A bold new study from Canada’s University of Victoria [48.5°N, 123.3°W] offers a sweeping view of what Ocean Thermal Energy Conversion (OTEC) might mean not just for clean energy, but for the Earth’s climate itself. Using a powerful climate-carbon model, researchers simulated centuries of global-scale OTEC deployment, showing that this technology — once seen as niche and geographically limited — could offer deep emissions cuts, steady renewable energy, and surprising climate co-benefits.
Mass deployment of OTEC could cool the planet, reduce ocean acidification, and even help stabilise major ocean currents — while supplying clean, continuous energy.
What Is OTEC?
OTEC works by using the natural temperature difference between warm tropical surface waters and cold deep ocean water (DOW), typically sourced from 1,000 metres below. That gradient powers turbines to generate electricity. It’s reliable, low-carbon, and most suited to tropical oceans.
What hasn’t been known until now is what would happen if we rolled out OTEC on a truly global scale — and over centuries. This study fills that gap.
A Climate Model That Looks Far Ahead
The team ran detailed simulations out to the year 2500 under various OTEC energy production scenarios (3 to 15 TW). These scenarios included realistic power generation growth, carbon offset calculations, and changes to ocean mixing. Crucially, they used a fully coupled Earth System Model to track knock-on effects in ocean chemistry, temperature, biology, and circulation.
Key Findings
- Reduced surface temperatures: Up to 4°C less warming in OTEC-heavy scenarios compared to fossil-fuel-dominated futures.
- CO2 drawdown: Emissions reductions from OTEC could offset up to 111% of historical human emissions.
- Stronger ocean circulation: The Atlantic Meridional Overturning Circulation (AMOC) — a key conveyor belt of global climate — declined less in OTEC scenarios.
- Acidification suppressed: OTEC cut surface ocean acidification significantly, helping vulnerable marine ecosystems.
- More nutrients, more life: Nutrient-rich deep water brought to the surface could increase biological productivity, helping sustain marine food chains.
But Not Without Trade-Offs
Cooling the tropics with deep water has a thermal ripple effect. The study warns of slight temperature increases in some polar regions post-OTEC deployment, possibly affecting ice sheet stability. Also, long after OTEC ends, its induced mixing could modestly raise sea surface temperatures if emissions reductions don’t continue.
Localised ecosystem impacts are another concern: bringing cold, acidic, nutrient-rich water to surface levels may disrupt delicate tropical habitats. So, large-scale deployment would need strong environmental safeguards.
Why It Matters Now
Most climate models focus on emissions reductions. Few examine the secondary impacts of how we achieve them. This study uniquely shows that the method of decarbonisation — in this case, OTEC — comes with global-scale ripple effects.
If managed wisely, OTEC could do more than replace fossil fuels: it could act as a tool for stabilising the climate. That gives it a rare dual value — as an energy solution and a geoengineering-like lever. For an ocean planet facing a climate crisis, that’s a potent combination.
While it may not be the first renewable that springs to mind, OTEC might just become one of the most influential — especially for nations with warm coastlines and big climate ambitions.
Source
Environmental impacts from the widespread implementation of ocean thermal energy conversion, Climatic Change, 2025-04-26
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