New data from Germany's Fraunhofer Institute reinforces worries about the variability of wind and solar power in Germany, giving a detailed picture of the first 40 weeks of 2012 from Jan. 1 to Oct. 7.
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The data illustrates the vulnerability of renewables when power demand surges on cold winter days when wind and solar are both weak at the same time. This kind of variability calls for substantial backup baseload fossil fuel generation and additional smart grid balancing.
The precise cost of this balancing is still unclear as European countries ramp up wind and solar capacity with the aim of reaching 2020 renewables targets.
Ideally, wind and solar in Europe are intended complement each other seasonally, with summer peaks for solar power balancing a lull in wind power and the reverse holding true in the winter.
Northern European anti-cyclonic weather in the winter months, bringing clear skies, low winds, cold temperatures and weak sunlight all while power demand is high reveals a potential perfect storm of circumstances leading to low power generation from wind and solar.
The week starting February 6, 2012 recorded the second lowest combined German wind and solar power generation of the 40 weeks studied, at 0.77 TWh, Fraunhofer Institute data shows.
The fact that French power demand hit at an all-time record of 102 GW during this same week highlights the extent to which variability will continue to be a problem for renewables, even with ever smarter grids.
German conventional power production from fossil fuels and nuclear also reached 2012 high on the evening of February 8, at 65.9 GW, with gas production in particular at 22.4 GW, very close to total gas-fired capacity of 24 GW.
Further analysis of the Fraunhofer data, at the hourly and daily level, shows wind power to be highly unpredictable at any time of the year, recording minimum generation of 1 per cent or less of installed capacity in each of the first nine months of the year.