Onshore wind turbines taller and more efficient

© Hollandse Hoogte / Flip Franssen
According to Statistics Netherlands (CBS), Dutch wind turbines collectively generated 7.6 billion kilowatt-hours (kWh) of electricity in 2015, i.e. an increase by more than 30 percent relative to 2014. In 2015, the Netherlands had 139 offshore and more than 2,000 onshore wind turbines and they are becoming taller and more efficient.

Last year, 6 percent of total Dutch electricity consumption was generated by wind turbines, matching the annual electricity consumption of 2.5 million households. Three-quarters of electricity used in the Netherlands is generated by burning natural gas and coal.

Third offshore wind farm

The overall capacity of Dutch wind farms has grown from 0.7 to 3.4 gigawatts (GW) between 2002 and 2015. The onshore capacity was more than 3 GW by the end of 2015, an increase by 0.4 GW compared to the end of 2014. Last year, a third offshore wind farm was completed taking offshore capacity to 0.4 GW. The first offshore turbines were installed in 2006.

Onshore wind turbines taller

In recent years, onshore wind turbines have become taller. Between 2002 and 2008 the number of turbines with a tower height (where the rotor blades are turning) between 51 and 70 m increased the most. In the ensuing period, the overall capacity generated by wind turbines increased mainly because new turbines taller than 70 m were built. Taller turbines are more powerful, so to reach the same capacity, fewer turbines are needed. After 2011, nearly three-quarters of the capacity increase was generated by wind turbines of 95 m or more.

Tallest one-third of wind turbines generate 60 percent of energy

As taller turbines catch more wind, they also generate more electricity, because they usually have bigger rotor blades. One-third of onshore wind turbines has a tower height of 71 m or more. Collectively, they account for more than 60 percent of wind energy generated in the Netherlands last year. Lower wind turbines (two-thirds of the total) account for slightly under 40 percent of wind energy.

Onshore wind turbines: number and capacity

Taller turbines more efficient

The rotor diameter, or swept area, determines the amount of electricity turbines can generate. Taller turbines usually have larger rotors making them more efficient. In 2015, the generated energy per m² of swept area averaged 1,000 kWh for turbines of 95 m or taller and less than 600 kWh for turbines of 30 m or lower. These values vary over the year, depending on the annual amount of wind.