The science behind frozen wind turbines – and how to keep them spinning through the winter

Winter is supposed to be the best season for wind power – the winds are stronger, and since air density increases as the temperature drops, more force is pushing on the blades. But winter also comes with a problem: freezing weather. Even light icing can produce enough surface roughness on wind turbine blades to reduce their aerodynamic efficiency, which reduces the amount of power they can produce, as Texas experienced in February. Frequent severe icing can cut a wind farm’s annual energy production by over 20%, costing the industry hundreds of millions of dollars. Power loss isn’t the only problem from icing, either. The uneven way ice forms on blades can create imbalances, causing a turbine’s parts to wear out more quickly. It can also induce vibrations that cause the turbines to shut down. In the case of extreme icing, restarting turbines may not be possible for hours and potentially days.

The solution is obvious: de-ice the blades, or find a way to keep ice from forming in the first place. So far, however, most of the strategies for keeping ice off wind turbines blades come from aviation. And airplane wings and wind turbines are built differently and operate under very different conditions. I am an aerospace and mechanical engineer, and my colleagues and I have been studying wind turbine icing physics over the past 10 years and exploring better solutions for turbine icing protection. Ice isn’t the same everywhere. It may come from precipitation, clouds or frost. It also freezes in different ways in different climates. For example, rime icing, formed when tiny, supercooled water droplets hit the surface, usually occurs in regions with relative dry air and colder temperatures, under 20 F. That’s what we typically see in Iowa and other Midwest states in the winter. Glaze icing is associated with much wetter air and warmer temperatures and is commonly seen on the Northeast coast. This is the worst type of ice for wind turbine blades. It forms complicated ice shapes because of its wet nature, which results in more power loss. It’s also likely what formed in Texas in February 2021 when the cold air from the north collided with the moist air from the Gulf Coast. While the majority of the power shut down by the storm was from natural gas, coal or nuclear, wind turbines also struggled.