Monthly Archives: June 2012

Jun 30 2012

Wind Energy – The European Top Producers

Most European countries are now investing into wind energy. Only very few of them may be considered as “old” players in the field. Among those which used wind power already back in 1990 were Spain, Denmark, the Netherlands, Belgium and Sweden.

Unfortunately, the data quality of some countries in the beginning stages was rather low so that we confine ourselves to comparing the average output in MWh/MW installed over the period 2000-2010. Taking this as a reference we get the following ranking among those countries which have a relatively long tradition of using wind energy:

Netherlands 2273 MWh/MW (low: 2077 high: 2473)

Spain 2233 MWh/MW (low: 1921 high: 2621)

Sweden 2080 MWh/MW (low: 1784 high: 2625)

Denmark 2028 MWh/MW (low: 1760 high: 2293)

Belgium 1929 MWh/MW (low: 1022 high: 2750)

Germany 1586 MWh/MW (low: 1392 high: 1785)

As indicated these are average values over the first decade of the 21st century. Needless to say that these mean values are rather virtual figures since in reality the availability of the driving force behind the facilities, i.e. the wind, is rather varying by nature. By the way, these figures have been calculated using our specific model which enables us to smooth out distortions due to capacity changes during each year.

The graphics below shows the evolution of wind power in those countries since 1990. The missing data points for some countries refer to the fact that the quality of those data does not fulfil our standards. Thus, we omitted them rather than doing guesswork.

Specific output of European wind farms in MWh per MW installed capacity.

It is quite remarkable that the mean performance between different countries can vary a lot. The most striking feature, however, is that Germany is seriously underperforming when compared to the leading producers in Europe. This may well indicate that selecting the location of a wind farm may not always have been the best choice. Other countries have apparently done a better job.

Jun 22 2012

Wind Energy – The Case of Denmark

Denmark is one of the leading producers of wind energy in the world. This is true not in absolute, but in relative terms. Being a small country Denmark simply does not have the capacity to compete with larger countries such as Spain or Germany when it comes to total output. The share of wind power in the electricity grid was 20.1 % in 2010. Portugal and Spain, the numbers two and three in the ranking, had shares of 17.0 and 14.6 %, respectively.

In a previous post we examined the specific performance of German wind farms. Now we will compare those findings with a similar investigation for Denmark. Fig. 1 shows the specific output of Danish wind energy in MWh/MW between 1990 and 2010. As usual we have applied our model to smooth out distortions caused by the building up of new capacity over a year. The remaining fluctuations are due to varying wind availability.

Fig. 1 Specific output of Danish wind farms in MWh/MW installed.

Fig. 2 gives a direct comparison between Germany and Denmark for the period 2001 till 2010. One striking feature of this picure is that Danish performance is consistently and considerably higher than the German one. On the averge, Danish facilities have an almost 29 % higher output in MWh/MW installed. Thus, their efficiency and productivity are much better than the ones of their southern neighbour.

Fig. 2 Specific output of wind farms in Germany and Denmark.

The average performance of German facilities was 1571 MWh/MW whereas Danish wind farms produced some 2026 MWh per MW installed. One of the reasons for this discrepancy may lie in the fact that Denmark has a higher share of offshore wind farms which tend to have a higher efficiency than the ones based on land.

Jun 8 2012

The Solar PV Index

Last week we investigated the performance of German wind farms which, after a massive surge in capacity over the past two decades, are now in a position to contribute substantially to the electricity mix (7.6 % in 2011 according to the national statistical office). However, as we have seen, this comes at a price. The contribution shows large and largely unpredictable variations which have a destabilising effect on the grid.

Another source of renewable energy which has gained a lot of support recently is solar PV. Like wind PV has soared dramatically  in the past years. Nevertheless, its overall contribution to the energy mix is very low (3.1 % of total power generation in 2011).  Moreover, like electricity produced by wind mills, PV is a factor of instability to the grid. The sun is not shining uniformly throughout the day. Passing clouds may severly impact the output of solar cells causing fluctuations in the supply chain.

Impressive growth rates in both capacity and production, are inclined to mislead the observer. A more thorough consideration of the situation of solar PV, however, will have to look at the output per MW installed. That is the quantity which allows us to assess the investment in that energy source.

Like in the case of wind farms, the expected productivity of solar PV depends heavily on the location. And thus, we should not be surprised to see huge differences between various installations. Here, however, we look at the global picture. This point of view is even more justified since Germany decided to abolish all nuclear plants by 2022 which, in turn, means a higher burden for all other sources of energy. As the country, simultaneously, is highly committed to reducing its carbon footprint renewables are bound to play a much larger role in the future.

Fig. 1 Solar PV in Germany. Average output per MW installed capacity and solar irradiation.

Fig. 1 shows the average PV output (P/C) in MWh/MW (blue curve) while the red curve refers to the average solar irradiation (SI) in kWh/sqm (r.h.s. scale). The performance per MW installed has been adjusted by using a specific model in order to account for extra capacity added over the course of a year. The two curves appear to follow a similar trend. Nevertheless, their correlation is quite weak. An increase in irradiation may even coincide with a downturn in specific production. Thus, on a global scale, more sunshine does not necessarily mean more solar energy produced. Over the period in question we get an average PV output of 868.8 MWh per MW installed with a spread ranging from less than 700 MWh/MW to 1157 MWh/MW.

Fig. 2 Solar PV in Germany. Deviation from mean output per MW installed (P/C) and solar irradiation (SI) in %.

Fig. 2 displays the deviations of both specific output P/C and solar irradiation SI in % over the period in question. This picture confirms the conclusions drawn from Fig. 1. The variations in PV performance are not necessarily reflected in the respective variations of solar irradiation. They may even go in opposite directions. Remarkably, the fluctuations in SI are much larger than the ones in P/C, at least on an annual scale.

As in the case of wind more capacity does not always mean more output. The availability of sunshine comes in as a crucial factor which may be decisive for the performance of a particular facility. And, like the wind, this quantity may vary a lot over the years as can be inferred from the green curve.

There is one more message hidden in Fig. 2. One may argue that due to the relatively small scale of solar PV in terms of the entire German power production, the variations in P/C do not fully reflect the varying nature of solar irradiation. In other words, one might expect them to become even larger as the number of PV installations increases. This in turn implies that the fluctuations in the power grid may be even disrupting than today.

In view of this it is of utmost importance to develop storage facilities for the solar energy produced. This should in fact be a priority.