Air Density Calculator

How Air Density Is Calculated

Air density directly affects wind turbine power output — denser air exerts more force on the blades. It varies with temperature, altitude, and humidity.

Ideal Gas Law for Air Density: ρ = P / (R_specific × T)

Where:

• ρ (rho) = air density in kg/m³
• P = atmospheric pressure in Pascals (Pa)
• R_specific = specific gas constant for dry air = 287.05 J/kg·K
• T = absolute temperature in Kelvin (K = °C + 273.15)

With Humidity Correction: ρ = (P_d / (R_d × T)) + (P_v / (R_v × T))

Where P_d = dry air pressure, P_v = water vapor partial pressure, R_v = 461.5 J/kg·K. Humid air is slightly less dense than dry air (water molecules replace heavier nitrogen/oxygen).

Worked Example: Standard sea level conditions: P = 101,325 Pa, T = 15°C = 288.15 K:

• ρ = 101,325 / (287.05 × 288.15) = 101,325 / 82,718 = 1.225 kg/m³

At Denver (1,609m altitude): P ≈ 83,600 Pa, T = 15°C:

• ρ = 83,600 / (287.05 × 288.15) = 1.013 kg/m³ — 17% less dense

Wind Turbine Power Effect: P = 0.5 × ρ × A × v³ × Cp

At Denver vs sea level with same wind speed: 17% less power output.

Air Density Reference Values:

• Sea level, 15°C: 1.225 kg/m³
• Sea level, 30°C: 1.165 kg/m³
• 1,000m altitude, 15°C: 1.112 kg/m³
• 2,000m altitude, 15°C: 1.006 kg/m³