The UK's second largest electricity generator has confirmed a near-20% drop in the output of wind energy and a 30% reduction in hydro generation in a shareholder statement.
In an operational update, managers at Scottish and Southern Energy (SSE) revealed a worrying slump in its renewable output.
Analysts say the huge drop is linked to the least windy year the UK has experienced but is seen as worrying as the nation's drive for sustainable, green energy is underpinned by the expansion of wind farms.
The SSE statement confirmed: “The total electricity output from hydro generation was 1,760GWh, a reduction of 30%; total output of wind energy was 1,314GWh, an increase of 13.5%; however, excluding new wind farms, output of wind energy was down by almost 20% on a like-for-like basis.”
The figures support research conducted by the Renewable Energy Foundation (REF) which used provisional January-to-December data to demonstrate the decrease.
Lack of wind is a problem because electricity cannot be stored in large quantities and the utility firms have to generate it instantly to match consumers' demand.
In a statement, the Renewable Energy Foundation (REF), said it is clear that overall, the load factor for 2010 was low in comparison with preceding years, indicating that winds in this year, and particularly in the winter 2009-2010, were themselves relatively low.
It said this finding is consistent with data from Ireland and Northern Ireland which showed output in 2010 was approximately 23.5%, as compared to 31% in the previous year, and the average figure of 32.3% for the years 2002 to 2009.
The REF statement added: “Wind power output is significantly variable and difficult to predict over several timescales, minutes, hours, days, weeks, months, and years.
“Variability over short time scales has been much discussed, and it is now well known that low
wind conditions can prevail at times of peak load over very large areas. For example, at 17.30
on the 7th of December 2010, when the 4th highest United Kingdom load of 60,050 MW was
recorded, the UK wind fleet of approximately 5,200 MW was producing about 300 MW (i.e. it
had a Load Factor of 5.8%).
“One of the largest wind farms in the United Kingdom, the 322 MW Whitelee Wind Farm was producing approximately 5 MW (i.e. Load Factor 1.6%).
“Load factor in other European countries at exactly this time was also low. The Irish wind fleet
was recording a load factor of approximately 18% (261 MW/1,425 MW), Germany 3%
(830MW/25,777 MW), and Denmark 4% (142 MW / 3,500 MW).
“Such figures confirm theoretical arguments that regardless of the size of the wind fleet the
United Kingdom will never be able to reduce its conventional generation fleet below peak load
plus a margin of approximately 10%.”