Wind turbine operation in icing conditions

  • Dimitar Stoyanov

    Student thesis: Doctoral ThesisDoctor of Philosophy


    Wind turbine operation in icing conditions has been researched for the last 30 years because of the impact of icing on both wind projects’ profitability and financial viability for wind sites, which offer abundance of wind kinetic energy. Much work has been published on modelling ice induced energy losses and quantifying the impact of icing on the overall performance of wind turbines. However, these findings have not led to universally integrated solutions and approaches to adapt wind turbines to different icing events by advanced operational strategies.

    This project used the numerical modelling approach for wind turbines subjected to icing to investigate how wind turbine performance in icing conditions can be improved through the design of different ice mitigation operational strategies. Icing events with variable duration, wind speed, ambient temperature and icing parameters were defined to obtain expected energy losses and ice mass accumulation for evaluating different operational strategies for ice mitigation. Wind tunnel experimental measurements were conducted to facilitate the comparison of XFoil and Fluent for estimating aerodynamic degradation and quantifying the sensitivity of predicted energy losses to aerodynamic modelling tools. For preliminary studies and conceptual design of operational strategies it was concluded that XFoil can be used for a range of icing events. Thus, it was used in combination with lewINT ice accretion code and blade element momentum method to demonstrate a novel approach for selecting the best operational strategy or set of strategies to achieve maximum energy generation during periods of icing.

    Derating by tip-speed ratio modification during icing was investigated with a focus on its application and advantages. Thus, unlike other studies, a systematic method for choosing modified tip-speed ratio values was developed based on the installed electrical generator and energy payback time scheme. The strategy was found extremely favourable for short and extreme icing events with reduction of icing losses up to 23 %, and accumulated ice mass up to 30 %. The method for comparison outlined in this project allowed derating to be compared against other operational strategies. It was established that for longer and milder icing events the design strategy should be maintained. Non-optimised anti-icing systems was found to be a preferred operational strategy for ambient temperatures above -5ºC providing the cost of the system was no higher than 2 % of the turbine’s capital cost and there were more than 43 short extreme or 26 long mild icing event occurrences per year. For the selected icing events, the operational shutdown strategy was not found to be a viable option. The presented method allows for the comparison of other ice mitigation strategies providing their cost for implementation and operation can be incorporated into the viability and performance analysis.

    The work covered in this project proposed a more holistic approach on studying ice mitigation strategies, which would facilitate integrated solutions and higher fidelity studies to develop novel ice mitigation techniques or advance current solutions. Further development of the presented methods would be needed to transfer the results that can be obtained from this analysis from preliminary conceptual design stage to prototype and test stages. However, this is one of the first studies to attempt advancing and designing different operational strategies together to achieve more effective adaption of wind turbines in cold climates.
    Date of AwardJul 2021
    Original languageEnglish
    Awarding Institution
    • Coventry University
    SupervisorJonathan Nixon (Supervisor), Hamid Sarlak Chivaee (Supervisor) & Mike Blundell (Supervisor)

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