With wind turbines constantly being exposed to the elements, one must wonder how they fare in extreme cold. After all, wind power is common in cold northern countries like Denmark, Sweden, and Canada. Cold air is also denser than warm air, which provides more energy, so installing wind farms in cold climates definitely has its benefits. But icy weather can take a toll on wind turbines and can even become a safety hazard.
Wind Turbines absolutely can freeze. Ice can form on the rotor and nacelle in extremely cold weather. But turbines in cold climates are built to operate in temperatures well below freezing, while turbines in warm climates may be unprepared for unusual cold snaps.
What Happens When Wind Turbines Freeze?
In cold weather, wind turbines can accumulate ice and snow on the exterior. This alters the aerodynamics and lowers the turbine’s efficiency. The ice alters the flow of air around the blade, reducing lift and creating more drag. The ice also adds extra weight to the turbine, making it harder to rotate and throwing the turbine off balance. Icy rotors might have unnatural vibrations and cause long-term damage to the turbine’s blades and internal components. Overall, icy turbines generate less power, which is especially bad in the wintertime, when people need as much energy as they can get.
Turbines that are already structurally unsound pose a larger risk in icy conditions. Turbine blades that have microcracks, or tiny fractures on the surface, can accumulate moisture within the blade shell. This causes delamination, where the plastic laminate starts to peel. In cold weather, this moisture freezes, causing the cracks to expand further and reducing the lifetime of the blades.
The ice can affect electronics and machinery in the turbine too. Oil becomes less viscous in low temperatures, meaning the bearings and gearbox won’t be well lubricated. Ice can also form on the electronics, causing short circuits and reduced functionality.
Icy turbines can also be dangerous. Chunks of ice have been known to fall off frozen turbines, which can potentially kill or injure people and animals directly underneath. If they’re still rotating, icy wind turbines can even launch chunks into the distance, creating dangerous icy projectiles. Wind turbine blades can be over 45 meters long, so even though they seem to rotate slowly, the tip speed can reach over 150 miles per hour. Frozen chunks of ice can be launched several hundred meters into the distance by a spinning blade.
So what do wind companies do when their turbines are frozen? They simply shut them down. Operating frozen wind turbines costs more, can damage the components, and can put people at risk of serious injury or death. Workers must de-ice the turbines before they can be turned on again. Sometimes, workers must carry out the de-icing by hand. Other times, de-icing agents are sprayed on the turbines via helicopter. Either way, it’s hard work.
But with so many wind farms in cold climates, why isn’t there a permanent remedy to solve the problem of frozen wind turbines? As it turns out, wind companies actually have solutions that allow their wind turbines to operate smoothly in icy weather.
Wind Turbines in Cold Climates
Wind turbines in places like Canada, Norway, and the northern reaches of the US are equipped to handle cold climates. Wind companies have created several tools that help them detect icy turbines and prevent ice build-up before it happens. Most wind turbines in high latitudes are made to withstand temperatures of up to -40 degrees F.
Wind turbines in frigid climates are usually equipped with cold-weather packages to ensure their operation in icy weather. This may consist of internal heaters to prevent the components like the yaw system, battery, gearbox, and generator from freezing over. They also employ water and ice-resistant coating to prevent the exterior, especially the blades, from icing over.
Lubricants like oil are especially vulnerable to cold weather, so special oils are used to make sure that the lubricant remains vicious in below-freezing temperatures. This keeps the gearbox and generator functioning smoothly when temperatures begin to go south. This is similar to the way your car may need a special type of motor oil in the wintertime.
Some companies have designed specialized blade materials and configurations to prevent the rotors from freezing. A Swedish company called Skellefteå Kraft uses heated carbon fiber blades on their wind turbines in the Arctic Circle. The blades are heated by an internal mechanism that circulates hot air through the blades.
Big wind companies like GE and Vestas regularly use these cold weather packages for their turbines. While they cost more, the money is well worth it. Cold air is dense and provides more energy for the same volume and airspeed compared to warmer air.
The best tool to prevent icy turbines is intelligence. Wind companies partner with meteorologists and tap into local weather forecasts to predict when they may need to employ their de-icing systems. They use complex algorithms to analyze air temperature, humidity, and wind speeds to predict icing events. This allows them to only use their cold-weather gear when necessary, saving them time, labor, and most importantly, money. One ice-detection system developed by Finnish company Wicetect is connected to an internal heater, which quickly warms the blades to a controlled temperature when ice is detected.
Texas Turbine Fiasco
These cold-weather packages are costly, so they’re only reserved for wind turbines in verifiably cold climates. The problem is that weather can be unpredictable, and unusual cold snaps sometimes happen out of the blue. This was the case in Texas in early 2021, when below-freezing temperatures blanketed the state, just a few months after seeing a record heatwave. The extreme cold put a strain on the state’s power grid, as they use electricity for heating as opposed to gas. Rolling blackouts were reported statewide, and many erroneously blamed frozen wind turbines for the blackout.
Texas receives nearly a quarter of its power from wind energy, more than any other state in the US. During the cold snap, nearly half of the wind turbines in the state shut down after freezing over. This did play a small role in the state’s power outages, but even with half the state’s wind turbines out of commission, Texas has a massive natural gas distribution system. Natural gas provides over 45% of the state’s electricity. The gas infrastructure is also vulnerable to extreme cold, as pipelines and plant machinery are prone to freezing. Wells, refineries, and fossil fuel plants all experienced shutdowns during the cold snap, which caused a sharp dip in the supply of electricity.
The biggest factor in the Texas power outages was simply the massive demand on the power grid. Texas has some of the lowest electricity prices in the country, meaning it’s cheaper to outfit homes with electric heating, unlike other areas of the country where gas heating is the norm. The cold weather forced millions to twist the dials on their thermostats, pushing the electrical grid to the limit and causing failures all across the state.
Wind turbines are susceptible to cold temperatures, but engineers have ways to prevent failures in cold climates. Companies like GE outfit their cold-weather turbines with internal heating mechanisms to keep the blades and internal machinery from icing over. This allows the turbines to operate in temperatures as cold as minus 40 degrees F. Without these adjustments, the blades can freeze over, potentially damaging the turbine. Some have even reported falling chunks of ice from frozen turbines, making them a serious safety hazard. Frozen wind turbines need to be shut down for maintenance, as workers must de-ice the machinery before resuming normal operations. Frozen turbines were even blamed for a series of power outages in Texas, even though other factors were at play. To prevent possible outages, engineers are employing high-tech solutions, like artificial intelligence and ice detection systems, to prevent future shutdowns.
Frequently Asked Questions
Wind turbines are prone to freezing. The blades, rotor hub, nacelle, and internal components are all vulnerable to ice build-up in cold temperatures.
Ice can damage the internal components of a wind turbine, freezing over electronics and lubricants. But ice has the biggest effect on the blades, which are thrown off balance and lose their aerodynamic properties when frozen, causing a lack of efficiency. Chunks of ice may also fall off the turbine, or worse, be launched by a spinning blade, creating a serious safety hazard.
Wind companies can outfit their turbines to operate in cold weather. They may use internal heating mechanisms and special materials to prevent the blades and machinery from freezing over. They also use sophisticated technology to predict when a freezing event may occur. Worst comes to worse, workers may need to de-ice the turbines by hand.
Frozen wind turbines were a small contributor to the power outages in Texas. Frozen gas pipes and a spike in demand were the main causes of the state’s power outages during the unusual cold snap in early 2021.
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