An innovative offshore wind farm in the frozen waters of northern Scandinavia has opened a new frontier for wind development that could result in dozens of gigawatts added around the world.

The 42MW Tahkoluoto near-shore array, close to the city of Pori on Finland’s western coast, became the world’s first offshore wind park in near-Arctic conditions when it was commissioned in September.

Belgium’s Jan de Nul group installed 10 Siemens Gamesa 4.2MW machines in the Gulf of Bothnia — the northernmost part of the Baltic Sea — in 8-15 metres of water on specially-designed gravity-based steel foundations able to withstand the heavy ice typical of Nordic winters.

Toni Sulameri, managing director of Tahkoluoto’s developer and operator, Suomen Hyötytuuli, tells Recharge that although freezing temperatures and ice can prohibit offshore construction work for up to six months per year — and require new solutions for foundations and O&M — he sees a potential for dozens of gigawatts of offshore wind in cold climate regions.

In the Gulf of Bothnia alone, there 18 other projects are in various stages of planning, including an up-to-300MW expansion of Tahkoluoto in windier, deeper waters further off the coast.

Esa Eranti, the founder of Eranti Engineering, a Finnish company specialised in offshore and Arctic engineering, sees a potential of 5-20GW of bottom-fixed offshore wind for the “best areas” off Finland, Sweden and Estonia.

Ice itself is not a big issue for offshore wind, says Hans Ohlsson, managing director for offshore at the Swedish unit of German developer WPD.

“If it is moving ice, maybe sometimes it can be a design challenge. In general, it is not so much worse compared to really high breaking waves in the North Sea,” Ohlsson tells Recharge. “Ice is not a disqualifying criterion for projects.”

LEEDCo

Eranti, who is also the ice expert for the 20.7MW Icebreaker project on Lake Erie near Cleveland, Ohio — which is scheduled for construction in 2019-20 — thinks the potential for offshore wind in freezing waters could be even bigger in North America.

Lorry Wagner, president of Icebreaker developer Lake Erie Energy Development Corp (LEEDCo), estimates the potential for offshore wind in the lake to be about 50GW, and for all of the Great Lakes a staggering 700GW — on the US side alone.

“What people don’t realise is that the Great Lakes are much bigger than the Atlantic coast of the US,” Wagner tells Recharge. But unlike the US east coast, wind farms on the Great Lakes would not be exposed to hurricanes, and would see steady wind speeds of up to nine metres per second — similar to those in the northern Baltic, and higher than those on much of the Atlantic seaboard.

“There is a lot of potential in a number of different states. Going forward, we certainly think there is quite a good industry here,” says Wagner.

Global Wind Energy Council secretary-general Steve Sawyer also thinks that the resource in the lakes is excellent and believes there could be significant areas around the world with a combination of demand, good wind and relatively light ice conditions.

“Protecting the installation from the ice will obviously add some cost, but if it’s light ice then perhaps it won’t be too large,” Sawyer cautions. “But it will be very situation specific.”

Ice-breaking foundations

Eranti, who carried out the conceptual design of the foundations used at Tahkoluoto that were then built by the Finnish unit of French engineering company TechnipFMC, says other developers can learn a lot from the project.

The gravity-based foundation design used at the Finnish site is a reinforced steel shell filled with ballast that is conical at the water line, so that when ice presses against the substructure, it pushes itself up the cone and then breaks off.

But the choice of foundation depends on soil conditions.

“The concept used at Pori is best applicable to hard bottom conditions, for example dense sand, moraine, gravel or rock,” Eranti says.

At Icebreaker, the foundation concept is a little different as the site location has a soft soil layer overlaying harder material and shale, and the water is deeper.

“Our conditions are such that we will use the mono-bucket foundation,” Wagner tells Recharge, adding that it will have a similar ice cone at the water level.

Turbines

Ice and freezing temperatures also affect wind turbines, but the strain on the machines is less crucial than the one on foundations, with OEMs already having years of experience with building onshore turbines for cold-climate regions.

The 4MW Siemens Gamesa turbines used at Tahkoluoto have a “special cold weather package including various heating elements and low- temperature liquid... to ensure that the turbine is able to operate under cold climate conditions”, says Morten Mathiasen, head of product lifecycle management on Siemens Gamesa’s G4 platform.

Most of the major turbine OEMs offer similar equipment — onshore, at least.

At Icebreaker, LEEDCo has chosen MHI Vestas as its preferred supplier, for specially adapted offshore versions of Vestas’ V126-3.45MW onshore machine.

Installation and O&M

Installing offshore turbines in freezing seas means that construction is generally expected to take place during the ice-free summer months. But O&M must take place year-round.

Suomen Hyötytuuli now uses a triple-hulled trimaran for maintenance during the summer, and a heavy steel boat that can break ice in the winter. The problem is that ice breaking boats are slow, at around 8-9 knots (15-17km/h), Sulameri explains.

When the ice layer is heavy, snow mobiles can also be used to reach near-shore arrays. For future projects further away from the coast, new ice-breaking crew vessels would need to be designed, which would likely be monohulls or trimarans.

“Those can break some ice, they can navigate in 20cm-thick ice at something like 15 or 16 knots,” Sulameri explains.

Turbines at Tahkoluoto also have heated boat landings to melt ice and snow, improving safety for maintenance crews.

Nevertheless, Sulameri believes that the need for special foundations and more complex O&M do not add too much to the cost of cold-climate offshore projects, especially at the kind of near-shore projects being planned off Finland and Sweden.

“We think that the benefits of near-shore are bigger than the disadvantage of ice. The impact to the cost of energy is not so big,” he says.

Ohlsson agrees. “There are also cost savings,” he says.

“When it is cold, the air density is to our advantage, we can produce more [energy]. So, [costs] would not be so much different. Compared to onshore, the impact of icing is much less.”

Sulameri estimates the levelised cost of energy (LCOE) at the Tahkoluoto array to come in at around €60 ($70.50) per MWh. This is lower than the lowest winning tender price of £57.50 (€64.10) per MWh at the UK’s recent offshore tender.

Prices and support

However, Sulameri says that to build out its 3GW cold-climate offshore portfolio, it will need to halve Tahkoluoto’s LCoE in order to beat future wholesale market prices — something that will only be possible with much larger turbines.

“When we go to 2023-25, [turbines will have] to be 12-15MW. To get the price down, that is very crucial. The bigger the turbines are, the easier the business case.”

Such turbines are expected to be on the market by 2024-25. (Orsted, the former Dong Energy, and EnBW recently won zero-subsidy offshore tenders in Germany that base their business case on the availability of such equipment).

Although Suomen Hyötytuuli received a one-off €20m grant from the Finnish government to help with the Tahkoluoto pilot, it is banking on a future without subsidies.

There are currently no specific support schemes for offshore wind in Sweden or Finland.

This is why WPD’s Gulf of Bothnia offshore projects — the 420MW Storgrundet off Sweden and the 480MW Suurhiekka off Finland — are on hold.

“Both projects are consented, and are in the pole position to get constructed as soon as the circumstances improve,” Ohlsson says.

In Sweden, even onshore, only the very best projects have the chance to succeed, because electricity prices in the NordPool wholesale market — as well as green certificate prices — are really low, Ohlsson explains.

Sweden is currently discussing whether or not to waive grid connection costs for offshore wind, which in combination with larger turbines in the future could make offshore wind competitive. And Finland is mulling to hold technology-neutral tenders for renewable energy in 2018 and 2019 as part of a new support regime, although the government has not mentioned any special rules for offshore.

The cost of offshore wind in the nascent US market is still far higher than in Europe — the country’s first offshore project, Block Island, is reportedly selling its power for $244/MWh — and that is without even accounting for the extra costs associated with extreme weather conditions.

In both of the pioneering regions for cold-climate offshore wind — the Baltic and the Great Lakes — much of the future development will depend on a mixture of favourable public policies, as well as larger turbines and bigger projects that can push costs down.

So while the potential of this frozen frontier is enormous, it may move at a glacial pace for a little while yet. 

Wind

Jumping into frozen waters: offshore wind takes on the icy seas