Posts Tagged ‘Encraft’

As flagged up by Tom at XCO2e, the Warwick wind trial final report (pdf) is out and the results aren’t good. Keeping in mind that the trials included only sub-2kW turbines, there are some important things to take away from the report:

  1. We consultants must be cautious – it’s not enough to take an average wind speed or a predicted output from the London Plan and think it has any relationship to reality. It’s becoming even clearer that a lot of site specific analysis is required before considering micro-wind.
  2. NOABL isn’t applicable in the built environment – the study found that the NOABL database consistently overestimated wind speeds by around 16x relative to measured data. The study recommends scaling factors for NOABL data that bring the predictions in line with measured data (these are based on a limited sampling period so should be treated with caution – but it’s a good start).
  3. Manufacturers can’t be trusted – using measured wind speeds and manufacturers’ power curves overestimated power output by 170% – 340%. As the report points out, there are other reasons why this might be: accuracy of monitoring equipment, response times, etc. But check out the graphs on page 30 of the report showing sampled power output vs. manufacturers’ Cp curves. OUCH!
  4. Micro-wind in the built environment may be a bad application of a good technology.

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According to the Guardian, most domestic turbines are only generating 5-10% of the manufacturers’ claims. Dramatic stuff but maybe not a huge surprise. I think there’s been a growing realisation among professionals in the built environment that small wind in built up areas rarely works.

But it’s important to remember that in most cases this poor performance is not the fault of the turbines themselves; they’ve just been placed badly by designers and over-hyped by manufacturers.

Located somewhere with decent wind (on the back of a sailboat, on top of a tall mast on a windy hill, etc) they’ll do the job. But bolted to the chimney of a Victorian semi in Surbiton? Almost definitely not. Even Ashenden House, a 13-storey tower in Elephant and Castle, hasn’t proved to be a salubrious place for turbines.

So blame the engineers and architects, blame manufacturers for short-sightedly over-hyping their own products, but don’t blame the turbines. It would be a mistake if we were to dismiss the technology as a result. Small wind still has an important role to play, even if that role is more limited than many people hoped.

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