Wind power output plummeted in 2010 with intermittent lows

A provocative new analysis of the UK’s wind power has indicated that the resource is considerably more intermittent than previously thought and that pumped storage hydro power cannot adequately be used to compensate for its fluctuations.

The analysis of UK wind generation was conducted with support from John Muir Trust, a UK-based charity dedicated to nature, to examine frequently made claims that the intermittency of wind power is mitigated by the ubiquity of the resource.

The study, which looked at wind energy supplied to the UK National Grid over 2010 and the start of this year, showed that wind energy generation ran at below 20 per cent of its rated capacity for more than half of the period compared to an anticipated average of close to 30 per cent.

The study’s findings for 2009 contrast with assertions that wind turbines generate on average 30 per cent of their rated capacity in a year, though not starkly, but the picture dimmed in 2010 when wind energy output fell further.

The average energy output from wind during the period was 27.18 per cent of metered capacity during 2009, compared with 21.14 per cent in 2010, averaging out at just over 24 per cent in the full period between 2008 and 2010.

The findings of the study point to the intermittency of wind as an energy resource, showing that wind generation was less than ten per cent of installed capacity for one third of the period examined.

Bringing the point home, the analysis found that in one day in late March 2011, the entire wind output for farms with a nameplate capacity of more than 3GW was just 9MW, while the average output from the resource during that month was 22 per cent.

For the equivalent of one in every 12 days examined, wind energy generation was running at less than 2.5 per cent of its full capacity, receding to below 1.25 per cent of full capacity for one day in every month.

The report said that wind output was particularly low at the four highest periods of peak demand in 2010, producing power at between 2.51 per cent and 2.59 per cent of metered capacity. Extremely low instances of wind were indiscriminate of seasons, according to the report, and not simply confined to winter months.

The authors of the report have warned the frequency of falling wind energy generation in the UK indicates that a major reassessment of the capacity credit of wind power is required.

On a more positive note the study found that wind output rose during March 2011 to in excess of 100MW and up to 166MW, but these moments were coupled with short drops in wind power output, indicating the need for a reassessment of the suitability of wind power to stimulate the output fluctuations of thermal power plants.

It also looked at whether pumped storage hydro can be used to fill an energy generation gap during prolonged periods of low wind.

But causing more reason for concern, the study found that the entire pumped storage hydro capacity in the UK can only provide back-up power for up to 22 hours, before the systems run out of water. The country’s pumped storage hydro capacity can provide up to about 2.78GW of power for up to five hours, which drops to just over 1GW before running out of the resource.

Wind power output plummeted in 2010 with intermittent lows