I received an email this week with a link to an article slating small wind based on the results of a recent test of small turbines in the Netherlands. The performance of these turbines during the test period seems relatively poor from a quick scan. The wind speeds averaged less than 4 m/s according to the records. Nevertheless, the winds are what they are. Even in relatively windy locations, the wind speed at heights below 50 metres above ground can be disappointing.
Who to believe and what can we tell from the results? Small wind energy can work very well in very windy locations. In less windy areas, i.e. most places, the wind speeds at 10 metres above ground can be about 4 m/s. At Dublin Airport, a pretty exposed site close to where around half of the population live, the wind speed is on average 5 m/s. Power output will be a good deal lower than the turbine's nameplate rating. There are several lessons:
Correct siting is very important. The success of a small wind energy site depends on a good understanding of the wind speed at the site. The wind information is often available ; it should be measured if not. Reports show an average wind speed, over the past five years, in Rotterdam of about 4 m/s; the results of the Schoondijke test may have been entirely predictable.
Consumers must have realistic expectations; depending on future energy prices, it may not be the best decision, in purely economic terms, to install a small wind turbine (at current equipment prices). Grid power, if available, may be cheaper, even over many years. Nevertheless, there are other reasons, as with buying a new car, for example, to own a wind turbine.
The success of a small wind energy site also depends on a good understanding of the wind turbine. Every effort must be made to ensure that purchasers understand the likely output from their machines; creating disappointed and frustrated customers does nothing to promote small wind energy.
Wind turbine cost is everything; if these can be made cheaper, then suddenly the economics change quickly. (The same thing happens to the economics when grid power becomes more expensive; in a less constructive way.)
Small wind energy works, but it must be implemented correctly. For anybody interested in small wind, I recommend reading Windpower Workshop by Hugh Piggott or Wind Energy Basics by Paul Gipe. Hugh Piggott's eclectic website contains pretty balanced information if you work through it.