UK's largest wind turbine trial yields poor resultWind turbines suited to fewer sites than predicted

09 July 2009

A domestic wind turbine

It's important to check if a domestic wind turbine is suitable for where you live

The largest field test of domestic wind turbines in the UK has found that fewer locations are suitable for home installed wind turbines than previously predicted - with wind turbines in urban areas yielding particularly poor results.

None of the building or roof mounted wind turbines installed in urban or suburban areas generated more than 200kWh, or £26 of electricity a year during the test, and in some cases used more electricity than they produced.

Based on the study and with current technology, it is estimated that around 450,000 UK householders would benefit from installing a domestic small scale wind turbine - generating enough electricity to power 825,000 homes a year.

The report from the Energy Saving Trust (EST), called 'Location Location Location', stresses the need to check if an area is appropriate for a wind turbine before installing one.

Wind turbines tested

The EST field trial tested the actual in-situ performance of 57 domestic wind turbine installations over a year, including 38 building mounted and 19 free standing turbines.

Whilst the building mounted turbines performed badly in urban areas, rural installations fared better, achieving 5% of their maximum electricity generating capacity - known as load factor - compared to the best urban turbine performance of below 3%. 10% load factors are often quoted by the industry.

According to the report: 'Building mounted turbines monitored in the field trial were primarily installed in urban and suburban locations that were shown to have inadequate wind speeds. The poor location of these turbines has significantly impacted the measured performance of such turbines.'

Free standing wind turbines

Results from free standing wind turbines were more positive, and the best performing free standing wind turbine sites - in remote rural locations, 'usually individual dwellings near the coast or on exposed land such as moors' - exceeded expectations with load factors of over 30%, and more closely agreed with manufacturer predictions.

Again, free standing wind turbines in built up areas did not perform as well due to insufficient wind speeds.

The report also noted that it was currently difficult to directly compare different types of wind turbine and the introduction of 'harmonised standards would help eliminate potential confusion for the consumer.'

Wind speed and location

The EST concluded that 'domestic wind turbines do work and can generate energy and carbon savings - but only when installed properly and sited in a location with an unobstructed and appropriate wind resource.' Installations in Scotland performed consistently better than elsewhere in the country.

Local wind speed was cited as a key factor in determining if a wind turbine was a suitable investment, and the EST recommends homeowners install an anemometer for at least three months in the same position intended for the wind turbine to get an accurate measure of wind speed before deciding to install one.

The report also said that the government's NOABL database, used to predict local wind speeds, 'has been shown to overestimate the wind speed at many sites, especially those in urban and suburban locations', mainly because it doesn't take into account obstructions such as neighbouring buildings or trees. 

The Carbon Trust's wind speed estimator was found to be a more realistic measure.

Customer feedback

A corresponding survey of wind turbine owners indicated that 85% installed a wind turbine in order to cut electricity bills, but it was difficult to judge if this had been achieved due to rising energy prices. Of those surveyed, 49% believed they had seen a reduction in their bills and 35% said they hadn't.

In terms of performance, 59% found their wind turbines reliable, 32% thought their turbine was noisy and 29% said the turbine caused vibrations.

Wind turbine advice

Dr Fiona Cochrane, Which? senior policy adviser said: 'We welcome today's report from the Energy Saving Trust into domestic wind turbines and support its call for the introduction of improved product and installation standards. Consumers should only consider installing a wind turbine if they live in an area with a suitable average wind speed - usually a remote rural location.

'The field tests show that many urban wind turbines performed badly because they were positioned poorly in an area with insufficient wind resource. Don't invest in a wind turbine until you've done your research and are sure it's right for you and your home - and do look too at the range of options and benefits for improving your home's energy efficiency.'

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