Convert speed and height values using familiar units. See increases and choose roughness for accuracy. Enter your data, then export results as CSV files.
This model scales wind speed with height using a wind shear exponent (α). It is often used for preliminary design and comparison across sites.
V(h) = Vref × (h / href)α
This model relates wind speed to surface roughness length (z0). Using a ratio form avoids friction velocity inputs when you have a reference speed.
V(h) = Vref × ln(h/z0) ÷ ln(href/z0)
WPD = 0.5 × ρ × V(h)3
Tip: If you have detailed met mast or lidar data, calibrate α or z0 from your dataset.
| Case | Vref (m/s) | Href (m) | Hub (m) | Profile input | Vhub (m/s) | Increase |
|---|---|---|---|---|---|---|
| A | 6.50 | 10 | 80 | α=0.14 | 8.70 | 33.8% |
| B | 7.20 | 10 | 100 | α=0.20 | 11.41 | 58.5% |
| C | 5.80 | 10 | 60 | α=0.28 | 9.58 | 65.2% |
| D | 7.00 | 10 | 80 | z0=0.03 m | 9.51 | 35.8% |
| E | 8.00 | 20 | 120 | z0=0.10 m | 10.71 | 33.8% |
These examples are illustrative. Use project-specific terrain and measurement practices.
Wind records are often available at 10 m or 20 m, while turbines commonly use 60–140 m hubs. A height adjustment converts reference measurements into a hub estimate that supports feasibility checks and early energy assumptions when full vertical profiles are not available.
The power law is an approximation using a wind shear exponent (α) that reflects stability and surface roughness. The log law uses a roughness length (z0) and a height ratio form when a reference speed is known. When you have a representative z0, the log approach can better match near-surface behavior.
For open water and smooth terrain, α is often near 0.10–0.12 and z0 may be below 0.01 m. Short grass or open flat sites use α about 0.14–0.18 with z0 around 0.03 m. Cropland and hedgerows may push α toward 0.18–0.25 and z0 near 0.10 m. Suburban zones can reach α 0.25–0.35 and z0 about 0.50 m, while dense urban areas may be higher.
Assume a site report lists 7.5 m/s at 10 m. Using α = 0.14 for open flat terrain, the hub estimate at 80 m is about 10.0% higher. At 1.225 kg/m³, the hub wind power density rises strongly because it scales with speed cubed.
| Vref | Href | Hub | Input | Vhub | WPD |
|---|---|---|---|---|---|
| 7.5 m/s | 10 m | 80 m | α = 0.14 | 8.25 m/s | ≈ 289 W/m² |
| 7.0 m/s | 10 m | 80 m | z0 = 0.03 m | 8.35 m/s | ≈ 297 W/m² |
Use the percent change to explain hub selection impacts, and use wind power density as a proxy for energy potential. Keep rounding consistent across documents, and export CSV or PDF results for QA logs, design notes, and procurement packages.
Use the power law for fast screening with a reasonable α preset. Use the log law when you have a defensible z0 for the site and want a roughness-based profile ratio.
This tool flags that case because hub-height adjustment is usually upward. If you truly need a lower height, swap the inputs or interpret the result as a downward extrapolation with the same method.
Start with a terrain-appropriate preset, then tune α using local vertical wind measurements if available. Typical onshore values often fall between 0.10 and 0.35 depending on roughness and stability.
Select a preset that matches the dominant upwind surface near the turbine. If you use a custom z0, keep it much smaller than both heights and consistent with the land cover used in your site model.
Wind power density scales with the cube of wind speed. A modest hub-speed increase can yield a large WPD change, so small differences in α or z0 can materially affect early energy expectations.
1.225 kg/m³ is a standard sea-level reference. For higher elevations or warmer conditions, density is lower. Use a project-specific density if your design basis includes temperature and altitude corrections.
They include the selected method, heights, reference speed, hub speed, percent increase, density, and wind power density. Exports help you document assumptions consistently across design reviews and field reports.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.