Measure the wind before you install a turbine
Posted by Cathy Debenham on 5 August 2009 at 9:08 am
Product and installation standards for domestic wind turbines are needed, as are improved wind speed prediction and better site assessments. These are some of the key conclusions of the Energy Saving Trust's microwind research published in July.
On measuring the wind speed, EST recommends that, where practical, people thinking of getting a wind turbine should use an anemometer for at least three months to find out their average wind speed. Its field trials found that the NOABL database, which is often used to determine a site's potential, over-estimates the wind speed at many sites. It is particularly likely to over-estimate in urban and suburban locations, as it doesn't consider the impact of local obstructions such as trees and buildings.
It also found that a number of manufacturers' power curves (which indicate expected performance of the turbine) are inaccurate or incorrect. That, combined with no one common method by which power curves are calculated, makes it difficult for potential customers to compare the performance of different products. EST advises people treat power curves with caution until new standards are in place. These have been developed by the Microgeneration Certification Scheme (MCS) and are expected to be in place by the end of 2009.
EST results confirmed Encraft's Warwick Wind Trials findings last year that building mounted turbines are not effective in urban or suburban areas. None of those tested generated more than 200kWh (or £26) a year. Even in a good site returns were low. The best performer was a 1.5kW turbine in Scotland which generated 975kWh (£127) of electricity. EST concluded that building mounted turbines work best when they have an adequate, unobstructed wind resource and are sited on the gable end of a building, above the ridge line.
The best performing free standing sites were always remote, rural locations - usually individual dwellings near the coast or on on exposed land such as moors. In these cases the amount of electricity generated tended to be in line with the manufacturer's predictions. Those sited in built up areas did not perform so well, generally because the wind strength was less than anticipated.
Using the field trial results EST has calculated that there are likely to be 455,650 domestic properties in the UK which are suitable for wind generation. If they all installed turbines it could generate 3.1 per cent of domestic energy demand.
Photo by brewbooks
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