Power Density Calculator
Calculate the wind power density at any site from wind speed and air density.
Wind power density (WPD) measures the amount of wind power available per square metre of rotor area. It is calculated as PD = 0.5 × ρ × v³, where ρ is air density (kg/m³) and v is wind speed (m/s). Because power is proportional to the cube of wind speed, even small increases in average wind speed dramatically increase available energy — a 10 % increase in wind speed raises available power by roughly 33 %.
WPD is used in preliminary site assessment to classify wind resource before committing to detailed measurement campaigns. Classes range informally from poor (below 100 W/m²) through moderate and good to excellent (above 500 W/m²). These thresholds are educational rules of thumb; real site feasibility requires long-term wind measurements and detailed energy modelling.
Wind power density
Formula: PD = ½ρv³ (W/m²). Power density grows with the cube of wind speed. Classification is an educational rule of thumb; site assessment requires long-term wind measurements.
How to use this tool
- Enter the average wind speed in m/s at hub height.
- Enter air density in kg/m³ (the standard sea-level value is 1.225; use the Air Density Calculator to find a site-specific value).
- Press Calculate to see power density in W/m² and kW/m², plus an educational site rating.
💡 Good to know
All calculations use standard, published formulas and simplified assumptions so beginners can build intuition. For real projects, always consult qualified engineers and site-specific data.
Frequently asked questions
What is a typical good wind power density?
Sites with a WPD of 300–500 W/m² at hub height are generally considered good for commercial wind development. Above 500 W/m² is excellent. Below 100 W/m² is usually uneconomical without subsidies.
Why does power scale with the cube of wind speed?
Wind carries kinetic energy proportional to the square of its speed, but the mass of air passing through the rotor each second is also proportional to speed. Multiply mass-flow-rate × kinetic energy and you get a v³ relationship.
How does air density affect power density?
Power is directly proportional to air density. High-altitude sites have lower air density (less mass per cubic metre), which reduces available power even at the same wind speed. Temperature also affects density: cold air is denser and contains more energy.
Is power density the same as a turbine's power output?
No. Power density is the raw energy available in the wind per square metre. A turbine extracts only a fraction of that — its power coefficient (Cp), capped at the Betz limit of 0.593. Real turbines achieve Cp of roughly 0.40–0.48.