Technical – Page 2 – Wind Turbine Magazine

As wind energy deployment increases across the globe, it is increasingly critical that wind turbines perform well under a variety of climatic conditions. For renewable energy sources to be reliable, they need to operate throughout the year. In fact, wind farms often have the best wind energy resource during the winter months. Therefore, winter energy production is critical, especially in cold climates. Many people wonder if wind turbines can actually freeze. Although wind turbines do not freeze, ice can form on the blades in extreme conditions, reducing or even halting electricity output. However, there are several approaches that prevent this from happening, including wind turbine de-icing equipment. https://youtu.be/eO-1tBwS_sY Let’s explore this important topic and how ice mitigation strategies are increasing wind turbine performance. Can wind turbines operate in cold weather? Yes, wind farms can operate reliably in below-freezing temperatures. However, wind turbines may require cold weather packages that provide heat to turbine components, including the blades, gearbox, pitch motors, battery, and yaw. This allows wind farms to operate in temperatures down to -30° Celcius (-22° Fahrenheit). For example, it is also critical to prevent icing on the turbines, especially to promote safety. Falling chunks of ice from wind turbines (known as ice throwing) can create a safety hazard to people, animals, or property. There are various wind turbine blade de-icing and anti-icing approaches to prevent ice accumulation, including water-resistant and ice-repelling coatings, heating, and operational strategies. Also, it is critical to use lubricants that maintain a proper viscosity during low temperatures if the wind turbines are operating in low temperatures. Are wind farms a reliable source of renewable energy in cold climates? One of the best ways to answer this is by looking at countries with low winter temperatures and many wind turbines. Indeed, wind energy is popular in some countries with cold climates, including Canada and Sweden, where 17 percent of their power comes from wind energy. According to Benjamin Sovacool, professor of energy policy at the University of Sussex in the U.K., "In Northern Europe, wind power operates very reliably in even colder temperatures including the upper Arctic regions of Finland, Norway, and Sweden.” However, according to Sovacool, proper cold-weather maintenance is essential. "As long as wind turbines are properly maintained and serviced, they can operate reliably in temperatures well below zero. Humans, to carry out servicing and maintenance and operation, are the most important factor, not the weather." What issues can low temperatures cause for wind turbines? For optimum performance and power generation, it is critical to prevent certain weather-related issues. Unfortunately, low temperatures can cause: Ice accumulation on turbine blades - Because frost makes the wind turbine blades less aerodynamic, it can reduce wind energy production.Severe icing on blades - This can cause wind turbine shutdowns completely, resulting in more power loss.Turbine imbalances - Uneven icing creates imbalances, resulting in wear and tear of equipment and excessive vibration that can cause the turbine to shut down.Ice throws - This issue occurs when pieces of ice detach from the wind turbine.Reduced access to wind farms - Cold weather can inhibit travel and prevent workers from performing essential maintenance. However, there are ways to protect wind turbines during frigid weather. These strategies help boost wind turbine reliability and power output while preventing equipment damage. What are the best cold-weather strategies for wind turbines? To promote wind energy generation during cold weather, effective strategies are needed, including cold weather packages and proper maintenance. According to the Canadian government, it isn’t clear which de-icing strategy is the most cost-effective and is an area for ongoing research. Because wind energy is a relatively new source of renewable power, the technology continues to rapidly evolve, and there is ongoing research into cold-weather performance. For example, a Swedish company called Skellefteå Kraft is experimenting with operating wind turbines in the Arctic. It is coating wind turbines with thin layers of carbon fibre[1] , which is heated up as needed to prevent ice accumulation. Unfortunately, other strategies of heating or circulating hot air inside the turbine blade can be relatively energy-intensive because blades on utility-scale wind farms are quite large. However, researchers at Iowa State University in the United States are exploring two strategies simultaneously: heating just the turbine blade’s edge, combined with water- and ice-repelling coatings. They are hoping to conserve energy and protect the wind energy equipment while promoting wind energy production in cold weather. Preliminary results from tests conducted in its Icing Research Tunnel are promising. Did frozen wind turbines cause the 2021 Texas Power Crisis? The Texas Power Crisis in the United States left 4.5 million households and businesses without electricity during its peak and many without clean drinking water. According to estimates, the financial damage of the event ranges between $195 billion and $295 billion. Sadly, there were also dozens of deaths due to the event, some from exposure to cold temperatures within homes after power outages caused HVAC equipment to fail. However, wind farms were not the leading cause of this massive power outage in Texas. Unseasonably low temperatures, and ice storms caused natural gas fields and coal and nuclear power plants to shut down. But, some politicians blamed wind energy as the main culprit, although evidence shows otherwise. [2] Wind farms are common in Texas and wind power generated 23 percent of the state’s electricity in 2020. However, nearly half of the Texas wind energy capacity was offline during the massive power outage. But, wind turbine outages were responsible for less than 13 percent of Texas’ total energy shortage. Although it is noteworthy, it wasn’t the main culprit. Unfortunately, many Texas wind farms are not designed for cold weather and do not have the cold weather packages necessary for optimum performance in unexpectedly frigid conditions. Because below freezing temperatures are rare in Texas, the energy infrastructure, including natural gas pipelines, power plants, and wind turbines, was not properly equipped. Why not equip all wind turbines for cold weather? Unfortunately, it can be expensive for all wind turbines to be equipped for frigid temperates. For example, a cold-weather package for a 2.5 MW turbine can cost up to $400,000. Although this might be well worth the expense for wind farms in Sweden or Canada, it probably isn’t cost-effective as a widespread solution in Texas, where below-freezing temperatures are rare. Because this is an area of ongoing research, it is likely that more cost-effective solutions are on the horizon. This could help lower the cost of wind energy while boosting clean energy output. However, the 2021 Texas Power Crisis does highlight that some power grids are not resilient during extreme weather. This topic is especially critical as climate change is causing more and more extreme weather events and erratic weather patterns. Are strategies for de-icing airplanes effective for wind turbines? On the surface, it would seem that strategies that are effective for preventing ice from forming on airplane wings would also work with wind turbines. However, there are some differences between aircraft wings and wind turbine blades, For example, wind turbine blades are usually made of polymer-based composites[3] , whereas airplane wings are made of metals, like aluminum alloy. And, metals are more effective at conducting heat than wind turbine blades. Unfortunately, wind turbine blades are more prone to damage from overheating. Also, blades are more likely to accumulate dust and dead insects than aircraft wings, which can slow water as it runs off the blade, encouraging the formation of ice. In addition, offshore wind farms are especially likely to come into contact with ocean spray. What turbine manufacturers offer cold-weather solutions? As one of the best wind turbine manufacturers for cold weather, Vestas offers several cold-weather solutions for many of its wind turbines. According to the company website, the Vestas Low Temperature option allows wind turbines to operate in temperatures as low as -30° Celcius and has been installed on over 5,000 wind turbines globally. The Vestas Ice Detection system enables operators to identify ice on the rotors with sensors on each blade and power-curve-based data. This information empowers operators to make informed decisions when creating operational strategies to promote safety and prevent wear and tear. The Vestas De-icing system pauses the wind turbine and then heats the blades and circulates warm air within them. The system centralizes the heat where it is most effective at de-icing, conserving energy. Also, Vestas Ice Assessment is a siting tool that uses meteorological models and algorithms to predict icing exposure on a potential project site. Therefore, this tool helps wind farm developers decide which turbines should be equipped with anti-icing systems, cutting costs when feasible. https://youtu.be/eO-1tBwS_sY[4] Also, Siemens Gamesa has a cold-weather strategy for wind turbines that utilities both passive and active de-icing mechanisms to promote safety and electricity generation. In addition, it features a smart ice detection system that controls anti and de-icing measures. Can wind turbines be retrofitted with anti-icing equipment? Yes, there are ways to retrofit existing wind farms to mitigate the impact of cold weather that can replace or bolster systems from the wind turbine manufacturer. Typically, it is best to add such components during the manufacturing process, but they can also be installed later. However, blade-heating systems typically require removing the blades. Blade-heating equipment Two companies with such systems are Borealis Wind based in Ontario, Canada, and Wicetec in Helsinki, Finland. According to Borealis Wind, its product removes ice in 30 minutes, can reduce downtime by 80 percent, and works by heating the interior of the blade. The Wicetec Ice Prevention System allows continuous turbine operation by reducing ice-induced downtime and reducing maintenance costs for gearboxes and bearings. Anti-ice wind turbine blade coatings In addition to heating, there are anti-ice coatings that can be applied to wind turbine blades. Elemental Coatings, based in Houston, Texas, makes coatings that can be applied on top of existing topcoats and paints. This company has expertise in anti-ice aerospace coatings and is bringing this experience to the wind energy industry. Its wind turbine blade coatings prevent ice buildup and ice throws yet require no active electronics. This start-up is currently testing its products on wind farms in Canada and China. Why is winter wind energy production important? Wind turbines do not emit greenhouse gases or require fossil fuels to operate. As countries across the globe seek to reduce greenhouse gas emissions and transition to cleaner sources of electricity, wind power is an essential aspect of clean energy development. However, the wind is an intermittent source of energy, and it is critical for wind projects to have the highest capacity factor possible. In many parts of the world, the winter months have the best wind energy resource. Being able to effectively generate wind power at low temperatures is critical for the industry to continue its strong growth trajectory, ensure strong wind power investment returns, and reduce dependence on fossil fuels.