The UK’s Department of Trade and Industry (DTI) has published initial annual performance reports on the UK’s first offshore wind farms, located at North Hoyle and Scroby Sands.

The report reveals that the plants have achieved a load factor of close to 30%, even in the face of a number of technical problems.

North Hoyle, the UK’s first offshore wind farm, was constructed during 2003 and comprises 30 V80 2 MW turbines manufactured and installed by Denmark’s Vestas under a turnkey contract, giving an installed capacity of 60 MW. The plant was installed 6-7 km off north Wales between Rhyl and Prestatyn at a total cost of £81 million ($154 million), equating to a cost of £1.35 million/MW ($2.5 million/MW).

The 60 MW Scroby Sands facility was constructed some 3 km off the Norfolk coast near Great Yarmouth at a total cost of £66.8 million ($127 million), which equates to a cost £1.11 million/MW ($2 million/MW) and £2.23 million/turbine ($4.2 million). The 30 V80 turbines were also from Vestas.

Both Scroby Sands and North Hoyle recorded availability of 84% or more, however an average capacity factor of 28.9% was reported at Scroby Sands, a result of poor availability in the latter months of 2005 which impacted on performance. A major cause for concern has been the gearbox bearings with a design fault prompting 27 generator side intermediate speed shaft bearings and 12 high speed shaft bearings to be replaced to date. Four generators have also been replaced with an alternative design.

Jason Scagell, director of E.ON UK Renewables, commented: “We were very happy with Scroby’s performance in the first half of the year, particularly as the operation was in its infancy, but the second half was less satisfactory due to a number of defects with the gearboxes and the generators. That meant we had to carry out an extensive programme of modifications but, despite that, the wind farm still generated 153GWh, which is around 90% of our forecast annual output.”

Although North Hoyle has the same turbines its capacity factor was somewhat higher at 36%, just shy of its budgeted capacity factor of 37.1%.

The report also details minimal impact on bird and sea life, a good safety record and claims valuable lessons have been learned for the future development of a key industry.

Each project received £10 million ($19 million) in government support and under the terms of these grants the developers are required to report back to the DTI for the initial three years of operation.

As well as a good technical performance, the wind farms have also received a positive response from the public with recent surveys indicating improved perception and a rise in support once the wind farm was in place.

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