Wind turbines wearing down faster than expected, study asserts

Special to E&E • Posted: Monday, January 7, 2013

Off-shore wind

How long will it last? A wind turbine planted in the Thames Estuary. Photo courtesy of Flickr.

Wind turbines installed in Denmark and the United Kingdom are wearing down faster than manufacturers expected, a new study claims.

The study is billed as the largest of its kind and looked at 3,000 onshore and offshore turbines in operation between 2000 and 2011. But it was published by the U.K.-based Renewable Energy Foundation (REF), a think tank that has campaigned against wind farms, which prompted the wind industry to accuse it of bias.

The study found that the average load factor, or the percentage of electricity a turbine produces versus maximum capacity, of U.K. onshore wind turbines declined from a peak of 24 percent in the first year of operation to 15 percent in the 10th year and 11 percent by year 15.

“Adjusted for age and wind availability, the overall performance of wind farms in the U.K. has deteriorated markedly since the beginning of the century,” said study author Gordon Hughes, an economist at Edinburgh University and a former energy adviser to the World Bank. “In addition, larger wind farms have systematically worse performance than smaller wind farms.”

The study didn’t investigate the reason for the decrease in the average load factor but speculated that it may have had something to do with the best sites for wind being used first or with mechanical breakdowns of the machines. Or perhaps developers found it hard to maintain the quality of the investments as they raced to add more capacity.

The study estimated that routine wear and tear will more than double the cost of electricity being produced by these wind farms in the next decade. If proved correct, that would not be good news for turbine manufacturers, operators and governments providing subsidies to the wind industry. They expect these machines to function effectively for 20 to 25 years.

Biggest turbine maker declines comment

Vestas, the world’s largest maker of wind turbines, said its machines are designed to operate optimally for 20 years and declined to comment on this study. Robert Norris, spokesman for RenewableUK, a British trade association for the wind, wave and tidal energy industries, said the study raises questions because it doesn’t seem to match the reports of wind farm operators themselves and because the author said his work had only been reviewed by “anonymous” peers.

“Our guys run these things for 20 years without a drop in performance,” Norris said. “Usually a study like this would be peer reviewed by a reputable, named scientist. REF campaigns very vigorously against wind energy. Their agenda is to undermine wind energy.”

In Denmark, the load factor decline is less steep, from a peak of 22 percent at installation to 18 percent by year 15, the study found. This may be because Danish turbines tended to be smaller and perhaps better maintained than the ones installed in Britain, author Hughes said.

“Whatever the reasons, the deterioration in initial performance means that the expected returns from the expansion in wind capacity, both for investors and in terms of the reduction in CO2 emissions, have been falling without a concomitant decrease in the private and social costs that are borne by customers and the general public,” Hughes said. “Clearly this is unsatisfactory at best, and it suggests that the benefits claimed for current policies cannot be taken at face value.”

The decline in the output of offshore wind farms was even more dramatic, according to Hughes. The load factor for offshore turbines he studied in Denmark fell from 39 percent initially to 15 percent 10 years after installation. But the study did say that it had little data on the Danish offshore turbines, so a few outliers may have skewed the result.

Industry groups question peer review

If the study is correct, older turbines will need to be replaced more quickly than the industry estimates, while more wind capacity than previously calculated will need to be installed if the U.K. government wants to meet its renewable energy targets by 2020.

The extra cost would be passed on to consumers, which already pay about £1 billion per year in a subsidy that is added to electricity bills.

“Investors expecting a return on their investment over 20 to 25 years will be disappointed,” said John Constable, the director of REF. “Policymakers expecting wind farms built before 2010 to be contributing towards CO2 targets in 2020 or later must allow for the likelihood that the total investment required to meet these targets will be much larger than previous forecasts have suggested. The lifetime cost per unit of electricity generated by wind power will be considerably higher than official estimates.”

If investors still build wind farms despite these findings, that means subsidies are too generous and should be reduced, Hughes said.

“Given that the author and publisher have a history of attacking wind energy and the fact that they do not say who peer reviewed the study, perhaps one should not take the study too seriously,” said Julian Scola, a spokesman for the European Wind Energy Association.