1. COMBINED DARRIEUS - SAVONIUS WIND TURBINE
By:-
Abhishek Srivastava |

2. Wind Turbine-Introduction
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy.
If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger.
If the mechanical energy is used to drive machinery, such as for grinding grain or pumping water, the device is called a windmill or wind pump.
Wind turbine uses environmental air and NOTHING else to generate electricity unlike other turbines be it thermal or hydro. |

3. Need of Wind Turbine
Isolated communities, that may otherwise rely on diesel generators may use wind turbines to displace diesel fuel consumption.
Individuals may purchase these systems to reduce or eliminate their dependence on grid electricity for economic or other reasons, or to reduce their carbon footprint.
Wind turbines have been used for household electricity generation in conjunction with battery storage over many decades in remote areas.
Without the depletion of our natural resources and causing pollution ,wind turbines can be used in remote places also. |

4. Types of Wind Turbine
The wind turbines are broadly classified into two categories:
Horizontal axis wind turbine(HAWT)
Vertical axis wind turbine(VAWT)
Darrieus turbine
Savonius turbine |

5. Vertical Axis Wind Turbine
Vertical Axis Wind Turbines have the main rotor shaft arranged vertically. Key advantages of this arrangement are that the turbine does not need to be pointed into the wind to be effective
With a vertical axis, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, hence improving accessibility for maintenance.
When a turbine is mounted on a rooftop, the building generally redirects wind over the roof and this can double the wind speed at the turbine for maximum wind energy and minimum wind turbulence |

6. VAWT Advantages
Lower construction cost as compared to HAWTs because there is no need to build a massive tower structure to support the heavy HAWT blades and turbine assembly;
Easier to maintain as the moving parts are located near the ground;
Does not need to turn to face the wind if the wind direction changes making them ideal in turbulent wind conditions.
Lower wind start-up speeds than HAWTs. Typically, they start creating electricity at 6 m.p.h.
Less likely to break in high winds as they usually have a lower Tip-Speed /Wind-Speed ratio.
 Low height useful at locations where laws do not permit structures to be placed high;
VAWTs are quieter and interfere less with TV, radio & radar signals;
VAWT systems can also directly drive pumps which may be used to store wind generated energy. |

7. Darrieus Turbine
The Darrieus rotor is a vertical axis type of wind turbine or VAWT. It’s powered by the Lift forces generated from a set of airfoil blades so it can reach blade speed much higher than the blowing wind speed.
The darrieus turbine is of two basic types:
Egg-beater type
H-rotor type |

8. Savonius Turbine
Savonius turbines are drag- type devices, consisting of two or three scoops. Because of the curvature, the scoops experience less drag when moving against the wind than when moving with the wind. The differential drag causes the Savonius turbine to spin
Because they are drag-type devices, Savonius turbines extract much less of the wind's power than other similarly-sized lift-type turbines. |

9. MY PROJECT |

10. Combined Darrieus & Savonius Turbine|

11. Advantages
Combination both of Savonius and Darrieus blade VAWT is able to operate at low wind speed and produce high efficiency to transfer wind energy to electrical power.
Power coffecient of the combination of two rotors is higher as compared to individual rotor’s.
The whole turbine is self starting.
It does’nt require greater heights for catching high velocity wind. |

12. Construction
The model is created by designing and fabricating a four blade Savonius rotor having a specific bucket diameter and a two blade Darrieus rotor (H-rotor type),on a single vertical shaft.
The material used in darrieus and savonius rotors are:
Darrieus rotor blades- Mild Steel
Savonius rotor blades- Mild Steel |

13. Dimensions Savonius rotor :- 2’ 7” Darrieus rotor blade :- 1’ 6”
Height
Wind Turbine :- 7’ 5’’
Darrieus Rotor :- 1’ 10’’
Savonius Rotor :- 1’ 11.5”
Diameter
Darrieus rotor :- 3’ 8”
Savonius rotor :- 2’ 7”
Shaft` :- 12 mm
BREADTH
Darrieus rotor blade :- 1’ 6”
Savonius rotor blade :- 1’2.5” |

14. CALCULATIONS Mass Flow Rate of wind :-
Where r= air density, A= swept area, V= Wind Velocity
K.E. of wind :- |

15. BETZ LIMIT
Albert Betz was a German physicist who in concluded that No wind turbine can convert more than 16/27 (59.3%) of the kinetic energy of the wind into mechanical energy turning a rotor. This is known as the Betz Limit [13] or Betz' Law.
Wind rotors extract energy by slowing down the wind. For a wind
turbine to be 100% efficient it would need to stop 100% of the wind - but then the rotor would have to be a solid disk and it would not turn and no kinetic energy would be converted.
So a factor called coffecient of performance ( ) is introduced.
K.E. of wind = |

16. TORQUE CALCULATIONS The torque acting can be calculated as :
-where P is the output power and w is the angular velocity.
-where n is the rotational speed in rpm
Therefore, |

17. APPLICATIONS
The turbine can be placed in low lying terrains to generate power.
India, apart from coastal region, wind velocity is relatively low and varies appreciably with seasons. This low velocity and seasonal winds imply a high cost of exploitation of wind energy.
Thus this design of wind turbine could solve the problem of small scale power requirement especially in the northern region. |

18. www.final-yearproject.com | www.finalyearthesis.com