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Cold-climate operations: why OEMs must avoid icey situations

Despite growing awareness of the potential for wind power projects in cold climates, turbine manufacturers have yet to deal convincingly with the threat of ice throws.

If you want to get an idea of the negative impact of ice build-up on turbines then just head to YouTube. What is worrying is not just that amateur video makers have captured ice throw situations that the industry says should not happen, but also that these images are being used to convince the public that cold-climate wind farms could be dangerous. Worst of all, that might be true.

“A lot of research work and development is underway in this context,” says Andreas Krenn, a project manager at the Austrian renewable energy consulting engineering firm Energiewerkstatt.

“But most ice detection sensors still do not work very reliably.”

Furthermore, he adds, the systems that original equipment manufacturers (OEMs) have developed to get rid of ice have yet to be rigorously tested by independent bodies out in the field.

Only Enercon, the German turbine maker, seems to have so far taken the icing challenge... more [truncated due to possible copyright]  

If you want to get an idea of the negative impact of ice build-up on turbines then just head to YouTube. What is worrying is not just that amateur video makers have captured ice throw situations that the industry says should not happen, but also that these images are being used to convince the public that cold-climate wind farms could be dangerous. Worst of all, that might be true.

“A lot of research work and development is underway in this context,” says Andreas Krenn, a project manager at the Austrian renewable energy consulting engineering firm Energiewerkstatt.

“But most ice detection sensors still do not work very reliably.”

Furthermore, he adds, the systems that original equipment manufacturers (OEMs) have developed to get rid of ice have yet to be rigorously tested by independent bodies out in the field.

Only Enercon, the German turbine maker, seems to have so far taken the icing challenge seriously, with a de-icing system based on circulating hot air inside rotor blades.

However, “even for the Enercon turbine there are just a few examples where results are available,” Krenn says. In particular, Enercon turbines’ ability to withstand very extreme conditions is largely untested.

De-icing systems

Other EOMs, such as Vestas Wind Systems of Denmark, have introduced de-icing systems, but Krenn points out that their efficacy has yet to be fully verified. So if you buy the turbine, you may be paying extra for a system that does not work as well as you hope.

The problem, Krenn says, is that until recently many turbine manufacturers, with the notable exception of Enercon, have been focusing on technologies for the offshore market.

But addressing cold climate issues is increasingly a priority as demand for wind power in the far northern hemisphere grows.

According to a study by the International Energy Agency’s Wind Task 19 group for wind energy in cold climates, by 2017 between 45GW and 50GW of capacity could be installed in areas of low temperature or light to heavy icing.

The distinction between temperature and icing is important because each has different effects on wind turbine operations. Extreme low temperatures can cause stress to some turbine components, and lead to freezing of fluids.

But such effects are relatively easy to deal with on a technical basis. And there are few places in the world, except perhaps regions such as Mongolia, characterised by very low temperatures and dry weather.

Safety risk

Icing, on the other hand, is a much greater concern for wind farm operators, first and foremost because of the safety risk posed by ice throws.

Since this hazard is widely recognised by the authorities, in many cold-weather markets wind farm operators are obliged to shut down turbines as soon as ice is detected on the blades.

This can significantly reduce wind farm profitability: some cold-climate markets can typically experience icy conditions up to 60 days a year. What can project owners do? As with much in the wind industry, it largely depends on the exact nature of the project.

Given that de-icing systems command a premium, in places where the risk of icing is slight then the operator may decide it is cheaper to buy a standard turbine design and write off a percentage of output by curtailing operations whenever ice appears.

Under more severe environments, though, it might pay to invest in Enercon machines and rely on their limited de-icing track record to boost output. Fortunately, however, it is likely only a matter of time before more options appear.

Given a surge in interest in cold-climate market opportunities, OEMs have been paying increasing attention to icing problems since 2010. Many now have de-icing systems on offer, and the availability of improved data can only be a matter of time.

Distributed wind

Meanwhile, some of the turbine makers looking to deal with ice might want to talk to their brethren in the distributed wind energy business. Urban Green Energy (UGE) of New York, USA, has plenty of experience of operating small turbines in freezing conditions, for example.

“UGE has deployed renewable energy solutions in a diverse range of arctic and polar regions including Scandinavia, Alaska, Northern Canada and even Antarctica,” says Robin Carol, the company’s communications and culture manager.

“Our standard vertical-axis wind turbines will perform at optimum efficiency at temperatures above -25ºC. However, UGE frequently works with customers in very cold climates to solve their specific energy challenges.”

In these cases, Carol says, UGE creates custom solutions designed to perform in even more extreme temperatures. “Our turbines have also undergone testing to ensure their performance and durability.”

UGE’s wind turbines have no stationary horizontal surfaces on which ice can build up, so there is no chance of icing or ice throw. “None of UGE's wind installations in extreme environments have had any issues with ice build up,” Carol comments. Large OEMs might want to take note.


Source: http://social.windenergyupd...

AUG 7 2014
http://www.windaction.org/posts/41039-cold-climate-operations-why-oems-must-avoid-icey-situations
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