Of all the ocean energies, marine winds have known the most important development during the last decades. They are a “renewable” which was easy to harness and which required only relatively modest capital investments. Sites are abundant, and a judicious choice permits to dampen the objections voiced because of the noise they cause. Marine wind “farms” have been implanted in numerous locations particularly in Northern and Western Europe. However environmental-linked objections are being raised, spurring engineers to devise new approaches.
Most of the ocean energies require engineering developments to be harnessed and produce electricity, except the marine winds and the tides. The WECS, as they were designated a quarter of a century ago, made first a timid appearance, but they were spurred on by ever climbing prices of fossil fuels and the need to reduce carbon dioxide emanations. The technical problems were rather rapidly solved and the first energy captors were erected on land, mountaintops, away from human habitat. The towering structures were not free from environmental impact, particularly noise and aesthetics.
Pylones have become taller and turbines larger. Everyone applauded the harnessing of marine winds but nobody wanted the pylones in his “backyard”. There is also concern that the machines may cause hecatombs of birds particularly during migration seasons An answer to noise, migrating birds routes, aesthetics has perhaps been found, at least in partim: siting of the marine wind turbines on floating—and movable—platforms. The design is ready and the construction on the books.
It did not stem the determination of some countries to replace by wind, centrals burning coal, oil, or nuclear products. Locations on the coast were favored and even better, offshore sites. From installations involving a few wind turbines, builders passed to sites where large numbers of turbines were installed. Utgrunden in the Baltic was inaugurated as one of the first “wind farms”. The proliferation of marine wind turbines occurred especially in Northern and Western Europe: Sweden, Denmark, Germany, Scotland, The Netherlands, to name a few countries. The success so impressed the Americans that they talked about placing turbines on Georges Bank off the coast of Maine, but it looks like that it is off the coast of Texas that a wind farm will be implanted.
Aeolian energy has been on the foreground for quite some time. The windmill of yesteryear is the undisputed ancestor of today’s aero-generator. Wind turbines can of course be installed inland, near-shore or even at sea. Twenty years ago proponents of wind power were derided as a new breed of Don Quichottes. Today even combinations of wind energy parks with coastal defense are being considered. Some thought is being given on capturing offshore winds energy through wind turbines placed along an artificial reef implanted as a recreational beach protection device against waves.
The high population concentration in European countries, their trend to move towards the coasts and the ensuing conurbation restrict the available area. Yet, various studies established that offshore wind resources are far higher than those on land. As water depth increases only slowly with distance from shore along many European coasts this favors mounting of offshore turbines.
Thirteen countries participated in the 2-year assessment project “Concerted Action on Offshore Wind Energy in Europe” (CA-OWEE); at its issue the view was held that by 2011 the wind parks installed in the coastal seas of Europe might be able to furnish the energy needed by the Union. Some interest has been also voiced in the United States East Coast regions and in Tasmania. All aspects of the problem were considered, including grid integration, but particular focusing was on economics. On-shore-placed turbines are definitely less expensive, so only multimegawatts centrals would be cost-effective. Higher initial expenses are due to foundations, but also for maintenance and operation. The lion’s share of costing is for the turbine (on-shore 71%, off-shore at least 50%), grid connections (on-shore
7.5 %, off-shore 18%) and foundations (on-shore 5.5%, off-shore about 16%). Land turbines cost considerably less than those used with marine installations. The moral of the story is that to reduce costs, the larger the turbine, the better; with rotor diameters of about 70 m a North Sea sited wind-turbine can produce annually between five and six million kilowatt/hour. There being no neighbors to complain of the noise, windmills at sea can safely turn 10-20 % faster than on land.
A park was built eight years ago on the IJsselmeer, in The Netherlands; a second park was inaugurated in 1996 (Medemblik and Dronten). Denmark built parks in 1991 and 1995, but the most recent is at Middelgrunden and is only two years old, and is the largest producer with 89,000 MWh/year. Sweden’s installations date from 1990, 1997-1998, and the newest completed recently. The Utgrun – den (marine wind-) park (2000) is Sweden’s largest with 38,000 MWh/year. The only British facility in operation is located near Blyth and is a relatively small producer with 12,000 MWh/year. Interestingly the Danish Middelgrunden facility is owned jointly by a 3,000+ members wind-energy cooperative and a local electricity utility.
The development of offshore wind farms may however be slowed as the market is liberalized; the cost of the kilowatt must be reasonable at production time or a project’s viability will unavoidably be put in jeopardy. It was thus pointed out that Europe may be left in the odd position of disposing of an environment-friendly and abundant energy resource, supported by public and governments alike, but without the market framework to foster its development.
Nine offshore wind farms are planned: five by Denmark (two in 20 02, then one each in 2003, 2004 and 2006), one by France (in 2002 near Brest), a near-shore one by The Netherlands (2003), another by Belgium (2003), and one by Ireland on Arklow Bank. Plans in Belgium include, as marine and fluvial installations an additional farm near Zeebrugge and another one along the Scheldt-Rhine canal, north of Antwerp.
A Danish company’s subsidiary—Vestas Mediterranean East—will sell some 47 wind turbines (850 kW) to Sicily for three wind projects to Asja Ambiente Italia; the total installed capacity will reach 40 MW and operations started early in 2007. They are dwarfed by the 52 turbine wind farm of Hadyard Hills (South Ayrshire). Thus far 171 MW of electricity generating wind turbines came on line in 2006, providing current for 80,000 household and over 665 MW were added to normal electricity production.
Danish and Dutch projects would produce a kWh for $0.049-0.067 compared to on-shore prices of $0.027-0.07. Production costs vary of course with the speed of the prevailing winds, turbine size, and plant dimensions, while technological refinements allow expecting one kWh to cost between $0.04 and 4.6. The Dutch estimate that on their sector of the continental shelf they could erect sufficient wind turbines to satisfy, by 2030 180% of the country’s electricity needs. This figure may have to be scaled down, however, as a study conducted in 1995 on behalf of the European Union; indeed, there are several sites where turbines cannot be placed, for instance because depths are too great or the distance to shore is. The same rather simplistic calculation ventured of the possibility that the British could capture at sea four times their electricity needs, the Irish fourteen and the Danes even seventeen.
At Zeebrugge, Belgium, a small park has been installed on the sea harbor breakwaters. Production amounts to 4.8 MW, a drop in the bucket for a country needing 15,000 MZ. Belgian authorities gave recently the green light for positioning fifty air turbines on an artificial island at 15 km (8.10 nautical miles) off-shore from the city-resort of Knokke-Heist. The contractor is Seanergy. The 1,000 MW produced are to provide electricity to 85,000 families. Construction is scheduled to start in 2003 and placing into service in 2004. Notwithstanding reports from similar projects concluding to benign influence on the marine environment, an impact study will be conducted. The installation is deemed to have a life span of 20 years and the contractors are held, by the contract, to remove all wastes. However, claiming aesthetic pollution (view cluttering from shore), the city of Knokke-Heist filed an objection with the Council of State to block the construction, even though, to minimize their visibility, the turbines will be painted gray to match the North Sea waters’ local color. Coming from a city that has, for many years, notoriously failed to provide adequate water purification facilities, one may raise a somewhat surprised
eyebrow__ Granted, the marine wind parks are not exactly attractive, yet they are
not really objectionable, the more so that they are visible at best as specks on the horizon.
The endless procedures came finally to a close in 2007 and the wind-park will be built. The delay has had one advantage: technology has progressed and the latest and largest turbines will be installed.
Tun0 Knob, on the Kattegat (Denmark) towers 40 m above the million kilograms concrete foundation placed at a depth of 3-5 m. Its wings spread about 15 m. But, on the positive side, the sea-turbines are 150% effective compared to their land-placed cousins.
And objections are raised in The Netherlands also, claiming deterioration of the polders’ landscape. Yet, the Dutch researchers, buttressed by loud Greenpeace endorsement, estimated already at the end of 1998 that 10,000 MW would be extracted from the North Sea by 2030, or 40% of the current electricity consumption. The government promised that by 2020 the energy used in the country would be generated by sustainable sources.
Wind power from the ocean has also been considered for providing the energy needed by pumps and desalination plants.
Marine winds are providing energy to 24 turbines in Zeebrugge; they have a total capacity of 5.2 MW. An isolated one in Middelkerke is rated at 660 kW, and five turbines, placed along the Baldwin (Boudewijn) Canal in Bruges have a total capacity of 3 MW.
The German DEWI (Deutsches Windenergie-Institut) conducted an in-depth study which concluded in 2000 that Belgium, The Netherlands, Denmark, Germany, and Great Britain could cover their entire 923 million MWh needs (1999 estimate) from offshore wind-energy. This would, however, require placing 100,000 2-MW turbines in North Sea sites.
Amongst plans often mentioned for Belgium are a wind-farm of 50 2-MW turbines off-shore Wenduine, upgrading of the Zeebrugge “windmills” and addition of two more, the new total of 26 would bring production up from 5.2 to 13 MW.
Such projects, understandably, distress tourism-conscious resort municipalities such as Knokke-Heist and Wenduine-Klemskerke-De Haan.