Wind Turbine Interface
Presented By: Ricardo Cuello
Date Performed: Nov.05.2009
Lab Partners: Adam Authier
Group 12 – AET1003
November 12, 2009
The goal of this lab was to demonstrate the basic operating principles of a wind turbine. In this case, a 3 Phase VAWT (Vertical Axis Wind Turbine) was usedconnected through the computer with a circuit board. The aim of the lab was to investigate the differences between the star and delta configuration. The Star configuration produced higher voltages than the Delta. The efficiency of this turbine was well below the theoretical value estimated using Betz law. Efficiencies were in the 0.05 to 0.38 percent ranges. Higher voltages were reached when acapacitor was used; a 10% more compared with the no capacitor configuration.
The development of renewable energy resources from both industrial and residential points of view highlights the importance of the environment’s protection. This is a global trend due to the finite amount of the classical energy resources. Wind energy does not pollute and it is readily available. Theenergy of the wind is extracted with a wind turbine. A wind turbine is a device that converts the kinetic energy of wind into mechanical energy. Then, this mechanical energy is converted to electrical energy using a generator. Most generators are permanent magnet generators. One of the main issues is the efficiency of that conversion.
The kinetic energy (E) carried by the wind with speed (v)is modeled by the following formula:
E= 12×m×v2 ( Formula 1 )
The derivative with respect the air mass flow over time is:
E=P= 12×ρ×A×v3 ( Formula 2 )
Where ρ is the density of air and A is the area.
But this kinetic energy cannot be captured 100% by a wind turbine. One of the wind capabilities is to flow around any obstacle. This flow causes the turbine to rotate and slows down thewind. Applying the first law of thermodynamics, the energy lost by the wind (kinetic) is transferred to mechanical energy in the turbine. However, if we capture 100% of the wind’s kinetic energy, then it will stop it. A balance must be found between stopping the air and forcing it to flow through the blades. This limitation is governed by Betz law. Betz law states that, independently of theturbine’s design, only 59.3% of the kinetic energy can be converted to mechanical energy(1).
(1) Betz Law [online] http://en.wikipedia.org/wiki/Betz%27_law
Figure 1. Energy transfer principle of a wind turbine. (2)
Now using formula 2, a theoretical maximum power that can be obtained from a wind turbine is:
E=P= 12×ρ×A×v3× 0.593 ( Formula 3 )
Wind turbines are classified depending of itsrotation axis. They can be horizontal or vertical. Currently, HAWT (Horizontal-Axis Wind Turbines) are more common than VAWT (Vertical Axis Wind Turbine). Every type of turbine has its own applications.
HAWT(3) | VAWT(3) |
Advantages | Disadvantages | Advantages | Disadvantages |
→Tall tower base access to stronger winds.→Variable blade pitch can be remotely adjusted.→High efficiency, sinceblades move perpendicular to the wind. | →Tall towers and long blades are difficult to transport (sometimes transportation is 20% of the cost).→Difficult to install ( big cranes ).→Their height disrupts the landscape.→Additional yaw control system is needed to face the turbine against the wind. | →Generator is located near the ground.→Lower noise signature.→No need for yaw mechanisms.→Easier tomaintain (close the ground).→Lower wind startup speeds than HWATs.→No massive structures. | →Wind speeds are lower close to the ground.→Increased chance of blade fatigue due to wind loading changes. |
One of main important components of wind turbine is the generator. As stated earlier, the most common type is permanent magnet generator (PMG). They are also called alternator because the current...