ICE COLD FACTS

Denmark Ice on wind turbine blades can pose a big threat to the performance. Industrial PhD fellow Marie Cecilie Pedersen from Denmark spent three months in Canada to learn more about ice formation in order to help her develop a model that Vattenfall can apply when looking for new areas to establish onshore wind farms in cold regions.

Studying ice is perhaps not the most obvious field for a Danish girl. But for Marie Cecilie Pedersen it has developed into a year-long fascination.

“I touched upon this topic during my Master thesis. And I heard that Vattenfall was looking more into the topic and especially the threats icing poses to wind turbines which could be production loss,  ice shedding and blade fatigue. So when Vattenfall presented research questions for a PhD thesis regarding icing, I applied for it and got it”, she explains.

Improved model
The topic Marie is looking into is part of the Turbine Icing Programme in Vattenfall, established after Vattenfall built the Stor-Rotliden wind farm in the Northern part of Sweden. Back then Vattenfall had expected a small percentage of production loss, but it turned out to be higher. Vattenfall learned that it was necessary to obtain a better knowledge about weather conditions such as icing and how to operate wind turbines in cold climate.

“The efficiency of a turbine drops when affected by ice. The geometry of the wing changes, when it has ice on it. Ice forms when the turbines are running and moisture below 0◦C, which is still liquid, hits the turbine blade and freezes immediately. My job is to try to come up with an improved model, where you can analyse the effect of all kinds of ice when planning to erect turbines in cold climate”.

“Costly affair”
It is very difficult to measure ice and understand all the possible shapes and structures. One of the best ways is to use cameras and study the images. In Gaspé, on the Gaspesie peninsula in the province of Quebec, you find the research centre ‘TechnoCentre éolien’.

“The centre is well known for their measuring equipment and the use of cameras and the fact that they have two test turbines and three well equipped meteorological masts at their disposal. This was why I went to Canada. Working there gave me access to a wealth of data and in-house knowledge, which helped me to a better understanding of where on the blades the icing appears. Once you have that knowledge, you have a better insight into how and where to de-ice, and what to demand from blade manufactures. De-icing is a costly affair and not just something you do on an entire blade – especially if it is not necessary”, Marie explains.

Preliminary findings
Going to Canada for three months was a part of the industrial PhD project, which Marie will finish at the end of 2016. Industrial means that you split your time spending half of it with a company and the other half at an university. So what is the status of the project?

“I have developed a two-dimensional model for growth of rime ice. The model can predict the new ice shapes and analyse the aerodynamic changes due to icing. Since you want your model to mimic reality as well as possible, I have worked with data from cold climate in order to understand it and to find out how to use the data as inputs and validation of my model”, Marie explains.

Better model
A natural question is of course how this will benefit Vattenfall in the future?

“Hopefully, Vattenfall will have a better and more detailed model for ice growth, which they can use to improve their current approach for prediction of production losses for cold climate sites. Another application of the work is towards deicing, where the model can help simulate the process of ice growth followed by deicing. And finally, maybe the results can be applied by Vattenfall’s forecasting team to add more detailed data about the icing process to their database. At least that is what I hope for”, she says with a smile.

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