De-Icing Wind Turbines

^{Image courtesy of Vestas}

As my outside thermometer struggles to achieve double-digits on the Fahrenheit scale (around -12^oC) I thought it would be an appropriate time to discuss the new Vestas De-icing System (VDS) for wind turbines. Cold climates often provide the best wind resource, but ice on turbines can reduce electricity production by up to 20%. Ice buildup can also cause unbalanced spinning of the rotor, leading to mechanical failure. In addition to inefficient operation and potential damage to the turbine, ice flying off of the turbine blades can pose a threat to life and property. These factors make de-icing technology a necessity in cold-weather regions.

Vestas developed an innovative de-icing system that combines sensors, databases, and communications. The system can be customized to each specific wind farm location and customer preference. VDS can detect an icing condition, shut down the turbine, and perform the de-icing procedure automatically. Rather than detecting actual ice buildup, the VDS algorithm measures several variables, including temperature, humidity, wind speed, and turbine output. When icing conditions are favorable and measured output levels are lower than predicted, the de-icing procedure is initiated. VDS is even smart enough to determine whether it’s worth shutting down the turbine to perform de-icing. If turbine production is just slightly low because of icing, it may be more economical to just continue running the turbine. On the other hand, if the energy output is low enough, it’s worth shutting it down and de-icing it; the improved efficiency will more than pay back the temporary down time.

Each turbine blade includes a small heating element and fan. The outer third of the blade and most of the blade’s leading edge are heated, since this is where icing is likely to occur. Since these turbines are utility-scale, a small amount of grid power (up to 150 kW) is used to run the heating system. (I know - 150 kW doesn’t sound like a small amount of power, but Vestas makes turbines in the 2 to 8 MW range. It’s all relative.) During de-icing, the turbine is shut down, so there’s no danger of it throwing ice around.

So far, the VDS concept has been successfully tested in Canada and a prototype has been installed in Sweden. The Swedish unit will be tested over the winter. Vestas has received orders for four turbines with VDS to be installed in Austria in 2014.

There are a variety of methods for reducing ice buildup on wind turbines, including heat, water resistant coatings, and controlled blade acceleration/deceleration to shake the ice off. It’ll be interesting to see which method emerges as the optimal technology for keeping our turbines spinning smoothly.

Now I need to throw another log into the wood stove!