RENEWABLE POWER GENERATION THROUGH SAVONIUS ROTOR (VERICAL AXIS WIND TURBINE)

RENEWABLE POWER GENERATION THROUGH SAVONIUS ROTOR (VERICAL AXIS WIND TURBINE)

RENEWABLE POWER GENERATION THROUGH SAVONIUS ROTOR (VERICAL AXIS WIND TURBINE)

OPTIMISATION OF SAVONIUS (VERTICAL AXIS) TURBINE

FOR RENEWABLE POWER GENERATION

INTRODUCTION:

Our present work describes the modification in design of the savonius rotor system which is simple in design , fabrication, maintenance and more suitable for small scale power generation applications. Savonius turbines are self starting, inexpensive and is least sensitive to wind direction which makes it more reliable for both urban and rural applications.

NEED FOR SAVONIUS WIND TURBINE SYSTEMS:

# The normal wind mills (axial) require a tower of 50- 70 m height.

# They require a large space owing to their large rotor vane (diameter ) span.

# They shut down during heavy or low turbulent wind conditions.

# They require a starter motor to overcome the initial inertia of the large rotor.

# They need an exclusive YAW mechanism for changing the direction of rotor against wind.

# They require a steady wind pattern so they cannot be installed everywhere.

All these draw backs of the normal axial wind mills favour the improvisation of savonius rotor and make our design a valid one.

BASIC SAVONIUS ROTOR SYSTEM:

The Savonius rotor is a vertical axis wind turbine with high starting torque. Its use has been limted till now because of the poor aerodynamic shape of rotor. Nevertheless these type of rotors are self starting , simple to construct and least sensitive to wind direction. So modifying it improve its overall performance would increase its potential of small scale power generation.

# 2 – 6 bladed radial turbine .

based on eqn :- No. of Blades = 8.5 (sin β) / (1 – r1 /r2)

# mainly uses drag rather than lift like Darrius rotor (vertical axis).

# doesn’t require a huge space like axial rotors (normal wind mills).

MODIFICATIONS DONE :

The following modifications are done inorder to increase the overall performance of the rotor.

i) Twisting the blades

ii) Back valves to reduce opposite drag

iii) Funneling the shaft

iv) Improving the aerodynamic shape

TWIST ANGLE OF THE BLADES:

The twisted blades offer low turbulence comparing to normal straight blades which contributes to the increase in the rotor speed. The blade profile is designed in such a way that the wind enters through the lower half and exits through the upper half with a streamlined flow. θ = 30 – 40 deg depending on the width of the blades.

# turbulence of the air flow is reduced .

# The twist angle makes the rotor insensitive to direction of the wind.

BACK VALVES :

# Reduces the opposite drag and prevents the back flow (acts like a NRV valve) and so

increases the speed

# It is designed in such a way that it can open only upto an angle of 30-45 degree.

The working of the valves :

* The valves shut down when the vane moves along the direction of the wind so that it increases the favourable drag.

* The valves open when they move opposite to the direction of the wind current thus reducing the opposite drag.

FUNNEL SHAPED SHAFT :

The shaft is funnel shaped so that the wind entering the lower half of the twisted vanes go through them without causing any turbulence. This reduces the overall turbulence and so reduces the opposite drag.

AERO DYNAMIC ROTOR :

To improve the aero dynamic characteristics and to reduce the opposite drag , thus increasing the overall efficieny.

CUSTOMISATION :

Through various design research and developments , the savonius rotor system can be customized into various forms. It could be incorporated onto an automobile or setup on top of a sky scraper or as a portable vertical axis wind mill.

CONCLUSION:

Thus we have proposed three major modifications in the savonius rotor which would increase the overall efficiency by 5-10 %. The main reason behind this paper is to create an awareness about this savonius among rural small scale power generation sector thus reaching another step in renewable power generation.