The Pragmatic Choice of Wind Model in Complex Terrain – Decision Tool Development
Creators: name: Barber, Sarah
name: Schubiger, Alain
name: Koller, Sara
name: Rumpf, Andreas
name: Knaus, Hermann
Publisher: name: Zenodo
Year: 2021
Subjects: Wind resource assessment
Wind energy
Costs
Decision tool

description: For a given Wind Resource Assessment (WRA) project, the modeller is faced with a difficult choice of simulation tools and calculation steps with varying accuracies, complexities and costs. The most cost-effective choice is expected to be a compromise between performance and cost (Figure 1). In order to help modellers choose the most suitable workflow for a given project, a new method for estimating the accuracy, or skill, and cost of a given workflow was developed previously (Barber et al. 2019). This method involves estimating scores for a range of weighted parameters relating to the skill and cost of the workflow, using a pre-defined template. The method was shown to work well for various tools at the Bolund Hill site (Berg et al., 2011), but further tests are required on different sites. For the present work, therefore, the method is tested at two further complex terrain sites as follows: Firstly, at the complex terrain site of Stoetten in southern Germany (Schulz et al., 2016), workflows are developed for carrying out WRAs using various simulation tools: ANSYS CFX and ANSYS Fluent as well as the commercial tools WindSIM and WindPro and the PALM (Raasch and Schröter, 2001). The skill and cost scores are estimated for each workflow according to (Barber et al. 2019) and (Barber et al. 2020a). WRAs are then carried out for each workflow based on input measurement data from a met mast, and the Annual Energy Production (AEP) of a fictive wind turbine positioned at a second location is estimated. Measurement data from a lidar at this second location is used to assess the accuracy of both the wind speed and AEP predictions from each workflow, allowing the actual skill score of each workflow to be determined. The actual costs of each workflow are determined from the real costs after completing the calculations. Secondly, at the complex terrain site of Perdigão in Portugal (Fernando et al., 2019), a new simulation challenge was designed and run (Barber et al., 2020b). The goal of this challenge was to collect data regarding the estimated and actual skill and cost scores of a range of different simulation tools for a complex terrain site. The same method is applied as described above, but for a range of workflows submitted by external challenge participants. Initial results of these two projects show that there are wide range of different factors affecting the accuracy of the AEP calculation, as well as the performance of the simulation tools themselves. For each site, the estimated skill and cost scores ("before") are compared to the actual scores ("after") of the wind speed simulation for each workflow in Figure 2, in order to assess the quality of the new method (the results of the AEP calculation will be shown in the presentation). For the Stoetten site, the different workflows are marked next to each point. It can be seen that, although there are some discrepancies in the absolute values, the shape of the "before" and "after" distributions are similar, both of them indicating that either the WindSim or CFX workflows are most efficient for this site. For the Perdigao site, the individual models are not marked due to confidentiality reasons. Similarly to the Stoetten site, a similar curve shape can be seen, indicating that it is possible to estimate the most suitable workflow for this site using this method.