Impact of Forest-Elevated Turbulence Levels on Wind Farm Performance

Jonas Kazda, M. Zendehbad, N. Chokani, R. S. Abhari

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This experimental work details the impact of forest-elevated turbulence levels on wind farm performance. In this regard, the wind flow field and power generation of wind turbines in two wind farms in flat forested terrain and flat unforested terrain are assessed. A mobile scanning LiDAR system is used to make measurements of the wind speed and turbulence intensity both in the undisturbed flow and downstream of a forest. Turbulence intensities up to 26% are measured immediately downstream of the forest at hub height, whereas in the undisturbed flow the turbulence intensity does not exceed 15%. While the turbulence levels decay as the wind flow evolves downstream, even at a downstream distance of 20 times the forest height, the turbulence intensities are above the undisturbed flow turbulence intensities. Turbulence dissipation rate is measured to be 8 times higher downstream of forest. On the other hand the deficit in wind speed that is measured immediately downstream of the forest is negligible at a downstream distance of 15 times the forest height. A comparison of the power performance of wind turbine without and with a forested fetch is made. It is shown that with a forested fetch there is a 30% loss in performance due to the forest-affected wind flow. Measurements at an isolated turbine show that higher turbulence causes higher fluctuations in generated power, with highest sensitivity observed for wind speeds in range of 8m/s-10m/s, which is below rated wind speed. Additionally, wind turbines in forested terrain show 2 times higher power curve scatter compared to similar turbines in unforested terrain. An assessment of the power production of the individual wind turbines in the two wind farms is made to assess the impact of forest-elevated turbulence levels on wake losses. It is seen that the wake losses are lower in forested terrain compared to unforested terrain.
Original languageEnglish
JournalInternational Journal of Gas Turbine, Propulsion and Power Systems (JGPP)
Issue number1
Pages (from-to)9-17
Publication statusPublished - 2017
Externally publishedYes


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