Performance values of wind power plants - too good to be true !?

Before you buy a wind power plant, you will ask yourself if you can rely on the manufacturer's data and if these correspond to the reality. You might also want to know, which performance you can expect.

The maximum achievable power of the wind energy is 59% according to Betz. Depending on the degree of efficiency, each wind turbine can convert only a certain proportion into a mechanical and a coupled generator thereof into electrical energy. Any performance data that is stated above this theoretically achievable maximum requires extreme caution. These are values that cannot be physically verified and are therefore highly likely to be incorrect. For this reason, we would like to give you the opportunity to check the performance data of our and of course also other small wind turbines and to simulate different constellations.

The basis for calculating the output power of a wind turbine is always the area swept by the rotor (projection area from the perspective of the wind direction, e.g. circular area for horizontal or rectangular area for vertical wind turbines) and, in addition to the air density, primarily the wind speed. These factors define the volume of air flowing through the rotor and thus the available energy in the wind. Then, the efficiency shows the relationship between the energy contained in the wind and the power that the wind turbine can obtain from it.

The power (P) in Watt is calculated with: P=(ρ*A*v³*cp)/2
Air density (ρ) here 1,22 kg/m³; rotor area (A) m²; wind speed (v) m/s; efficiency (cp) e.g. 0,2 for 20%

Example: (1,22 * 0,304 * 12³ * 0,16) / 2 = 51,3 Watt (ElvWiS^® III rotor)

Here we also provide you with a calculator that you can use to quickly simulate various constellations of rotor area, wind speed and efficiency:

For our vertical turbines, enter the height and width of the swept rotor surface in the calculator, using the following dimensions for the different rotor sizes:

ElvWiS^® 125S (Savonius): 45 x 30 cm

ElvWiS^® 25S (Savonius): 22 x 30 cm

ElvWiS^® I (Savonius): 40 x 30 cm

ElvWiS^® II (Savonius): 80 x 30 cm

ElvWiS^® III (Savonius): 80 x 38 cm

The power calculation for our wind turbines refers to average rotor efficiency values of 16 % for Savonius turbines, which were determined by us in the wind tunnel, as well as a nominal power at 12 m/s and a maximum power at 20 m/s.

For in the article descriptions and the power calculator stated values, the air density is based on 1.22 kg/m³.

The values shown here were determined on the smaller ElvWiS^® I and 125S turbines, at larger turbines, the efficiency ratio shifts especially at low wind speeds due to the lower influence of the ball bearing in favor of the system efficiency (refer to YouTube video: "ElvWiS II Windturbine; schwacher Wind - hoher Wirkungsgrad").

To get a feeling for the wind power, it is important to know that the energy in the wind increases eightfold when the wind speed is doubled. This means that the turbines can generate relatively little power at low wind speeds, but at higher wind speeds, power production increases dramatically.

For a realistic estimate of the energy yield you need to know:
When calculating the power values, please keep in mind that we only indicate the mechanically converted rotor power, which actually can be converted into electrical power, as the finally delivered electrical power can vary greatly depending on the load, charge controller and batterie charge level. Our brushless and cogging-free disc generators are optimally matched to the respective rotors and achieve efficiencies up to 96 % when converting the mechanical power into electrical energy, which is a very good value. Also note that the location and environment of the turbine significantly affect the wind conditions; The highest possible performance can only be achieved with a free wind access without turbulences.
Important: The rotor performances given by us are not to be confused with the generator power, for which the specified power values refer exclusivly to the generator (not the wind turbine) under full load with power adjustment.

Best regards
Your IDEEN-SCHMIEDE