xOffshore wind works. Latest operating data from two offshore wind power stations in Denmark -- the 165.6 MW Nysted facility and the 23 MW Samsø plant -- demonstrate that the technology is living up to expectations and delivering electricity effectively. The capacity factor at Nysted in 2004 was a shade under 40%, about 2% below projections. The capacity factor at Samsø was 36%. These are high levels of effectiveness compared with wind plant on average sites on land and demonstrate the greater wind resource at sea. Both Nysted and Samsø are equipped with Bonus 2.3 MW turbines and were installed in 2003.
xOffshore wind also works over time. A project of 11 Bonus 450 kW turbines installed in Danish waters in the Baltic Sea in 1991 is still going strong. Between 2000 and 2004, each machine at Vindeby was generating close to its target 1000 MWh every year. Also the Danish Tunø plant of Vestas 500 kW turbines, installed in 1995 about four kilometres off the east coast of Jutland, has performed well, logging a capacity factor of 31% between 1996 and 2003.
xAs with all technology, particularly when it is new, offshore wind has had its problems. Failure of major components at two other Danish facilities, the 160 MW Horns Reef station in the North Sea and the 40 MW Middelgrund project off Copenhagen, have been well publicised. But few of the technology failures, if any, can be traced to peculiarly "offshore" problems. None of them represent a fundamental spoke-in-the-wheel for the concept of offshore wind.
xNearly all the problems appear to be associated with failures, somewhere along the line, to provide some components according to specification. At Horns Rev it seems the insulation thickness on transformer windings was inadequate and protection of the transformers from salt laden air was not good enough (Windpower Monthly, March 2004). Problems with transformers are also plaguing Middelgrund (page 21). At Horns Reef the original transformers from ABB were replaced with equipment mainly supplied by Siemens. At Middelgrund, it is Siemens transformers that problems are occurring with.
xThe salt environment is likely to expose weaknesses that may not occur onshore, or earlier than they would have occurred. There is no evidence of fundamental design failures -- or any reason why components cannot be made to function just as well offshore as on land. The tendency is to view offshore winds as hostile, but that hostility is almost entirely manifested in the corrosive properties of salt-laden air. Protecting wind turbines from its ingress is not particularly difficult. The electrics of cars arguably have far worse thrown at them from the salt-laden muck that covers many roads in winter -- and they survive. Offshore, turbulence levels and wind shear are lower than onshore. That means lower dynamic loads. Extreme winds are also mostly lower than those likely to be found on Scottish hilltops or at the Tararua wind farm in New Zealand. It adds up to less strain on equipment, not more.
xxIndeed, the current generation of offshore wind turbines are not specifically designed for offshore use, according to their manufacturers, but "marinised" to withstand the salt climate. Technical chief at Vestas, Lars Budtz, says that in general Vestas makes standard wind turbines. Its offshore turbines are onshore models with maritime features, in much the same way that Vestas adapts standard turbines to high or low temperature climates for use on land, he says. Customers for offshore turbines, however, may have specific demands for what they want built into a turbine, which Vestas complies with, says Budtz. Palle Nørgaard at Siemens Power Generation (owner of the former Bonus), says his company adopts the same approach.
xSo while machines of 3 MW and more are classified as "offshore turbines," even by their manufacturers, the classification is apparently related to sheer size and the likelihood that such large machines will not be employed on land in large numbers, rather than a specifically different design concept. Vestas has a 5 MW machine on the drawing board and is testing a 4.2 MW in northern Denmark, although this turbine no longer appears in its machine listings. At the same site, Bonus is testing a 3.6 MW machine. A series of other contenders for the offshore market are also testing prototypes (table 2).
xxWhile the technology is giving no just cause for serious alarm, the cost of offshore wind is coming in higher than expected. A projection by the UK's Department of Trade industry, made in November 2002 based on wind industry estimates, is way off mark compared with a cost breakdown made only a year later (table 1). The DTI projection considerably underestimated the cost of foundations and of "other" items. These are development expenses (securing of consents, preparation of environmental impact assessment, and geological surveys), preliminary management works (including insurance and finance costs), wind farm monitoring, and the cost associated with lack of access due to poor weather conditions.
xWind measurements alone can cost up to EUR 1.5 million and construction delays considerably more. Low "interest during construction" charges are an advantage of onshore wind, but a three month delay to an offshore project can increase costs by around EUR 20/kW installed. Moreover, as has been painfully demonstrated at Horns Reef, the cost of rectifying technology problems offshore are much higher than onshore.
xCosts should come down (Windpower Monthly, January 2005), but there are stumbling blocks. First, the seriously large wind turbines expected to make a significant difference to total costs are either still on the drawing board or no further than prototype testing. Larger machines mean fewer of them in each wind station, which will lower the total cost of foundations, electrical work and at least some of those "other" costs. Presuming that prototypes will need at least two years of operational testing, if not more, wind turbines larger than 3 MW (and only Vestas is today offering one of that size commercially) will not be on the market for offshore use until 2007, at the earliest.
xSecond, the slow pace of offshore wind development using today's technology -- with projects two and three years behind their original schedule -- is creating a vicious circle of inaction. The sluggish rate of progress means that the reduction of costs that comes with experience -- "learning by doing" -- is not being realised. And because costs are not coming down as projected, investors are waiting until they do.
xDenmark, once again, may break the logjam. Government tenders are out for two, 200 MW wind plant, extensions of the existing Horns Reef and Nysted plant (Windpower Monthly, March 2005). Using the experience gained at the earlier wind farms and assuming existing cable links to shore can be used, prices should come down.