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Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
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https://doi.org/10.5194/wes-2020-62
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-2020-62
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 09 Apr 2020

Submitted as: research article | 09 Apr 2020

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A revised version of this preprint was accepted for the journal WES and is expected to appear here in due course.

Validation of uncertainty reduction by using multiple transfer locations for WRF-CFD coupling in numerical wind energy assessments

Rolf-Erik Keck and Niklas Sondell Rolf-Erik Keck and Niklas Sondell
  • Modern Energy, Karlstad, Sweden

Abstract. This paper describes a method for reducing the uncertainty associated with utilizing fully numerical models for wind resource assessment in the early stages of project development. The presented method is based on a combination of numerical weather predictions (NWP) and microscale downscaling using computational fluid dynamics (CFD) to predict the local wind resource. Numerical modelling is (at least) two orders of magnitude less expensive and time consuming compared to conventional measurements. As a consequence, using numerical methods could enable a wind project developer to evaluate a larger number of potential sites before making an investment. This would likely increase the chances of finding the best available projects.

A technique is described, multiple transfer location analysis (MTLA), where several different locations for performing the data transfer between the NWP and the CFD model are evaluated. Independent CFD analyses are conducted for each evaluated data transfer location. As a result, MTLA will generate multiple independent observations of the data transfer between the NWP and the CFD model. This results in a reduced uncertainty in the data transfer, but more importantly MTLA will identify locations where the result of the data transfer deviates from the neighboring locations. This will enable further investigation of the outliers, and give the analyst a possibility to corrected erroneous predictions. The second part is found to reduce the number and magnitude of large deviations in the numerical predictions relative to the reference measurements.

The Modern Energy Wind Assessment Model (ME-WAM) with and without MTLA is validated against field measurements. The validation sample for ME-WAM without MTLA consist of 35 observations, and gives a mean bias of −0.10 m/s and a standard deviation of 0.44 m/s. ME-WAM with MTLA is validated against a sample of 45 observations, and the mean bias is found to be +0.05 m/s with a standard deviation of 0.26 m/s. After adjusting for the composition of the two samples with regards to number of sites with complex terrain, the reduction in variability achieved by MTLA is quantified to 11 % of the standard deviation for non-complex sites and 35 % for complex sites.

Rolf-Erik Keck and Niklas Sondell

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Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Rolf-Erik Keck and Niklas Sondell

Rolf-Erik Keck and Niklas Sondell

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Latest update: 07 Jul 2020
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Short summary
A method for performing numerical wind resource assessments in the absence of on-site measurements is presented and validated against field measurements. Numerical wind resource assessment is at least two orders of magnitude faster and less expensive than using conventional site measurements. This enables analysis of a larger number of projects and thereby increase the chances of discovering the best available sites. The uncertainty in mean wind speed predictions is found to be about 4 %.
A method for performing numerical wind resource assessments in the absence of on-site...
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