The significance of bypass transition on the annual energy production of an offshore wind turbine

Aidan Duffy,Grant Ingram,Simon Hogg

doi:10.1002/we.2697

Abstract

AbstractAwareness of leading‐edge erosion (LEE) on wind turbine blades, and the impacts it can have on annual energy production (AEP) have increased significantly over recent years. This is especially important in offshore environments, where a combination of more extreme weather and higher tip speeds result in higher rates of erosion. In this paper the impact of LEE on AEP has been quantified and the derived method validated. The DTU 10‐MW reference wind turbine (RWT) is used to demonstrate the method. An equivalent sand grain roughness approach in computational fluid dynamics (CFD) is used to simulate clean and roughened aerofoil performance. These CFD results are applied to a blade element momentum (BEM) model of the turbine to generate clean and eroded power curves. Finally, a wind distribution from Anholt offshore wind farm is used to estimate the AEP for the clean and eroded cases. An AEP loss of 0.7% was computed for the specific case considered in this study. This result is benchmarked against those from previously published studies. Most research into LEE has thus far focussed on either estimating the impacts on AEP or mitigating against them, with less emphasis on understanding the physical aerodynamic changes that result in reduced energy output. In this paper, the significance of bypass transition on the AEP loss caused by roughness, specifically as it relates to the operational angles of attack of the blade, is examined and found to impact turbine efficiency in this case for over 56% of the total operating time.

Highlights

It is recognised that the offshore wind sector has a major role to play in decarbonising electricity generation, in countries with relatively shallow coastal waters such as the UK
The 0.70% Annual Energy Production (AEP) reduction due to blade erosion calculated in this study is considered to be largely representative of what may be expected after the first few years of operation for a current generation offshore wind turbine under the conditions detailed in this paper
The method is based on using Ansys Fluent CFD calculations validated for clean aerofoil sections, to calculate the effect on blade section performance when erosion damage is simulated on the leading edge

Summary

Introduction

It is recognised that the offshore wind sector has a major role to play in decarbonising electricity generation, in countries with relatively shallow coastal waters such as the UK. The results from the various studies described above show a variation in the predicted impact of blade erosion damage on wind turbine AEP, from 0.5% to 24%.

Results

Conclusion