Turbine age

Here we look at the age distribution of all decommissioned turbines and for how long turbines survive after being installed.

The average age of the 3442 decommissioned turbines is 17.9 years. The longest serving turbine was in service for 40.07 years and the shortest was in service for just 24 hours.

The figure blow shows a histogram of the ages. Most turbines are in service for 15-20 years with a few lasting as long as 40 years! Note that these numbers represent decommissioned turbines and thus are not representative for the expected lifetime of currently active turbines.

The first turbine registered in Denmark was commissioned on December 15, 1977 and was in service for 25 years. The oldest turbine registered in Denmark was commissioned on February 14, 1980 and was in service for 40 years! Long lifetimes in both cases.

The figure below shows the survival rate of turbines for each year of installation. Each line starts at the number of turbines that were installed during that year and decreases over time as those turbines are decommissioned. The lines are colored by decade of installation. We see that most of the turbines installed in the late 80's were decommissioned rapidly during 2002 (orange lines). Many of the turbines from the early 90's have been decommissioned between 2000 and 2015, while most of the turbines from the late 90's are still active. Turbines that were installed in 2000 or later are mostly still active about 20 years later.

Tip: Double-click a decade in the legend on the left in the figure below for increased legibility.

Size of turbines: height and rotor radius

We saw in the first section that the capacity per turbine has increased over time. But how large are the turbines and how has their size increased over time?

The oldest turbine registered in Denmark was commissioned on February 14, 1980. It had a capacity of 22 kW, a hub height of 18 meters and a rotor diameter of 10 meters. In comparison the largest current turbine registered in Denmark was commissioned on December 9, 2021. It has a capacity of 14,000 kW, a hub height of 160 meters and a rotor diameter of 122 meters!

In the figure below we show the development of average hub height and rotor radius over time. For each year we show the average values of all turbines installed in that year. The hub height is the distance from the base of the turbine to the center of the rotor.

The numbers seem suspiciously low for the two turbines installed in 1977, but have since grown steadily. The two dips around 2007 and 2015 coincide with periods of low installation of offshore turbines, which tend to be significantly larger than onshore turbines.

For a detailed study of the development of turbine sizes and power rating, see this recent paper.

Annual capacity factors

A capacity factor, in some industries called load factor, is:

The ratio of the net electricity generated, for the time considered, to the energy that could have been generated at continuous full-power operation during the same period. (source)

In simple terms: an annual capacity factor of X% means a turbine is generating electricity at an average of X% of its capacity every hour of the year.

The capacity factor of a wind turbine is an important metric for investors: higher capacity factor means higher power output and higher return on investment. For a thorough study of power output and declining capacity factors over a turbine's lifetime, see this open source research article.

In this section there are four figures:

1. Annual power production for onshore and offshore turbines
2. Average annual capacity factor for onshore and offshore turbines
3. Annual onshore capacity factors split by year of installation and colored by decade of installation
4. Annual offshore capacity factors split by year of installation and colored by decade of installation

In all figures turbines are included for every whole year they have been producing. That means a turbine installed in one year is counted from the following year onwards and excluded for the year that it's decommissioned.

The first two figures show the annual power production and average capacity factor for onshore and offshore turbines separately. The capacity factor for onshore turbines have been fairly stable between 20-30% for several decades. For offshore turbines there was a significant jump in 2002 and since then it's been above 40% on average. Offshore wind turbines are expected to have higher capacity factors than onshore wind turbines for two main reasons: 1) typical wind speeds are higher at sea than on land (no trees and buildings to slow it down), and 2) they reach higher in the atmosphere where the wind tends to be more stable. In this figure it's not possible to distinguish the contribution to the average capacity factor from aging and new turbines. More on that in the following two figures.

The two figures below show the annual average capacity factor split by year of installation. In an attempt to make it easier to get an overview, each line is colored by the decade of installation. A general result for both figures is that more recently installed turbines initially have a higher capacity factor. For almost all of the lines shown the capacity factor decreases slowly over time. That is consistent with this open source research article (same as linked above), which, among other results, found that "performance decline with age is seen in all farms and all generations of turbines" and "onshore wind farm output falls 16% a decade, possibly due to availability and wear".

The numbers look suspicious for the onshore turbines installed in 1977 and 1978. All we can say is that's how the numbers were reported. Only whole years of production are included. So turbines installed throughout 2020 will appear in 2022 when production data for all of 2021 is reported.

Tip: Double-click a decade in the legend in the figures below for increased legibility.

Higher resolution capacity factors

In this section we explore average capacity factors in higher temporal resolution using production data from the ENTSO-E Transparency Platform together with the time series of installed capacity per day from the first section above. These figures are updated less frequently.

The four figures in this section show:

1. Annual average capacity factor
2. Monthly average capacity factor
3. Daily average capacity factor
4. Hourly average capacity factor

Not surprisingly the variation of the capacity factor increases with increasing temporal resolution. At an hourly resolution we see hours of close to zero production and hours at close to 90% capacity. This is a very different picture than the flat pattern of 20-30% for annual capacity factors. It highlights the challenge of keeping the electricity system in balance with increasing shares of variable renewable energy sources.

Tip: Remember that the figures are interactive, so you can zoom in on periods that interest you.

Wind power share of total power generation

Here we look into how much electricity is generated from wind power and how much it contributes to the total power generation.

The first of the three figures below shows how much power is produced from wind power per year from 6.6 TWh in 2005 to now more than 16 TWh.

The second figure shows the wind power share of the total annual electricity generation. In 2005 it was just below 20% and now it's well above 50%. The third figure shows the share of wind power on a monthly basis. Here we see a cyclic variation with lows during summer and highs during winter.

The data for these figures is updated less frequently than the turbine database.

Municipality statistics: distances to and number of turbines

In the table below you can compare between municipalities (every column can be sorted). We have calculated shortest, longest and average distance from turbines to addresses within each municipality. We also included number of turbines, installed capacity and number of inhabitants from here. Very small turbines with a capacity below 100 kW have been excluded as these are usually placed on a property.

The distance from a turbine to nearest house has to be at least four times the total height (hub height + rotor radius) as described here. Note that some of the distances in the table might not be accurate because not all addresses in the address database correspond to houses. The results have not been validated.

There are currently 21 municipalities with no turbines: Lyngby-Taarbæk, Furesø, Ballerup, Fredensborg, Rødovre, Frederiksberg, Vallensbæk, Rudersdal, Helsingør, Dragør, Gladsaxe, Herlev, Furesø, Egedal, Hørsholm, Brøndby, Ishøj, Tårnby, Glostrup, Gentofte, and Albertslund.