Understanding Wind Energy Capacity and Performance: How Often Do Wind Turbines Face Insufficient Wind Conditions?

The operation of wind turbines is often misunderstood in terms of their ability to generate electricity. It’s not as simple as saying there’s 'not enough wind' to power turbines, as the conversion of wind's kinetic energy into electrical energy involves an intricate process.

Conversion of Wind Energy

Wind turbines convert the wind's kinetic energy into rotational and, eventually, electromagnetic energy. However, only a fraction of the input wind energy is converted into useful electrical energy. Generally, more than 50% of the input wind energy ends up as electromagnetic energy. This conversion efficiency increases with wind speed, up to the turbine's design limit, which is typically around 25 m/s (56 mph).

Low Wind Speeds and Electricity Generation

Even at low wind speeds, such as around 5 m/s (11 mph), wind turbines can still produce a few watts of electricity. However, this is far from the turbine’s nominal capacity, which is typically stated based on a continuous air stream of around 13 m/s (47 km/h or 29 mph).

A better question to ask would be, “What percentage of the nominal generating capacity does a wind turbine typically achieve?” Globally, wind turbines generate approximately 25% of their nominal installed capacity, though this varies from country to country.

Capacity Factor and Wind Turbine Performance

Capacity factor provides a rough estimate of a turbine's performance. However, for precise figures, one must measure actual performance over time. For example, Western Europe experienced low wind conditions in February 2013, and in the UK from 2020 to 2021, there were periods with up to 11 days of low wind.

Backup systems like natural gas are essential to support wind energy during low-wind periods. In Germany, 2021 saw a reduction in wind-generated electricity, with the first six months producing just 46.8 terawatt hours, which is over one-quarter less than the 59.4 TWh produced in the first half of 2020. Offshore wind generation also dropped by 16% to 11.7 TWh during the same period.

Investment in Wind Generators

Investors look for locations with consistent wind speeds of at least 10 m/s (22 mph), and some areas have records of days with no or low wind speeds. Denmark, being a leader in wind power, has shared data on these conditions. Ideal locations for wind generators are those with minimal days of insufficient wind and consistent wind speeds that match the turbine’s maximum power output.

Therefore, the question of 'how often are there not enough wind to power wind turbines?' can be answered by looking at specific wind conditions in targeted areas, where wind speeds are consistently high.