Wind Resource Assessment Calculator
Estimate the energy density of a wind site using average wind speed and the Weibull shape parameter. Use this when evaluating whether a location has sufficient wind potential for turbine installation.
About this calculator
Wind energy potential is not simply proportional to average wind speed — it scales with the cube of speed. This calculator uses the Weibull distribution, a standard model for wind speed variability, to estimate the mean cubic wind speed at a site. The formula is: meanCubicWindSpeed = averageWindSpeed³ × exp(3 × ln(√π / 2) / k), where k is the Weibull shape parameter. A higher k means wind speeds are more consistent (narrow distribution), while a lower k indicates more variable winds. The result is proportional to the wind power density at the site, helping engineers and developers compare locations and determine whether a site meets the threshold for viable energy generation — typically above 200–300 W/m².
How to use
Suppose a coastal site has an average wind speed of 7 m/s and a Weibull shape parameter of 2.0 (a typical value for many sites). Step 1: Cube the wind speed: 7³ = 343. Step 2: Compute the exponent: 3 × ln(√π / 2) / 2.0 = 3 × ln(0.8862) / 2.0 ≈ 3 × (−0.1208) / 2.0 ≈ −0.1812. Step 3: exp(−0.1812) ≈ 0.8343. Step 4: 343 × 0.8343 ≈ 286.2 m³/s³. This value feeds directly into power density calculations for the site.
Frequently asked questions
What is the Weibull shape parameter and how does it affect wind resource assessment?
The Weibull shape parameter (k) describes how concentrated or spread out the wind speed distribution is at a site. A k value of 2 is called the Rayleigh distribution and is a common approximation for many wind sites worldwide. Higher k values (above 2.5) indicate steadier winds, which generally produce more predictable and higher energy yields. Lower k values mean more variable winds, which can reduce the effective energy capture even if the average speed looks acceptable.
How does average wind speed relate to wind power density at a site?
Wind power density is proportional to the cube of wind speed, not the average speed itself — this is a critical distinction. Because of this cubic relationship, a site with 8 m/s average speed has roughly twice the power potential of a 6.3 m/s site. The Weibull-corrected mean cubic speed accounts for the full distribution of speeds experienced over time, giving a more accurate picture of energy potential than average speed alone. Engineers use this metric when screening sites before committing to expensive measurements or turbine installations.
What wind resource assessment values indicate a commercially viable wind site?
A site is generally considered commercially viable when its wind power density exceeds 200–300 W/m² at hub height, corresponding to average wind speeds above roughly 6–7 m/s. Class 3 wind resources (mean speed ~6.4 m/s at 50 m) are typically the minimum threshold for utility-scale development. Sites with power densities above 400 W/m² (Class 4 and above) are considered excellent. Local terrain, turbulence intensity, and grid access also influence final viability alongside raw resource quality.