Small wind / Buyer questions
Energy and economics
How can I avoid applying an air-density correction twice in wind-energy modelling?
The short answer
Air-density treatment can be duplicated when a site-adjusted curve is combined with software that independently applies another correction. Avoid this by tracing where density enters the calculation and identifying which data are reference values and which are already adapted. The goal is one consistent physical treatment, not the largest number of adjustments.
Draw the modelling chain
List the original curve, any intermediate curve or speed transformation, the atmospheric input and the software options. Record who produced each file and which reference conditions it represents. A filename containing site or corrected is not sufficient evidence of its contents.
Ask whether the imported wind speed is measured speed, density-equivalent speed or another processed quantity. Applying a second transformation without knowing the first one can quietly change the model's meaning.
Test one controlled reference case
Run or inspect a case at the curve's stated reference conditions. Then change the intended atmospheric treatment while holding other inputs fixed. The response should follow the documented method. An unexplained extra reduction or increase is a reason to investigate the chain.
Do not use this check to invent a new correction formula. The applicable approach still depends on the turbine curve and modelling method. Preserve configuration-specific limitations where the available documentation is incomplete.
Make responsibility explicit in the handover
State which party supplies the reference curve, which party adapts it and which software applies the final treatment. Include the settings and file versions needed to reproduce the result. This is especially useful when a supplier, consultant and integrator exchange processed files.
If a duplicated correction is found, revise the affected energy outputs and explain the change as a modelling correction. It should not be described as improved equipment performance or a newly discovered wind resource. The revised result remains subject to the wider resource, siting and operating assumptions of the project.
Sources
- System Advisor Model documentation: wind-resource inputs and time-series limitations
- System Advisor Model documentation: turbine curves, hub height and shear
Examples are illustrative. Confirm product-specific performance, compatibility and supply scope in the applicable documents.