How Much Energy Does a Wind Turbine Produce?

Wind energy is of the fastest-growing clean energy solutions, and wind turbines are one of the best ways to harness the unbelievable power of wind energy.

But how much energy can we extract from the wind? And how efficient are wind turbines in doing so?

According to the U.S. Wind Turbine Database, the mean turbine capacity in 2020 is 2.75 megawatts (MW). At a 42% capacity factor, an average turbine generates over 843,000 kWh per month. In other words, an average wind turbine produces enough energy to power 940 average U.S. homes! This is assuming that the average U.S. home uses 893 kilowatt-hours (kWh) of electricity per month.

If we dive into the numbers behind wind turbine energy production, we can find out just how much energy they produce and what factors affect their output.

Factors affecting the energy output of wind turbines

Some factors are related to the wind turbine itself and its components, while others have more to do with factors outside of human influence. Here are some of those factors: 

Average Wind Speed

The relation between wind speed and power generation
The relation between wind speed and power generation by M. Ahsanul Alam

The faster the wind, the faster the rotor in the wind turbine will rotate, resulting in more energy output. 

Air Density

The relation between wind density and wind speed
The relation between wind density and wind speed by Alexander Bolonkin

The lower the air density, the weaker the wind, and vice versa.

Weaker wind won’t generate enough lift power to rotate the blades, which means that the rotor will spin slower, and you will receive less energy output.

Temperature

The relation between temperature and wind speed
The relation between temperature and wind speed by Ankur Desai

Wind turbines operate optimally in temperatures ranging between -20 to 50 degrees celsius.

If the temperature exceeds that range, the air density will be lower, which will result in less energy output, as we discussed earlier.

Betz Limit

Betz limit (Limit, n.d.)
Illustration of the Betz limit by Andrew de Juan

In 1919, a German physicist named Albert Betz did some calculations and concluded that the maximum energy harnessed from wind wouldn’t exceed 59.3% of the wind’s kinetic energy. This is known as the Betz limit.

In other words, the best wind turbine a man can make is capable of extracting only 59.3% of the wind’s kinetic energy (wind speed X cross-sectional area).

This limit applies to any wind turbine, no matter how big or small it is, and to this day, the best wind turbines can only achieve 70-80% of the Betz limit (i.e. 40% of the wind’s kinetic energy). 

Tower Height

The relation between tower height and power output
The relation between tower height and power output by Mohamed El-Ahmar

As you know, wind is much faster at higher altitudes. This means that the higher the tower, the faster the wind. In turn, the rotor will rotate faster, resulting in increased energy output.

Blade/Rotor Diameter

The relation between rotor diameter and power output
The relation between rotor diameter and power output by Stephen R Turnock

Longer blades allow wind turbines to sweep more area and capture more wind, which results in increased energy output.

Gearbox

The relation between gearbox efficiency and power output
The relation between gearbox efficiency and power output by Navid Goudarzi

The gearbox transfers rotational energy from the rotor to a generator, producing electricity.

The more efficient the gearbox is, the less energy it will waste on heat and friction, thus increasing the energy output of the wind turbine.

Generator Efficiency

The relation between generator efficiency and load
The relation between generator efficiency and load by Santhanakrishnan Thirumalai

The more efficient your generator is at converting the energy from motion to electric power, the more electricity you will get.

How much power does a wind turbine generate?

Wind turbines come in models and different sizes, each with unique efficiencies and blade lengths, so it can be difficult to measure the exact output of every type of wind turbine.

Using this equation, we can calculate the theoretical power output of a wind turbine with any known parameters.

Speed vs. power output characteristics of a wind turbine Wind speed changes continuously and its magnitude are random over any interval. For simulation of randomly changing wind speed, probability distribution of the random number should be known. The average wind speed is usually considered constant for some intervals (say about 10 minutes). The fluctuations during such intervals can be considered to be combination of constant and sinusoidal variation around the mean speed, V m. A typical formula is [9], 2 2 [1 0.2 cos( ) 0.5 cos( )] 20 600 m t t V V ω
How to calculate the power output of wind turbines by Wind Power Engineering
P = Power output
Cp = Maximum power coefficient (0.25 to 0.45)
ρ = Air density
A = Rotor swept area
V = Wind speed
k = 0.000133

To save you the trouble, we made a list of wind turbine output for several sizes of turbines:

Rotor Diameter/m Tower Height/m Rated Power/kW Annual Production/MWh
20 40 80 95
30 50 250 400
46 78 600 1250
70 100 1500 3500
90 105 3000 6900
130 150 7000 15000

Note: These numbers are theoretical. They are merely here to give you an idea of what the different physical specifications will achieve in energy output.

While the numbers themselves are just theoretical, the equations used to calculate them are not. These same equations have been in use for a while now and are reliable.

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