Jules Verne imagined this limitless power source in Victorian times – now 21st-century engineers say heat trapped in the oceans could provide electricity for the world

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IF ANY energy source is worthy of the name “steampunk”, it is surely ocean thermal energy conversion. Victorian-era science fiction? Check: Jules Verne mused about its potential in Twenty Thousand Leagues Under the Sea in 1870. Mechanical, vaguely 19th-century technology? Check. Compelling candidate for renewable energy in a post-apocalyptic future? Tick that box as well.

Claims for it have certainly been grandiose. In theory, ocean thermal energy conversion (OTEC) could provide 4000 times the world’s energy needs in any given year, with neither pollution nor greenhouse gases to show for it. In the real world, however, it has long been written off as impractical.

This year, a surprising number of projects are getting under way around the world, helmed not by quixotic visionaries but by hard-nosed pragmatists such as those at aerospace giant Lockheed Martin. So what’s changed?

“Jules Verne mused about getting energy from stored heat in the ocean in 1870”

It’s possible that Verne dreamed up the idea for OTEC to help out Captain Nemo, the protagonist of Verne’s deep-sea yarn who needed electricity to power his submarine, the Nautilus – it is the first written mention of the idea. “By establishing a circuit between two wires plunged to different depths, [it should be possible] to obtain electricity by the difference of temperature to which they would have been exposed,” Nemo told his shipmate. Eleven years after the book was published, French physicist Jacques-Arsène d’Arsonval proposed the first practical design for a power plant that does exactly that. Instead of using wires, he used pipes to exploit the temperature difference between the cold deep ocean and the warm surface waters to generate steam energy. …