A floating power platform designed to harness the temperature difference between warm surface water and cold deep ocean water has cleared a major technical hurdle. UK-based Global OTEC Resources received its first certificate of approval for the installation methodology of a cold-water riser — the pipe system at the heart of the technology — marking the closest ocean thermal energy conversion (OTEC) has ever come to commercial reality.
At a glance
- OTEC certification: Marine warranty surveyor ABL Group granted the certificate of approval, providing independent third-party validation for a technology that has struggled to move beyond prototypes for nearly a century.
- Floating platform: Global OTEC’s flagship vessel, named Dominique, is a 1.5-MW system planned for deployment off the coast of São Tomé and Príncipe, a small island nation in the Gulf of Guinea, by 2025 C.E.
- Baseload ocean power: Unlike solar or wind, a functioning OTEC system can generate electricity continuously — 24 hours a day, 365 days a year — because deep ocean temperature gradients remain constant regardless of weather.
A 140-year idea finally within reach
The concept of ocean thermal energy conversion dates to 1881 C.E., when French physicist Jacques Arsène d’Arsonval proposed using the ocean’s stored solar energy to generate power. The basic physics are straightforward. Tropical oceans maintain a temperature difference of at least 36°F between warm surface water and cold deep seawater. Run a thermodynamic cycle across that gradient and you get electricity — plus, as a byproduct, fresh drinking water and cold water usable for refrigeration.
The challenge has always been engineering. The first experimental OTEC turbine — a 22-kW low-pressure system — ran in 1930 C.E. More than a dozen prototypes have been tested in the decades since. None reached commercial scale. The cold-water pipe, or riser, has been a recurring failure point: deploying a large pipe thousands of feet into the ocean from a floating platform, and keeping it there, is a genuinely difficult problem.
That is exactly what the new ABL Group certification addresses. By formally validating Global OTEC’s riser installation methodology from the earliest design stage, the company is building the kind of documented technical record that previous OTEC projects lacked. “History is an important teacher, and we are committed to learning from it,” said Global OTEC founder and CEO Dan Grech. “Failure of previous OTEC projects highlights where we should exercise caution, so third-party technical due diligence from the earliest stage is important for our success.”
Why São Tomé and Príncipe
The choice of location is not incidental. São Tomé and Príncipe sits near the equator in the Gulf of Guinea, where surface water temperatures and deep-water cold are both stable year-round — ideal OTEC conditions. The island nation, with a population of roughly 220,000, also depends heavily on imported fossil fuels for electricity. A reliable local baseload renewable source would reduce both energy costs and carbon emissions for a country that contributes almost nothing to global warming but sits on the front line of its effects.
This reflects a broader pattern in OTEC development. The technology’s best sites are in tropical island nations — places in the Pacific, Caribbean, and Atlantic that face high energy import costs and genuine vulnerability to climate disruption. Global OTEC has framed its work explicitly around energy access in these communities, not just technology demonstration.
How the system works
The Dominique platform will use a closed-cycle OTEC system. Warm surface seawater — around 26°C — heats a working fluid with a low boiling point, typically ammonia, causing it to vaporize and spin a turbine. Cold seawater drawn up from depth condenses the vapor back to liquid, completing the cycle. The platform floats above deep water, drawing cold water directly from below through the riser pipe.
One of the most significant prior tests of this approach was the U.S. Department of Energy’s OTEC-1 project, a 1-MW closed-cycle test loop that ran from 1980 C.E. to 1981 C.E. It proved that large cold-water pipes could be deployed from a floating vessel — but also showed how technically demanding that deployment is. The IEA’s Ocean Energy Systems program has noted that successful cold-water pipe installation remains a “key uncertainty for OTEC,” which makes Global OTEC’s certification milestone directly meaningful.
What still needs to happen
A design certification is not a commissioned power plant. The Dominique platform still needs to be built, transported, and installed — each step carrying real engineering risk in a technology sector with a long history of projects that stalled before reaching the water. The 2025 C.E. target date is ambitious, and OTEC’s track record justifies measured expectations.
Cost remains an open question too. OTEC systems require large heat exchangers, long pipe systems, and robust offshore infrastructure — capital costs that have historically made the technology hard to finance even when the engineering works. Whether the Dominique project can demonstrate an economically viable model, not just a functioning one, will determine whether this certification leads to a genuine new chapter in ocean energy or another promising prototype without successors.
Still, the progress is real. OTEC sits alongside other emerging ocean energy technologies that the IEA’s Ocean Energy Systems program tracks as part of the long-term renewable energy mix. Global OTEC Resources is the first company to bring a commercial-scale system to this stage of verified design approval. For small island nations looking for stable, locally generated clean power, that matters — and it matters that a U.K. firm chose an African island nation as the site to prove it.
The IEA’s OES technology collaboration program has long highlighted OTEC’s potential as a continuous baseload source in tropical regions, noting that the ocean covers around 70% of Earth’s surface and absorbs vast quantities of solar energy that current renewable technologies leave untapped. ABL Group’s independent validation now gives that potential something it has rarely had: a credible technical pathway forward.
Read more
For more on this story, see: POWER Magazine — OTEC: A Long-Stalled Baseload Ocean Power Technology Is Seeing a Swell
For more from Good News for Humankind, see:
- Renewables now make up at least 49% of global power capacity
- Ghana establishes a marine protected area at Cape Three Points
- The Good News for Humankind archive on renewable energy
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