The figure of 23.5% average capacity factor for Irish windfarms seems low compared to British figures in the report below.  Does anyone have a source for average annaula capacity factors for wind energy either at national or windfarm level?  I am anxious to substantiate the frequently heard assertion that "Ireland has the best wind resource in Europe".
British Wind Association PDF

The report makes much of the fact that a recent estimate of the average capacity factor of wind in Germany in 2003 was 15% and that the average capacity factor in the UK was 24%. It fails to acknowledge that:

• Average wind speeds in Germany are significantly lower than those in the UK, and
  
• 2003 was a low wind year. The average capacity factor of UK wind has varied from the 2003 low to 31% in 19988. It is quite incorrect to say (REF, para 4), "this figure [30%] has never been achieved"
  
• Assessments of the economics of generating plant invariably use load factors that are realistic for the particular plant, but may well be higher than national averages. The load factor of UK nuclear plant, for example, varied between 72.6% and 80.4% during the 10 years from 1994 to 2003 and yet the Royal Academy of Engineering report cited by the REF suggests that ".. availabilities exceeding 90% should be achievable"
  
• Several wind farm operators have reported capacity factors significantly greater than 30%. Scottish Power, for example, expects its best sites to have capacity factors between 35% and 40%9. npower renewables has reported long-term capacity factors between 36% and 40% for five of their wind farms10 each. The output from the npower wind farms at times of peak electricity demand was above average, which contradicts claims in the REF report that wind power is not available at times of peak demand
  
• The increasing number of developments in Scotland, where sites are known to be very windy, and in offshore waters is likely to increase UK average capacity factors

Index of Frank's Diaries