Wind resource modelling has its origins in the 1970’s. Since then much has changed in terms of the models used and the methods for wind data collection. However, one thing that has not changed significantly is the overall methodology used to create a high resolution wind map across a wind farm for the purpose of optimising turbine locations.
Windlab has been working to develop a much more modern and accurate methodology that makes optimum use of all on-site measurements combined with state-of-the-art regional-scale and very high resolution flow modelling. This modelling system is called WindScape Hybrid Deterministic Statistical Method (HDSM).
The Problem with Industry Standard Wind Resource Assessment
Two views can be taken of modern wind resource assessment – top-down and bottom-up. In the former a regional scale atmospheric model is used to calculate the broad-scale wind patterns. These calculations are typically driven by global weather data that is collected and stored across the globe. Calculations of this type can accurately represent broad scale weather patterns that occur over several hours to several days.
The bottom-up view is much more like the traditional method used in wind engineering. Wind measurements are collected at one or a few locations across a prospective wind farm and the wind climate is extrapolated to the locations of proposed wind turbines. Fine scale flow models are typically used in both of these methods to account for fine scale topographic features and surface types that affect the wind climate locally.
The advantage of the top-down method is that it can account for broad variability in the wind climate, which can be significant across distances of several kilometres – as many wind farms span. Its disadvantage is that the calculation, though driven by global meteorological data, does not contain information from locally collected measurements. Conversely, the advantage of the bottom-up or conventional wind engineering methodology is that it is the direct product of local measurements. This is clearly important in technical and financial due diligence as it encompasses both high quality local measurements and wind climate. However, what this method lacks is the ability to account for the broad scale variability in wind climate noted in the description of the top-down method.
WindScape HDSM is a new technology that combines meso- and microscale models along with measurements. WindScape HDSM calculates an optimised wind resource estimate that accounts for broad scale variability of the wind climate across a wind farm site as well as more commonly calculated microscale variations due to topographic forcing, surface roughness changes and distributed drag within vegetative canopies. WindScape HDSM uses measurements and statistical transfer functions to bridge the gap between mesoscale and microscale model calculations and in doing so takes advantage of the best aspects of currently available modelling technology and valuable on-site measurements.