Written by Barbara Rook
It can be tough to predict, and even tougher to manage. But wind-farm operators are finding success navigating around Mother Nature in cold climates.
After experiencing significant wind-farm downtime due to ice buildup on turbine blades, the operators of the 150-turbine Lac Alfred wind farm, near Amqui, Quebec, sought new ideas for retrofitting the blades with an anti-icing technology. They turned to Wicetect OY’s patented Ice Prevention System (WIPS). After testing the system on two turbines, the application was expanded to an additional 10 units the following year.
The WIPS blade-heating elements consist of carbon-based electrical heaters, which let the blade surface heat quickly — but to a controlled temperature — once ice is detected. The thin (0.5 mm) heater, including a glass fabric protection layer, does not interfere with the unit’s aerodynamics.
However, the biggest challenge was retrofitting an efficient de-icing system on existing, four-year-old wind turbines, according to Sebastien Goupil-Dumont, manager – Generation at EDF Renewable Energy Inc. EDF RE acted as project manager.
“To ensure a high-quality end product, it was decided that the blade work had to be done on the ground, in a remote location, instead of trying to do all of it up tower, using platforms,” explains Goupil-Dumont. So far the retrofit, though costly, is producing positive results.
“Our goal is to achieve a 70 to 80% energy recovery of the icing losses,” he says. “After two full winters of operation, the results vary from one turbine to another but we are close to reaching our goal.”
By partnering with vendors and collaborators, EDF RE works diligently to optimize the efficiency of the system. “Icing is a never-ending subject and we work hard every summer to improve and get ready for the next winter,” he adds.
Like Lac Alfred, the 33-turbine Caribou Wind Farm in New Brunswick, Canada, is also testing Wicetec’s WIPS technology.
“We’re looking at whether it could be effective for Caribou,” says site manager, Mark Hachey. “We would test one or two turbines through at least one winter. The longer you test, the better the results.”
In the past, the lack of significant icing has hampered Caribou’s efforts to test different de-icing technologies. One manufacturer supplied Caribou with six prototype blades outfitted with a heated blade system that uses hot air — the only such blades in the world, according to Hachey. However, without significant icing conditions for a couple of years, the testing was inconclusive. In addition, the technology would have required Caribou to replace 99 blades at a cost in the tens of millions of dollars.
Caribou has tried several other de-icing options, including electrically heated tiles, painting portions of the blades with black paint to absorb UV energy, a coating applied by helicopter, and a complicated R&D product. Results ranged from impractical to inefficient and costly.
Still, Hachey is optimistic. “With every passing year, there are solutions that have lower upfront costs,” he says.
In the meantime, the company built a portable metal roof device to shield workers from shedding and falling ice so they can access the wind turbine to resume operations. They also contracted with a company to remove blade ice “from the ground up,” says Hachey. The benefit, he adds, is only paying for the service when needed. The ROI on other technologies can result in “poor economics” when the winters are warmer and fail to require anti- or de-icing intervention.
Preventing such icing, by using data that forecasts the potential for ice conditions, can predict events in advance, saving energy and minimizing risks.
Capstone Infrastructure, a Canadian trust that invests in power-generation assets, is partnering with applied research center, Nergica, to assess developing algorithms. This system would predict atmospheric conditions likely to cause icing events, according to Tom Burge, Capstone’s Director of Wind Operations, Eastern Canada.
The technology behind the forecasting is a combination of data and alerts sent to wind operators ahead of a predicted event, according to Antoine Amosse, Analyst, Research and Innovation at Nergica. Amosse told attendees at a recent technology and engineering conference that Nergica’s system retrieves data throughout the day and builds an algorithm that considers wind speed, direction and gusts, temperature, sky conditions, and accumulated precipitation. The system can generate alerts 12 to one hour before a weather event. Operators can then kickstart their heating system in advance to prevent ice accretion.
“Currently, our forced hot-air system waits to detect a drop in the power curve once ice has begun to form,” explains Burge. “The goal is to get the blades to a heated state to keep that first bond layer of ice from forming on the fiberglass.”
Better predictability also lets operators determine if and when to shut down wind-farm operations altogether. “There are instances where you’re better off waiting for the sun to melt the ice,” says Burge. If the models indicate severe icing probability — ice forming too thick or too fast — then running the system will be futile. “Otherwise, you can burn energy for days,” he adds.
To that end, Capstone also measures solar radiation to identify when the sun is promoting ice melt. “We want to optimize the system for each icing event. Currently, the system treats all events the same. We need different strategies for different types of events,” he says.
Turbine manufacturer, Enercon, is also partnering with Capstone to ensure the forecasting model will integrate with their equipment.
Enercon currently employs its blade-heating system on almost 700 wind turbines in Canada. The manufacturer is working with Nergica to conduct a large statistical review of past performance over the last two years, according to Tarik Daquone, Technical Conformity Engineer at Enercon. “We want to show that the blade-heating system has clearly increased the yield.” Key to that performance, he claims, is that Enercon’s blade-heating system can be used while the turbine is operating, allowing the turbine to produce 70 to 80% of its energy generation during icing events.
Meanwhile, Nergica is also working on ideas to minimize production loss due to icing, using a combination of forecasting, detection, and mitigation. The research center, based in Gaspé, Quebec, is assessing the feasibility of using turbine-mounted cameras to analyze the severity, intensity, and duration of the icing.
Charles Godreau, Project Manager, Research and Innovation for Nergica told a recent New Energy Update webinar audience the cameras feature a heated ice shield, remote access, and night vision. Also under development are lasers and microwaves.
The benefits of the R&D efforts are significant. Some estimates indicate an effective ice-management system can minimize power losses up to 15 to 20%.
“You can only swallow so much loss,” says Caribou’s Hachey, who knows firsthand the downside of downtime. “We have to guarantee [the provincial government] a certain amount of power per year.”
Early challenges six to eight years ago meant shutdowns. Currently, Caribou is exceeding its contractual obligations and continuously evaluating emerging technologies through trial and error.