Are wind turbines afraid of the cold? Will frozen wind turbine blades derive any ramifications? The wind storm that raged Texas last month and resulted in the most severe power outage from the impact inflicted on wind and thermal power plants had prompted the society to ponder on the possible consequences of cold weather on wind turbines and the reasons behind. Scientists have recently replied subtly on the issue that frozen wind turbine blades will reduce the rotation speed of wind turbines, which drastically lowers the power generation volume by 80%.

A further observation on the sites of wind farms in the world also shows that several of them are located in areas with cold climate and substantial differences in temperature like Northern Europe. The coldest wind farm in the world is perhaps the Ross Island Wind Farm (RIFW) located in Crater Hill, Antarctica that was co-established by New Zealand and US teams, which possesses a capacity of 0.99MW under a low temperature environment measuring at an average of minus tens of degrees, and is able to provide 11% electricity for the Scott Base of New Zealand and the McMurdo Station of the US since 2010.

Hence, it is evident that wind farms are able to operate in a location as cold as the Antarctica, though the particular area is one of the few ice-free zones in Ross Island. So, the question is, how will icing create challenges for the wind turbines? According to the field study conducted by Aerospace Professor Martin C. Jischke of the Iowa State University and Dr. Hui Hu of the Aircraft Icing Physics and Anti-/De-icing Technology Laboratory (Iowa State University), 30cm of accumulated ice can be found on the tip of wind turbine blades under a humid and cold environment that will not only damage the aerodynamic design initially adopted for wind turbine blades, but also impact the balance of wind turbines.

Field observation is a research method that relies on perceptual proof. However, it is relatively complicated, since it does not come with research permissions, and suppliers are not willing to share and announce the performance on wind power. Hence, the research team started to work with the North China Electric Power University through the National Science Foundation (NSF), and unfolded the research on a 50MW wind farm at the mountainous areas in eastern China.

This anonymous wind farm is situated on a ridge, and is formed with 34 units of wind turbines measuring at approximately 1.5MW each, for which the research team believes are about the same quantity that US wind farms adopt. In addition, the close proximity of the wind farm to the East China Sea derives relatively abundance of water vapor and an icing condition that is similar to that of the Gulf of Mexico, and Texas will start to snow once the cold air mass introduced by cold front is in contact with the water vapor of the Gulf of Mexico. In comparison, the winter of Iowa is comparatively dry.

This research environment adopted by the team of the Iowa State University is significantly humid and cold due to the high altitude, as well as being situated at the top of the hill, and the close proximity to the sea, where the research team captures the changes in the wind turbines that measure at 50m in height within 30 hours under environmental conditions such as frozen rain, freezing drizzle, wet snow, and rime ice.

The photos of the drones indicate that the entire wind turbine blades are covered with ice, and layers of accumulated ice can be seen from the lateral side of the blade, especially with the tip of the blade, where an accumulation of 30cm is discovered. The research team then compared it with an environment with no icing through the control and data collection system built within the wind turbines, and pointed out that despite strong winds, the significant layers of icing on the blades will decrease the rotation speed of the wind turbines, and even result in frequent downtimes that will induce 80% of power generation loss.

Although each wind farm possesses different conditions, and that this particular result may not be replicated for other wind farms, it does manifest the impact of icing on wind turbines, and that a more efficient de-icing method will have to be invented for the wind turbine blades to rotate perpetually.

 (Cover photo source: Iowa State University)