Windsave goes bust revealing the truth about micro wind power

The residential arm of Scottish micro wind generation company Windsave, which supplied roof-mounted wind turbines to former energy minister Brian Wilson, has gone into liquidation.

Hands up those who aren't surprised - even that it took so long.

In 2003 this Scottish company began promoting roof mounted domestic turbines using Photoshopped montages. Despite cries from practitioners in the field -- including this blogger - that the performance figures it was quoting didn’t make any sense - and in fact broke the laws of physics - Brian Wilson, the then UK energy minister, and another Scot, became convinced.

A PR exercise was mounted with his help that succeeded amongst other things in persuading DIY chain B&Q to retail them. In June 2006 their Plug’n’Save system won the title of “Best New Product” at the European Business Awards for the Environment. Hundreds of optimistic householders parted with their cash.

At the beginning of 2009 B&Q finally admitted that they didn’t work and withdrew them from sale in response to many disgruntled owners' angry complaints. They had been told they would be able to generate a good proportion of their electricity and recoup their costs in a few years. Some were lucky to generate a miserable few kilowatt-hours over the entire year.

Real data

The results of a substantial monitoring exercise of real micro-wind turbines in situ both on urban rooftops and free standing in rural areas was published in July 2009 by the Energy Saving Trust and confirmed what the technical experts and those unfortunate householders already knew: that wind speeds in urban areas coupled with the turbulence caused by nearby buildings mean that the speed of 5m/s required for contemporary turbines to operate efficiently is never reached in an urban situation.

To put it bluntly: domestic scale wind turbines only work in the countryside.

And there they work very well: the results of the field monitoring show that “a properly sited and positioned 6kW rated free standing pole mounted turbine with a similar annual performance would be expected to generate approximately 18,000 kWh per annum.” In today’s English money that is £2,340. It represents a very quick payback.

The success of a wind turbine is measured by its load factor and the higher the number the better. The performance of free standing turbines in the survey frequently exceeded the manufacturers’ quoted annual load factors of 17%; the average was 19%, and the best were 30%. By abysmal contrast, “No urban or suburban building mounted sites generated more than 200kWh or £26 per annum, corresponding to load factors of 3% or less.”

No wonder those B&Q customers were upset.

Where micro wind works

Turbines need an uninterrupted wind flow and the higher above the ground the more wind there is. This is why they are commonly mounted on 10m or 25m poles and in exposed places. The same survey by the Energy Saving Trust estimates that in the UK 1.9% of homes are situated in conditions like this and can make use of wind power. That is 455,650 households.

If they all installed 6kW wind turbines than the annual generation from them would be in the order of 3,459GWh. This is the amount of electricity used by twice that number of homes - approximately 870,000, or nearly 1% of the UK is electricity requirements and over 3% of its domestic demand. So they would need to be grid connected - and they could generate an income from their sales. This would then decrease the payback period, especially if feed-in tariffs are available. Without them, the payback period is something like six or seven years under these conditions.

In other words, it’s worth doing in these places and nowhere else. The annual average wind speed needs to be greater than 5 m/s and is preferably measured with an anemometer for 12 months before designing the system, but desktop evaluation can be made first to see if it’s worthwhile doing this by looking at figures from the Met Office. But because local conditions can vary enormously - for example due to thermal updraughts, local topography or sea breezes - there is nothing like real on-site measurement.

Windsave's directors are blaming the planning laws for the fact that they have gone bust. No, gentlemen, it's the laws of physics, something an energy minister ought to be aware of.