Floating wind power is no longer science fiction. Promising results from five test platforms operating worldwide—including three in Japan—are turning into project plans for a first generation of floating wind farms. Industry analyst Annette Bossler, who runs Bremen, Maine-based Main(e) International Consulting, predicts that the number of test platforms will nearly double over the next two years and that commercialization is within site. "By 2018-2019 you will start to see the first really large-scale commercial use of floating platforms," predicts Bossler.
Putting wind turbines on offshore platforms akin to those developed for the petroleum industry provides a means of exploiting high-quality offshore winds—which are stronger and more consistent than onshore winds—in waters too deep for today's bottom-fixed foundations. The Department of Energy calls floating wind the future of offshore wind because over 60 percent of U.S. offshore wind resources—and nearly all of those off the West Coast—blow over deep water.
Last month, Seattle-based Principle Power secured $47 million in federal funding to test that potential 29 kilometers out from Coos Bay, Oregon. It has partnered with Rhode Island-based offshore wind developer Deepwater Wind to tether platforms for five 6-megawatt wind turbines in over 300 meters of water—way beyond the 50-meter maximum depth for fixed foundations such as those that Deepwater Wind plans to use at its East Coast sites.
Floating turbines also offer potential cost savings. Floating platforms and their turbines are fully manufactured on shore, then towed out and tethered to the seabed. By contrast, fixing foundations to the seabed and then bolting on massive turbines requires specialized vessels, which cost upwards of US $200 000 per day to rent—whether or not the weather permits their use.
Bossler says floating platforms can also achieve cost savings through serial manufacturing. Whereas fixed foundations must be tailored to each turbine site's depth and seabed conditions, every platform in a floating array can be identical.

Prototype testing is assuaging doubts about floating platforms' ability to stabilize massive offshore wind turbines against wave action as well as their ability endure punishing offshore storms. Principle Power's array of 6-MW turbines will sit atop larger versions of a prototype that has carried a 2-MW turbine in Portuguese water since 2011 (photo at right / Principle Power). The semi-submersible platform is, like a glacier, mostly below water; its stability derives from water moving around the platform, as well as ballast water moving within it.
This month also marks one year of operation of a floating test turbine in Penobscot Bay (photo at top). It remains the only offshore wind turbine in U.S. waters. The 20-kilowatt prototype installed by a University of Maine-led consortium is just one-eighth the size of a 6-MW turbine. But its smaller scale actually provides an accelerated means of "de-risking" the design, according to Habib Dagher, the University of Maine structural engineer and composites expert who directs its DeepCwind Consortium.
Dagher says the platform relies only on water flowing around it for stability, yet is proving extremely stable through waves that—given its 1:8 scale—equate to 23-meter hurricane-scale assaults. "It saw 100-to-500-year storms relative to its size, and its maximum inclination angle was just 5.9 degrees off of vertical," says Dagher.
While Dagher's consortium lost out to Principle Power in the current round of DOE project funding, its plans to install two 6-MW turbines off Maine's coast may yet hold water. Maine has only deep water, and state regulators eager to jumpstart offshore wind development guaranteed DeepCwind a generous 23 cents per kilowatt-hour for its power. That power purchase deal is worth over $240 million, says Dagher, and is something that other U.S. offshore wind developers are struggling to secure.
Then there is DeepCwind's unique materials technologies, which it asserts could slim the cost of offshore wind power by more than half by the mid-2020s. DeepCwind replaces steel with corrosion-resistant concrete in its platform and with comparatively lightweight composites in its turbine tower.
Bossler says cost reduction will be critical to commercializing floating wind power. This is true even in Japan, where idled nuclear plants and soaring power costs are accelerating floating wind development. But she declines comment on whether DeepCwind's solution is the way forward. "I do work for a competitor," she says.
The Conversation (0)
This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

The number of charging stations in Utrecht has risen sharply over the past decade.

“People are buying more and more electric cars,” says Eerenberg, the alderman. City officials noticed a surge in such purchases in recent years, only to hear complaints from Utrechters that they then had to go through a long application process to have a charger installed where they could use it. Eerenberg, a computer scientist by training, is still working to unwind these knots. He realizes that the city has to go faster if it is to meet the Dutch government’s mandate for all new cars to be zero-emission in eight years.

The amount of energy being used to charge EVs in Utrecht has skyrocketed in recent years.

Although similar mandates to put more zero-emission vehicles on the road in New York and California failed in the past, the pressure for vehicle electrification is higher now. And Utrecht city officials want to get ahead of demand for greener transportation solutions. This is a city that just built a central underground parking garage for 12,500 bicycles and spent years digging up a freeway that ran through the center of town, replacing it with a canal in the name of clean air and healthy urban living.

A driving force in shaping these changes is Matthijs Kok, the city’s energy-transition manager. He took me on a tour—by bicycle, naturally—of Utrecht’s new green infrastructure, pointing to some recent additions, like a stationary battery designed to store solar energy from the many panels slated for installation at a local public housing development.

This map of Utrecht shows the city’s EV-charging infrastructure. Orange dots are the locations of existing charging stations; red dots denote charging stations under development. Green dots are possible sites for future charging stations.

“This is why we all do it,” Kok says, stepping away from his propped-up bike and pointing to a brick shed that houses a 400-kilowatt transformer. These transformers are the final link in the chain that runs from the power-generating plant to high-tension wires to medium-voltage substations to low-voltage transformers to people’s kitchens.

There are thousands of these transformers in a typical city. But if too many electric cars in one area need charging, transformers like this can easily become overloaded. Bidirectional charging promises to ease such problems.

Kok works with others in city government to compile data and create maps, dividing the city into neighborhoods. Each one is annotated with data on population, types of households, vehicles, and other data. Together with a contracted data-science group, and with input from ordinary citizens, they developed a policy-driven algorithm to help pick the best locations for new charging stations. The city also included incentives for deploying bidirectional chargers in its 10-year contracts with vehicle charge-station operators. So, in these chargers went.

Experts expect bidirectional charging to work particularly well for vehicles that are part of a fleet whose movements are predictable. In such cases, an operator can readily program when to charge and discharge a car’s battery.

We Drive Solar earns credit by sending battery power from its fleet to the local grid during times of peak demand and charges the cars’ batteries back up during off-peak hours. If it does that well, drivers don’t lose any range they might need when they pick up their cars. And these daily energy trades help to keep prices down for subscribers.

Encouraging car-sharing schemes like We Drive Solar appeals to Utrecht officials because of the struggle with parking—a chronic ailment common to most growing cities. A huge construction site near the Utrecht city center will soon add 10,000 new apartments. Additional housing is welcome, but 10,000 additional cars would not be. Planners want the ratio to be more like one car for every 10 households—and the amount of dedicated public parking in the new neighborhoods will reflect that goal.

This photograph shows four parked vehicles, each with the words \u201cWe Drive Solar\u201d prominently displayed, and each plugged into a charge point.Some of the cars available from We Drive Solar, including these Hyundai Ioniq 5s, are capable of bidirectional charging.We Drive Solar

Projections for the large-scale electrification of transportation in Europe are daunting. According to a Eurelectric/Deloitte report, there could be 50 million to 70 million electric vehicles in Europe by 2030, requiring several million new charging points, bidirectional or otherwise. Power-distribution grids will need hundreds of billions of euros in investment to support these new stations.

The morning before Eerenberg sat down with me at city hall to explain Utrecht’s charge-station planning algorithm, war broke out in Ukraine. Energy prices now strain many households to the breaking point. Gasoline has reached $6 a gallon (if not more) in some places in the United States. In Germany in mid-June, the driver of a modest VW Golf had to pay about €100 (more than $100) to fill the tank. In the U.K., utility bills shot up on average by more than 50 percent on the first of April.

The war upended energy policies across the European continent and around the world, focusing people’s attention on energy independence and security, and reinforcing policies already in motion, such as the creation of emission-free zones in city centers and the replacement of conventional cars with electric ones. How best to bring about the needed changes is often unclear, but modeling can help.

Nico Brinkel, who is working on his doctorate in Wilfried van Sark’s photovoltaics-integration lab at Utrecht University, focuses his models at the local level. In his calculations, he figures that, in and around Utrecht, low-voltage grid reinforcements cost about €17,000 per transformer and about €100,000 per kilometer of replacement cable. “If we are moving to a fully electrical system, if we’re adding a lot of wind energy, a lot of solar, a lot of heat pumps, a lot of electric vehicles…,” his voice trails off. “Our grid was not designed for this.”

But the electrical infrastructure will have to keep up. One of Brinkel’s studies suggests that if a good fraction of the EV chargers are bidirectional, such costs could be spread out in a more manageable way. “Ideally, I think it would be best if all of the new chargers were bidirectional,” he says. “The extra costs are not that high.”

Berg doesn’t need convincing. He has been thinking about what bidirectional charging offers the whole of the Netherlands. He figures that 1.5 million EVs with bidirectional capabilities—in a country of 8 million cars—would balance the national grid. “You could do anything with renewable energy then,” he says.

Seeing that his country is starting with just hundreds of cars capable of bidirectional charging, 1.5 million is a big number. But one day, the Dutch might actually get there.

This article appears in the August 2022 print issue as “A Road Test for Vehicle-to-Grid Tech.”

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