Methods for high-accuracy wind resource assessment to support distributed wind turbine siting
Abstract. Public wind resource datasets are central to wind energy planning, particularly for distributed wind installations where it may be infeasible to collect on-site measurements or run bespoke simulations. Yet despite their broad use, the site-level accuracy at hub height remains only partially quantified. This work addresses this gap in two steps: (i) we develop a unified, observation-based benchmark to evaluate the performance of the most common models used in industry, and (ii) we propose a new machine-learned ensemble approach that leverages multiple models to synthesize improved estimates that address the shortcomings of individual models. For each dataset and observation series we form long-term empirical wind speed quantiles. This quantile representation allows us to compare products with different periods of record without requiring temporal overlap and evaluate both wind speed distribution errors and site-level mean biases. Results show that the ensemble method reduces quantile-dependent mean bias to near zero across the distribution and lowers mean absolute bias in long-term mean wind speed by roughly one-third relative to the best-performing individual dataset. Finally, we use the trained model to produce a national, gridded set of wind speed quantiles for the publicly accessible WindWatts platform. Together, the benchmark, ensemble model, and deployment dataset demonstrate that machine learning can meaningfully correct and combine existing public datasets, providing more reliable, distributional wind resource information for early-stage assessment and planning.
The paper addresses an important problem: whether machine learning can improve public wind-resource products for wind assessment by combining multiple model datasets with observational data. The observational archive is potentially valuable, and the quantile-based framework is interesting. However, I do not think the current validation is sufficient to support the main claims, especially regarding hub-height performance and practical usefulness for wind-energy siting. My main concerns are listed below.
A central methodological issue is the relationship between 10 m wind and hub-height wind-resource assessment. Ten-meter winds observationally are strongly influenced by local exposure, roughness, obstacles. In models such as WRF, 10 m wind is a diagnostic quantity and may behave differently from winds on other vertical levels. Therefore, good performance at 10 m does not necessarily imply good performance at hub height. Because this paper combines ASOS 10 m observations with GS measurements, it needs to demonstrate explicitly that the method improves hub-height estimates, not merely near-surface winds.
From a different angle, I would like to reflect on the relationship between observation that is a point-like measurement and model output that represents the average wind speed over a grid-cell. This distinction is less important in flat terrain where the wind speed is spatially similar. However, this is very important when talking about complex terrain or coastal regions. In addition, measurements are not randomly distributed across grid cell. People carrying out measurements will put the met masts on top of hills and not in the valleys.
Major comments:
Minor comments:
Conclusion:
The paper claims improved wind-energy-relevant hub-height assessment, but the validation may be dominated by lower-height measurements and the final WEM product may be too close to GWA, and too coarse spatially, to justify the strength of the claimed practical improvement.
To support the main claims, I would expect the authors to provide:
(1) height-stratified performance metrics specifically above 50 m and above 80 m, especially WEM versus GWA metrics;
(2) a clearer justification for ignoring temporal mismatch and interannual variability including information about the timeseries lengths in GS dataset.
(3) more support for the independence of models, preferably, based in actual statistics comparing model data with to observations
(4) a discussion of whether the ERA5-grid WEM product can improve on the 250 m GWA product for complex-terrain siting.