Nuon -- a Dutch power company which has formed the NoordZeewind consortium together with energy giant Shell -- had otherwise considered dropping out of the EUR 200 million project when the government announced its new environmental electricity production subsidy. In the renewables support package, a new EUR 0.029/kWh tax on green power sales will be compensated for by an offshore wind production incentive of EUR 0.068/kWh (Windpower Monthly, January 2003) paid on top of the sales price. NoordZeewind had originally said it needed an incentive of least EUR 0.077/kWh to cover the financial risks of the development, which is set to be built off the Dutch coast at Egmond aan Zee. "Our initial reaction was prompted by shock," says Nuon's David Uitdenbogaard. "On further analysis and after extensive talks with the economics ministry we have concluded that the project is in fact commercially feasible," he adds.
The permit application process has continued on schedule. Since July, Nuon and Shell have conducted seabed surveys and wind measurements at the site, where water depths range from 15-20 metres. Work is also underway on the environmental impact report required for a marine construction permit, expected in early 2004, says the consortium. Construction by marine building concern Ballast Nedam would then start that year.
Nuon's resolve to continue with the NSW was welcomed by members of the cross-industry Dutch Offshore Wind Energy Converter (DOWEC) program, which installed a prototype 2.75 MW unit produced by NEG Micon at the test facilities of the Dutch Energy Research Centre (ECN) in late February. The NSW will be equipped with 36 of these variable speed, pitch controlled units. The DOWEC development group consists of NEG Micon, ECN, blade manufacturer LM Glasfiber, marine and dredging contractors Van Oord ACZ, Technical University Delft, and Ballast Nedam. For NEG Micon the onshore test is intended mainly to test maintenance ideas and other issues. At its present site, the turbine is expected to produce 8.5 million kWh a year.
"At sea we are working towards 95% availability," says the ECN's Ben Hendriks. "This model assumes the continual presence of a supply ship and that most failures will be able to be dealt with by the supply ship." For a 100 MW station such as the NSW, continual service by a supply vessel is not economically realistic and availability rates are more likely to be around 90%, he says. Important factors include the likelihood of damage to cables from ships. "For the NSW we have calculated the risk at one break per 100 kilometres annually," he says. The NSW is just eight to ten kilometres off the coast.
ECN is using the prototype to try out load measurement programs and a new French-sourced glass fibre system for measuring load forces on the rotors. With a 92 metre rotor the risk of lightning strikes makes the usual copper wire measurement system too dangerous, says Hendriks. In the longer term, ECN is developing a 6 MW machine for use in a 500 MW offshore wind farm. Whether the unit will actually be produced by the development group is uncertain, but initial results of the study will be published at this month's offshore wind conference in Naples, with further results announced at the European Wind Energy Association conference in June.