Wind Technology Fundamentals

Wind energy is the wind’s kinetic energy converted to electrical energy via an alternator.

Kinetic Energy (K.E.) is given by the equation:

K.E. = 1/2 mv2

“m” for a wind turbine is the mass of air available to turn the turbine

“m” is in lb. or g. or kg.

with “v” = velocity of wind in m/s2 (metric units)

The “m” or mass of air is the volume of air * density of air; m=v*ρ

How is volume determined for a flowing mass of air?

Volume is determined by the (Velocity of air (V)) * (Air swept by the wind turbine (A))

Volume = V * A

A = area swept by the wind turbine

V = velocity of wind

Combining these equations results in …

 K.E. = 1/2 mv2

= 1/2(ρ*A*v3)

Therefore, energy generated by a wind turbine is determined by two key factors:

  • Area swept by the wind turbine
  • Velocity of air

An increase in the area increases the energy linearly.  If the area doubles, then energy doubles. However, most HAWTs’ sweep an area that is a circle. So if the radius is doubled, the area increases fourfold. Therefore, the energy increases fourfold. The effect is magnified due to the relationship between the area and radius (π*r2) for a circle, which is the area swept by a HAWT.

How does the industry leverage this information?

Horizontal Axis Wind Turbine (HAWT) manufacturers often attempt to increase the area in order to increase the power produced. However, increasing the area causes an increase in the radius of the wings.  This causes other complications such as weight, tower height, velocity, and others.

Significant engineering efforts have been used to overcome these issues. There is a physical limit that the area can be increased (or the radius of the wings can be increased).  When the wings are very long, strong materials are needed.  If the material is not strong enough, the wing can collapse on itself.

How does “velocity” impact energy output?

Energy produced varies as the cube of the wind velocity.

Thus, doubling the velocity of the wind causes energy output to increase by a factor of eight (cubed).

One way to increase the velocity of the wind is to put the wind turbine higher and higher. Another way to increase velocity is to use Bernoulli’s Principle to increase the velocity of wind. Bernoulli’s principle can be illustrated here in a simple garden hose example.

How does the industry leverage this information?

There are 3 methods commonly used by manufacturers to increase the velocity of the wind.

(i)                  Install the turbines on tall towers. The taller the tower, the higher the wind velocity.

(ii)                Find areas on the planet where there is high wind such as offshore, mountain passes, etc. The problem encountered here is the impact on wildlife as well as challenges in transporting the power where it can be consumed.

(iii)               Tether a wind turbine to a kite or drone or a self-propelled drone to make that object fly in an endless loop using the tether as a means to transport power from kite to ground.

(iv)               Use Bernoulli’s Principle to accelerate the wind

How does Alchemy Power leverage this information?

Alchemy has designed a patented accelerator to increase the wind speed going over the turbine blades.  Net impact of the increase in wind speed gained by the accelerator results in a cubed increase in power.  Therefore, a 25% gain in speed causes an increase of 95% in power.