Lauri Ulm, Enefit Green's head of wind energy, said that since the sea in the Baltic can freeze over in winter, stronger foundations and groundwork is needed, to avoid potential damage as a result.

Ulm told ERR's radio news that: "In the case of the [planned] Gulf of Riga wind farm, we conducted separate ice measurements using a device that sounded to the sea bottom, and analyzed how ice forms in the area."

"In this way, we can model very well how sea ice ice acts in the Gulf, and decide what technical solution might be used, to allow the best functioning."

At the same time, sea ice exhibits different properties in different areas of the same sea, Ulm added, hence the work being done.

Well above the sea surface, cold weather can also be an issue, can could lead to turbine blades freezing over.

Ullm said: "We are working on the Tolpanvaara wind farm off the coast of Finland, for instance. There, we are installing blades which are heated, and so which can melt the ice."

At the same time, the Baltic is less rough than, say, the North Sea, much shallower and less saline, while turbines can be located quite close to shore and so maintained easily.

These plus points will help a lower price of electricity than would otherwise be the case, he said.

Professor Ivo Palu of Tallinn University of Technology (TalTech) meanwhile said that wind farms are seldom constructed in icy waters.

He said: "I guess there are only two examples at the moment; one wind farm in Finland, and the other in Sweden. These are relatively new. I just looked at their production output and they are not really in the picture yet, they are new developments in that sense."

Drifting ice is particularly hazardous, he said, whereas stationary pack ice is easier to predict in terms of its effect.

All this also raises the question as to whether wind turbines should be installed on the same foundation, as is the case in ice-free waters, or whether a different set up should be used, Palu said, adding there is no single, definitive answer to this.

Lauri Ulm said that a balance must be struck here, adding the turbines certainly need to be durable – with the worst-case scenarios over a hundred-year period needing to be factored in.

This in act would entail a completely frozen-over Gulf of Riga, he added.

Ultimately, offshore wind farms off Estonia can be competitive if done right, he added.

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