Wind Generation is low on the Coldest Winter Days

While for solar generation the seasonal variations are obvious, for wind the seasonal variations are less obvious and are different in different regions of Europe.

This page first demonstrates that wind electricity generation in winter in most European countries is significantly lower on the coldest half of days compared to the warmest half of day by up to nearly 50%. Then, the raw wind speed data is presented showing the raw wind speed is also lower on the cold days than the warm days. The feature of wind turbine operations with a cut-in speed of around 13 km/hr below which no electricity is generated show this lack of wind is the cause of the low generation rather than any effect of ice on the turbines.

Wind Generation Data

In many countries in NW Europe the wind generation is higher in winter than in summer but during the winter there is a strong temperature variation with the wind generation being significantly lower, on average, during cold days than on warm days. The table below shows the situation in the winter months (Dec, Jan, Feb) from Jan 2018 to Dec 2022. The data for wind generation and temperature is averaged over one day and the divided into the sets of days (cold and warm) with average country temperature less than the median (value where half days are below and half days above) and days greater than the median. The table below shows the ratio of wind generation of the set of cold day to the set of warm days for six countries. It can be seen that for France the wind generation, on average, is nearly half on cold days compared to warm days.

Ratio of wind generation for the coldest and warmest days for six countries.

Variations of wind generation with temperature in winter for France, Belgium, Poland, Germany, Netherlands and United Kingdom as indicated. The temperature is the average over many weather stations distributed around the country. The scatter plot, on the left, shows for each plot in the winter, from Jan 2018 to Dec 2022, the wind generation versus  country average temperature for each winter day (Dec, Jan, Feb). The histograms, on the right, show the distribution of wind generation for cold days (T < median T) in blue and for warm days (T > Median T) in orange.

Weather Station Wind Speed Data

To understand the origin of the strong correlation between wind electricity generation, the wind speed data from the weather stations is analysed. In the analysis both the daily average wind speed and the daily average temperature at the same weather station are compared for European countries. The correlation plots are shown for a few example countries in the figure below.

Wind speed measurements compared to temperature at individual weather stations in Germany, Sweden and the United Kingdom. The data is for winters days (Dec, Jan, Feb) for 5 winters from Dec 2017 to Feb 2022. For the scatter plots one point is the daily average wind speed and temperature for 34, 21, 32 weather stations for each country respectively. The weather stations are on land and chosen to be roughly uniformly distributed around the area of the country at elevations < 750m. The histograms separated and compare the wind speed data for each of the points for cold days with temperatures less than the country median and warm days greater than the median.

These three example plots show strong correlations and separation between cold and warm days in wind speed data which are similar to the wind electricity generation data shown above.

The reason why the electricity generation data is so different between cold and warm days is due to the functioning of the wind turbines which have a cut-in in speed below which the turbines do not turn and produce zero electricity.

Operational range of a typical wind turbine with a cut-in speed of 13 km/hr below which the turbine produces zero electricity and the rated speed of 50 km/sec at which the wind turbine generates with the full rated power of the name-plate capacity.

In the figure below this operational range of a wind turbine is compared to the winter wind speed in the three examples countries. The cut-in speed is close to the median wind speed in these examples and so a large part of the wind spectrum  is wasted and produces no electricity.

Winter wind speed distribution for winter over Germany, Sweden and the United Kingdom compared to the region (in red ) where a typical wind turbine generates electricity.