How to Calculate Wind Energy

Wind is made up of moving air molecules which have mass - though not much. Any moving object with mass carries Kinetic Energy in an amount which is expressed by the equation:

Kinetic Energy = 0.5 x Mass x Velocity2

Where the mass is measured in kg, the velocity in m/s, and the kinetic energy is given in joules.

Air has a known density (around 1.23 kg/m3 at sea level), so the mass of air hitting a wind turbine (which sweeps a known area) each second is given by the following equation:

Mass/sec (kg/s) = Velocity (m/s) x Area (m2) x Density (kg/m3)

Therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the Mass/sec calculation into the standard kinetic energy equation given above, resulting in the following vital equation:

Power = 0.5 x Swept Area x Air Density x Velocity3

Where power is given in watts (i.e. joules/second), the swept area in square metres, the Air Density in kilograms per cubic metre, and the velocity in metres per second.

How to Calculate Air Density

The evaluation of the air density is essential for wind measurements, as the air density varies largely on different levels and degrees. The air pressure difference between – 10° C and + 30 ° C  is 0.177 kg/m3.
Air Density is:

in kg/m3; air pressure = p, gas constant R, temperature in Kelvin = T

What is the Measuring Unit for Wind Energy

Wind energy is measured in kilowatt hours (kWh) or megawatt hours (MWh), plus the time period, e.g. per year and per hour.