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Clean energy journalism for a cooler tomorrow

Offshore wind farms could double as electric charging stations for ships

Shipping giant Maersk and other firms are developing tech to help the maritime industry ditch dirty diesel and run on wind power.
By Maria Gallucci

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Vessels service an offshore wind farm near Walney, in northwest England. (Ørsted)

Offshore wind farms already provide gigawatts of clean electricity to the grid worldwide. Now efforts are underway to supply some of that wind-blown power directly to ships.

Most vessels burn dirty diesel fuels to carry people and cargo across the water, trailing large amounts of greenhouse gases and toxic air pollution in their wake. In 2021, carbon dioxide emissions from the global shipping industry rose by 4.9 percent over the previous year amid a surge in seaborne trade.

At the same time, offshore wind installations are booming off the coasts of European and Asian countries. The United States, which has long lagged in offshore wind, now has dozens of projects in the works.

To fuel ships with offshore wind, companies are taking a variety of approaches. Some are developing mooring buoys, akin to bobbing electric-vehicle charging stations that are tied to wind farms via underwater cables. Diesel-burning ships can connect to these devices to keep their lights on instead of idling their engines. As more electric vessels hit the water, they can plug in to replenish their batteries at sea.

An illustration shows an offshore wind service vessel drawing power from a Stillstrom charging buoy. (Maersk Supply Service)

Another concept puts charging equipment on the side of towering turbines themselves to boost battery-powered vessels. In this case, service ships ferrying crew and equipment to build and maintain wind farms are powered by the very electricity they’re helping to produce.

Such technologies are already in development. At least three wind-to-ship projects are set to start pilot testing this year in the United Kingdom — which until recently had the highest amount of total offshore wind capacity installed in the world, with nearly 10.4 gigawatts at the end of 2020. (China now holds the top spot after reportedly adding a record 16.9 gigawatts in 2021 alone.)

Offshore wind is a really opportune place to begin looking at the challenge of decarbonizing shipping,” said Stuart Barnes of Offshore Renewable Energy Catapult, a public-private research and development center based in Glasgow, Scotland.

It has the potential to be a springboard for the whole of maritime” activity, Barnes, a regional partnership manager, told Canary Media.

Project No. 1: Maersk’s charging buoys will tackle diesel pollution from ships 

Shipping giant Maersk is behind one of the first projects pursuing this concept, and it’s going the buoy route. In January, Maersk’s offshore marine service division launched a new venture, called Stillstrom, to develop and commercialize its offshore charging station design.

Stillstrom is mainly focused on curbing pollution from diesel-burning cargo ships that are waiting to enter ports. The company estimates that roughly 3,500 commercial vessels are idling their engines at any given point worldwide, emitting planet-warming gases and harmful particulate matter while running up fuel bills.

In the United States, this problem is particularly pronounced outside the ports of Los Angeles and Long Beach in California. Pandemic-related disruptions have caused record crowds of idling container ships over the last year, which is driving a spike in harmful air pollution.

Shoreside, more diesel-burning vessels are adding equipment to be able to plug into electrical supplies alongside docks. But ships anchored dozens of miles offshore must keep running their auxiliary engines to keep lights, plumbing and communications equipment in operation as they wait.

The idea was, How can we bring shore power offshore?’” said Sebastian Klasterer Toft, who manages the Stillstrom venture at Maersk Supply Service.

An illustration of Stillstrom's offshore charging buoy, which will allow idling vessels to plug in and turn off their diesel engines. (Maersk Supply Service)

In the U.K., many ports have both clusters of idling ships and offshore wind turbines twirling nearby, making the two industries conveniently close for pairing.

Stillstrom is currently building a prototype of its offshore charging buoy, Toft said. The plan is to install the buoy near an offshore wind farm operated by Ørsted in the North Sea sometime between July and September this year.

A transmission line will carry electricity from the wind farm’s land-based infrastructure out to the bobbing buoy. The prototype device can generate less than 1 megawatt of power and is capable of converting high-voltage electricity from the grid to the low-voltage power suitable for ships. During sea trials, Stillstrom will test the setup on one of Ørsted’s service operation vessels, which are typically about 300 feet long and provide accommodations for technicians as they’re out at sea to repair and maintain wind farms.

The prototype buoy will undergo six to nine months of testing, after which Stillstrom plans to deploy commercial-scale buoys aside 50 to 100 ports by 2028. The company aims to eliminate 5.5 million metric tons of carbon dioxide emissions over five years while also curbing air and noise pollution, Toft said.

Project No. 2: Oasis buoys will power wind-farm service vessels

Oasis Marine Power, a company based in Aberdeen, Scotland, is also building an offshore charging buoy. But rather than eyeing idling cargo ships, the firm is targeting the smaller vessels that service offshore wind farms.

At least 11,000 vessels are used for work on offshore installations, including wind farms and oil and gas platforms. A small but growing share of them uses batteries for some or all of their propulsion. The vessels that service wind farms typically make short, frequent trips between a port and offshore turbines, which means they’re generally easier to electrify than, say, an ocean-crossing container ship with huge power requirements and extended travel times, said Catapult’s Barnes.

The Oasis charging buoy is an extension of the ones the firm designs for leisure yachts, only much larger and more complex, according to the company, which is a subsidiary of the marine engineering design firm Jebb Smith.

Oasis Marine Power's offshore charging buoy is shown during sea trials at the Port of Cromarty Firth in Scotland. (Oasis Marine Power)

The offshore charging device will initially supply 2 to 3 megawatts of power, enough to fully replenish the battery systems on crew transfer vessels, a type of service ship that is typically no longer than 100 feet.

In January, Oasis completed a weeklong sea trial in the Scottish Port of Cromarty Firth to test the buoy’s design and how well it connects to vessels. The company plans to do further electrical testing before hooking the buoy to an offshore wind farm for a six-month trial period.

We are working closely with wind farm operators to meet their needs,” the company stated in an email.

Project No. 3: MJR will charge electric ships directly from turbines

The third U.K.-based initiative eschews the buoy concept in favor of using actual turbines.

MJR Power & Automation, a marine services company based in England, is developing a system to charge electric service vessels by plugging them directly into the base of an offshore wind farm. The firm is partnering with Catapult, ship operator Tidal Transit and an unnamed offshore wind developer to pilot the concept.

As the partners see it, a crew transfer vessel can dock at the turbine. A multipronged plug then emerges and connects to the vessel, charging the battery system so the ship can spend more time at sea.

MJR plans to begin a full demonstration of the system this spring in the North Sea. Initially, the project will be tested on a diesel-powered crew transfer vessel with external batteries added on the deck, since an electric ship isn’t available, Barnes said. The U.K.’s Department for Transport recently awarded £2 million ($2.7 million) for the demonstration project as part of its Clean Maritime Demonstration Competition.

Barnes said the offshore charging project has drawn widespread attention from wind farm developers, turbine builders and vessel operators in Europe since it was announced last year. He noted that, as the United States scales up its nascent offshore wind industry, the charging technology could transfer across the Atlantic Ocean, as well.

There’s a huge interest, and not just in the U.K.,” he said.

Safety is a key challenge wherever water and electricity meet

Beyond testing new technologies, the companies say they’re working to ensure their mooring buoys and giant extension cords are safe to use — and don’t risk electrocuting the technicians handling cables or damaging ships’ equipment.

For instance, if a person drops an electrified line into the water, the system should be sufficiently insulated to handle the plunge. Charging equipment also needs to be fortified against corrosion and other water-related impacts. Lithium-ion batteries in particular can leak toxic cobalt into the environment when exposed to or immersed in seawater, according to a 2021 paper by engineers in South Korea.

Toft, of Maersk’s Stillstrom venture, said that safety precautions are ingrained” into both the design and operability of his company’s charging buoys. Stillstrom is also working with classification societies including DNV GL to ensure the offshore buoy system complies with industry standards. Barnes said the MJR-led initiative is likewise working with regulators to ensure the project meets codes for vessel safety and electric-charging infrastructure.

Looking ahead, offshore charging infrastructure may have a bigger role to play beyond reducing dirty diesel exhaust or providing juice to electric service vessels.

Giant cargo ships burning alternative fuels could also plug into buoys to conserve their precious fuel supply. Maersk is betting heavily that green” methanol and ammonia — which can be made using renewable electricity — will replace today’s oil-based marine fuels. However, both alternatives are still extremely expensive to produce and are currently in scarce supply.

Using electricity wherever you can just makes a ton of sense,” Toft said. We see our service as part of an infrastructure that allows the transition to a net-zero offshore future.”

Maria Gallucci is a senior reporter at Canary Media. She covers emerging clean energy technologies and efforts to electrify transportation and decarbonize heavy industry.