How wind and PV complement each other

From January to June 2012, data published on the EEX web site show that, if well balanced, PV and wind production can complement each other along the seasons, leading to an easier to manage increasing contribution of variable but predictable renewable energy sources. A guest article by French expert Bernard Chabot.

From January to June 2012, the average wind contribution amounted to 9.52 %; PV, 6.62 % of the total 218 TWh produced in this first half of 2012. Combined wind and PV penetration rate in the same period was 16.1 %. Maximum wind production came in February (11.1 %), PV, in May (12.3 %); their combined production was then 21 %. The minimum combined production in January was 11.1%, a much less windy month than December 2011 and February 2012. Figure 1 shows the 2012 monthly electricity production from wind, PV and conventional power plants larger than 100 MW.

Figure 1: monthly electricity production from wind, PV and conventional power plants > 100 MW.

Total production from those three types of power plant is used here to define specific monthly penetration rates of wind and PV shown in Figure 2.

Figure 2: share of electricity production from wind, PV and conventional power plants > 100 MW.

From those two figures, one can verify that wind and PV production complement each other, but that in order to flatten their total production in cold months, the relative contribution of wind power, and hence its relative installed capacity, should be increased.

Figure 3: increase of the monthly sum of wind, PV and [wind + PV] production in the first half of 2012

Figures 4 and 5 show the absolute and relative daily production of wind, PV and larger than 100 MW conventional power plants in June 2012.

The decrease of total production on weekends is clearly visible. One can see that the variability of PV production is smaller than of wind power.

Figure 4: daily electricity production on June 2012.

The maximum wind power daily penetration rate (22.7 %) came on Sunday June 9; for PV, the maximum (17.12 %) was on Saturday, June 30. For the [wind + PV] total, the maximum penetration rate was more than one third at 33.66 % on Saturday, June 9 (20.41 % wind and 13.25 % PV).  Here, there is also a “smoothing effect” by combining wind and PV, a very interesting result to facilitate a large increase of the renewable energy part on the grid. 

Figure 5: share of wind and PV production in June 2012.

Figure 6 summarizes the sum of monthly production from wind, PV and [wind + PV]. A simple extrapolation by a factor of 2 would lead to a total 2012 production of more than 70 TWh (42 TWh from wind and 28 from PV). Figure 6 gives an example of hourly penetration rates in June 2012.

The maximum hourly PV penetration rate was around 37 % on June 25 around noon. The wind maximum penetration rate was around 33 % in the night of June 24th. The maximum one for [wind + PV] was 53 % on June 9 around noon (27.5 % PV and 25.5 % wind). This combined rate was higher than 30 % half the days of June 2012.

Figure 6: hourly penetration rate of wind, PV and [wind + PV] in June 2012

This analysis confirms the important and increasing impact that wind and PV have already on the power production in Germany. It shows also how important it is to analyze the combination between those two variable renewable technologies as their balanced development can lead both to a complementary production along the seasons and a “smoothing effect” on their maximum combined instantaneous production. Those two factors will facilitate their increase share in the electricity mix in Germany already decided within the frame of the European directive on renewables and within the ongoing German energy transition.

Historical renewable energy installed capacities and electricity productions are well documented in Germany, and a recent article showed their rapid increase up to the end of 2011, particularly since the German Renewable Energy Act was passed. (Bernard Chabot/Craig Morris).