 30 seconds, and the next test will show how long it can stay on.