What Works for Wind Power Could Also Work Under the Sea

A wind-power pioneer wants to tap the oceans for energy.

Aquantis is developing marine turbines to deploy off the U.K. and Florida coasts.
Source: Aquantis

Jim Dehlsen, a 79-year-old wind-energy pioneer who sold one turbine company to Enron and took another public, has spent his life thinking about the best way to make blades turn in the sky. For his latest effort, he’s flipping a turbine upside down and plunging it dozens of meters into the ocean, in waters that are up to 300 meters deep. There, marine currents rotate the 13.5-meter long blades to pull power from the sea.

Aquantis, Dehlsen’s Santa Barbara, Calif., company, will start deploying turbines in 2018 in waters near Wales and the Isle of Wight. Its most ambitious project is a 200-megawatt field of marine turbines in the strong Gulf Stream off the coast of Florida, due to come online in 2019 or 2020. The world’s oceans remain relatively untapped as an energy source, compared with wind and solar. By 2030, Dehlsen says, marine energy could serve 8 percent or 9 percent of U.S. power needs. “The oceans are the major remaining potential for renewable energy,” he says. “Getting on that now is really urgent.”

It took wind at least 15 years to become a viable, cost-effective resource. In the late 1970s, when scientists first started experimenting with wind turbines, “people laughed at you and said, ‘Wind will never work,’ ” says Robert Thresher, a research fellow at the National Renewable Energy Laboratory in Golden, Colo. In the ’80s and ’90s, the industry settled on the three-blade turbine design considered the standard today. Many aspects of turbine design can be applied to the oceans, adjusted to handle the slower, heftier fluid dynamics of seawater.

Illustration by 731

Aquantis is developing systems to capture energy from waves, from tidal currents, which switch direction twice a day, and from gyre, or steady, currents. Much of Dehlsen’s obsession these days is with the Gulf Stream. Its constant current can rotate turbines day and night, allowing Aquantis to squeeze more power out of each turbine. That will cut the price per kilowatt-hour. “Because the stream flows all the time, it’s probably the one that can become cost-effective most easily,” Thresher says.

Aquantis, which isn’t the first company to design underwater turbines, wants to lower the cost of marine energy. Dehlsen says deploying an Aquantis device—towing it out to sea, filling it with seawater ballast, then anchoring it—runs about $347,000 per turbine. The rotor’s two blades can withstand huge volumes of water moving as fast as 4 knots. The topmost part floats just above the surface, and the rest of the equipment is held in place with mooring lines to the ocean floor, making it quicker to deploy and cheaper to maintain. Repair crews take an elevator down the shaft.

Rival turbine makers dig deep into the ocean floor to anchor the machinery so that it can withstand the strength of the currents; their repairs require raising the structure to the surface. That pushes up the cost significantly, Dehlsen says, to about five to seven times more than Aquantis’s.
Dehlsen plans to install his turbines in a few test sites and sell power to the grid. He sees a second revenue stream in marine turbines housing data centers for the world’s tech giants, using the turbine’s shaft as a storage area for racks of servers. That can save companies money on air conditioning by using cold ocean water to cool the equipment. Aquantis designed and built a pilot test chamber for Microsoft that housed a data center underwater for 105 days off California’s San Luis Obispo pier last year. The test was a success, Microsoft said, with minimal ocean heating and no leaks or hardware failures. Dehlsen is reaching out to Apple, Facebook, and Google about similar efforts.

Dehlsen is courting tech companies and investors while trying to lock down test sites from the north coast of Brazil to Cape Agulhas, on the southern tip of Africa. Little testing has taken place in the U.S. Aquantis has won Department of Energy grants and received some venture capital from Mistubishi Heavy Industries. Dehlsen has self-funded a lot of the work; additional income comes from projects like the data center program. His track record in renewable energy reassures potential partners, says Charles Vinick, Aquantis’s chief executive officer. “Jim is seen as the father of American wind—that opens the door.”

Marine turbines face some challenges, such as concerns over unknown environmental effects. Their blades could strike whales or create noise that confuses sea life. Dehlsen says studies conducted in the U.K. show turbines are safe for fish and marine life. The bigger challenge, he says, is creating marine energy that is cost-competitive. He expects to get to less than 10¢ a kilowatt-hour in three to five years. (Wind energy hovers from 3¢ to 8¢ a kilowatt-hour, solar from 4¢ to 7¢, and conventional gas from 5¢ to 8¢.) “In renewable energy, people get enthusiastic about an idea, and yes, maybe you can make electricity. But if it’s 8¢ a kilowatt-hour, so what?” he says. “Don’t even bother.”
Dehlsen’s best argument may be a slide in his presentation about the urgency of global warming. “The time that’s left in which we can make a change is relatively short,” he says. “Five to 10 years, and you’re beyond being able to stem it.”

The bottom line: Aquantis says marine energy could serve 8 percent or 9 percent of U.S. power needs by 2030.

(Corrects information about the length of the turbine blades and how deep they're placed in the ocean in the first paragraph, and venture capital invested in Aquantis in the seventh paragraph.)