Introduction
Small scale wind turbines are used to generate supplementary electricity for a range of applications and environments. Small scale wind turbines have several design considerations for improving power output as a function of modifying blade aerodynamics. Manipulating blade pitch as a function of speed and rotor speed can produce optimal angles of attack. Producing an optimal angle of attack for a given wind speed and rotor speed increases power output over a greater range of wind speeds. The objective of this project is to design and analysis a wind turbine rotor that self-optimizes the pitch angle of its blades, achieving maximum conversion efficiency from wind to electricity over the range of operating wind speeds. The Variable Pitch Rotor team is developing a new variable pitch rotor to be retrofitted on a 300 W Air Breeze small-scale wind turbine. The new variable pitch rotor self optimizes the pitch angle passively by using centripetal force to pitch the blades as a function of the rotor speed. In order to prevent damage from high rotational speeds, a fixed pitch turbine must reduce speed considerably or shut down. Variable pitch turbines offer a solution to both these problems. A variable pitch design adjusts to an optimal blade pitch in order to continuously maintain an optimum aerodynamic efficiency through angle of attack. The result is more efficient generation of power across a wider range of wind speeds, including speeds that would be undesirable to a fixed pitch turbine
Design Requirements
The following design requirements are made to verify the performance of the new variable pitch rotor turbine:
- The new design must demonstrate an increased power output over the wind speed range of 4-7 m/s.
- The blades should be able to pitch a total of 15° at a minimum rate of 3° per second (VP Turbines, 2010).
- The mechanism must be able to operate in typical weather conditions, and be waterproof.
Design Analysis
- Shaft Assembly
Blade bending moments are present and are designated as either flapwise moment or
edgewise moment The flapwise bending moment will cause the blades to bend downwind.
Edgewise moments are parallel to the rotor axis and give rise to the power-producing torque.
In addition, torque due to the wind on the blades is also present
Conclusion
We conclude that this system can be used for practical applications. It is observed that though
the power output is low over a designated wind speed but as the wind speed increases the
power generated by the rotor increases and efficiency increases on increasing of the angle of
attack. It is a safe, simple but expensive system to be fabricated it out. It is pollution free and
low maintenance is required if it is install. This could prove to be the solution for the current
energy crisis. .
