Tuesday, November 15, 2005

New wind report blows away myths of proponents

A report that Britain has the best wind resource in Europe has been getting a lot of attention lately. This has in fact long been known and is evident in the higher capacity factor (actual output vs. full capacity) of installed wind turbines: 25% in the U.K. versus 15-20% on the continent.

Rather than looking just at averages, the recent government-commissioned study from Oxford
University's Environmental Change Institute found that Britain is never becalmed. The researchers examined 35 years of meteorological data and found not one hour when the wind wasn't blowing at least 4 m/s somewhere in the island kingdom, that being the wind speed at which most industrial turbines start generating electricity. They also found that the wind is below that speed in more than 90% of the country only 1-2 hours per year. From this, they argue -- and news articles duly echo -- that wind power is not intermittent as opponents claim and is therefore a reliable source of energy.

The report itself (beyond the executive summary), however, distinguishes between intermittency and variability, noting that "it is the variation in output from one hour to the next [let alone one minute to the next] that poses challenges for its integration into electricity networks."

The electricity produced by a wind turbine at 4 m/s is the merest trickle, which the report also explains. So the planned tens of thousands of wind turbines would be justified by proponents because in one region there will always be a trickle of production. Rather than defeating the argument of wind power's intermittency, this study in fact underscores it by emphasizing the need for many widely dispersed wind plants to essentially act as a single small plant.

Even then, as the report also explains, the need for conventional capacity would be minimally reduced, "due to the variability of wind power." In their example, which assumes a 35% capacity factor for wind (despite elsewhere citing the actual 27% long-term average), the addition of 13 GW of wind plant capacity to an 84-GW network could replace only 3 GW of conventional capacity. They also explain that spinning reserve must be added as well to back up the wind, so some of that 3 GW has to remain. Their estimate is a very optimistic 5% of wind capacity, or 0.65 GW in the example, but German grid manager Eon Netz has determined their need for spinning reserve to be at least 50%. Even halving that need by assuming the U.K.'s wind is so much more steady than Germany's would mean that no conventional capacity would actually be displaced.

In addition to the new wind capacity (without any reduction of other capacity, and possibly an increase of conventional capacity for spinning standby), the report describes the need for new and upgraded transmission capacity and the costs of integrating nondispatchable and highly variable wind power.

Thus wind power is an expensive land-intensive intrusion that fails to make a meaningful contribution to our energy needs nor to cleaning up our ongoing energy use.

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