India Is Building a Power Plant That Uses the Difference Between Warm and Cold Seawater to Make Electricity Around the Clock

India’s Lakshadweep project could show whether ocean heat can deliver reliable power and fresh water.

On Kavaratti, an island in India’s Lakshadweep archipelago, engineers are building a power plant that will run on the temperature difference between warm surface water and the cold ocean below.

The system will draw seawater from about 1,000 meters deep and use that contrast to generate 65 kilowatts of electricity while producing 100,000 liters of fresh water a day, according to India’s National Institute of Ocean Technology (NIOT).

The technology, called ocean thermal energy conversion, or OTEC, turns the ocean’s vertical temperature gradient into electricity. It has enticed engineers for more than a century because, unlike solar and wind power, that gradient persists day and night. Yet OTEC has repeatedly stalled before commercialization. Its biggest obstacle is that the small temperature difference between warm and cold seawater allows OTEC systems to convert only about 3 to 5 percent of the available heat into electricity.

That forces plants to move enormous volumes of seawater through large heat exchangers and, often, through a pipe extending hundreds of meters into the deep ocean. The upfront capital costs are immense. Lakshadweep will test whether OTEC can become useful anyway — not by beating giant solar farms on price, but by solving several costly island problems at once.

A power plant built between warm and cold water

Most OTEC designs use a closed loop. Warm surface seawater heats a low-boiling fluid such as ammonia. Its vapor turns a turbine, then cold deep seawater condenses it so the cycle can begin again.

Kavaratti will use an open-cycle approach. Pumps create a vacuum that lets warm seawater itself boil at a low temperature. The resulting low-pressure steam turns a turbine and then condenses against deep cold water, producing fresh water as well as power.

“What we are doing is scalable in numbers for islands and remote communities. This can be a market strategy,” Purnima Jalihal, the former head of NIOT’s energy and fresh water division, told IEEE Spectrum.

Engineers have built experimental OTEC plants since the 1930s. But the field’s ambitions remain much larger than its operating record.

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A 2025 review of the technology places OTEC’s theoretical global potential at 8 to 10 terawatts and identifies three major research directions: better thermodynamic cycles, integration with other energy sources and valuable byproducts such as fresh water, cooling and hydrogen.

Another study estimated OTEC resources across U.S. states, territories and freely associated states at about 4,600 terawatt-hours per year, roughly 110 percent of U.S. electricity generation in 2019. A 2022 study projected that global OTEC potential could rise about 46 percent by late century under a high-emissions scenario.

The pipe may matter more than the turbine

The main barriers for OTEC have always been cost and reliability. NIOT first learned that the hard way in 2002, when it attempted a 1-megawatt offshore project. During construction, workers lost its 1,000-meter cold-water pipe to the sea, ending the project for good.

To this day, the pipes remain one of OTEC’s hardest engineering problems. Commercial plants must pump extraordinary amounts of water, while offshore pipes become immense structures exposed continuously to waves, currents and storms.

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That is why the EU-backed PLOTEC project in the Canary Islands is focused not on generating electricity but on testing an offshore OTEC platform. Its floating prototype is designed to test whether an offshore platform and its long cold-water intake pipe can withstand rough seas and extreme storms. In April 2026, Global OTEC announced that it had installed the prototype and connected its vertical seawater intake pipe at a test site off the Canary Islands.

The 2025 review mentioned earlier estimates put the price of electricity from a 10-megawatt OTEC plant at roughly 20 to 67 cents per kilowatt-hour in the studies it examined, substantially more than wind or solar.

Why islands may be the first place it works

For remote tropical islands, however, OTEC does not have to beat the cheapest mainland renewable project. It has to beat imported diesel, desalination costs and air-conditioning bills.

Lakshadweep already uses NIOT’s low-temperature thermal desalination technology. The new installation is designed to use OTEC power to run desalination without drawing electricity from the diesel-powered island grid. The roughly $5.3 million project could save about $210,000 to $260,000 a year in diesel costs.

Cold deep seawater can also cool buildings through seawater air-conditioning, while electricity can be converted into hydrogen or ammonia for storage.

There are, however, also some obvious environmental concerns. Pumping deep water upward can move nutrients, dissolved carbon and organisms into unfamiliar layers. Deep discharge and careful siting may reduce some of the risks, but large plants have not operated long enough to settle the concerns.