A giant offshore wind farm built around a Baltic Sea island could send electricity into the transmission grids of at least four countries and be used to power a giant electrolyser to extract hydrogen from water. The energy vision from offshore wind developer Ørsted includes locating the electrolyser in Copenhagen to provide ready access to a market for sales of hydrogen for powering ships, planes and trucks

THE PLAN Locate a giant expandable wind farm around the Danish island of Bornholm to send electricity to mainland Denmark and neighbouring countries. On windy days, divert some of the electricity for production of hydrogen to meet demand for green energy for commercial transportation of goods and people by land, sea and air

ADVANTAGES The project can be built in stages and has the potential capacity and flexibility to meet more than grid demand; wind potential is good around Bornholm and the island is relatively close to populated areas that need large volumes of clean energy

UNKNOWNS Assessments of the vision’s economic viability and environmental impact have yet to be undertaken and large-scale demand for hydrogen has yet to transpire

Denmark’s partly state owned offshore wind plant developer, Ørsted, is thinking big about hydrogen. In a vision it has dubbed “the world’s first energy island”, Ørsted’s idea is to use the Danish island of Bornholm, south of Sweden in the Baltic Sea, as the hub for a giant offshore wind farm. The facility would send its production into the power grids of the countries that surround Bornholm, but on windy days, in periods when grid demand was low, some of the wind farm’s output would be diverted and used to extract hydrogen from water through electrolysis.

Ørsted believes that by locating a giant electrolyser near a mainland coastal city, such as Copenhagen, a ready market for the hydrogen would exist nearby in the form of lots of demand for clean energy from hard-to-electrify transport, including airplanes, ships and heavy trucks. Most of the wind farm’s electricity, however, would be sold into the Danish grid and that of countries surrounding Bornholm, such as Sweden, Poland and Germany. Bornholm, with a population of just 40,000, has limited demand.

The energy island vision is a further demonstration of just how far Ørsted has come in a few years, abandoning its identity as a fossil fuel utility and offshore gas company to massively invest in becoming the world’s leading offshore wind developer. The company has reduced carbon emissions from the energy it supplies by 83% compared to 2006. “Bornholm is an ideal location for a new wind cluster,” says Ulrik Stridbæk, vice president at Ørsted. “It has great wind conditions and is well situated to connect with other countries and mainland Denmark.”

The energy island is a “very good idea,” says Brian Vad Mathiesen, professor in energy planning at Aalborg University, Denmark. “It is flexible and can be expanded step by step. We can start now and it holds great opportunities for a broader regional expansion of renewable energy.” Søren Dyck-Madsen, senior advisor at green think tank Concito agrees, but wants to know how the electricity would be converted for non-grid uses. “This is not very clear,” he says.

Dan Jørgensen, Danish minister of Climate, Energy and Utilities, has called the idea “very interesting” and the government has put aside €4 million in 2020, €3.6 million in 2021 and €1 million in 2022 to explore the prospect of building energy islands, with Bornholm as one option for a land-based hub.

Ørsted is urging ministers to take a concrete step and issue an open tender for bids to develop a 1 GW wind farm at Rønne Banke, a shallow area south west of Bornholm with space for an expansion to 5 GW. Ørsted would not necessarily emerge as the winning bidder — the past two open offshore tenders in Denmark were won by Swedish rival Vattenfall. A Rønne Bank wind plant could be delivering power to Denmark and Poland by 2028, dependent on the construction of a transmission link between the two countries which Denmark has proposed under the EU’s Ten Year Network Development Plan, says Ørsted.


The huge scale of offshore wind farms being built in northern Europe is bringing a new understanding of just how much electricity can be gleaned from the wind on land and at sea, far more than needed to meet grid demand, even when electrification of transport and space heating gathers pace. Renewable energy is available in such abundance that as its generation cost falls, renewables electricity cannot only meet grid demand, it can be converted via hydrogen to ammonia, methane or liquid methanol.

“There is huge potential to use surplus wind power for fuels and the technology is already developed,” says Dyck-Madsen from Concito. “But this is not being done at scale yet because it is expensive and the energy waste from the process is often high.” As the costs of wind power fall and the technologies mature, however, he sees potential in scaling up the production of synthetic fuels, particularly from the resource offshore.

Denmark generates more electricity from the wind than any other country. Over 40% of grid demand was met by wind turbines within its boundaries in 2017 and 2018. Today the country has 14 offshore wind farms with a total capacity of 1699 megawatts (MW) and another 13 offshore wind projects in the pipeline. Developing offshore wind remains high on the country’s political agenda and the government is even considering creating an artificial energy island with thousands of wind turbines in the North Sea, to the west of the country.

The existing island of Bornholm lies in the Baltic Sea to the east of Denmark. Vad Mathiesen says it makes more sense to focus on Bornholm and its surroundings than to build an island from scratch. Creating an artificial island would be “very expensive and technologically difficult”, he says. “The challenge is to find suitable locations for large quantities of renewable energy, which are also close to large consumption centres.”

Bornholm ticks the right boxes. It is relatively close to land and as a hub for a series of vast wind turbine arrays could supply a much larger market than just Denmark. Søren Dyck-Madsen believes that wind energy islands in both the North Sea and Baltic Sea are necessary for Denmark to reach its ambitious climate and clean energy goals. He concedes, however, that starting with Bornholm would be the right way forward.

Longer term, Ørsted sees the Bornholm project reaching 5 GW of power generating capacity, more than enough to cover the needs of five million Danish households. At peak production times, the energy island could generate more power than required by Denmark and the power systems in neighbouring countries it was connected to, says the company. In that case, the surplus could be converted via electrolysis into fuel for ships, trucks and airplanes. The greater Copenhagen area boasts a big airport and a large vehicle fleet looking for clean energy solutions. The city is a good location for a power-to-X plant, says Ørsted, where “X” represents any synthetic fuel or storage medium. Such is the distance between Copenhagen and Bornholm, the economics of converting AC output to DC and back again would likely stack up for using a high voltage direct current (HVDC) undersea transmission cable to the mainland.

Dyck-Madsen agrees that an HVDC link makes sense. “Bornholm with its 40,000 residents does not have a big enough scale heating system to use all the surplus heat that would stem from the power-to-fuel process. Copenhagen does,” he states. But before going further, he would like to see economic and environmental impact assessments to understand better the project and its chances of becoming reality.

TEXT Anna Fenger Schefte




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