Full disclosure – part of my business activity is developing subsea cables for use in wind and wave farms, so I do have a vested interest in offshore wind succeeding.

Fact is that it isn’t delivering. Here in the UK and Northern Europe, wind and wave infrastructure spending is going gangbusters – but because of government subsidies. It makes sense in the UK as the North Sea oil output declines and they have limited other energy resources but in a country with the resources of the US, the equation just doesn’t really work.

The coldest periods tend to be during intervals of high pressure when there is the most calm and often at late at night when the high demand industrial activities are inactive, so to some degree, the energy demand and windfarm generation curves are inversely correlated. Interesting reading, excerpts below:

New analysis of wind energy supplied to the UK National Grid in recent years has shown that wind farms produce significantly less electricity than had been thought, and that they cause more problems for the Grid than had been believed.

The report (28-page PDF/944 KB) was commissioned by conservation charity the John Muir Trust and carried out by consulting engineer Stuart Young. It measured electricity actually metered as being delivered to the National Grid.

In general it tends to be assumed that a wind farm will generate an average of 30 per cent of its maximum capacity over time. However the new study shows that this is actually untrue, with the turbines measured by the Grid turning in performances which were significantly worse:

Average output from wind was 27.18% of metered capacity in 2009, 21.14% in 2010, and 24.08% between November 2008 and December 2010 inclusive.

In general, then, one should assume that a wind farm will generate no more than 25 per cent of maximum capacity over time (and indeed this seems set to get worse as new super-large turbines come into service). Even over a year this will be up or down by a few per cent, making planning more difficult.

It gets worse, too, as wind power frequently drops to almost nothing. It tends to do this quite often just when demand is at its early-evening peak:

At each of the four highest peak demands of 2010 wind output was low being respectively 4.72%, 5.51%, 2.59% and 2.51% of capacity at peak demand.

Thus when wind farmers have a lot of power they will actually pay to get it onto the grid if necessary in order to obtain the lucrative ROCs which provide most of their revenue, forcing all non-renewable providers out of the market. If the wind is blowing hard and demand is low, there may nonetheless be just too much wind electricity for the grid to use, and this may happen quite often:

The incidence of high wind and low demand can occur at any time of year. As connected wind capacity increases there will come a point when no more thermal plant can be constrained off to accommodate wind power. In the illustrated 30GW connected wind capacity model [as planned for by the UK government at the moment] this scenario occurs 78 times, or three times a month on average. This indicates the requirement for a major reassessment of how much wind capacity can be tolerated by the Grid.

Drill, Baby, Drill.