Seattle-based Endurance Energy, developer of subsea geothermal power systems, has announced that it has drilled the world’s first offshore geothermal well in an end-to-end demonstration of subsea geothermal power designed to test the engineering realities of operating a geothermal system on the ocean floor.
During a three-week Adélie test deployment at Axial Seamount, 300 miles off the Oregon coast, Endurance drilled a geothermal well 5,000 feet beneath the surface, which produced hydrothermal fluid at 260° celsius.
A three-ton power plant was installed on the seafloor, and operated remotely over the National Science Foundation’s Regional Cabled Array, a seafloor fibre-optic network operated by the University of Washington as part of the Ocean Observatories Initiative. As the fluid was insufficient to run the plant, the turbine was connected to a nearby natural vent flowing at approximately 281°C (538°F), reaching approximately 26,000 rpm. For 8.7 seconds, the system generated more electricity than it consumed—a median of around 2 kilowatts net and a peak of 16.5 kilowatts net. The net-positive run at the nearby natural vent ended when battery overcurrent protection stopped the system. During a restart attempt, a power cable feeding the refrigerant pump failed, ending the dive.
The deployment produced data on seafloor drilling, well flow, heat transfer, mineral buildup, high-temperature power generation, and long-distance control of subsea equipment, information Endurance will use to build its next system.
What comes next?
Following on from the test, Endurance is planning to deploy a refurbished and upgraded version of Adélie designed to target higher power and longer sustained generation. The company expects deeper wells to deliver the greater flow needed for sustained generation. In parallel, Endurance is developing Leopard, its 2-megawatt commercial generator.
When commercialised, it is envisaged that subsea geothermal systems could convert the heat beneath the ocean floor into continuous clean electricity for coastal grids and industrial sites and data centres around the Pacific and worldwide.
“On Sept. 27, we put a power plant on an active underwater volcano and made power,” said Andrew Redd, founder and CEO of Endurance Energy. “This historic milestone is also our first end-to-end test. We now know, firsthand, what works at depth, what needs to be improved, and how to build the next system for sustained commercial generation.”