Towards standards in the analysis of wind turbines operating in cold climate. Part B: Methodology for evaluating wind turbine alternative operational strategies

Abstract

Alternative operational strategies are now being used to cope with the challenges of icing on wind turbines. However, there are currently no generally accepted standards for the performance analysis of wind turbines using such alternative operational strategies. Hence, this is an important research topic that needs to be addressed. The aforementioned alternative operational strategies include ice protection systems (installation or modification) and alternative turbine control strategies. The interest surrounding the performance analysis of such strategies is rising since, as the demand for ice protection systems from wind turbine original equipment manufacturer and retrofits providers is increasing worldwide, operators are requesting warranties surrounding their performance. Due to their novelty, operators often prefer to test alternative operational strategies on a few turbines before deploying them on every turbines of a wind farm. In those situations, a standard and robust method is needed to evaluate the strategy before a full-scale extension. This paper proposes a methodology based on the experience gathered on five undisclosed wind farms where different operational strategies were implanted. Through case studies, the current metrics used to assess the performance of alternative operational strategies are reviewed and two new metrics that address the main issues with the current indicators are proposed. These new metrics can estimate the energy reclaimed through the use of alternative operational strategies. This paper also presents a methodology for selecting the best turbines that will be used as a reference to evaluate the performance of the turbines with the alternative operational strategies. Standardized metrics with the right turbines used as a reference will help to provide a clearer overview of the performance of wind turbines in icing conditions. Furthermore, it will help to reduce the uncertainties on the gains achieved through alternative operational strategies. The proposed methodology can be used by operators to compute the payback and quantify the added value of such modifications on their wind farm. It also helps to understand when a strategy is efficient, therefore helping to improve the development of new alternative operational strategies. Finally, using this methodology, through a case study, we demonstrated that the three control turbines could have recovered between 54 and 56% of their icing losses if they were equipped with a Borealis Wind Ice Protection System (IPS).