The micro-wind industry has reacted with defiance to trial results published on Tuesday that showed building-mounted wind turbines performing well below suppliers’ claims

Despite some surprise at the poor results, for the most part the industry has insisted that the trials simply showed what was already known.

Small wind manager at the British Wind Energy Association (BWEA), Alex Murley, said: “What is not surprising is that poor sites will yield poor results.”

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The Warwick Wind Trials, carried out by engineering consultancy Encraft, found that wind turbines in a variety of sites performed, on average, at 5-10% the level claimed by manufacturers.

Mr Murley continued: “The results show that turbines need to be placed in environments that offer good wind speeds. The UK is the windiest country in Europe and there are thousands of such sites, many of which have been utilised to good effect and offer owners of small wind systems savings on their electricity bills, and an opportunity to export surplus energy to the grid.”

Likewise, David Sharman of Ampair, a micro-wind turbine company that took part in the trials, said that the results don’t reveal anything new.

“We’re not surprised at the results at all, we think they’re very representative of urban gird connected micro-wind,” he said. “If there is no wind, then there will be no wind resource.”

“We’re very happy with Ampair’s performance, and we’re please that we had the highest annual power output, the highest capacity factor, and the most honest power curve,” he added.

Data

Micro-wind turbine company Quiet Revolution, which had no part in the trials, criticised the report’s methodology.

Stephen Crosher, design director at Quiet Revolution, said: “Many of the turbines used in the trial have been installed in unsuitable locations, with trees or buildings masking wind from dominant wind directions. It is no surprise that the results are poor.”

He added: “The turbines are also installed very close to the ground within the ground boundary layer where much of the power from the wind has been removed by trees.”

Mr Crosher went on to question the accuracy of the results, saying: “In some cases, the anemometer was installed downwind of the turbine, which invalidates the results. The anemometers used were of low quality. Average the data over long time periods, and their accuracy is questionable.”

He continued: “We went to Warwick shortly after the trial was set up and our view of the data presented at that time was not statistically meaningful and did not even distinguish between the rated output of the turbines concerned. In our view the trial is without meaning and does not represent good practice for siting or installation of wind turbines in any way.”

Marketing

But the report’s most controversial accusation was of “aggressive and over-optimistic” marketing by micro-wind turbine companies which Encraft’s managing director said had lead to customers being “exploited”.

The BWEA has flatly denied that micro-wind companies had mis-marketed their products. Speaking to New Energy Focus yesterday, Mr Murley said: “I don’t accept the claim that the wind industry has been marketing products unethically. The industry has developed robust standards over the past few years, and different products can be compared on that basis.”

“This serves to safeguard the validity of manufacturers’ claims and outlines the importance of site location,” Mr Murley continued.

He added: “I’d also call from consumers to make better use of these standards on the BWEA website.”

However, Mr Sharman, who is managing director of Ampair, admitted that the study’s conclusions could not be ignored, saying: “It is obvious that some companies have been guilty of over-marketing”.

“However, the results of this trial have brought the consequences home to some companies, who have learnt and have changed their behaviour. We’ve seen that already.”

For this reason, continued Mr Sharman, the criticisms outlined in the Warwick Wind Trials report are not likely to damage the wind industry significantly.

The BWEA’s Mr Murley defended the wind industry’s reputation, saying: “The overwhelming majority of small wind system installations are a success in terms of commercial viability and we have seen annual sector growth of 80%, projected to carry on into 2009 and 2010.

“The Warwick trials should not be interpreted as demonstrating that wind is not viable. We know that it is, and the experience of thousands of UK users bears this out.”

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