Great perspectives in offshore wind

[Picture: Here you can see a map of Denmark]

Danish wind turbine expansion has developed rapidly in recent years. Future offshore wind farms will be established on market-based conditions following calls for tender.

With a couple of pilot projects in the 1990s and a number of large demonstration projects in recent years, Denmark has taken the lead in exploiting the specially favourable wind conditions at sea for CO₂ free electricity production from large MW wind turbines. Danish experience encompasses the special production conditions with stronger wind and less turbulence at sea, the technical conditions for grid connection, and the environmental impacts. There is great interest in Danish experience at international level and several other European countries are running offshore wind turbine projects.

Higher production

Interest in the potential of the development of offshore wind energy has grown more or less in step with the upscaling of wind turbines. The overall maximum height of the tower and rotor of the wind turbine of about 150 meters, meant that the MW wind turbines would dominate the landscape and that the precondition for continued large-scale development of wind energy in Denmark would be the exploitation of the offshore potential.

The mapping of potential major sites for offshore wind farms in 1997 identified an immediate potential of approximately 4,000 MW in Danish waters. However, there are many indications that in step with the development of more cost-efficient foundations more sites can be found because the wind turbines can be located at greater depths than foreseen in 1997.

The increased costs of foundations, grid connection etc. and for service inspections for offshore wind farms will to a steadily increasing extent be balanced by higher production and longer lifetimes. The additional costs of electricity production from offshore wind farms for the large-scale demonstration projects in Horn Rev and Nysted have been estimated as 20% in relation to good locations ashore. But when the experience from these projects can be incorporated in coming projects, the additional costs are expected to be significantly reduced.

On Market Terms

During the 1990s Denmark implemented two pilot projects that provided crucially new knowledge about the economic and environmental conditions for developing offshore wind farms. Since 2001 these projects have been followed up by three large-sale demonstration projects at Copenhagen (Middelgrunden), Horns Rev at Esbjerg and Nysted at Rødsand, respectively, with a total installed output of approximately 200 MW and wind turbines of 2-2.3 MW. Wind turbines of up to 3 MW are to be tested in some near-shore areas in the coming years.

The two large demonstration projects at Horns Rev and Nysted were constructed following orders from the government to the power plants. The original plan was that five demonstration plants with a total output of approximately 750 MW should be established on similar terms. But following the liberalisation of the electricity market, the Danish government has decided that open invitations to submit tenders should be issued for further offshore wind farm projects and that production should be on market terms.

The Danish Energy Authority has analysed where and on what economic and environmental terms future offshore wind farms can be established. The government is expected to call for tenders for the next project so that the first commercial offshore wind farm can start production for the Nordic electricity market from 2007.

The economic framework conditions will depend to a high degree on the way in which CO₂ free electricity production is integrated in the European electricity market. But under all circumstances the Danish government wishes to call for tenders for projects internationally so that increased competition can lead to the cheapest possible CO₂ reduction from future large-scale offshore wind farms.

Case

150,000 Households supplied by 80 wind turbines

The largest offshore wind farm in the world to date, at Horns Rev about 40 km west of Esbjerg, began producing electricity for the Danish grid in autumn 2002. This followed a lengthy preparatory phase with economic feasibility studies, environmental monitoring pro-grammes, analyses of cost-efficient foundations, testing of prototype wind turbines on land etc. The project was carried out with Elsam, the electricity production company, as developer, on the basis of an order issued by the then government.

The project consists of 80 2 MW Vestas V80 wind turbines erected on foundations of drilled monopiles. The wind turbines are connected to a transformer substation erected by the electricity system-responsible utility company, Eltra, which has also laid the submarine cable that transports the electricity produced to the Danish electricity system.

The wind turbines are located in an area covering about 20 km² at a distance of 14-20 km from land. Water depths vary between 6 and 14 meters. The turbines, each of which weighs about 450 tons, have been erected with the help of specially constructed jackup vessels. The hubheight of the turbines is 70 meters, with a rotor diameter of 80 meters. Total construction costs amount to approximately DKK 2 billion (about 265 million euros).

Under average wind conditions the offshore wind farm will produce approximately 600 GWh a year, corresponding to electricity consumption in 150,000 households. As a warning of the market-based operating conditions for Danish offshore wind farms, the production does not form part of the electricity production from environmentally friendly production plants that is subject to a purchase obligation. Elsam has, however, obtained a guaranteed price of DKK 0.33/kWh for production that approximately corresponds to the first ten years of operation of an expected lifetime of a minimum of 25 years.

Further information:

Information Officer Jens Nybo Jensen,
Elsam A/S,
Phone: +45 76 22 20 11,
Mobile: +45 51 24 96 89,
E-mail: jnj@elsam.com

[Picture: Here you can see a diagram about existing and approved off-shore capacity (MW)]

[Picture: Here you can see the offshore wind farm at Horns Rev]

The offshore wind farm at Horns Rev is the biggest in the world to date, and further development in the area is possible.

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