Monthly record of wind power generation

After a winter characterized by a calmed atmosphere, during which the Iberian Peninsula has been affected by a constant high pressure blocking, April has brought a substantial change. These changes on the atmospheric patterns have yielded into a more continuous passage of low pressure systems, generating frequent unstable weather conditions over the Peninsula characterized by a considerable increase on the precipitations, temperatures below average and an important increase of the mean wind speed all over the territory.    

As a consequence, wind energy production during last month of April has reached a new record, having exceeded the figure of 5000GWh (more in particular 5357GWh) and it has covered around the 25,7% of the electric demand of the country. In the same manner, during last month of April, and more in particular on the 18th of April at 16:41PM, a historical instantaneous power production maximum was hit with a total of 16636MW (see Figure 1). Meanwhile, the electricity demand coverage with wind power reached a new ceiling with 61,06% on the 19th of April at 1:37AM.

Figure 1: Production in MW during the 28th of April 2012 (Source: Red Eléctrica Española)

All records topped during this month are the result of the combination of two key factors: on the one hand, the consecutive increase of installed power in Spain (it increased in more than 5% during 2011), and on the other, the favorable meteorological conditions previously mentioned. It is this second factor on which we are going to focus with more detail.

As it was described on the first paragraph, the prevailing atmospheric pattern throughout the whole winter has been the high pressure blocking, that is, an Azores Anticyclone much more strengthened than usual towards the west of the Iberian Peninsula and located much more to the north from what is typical for this time of the year as it can be checked on Figure 2. This situation has caused an almost total absence of low pressure systems crossing the Iberian Peninsula which bring precipitations and stronger winds. In fact, 2011-2012 winter has set a record as one of the driest in all historical series and, in particular, the driest in the city of Madrid since data began to be recorded 153 years ago.  

In Figure 2, the continuous blocking situation can be observed, as well as the dramatic reduction on the surface wind speed all along the European Atlantic coast, being especially significant over the west and northwest of the Iberian Peninsula, where the anomalies reached values between 1 and 2m/s. This wind speed reduction affected more significantly on the wind farms energy production of Galicia and Castilla y León, which by the end of 2011 added up to almost 40% of the Spanish installed wind power.

Figure 2: Sea level pressure and surface wind speed anomalies from January to March on 2012 in relation to the mean value of the series 1981-2010 (Source: NCEP/NCAR Reanalysis from the NOAA)

Nonetheless, it is worth remarking that synoptic situation during February with a permanent high pressure on central Europe and a very strong cold low pressure system over the Mediterranean Sea channeling strong north and northeast winds, allowed reaching power production levels extremely high during this month. Thus, all wind farms located at the Northeast of the Iberian Península noticed a significant increase on their energy production given the wind speed positive anomalies of 1 to 3m/s (see Figure 3). In fact, wind energy production during February reached 4884GWh.   

Figure 3: Surface wind speed anomalies during February 2012 in relation to the mean value of the series 1981-2010 (Source: NCEP/NCAR Reanalysis from the NOAA)

On Figure 4, the previously described configuration can be observed for the 4th of February. During these first days of the month, wind gusts topped up to 90 to 100km/h over many areas of the Ebro Valley and extended areas of Cataluña.

Figure 4: Sea level pressure and geopotential height at 500mb prediction for the 4th of February at 7AM (Source: www.meteociel.fr)

During April, the atmospheric panorama turned the other way around. The dominating high pressure pattern throughout the whole winter moved further to the west and tended to weaken in relation to previous months. This new situation led to a considerable increase of number of low pressure systems crossing the national territory. Thus, in Figure 5, a very clear pressure negative anomaly can be detected over the western side of Europe. As it can be seen, this change in the pattern opened the door to moderate westerly winds which affected homogeneously the whole Iberian Peninsula, registering positive surface wind speed anomalies between 0.5 to 1.5m/s, thus setting the monthly wind energy record.    

Figure 5: Sea level pressure and surface wind speed anomalies on April 2012 in relation to the mean value of the series 1981-2010 (Source: NCEP/NCAR Reanalysis from the NOAA)

As a representative example of the prevailing wind regime, Figure 6 shows the synoptic situation of April 18th, when strong westerly winds dominated the atmospheric situation (this is given by the fact that isobars were very close to each other, and the closer they get, the stronger is the pressure gradient and the more intense the winds are).

Figure 6: Sea level pressure and geopotential height at 500mb prediction for the 4th of February at 20 PM (Source: www.meteociel.fr)