k = 2, c = 7.33 m/s, mean 6.5 m/s. Typical mid-latitude wind variability (close to Rayleigh, k = 2). A turbine with 3 m/s cut-in would spin about 85% of the year.
Shape k / scale c
2 / 7.33 m/s
mean 6.5 m/s
Mean speed
6.5m/s
σ 3.4 m/s
Median speed
6.11m/s
Most probable speed
5.19m/s
Speed carrying max energy
10.37m/s
Energy pattern factor
1.91
mean(v³)/mean(v)³
Operating hours
7,410h/yr
3–25 m/s · 85% of time
Hours at rated power
750h/yr
≥ 11.5 m/s
Calm hours (below cut-in)
1,350h/yr
Storm hours (above cut-out)
0.1h/yr
Hours per speed bin
| Bin (m/s) | Probability | Hours/yr | Days/yr | Cumulative | % of energy |
|---|---|---|---|---|---|
| 0–1 | 1.84% | 161 | 6.7 | 1.8% | 0% |
| 1–2 | 5.32% | 466 | 19.4 | 7.2% | 0% |
| 2–3 | 8.24% | 722 | 30.1 | 15.4% | 0.3% |
| 3–4 | 10.32% | 904 | 37.7 | 25.7% | 0.9% |
| 4–5 | 11.44% | 1,002 | 41.8 | 37.2% | 2% |
| 5–6 | 11.62% | 1,018 | 42.4 | 48.8% | 3.7% |
| 6–7 | 10.99% | 963 | 40.1 | 59.8% | 5.8% |
| 7–8 | 9.79% | 857 | 35.7 | 69.6% | 7.9% |
| 8–9 | 8.25% | 722 | 30.1 | 77.8% | 9.6% |
| 9–10 | 6.6% | 578 | 24.1 | 84.4% | 10.8% |
| 10–11 | 5.04% | 441 | 18.4 | 89.5% | 11.1% |
| 11–12 | 3.67% | 321 | 13.4 | 93.1% | 10.6% |
| 12–13 | 2.56% | 224 | 9.3 | 95.7% | 9.5% |
| 13–14 | 1.71% | 149 | 6.2 | 97.4% | 8% |
| 14–15 | 1.09% | 95 | 4 | 98.5% | 6.3% |
| 15–16 | 0.67% | 59 | 2.4 | 99.1% | 4.7% |
| 16–17 | 0.39% | 34 | 1.4 | 99.5% | 3.3% |
| 17–18 | 0.22% | 19 | 0.8 | 99.8% | 2.3% |
| 18–19 | 0.12% | 11 | 0.4 | 99.9% | 1.4% |
| 19–20 | 0.06% | 6 | 0.2 | 99.9% | 0.9% |
| 20–21 | 0.03% | 3 | 0.1 | 100% | 0.5% |
| 21–22 | 0.02% | 1 | 0.1 | 100% | 0.3% |
| 22–23 | 0.01% | 1 | 0 | 100% | 0.2% |
- Weibull fits most sites well, but not all: bimodal climates (sea breeze + synoptic winds) and very calm sites can deviate, so compare with a histogram of measured data.
- k and c depend on height: k usually rises slightly up to ~100 m, then falls; c scales roughly with the mean speed.