Design and Fabrication of Savonius Vertical Axis Windmill · Design and Fabrication of Savonius...

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Design and Fabrication of Savonius Vertical Axis Windmill

A.VembathuRajesh1, C.Mathalai Sundaram

2, V.Sivaganesan

3, B.Nagarajan

4, S.Harikishore

5

1Assistant Professor, Mechanical Engineering, Nadar Saraswathi College of Engineering and Technology,

Theni 2Principal, Nadar Saraswathi College of Engineering and Technology, Theni

3,4,5Assistant Professors, Mechanical Engineering, Nadar Saraswathi College of Engineering and Technology,

Theni

Abstract — Increasing demand for energy in recent years has been a rise in

development of alternative energy sources. In the present work, VERTICAL AXIS WIND

MILL turbine is being designed and fabricated as for the specification. The VAWT turbine

blades are designed as Savonius blade shape, with less weight and more stiffness. The

assembled VAWT will be mounted on the area where air velocity is maximum which is enough

for producing energy and electric power. VAWT is a special purpose wind mill designed in

such a way that the blades are like a half drum type connected to the shaft at the centre of the

assembly which in turn connected to the generator, generates the power. The power developed

by the VAWT is shorted in battery. This power is used for some useful application.

Keywords-savonious; windmill, vertical axis.

I. INTRODUCTION

The renewable energy is considered as a new technology and an alternating energy source to be used

instead of fossil fuel, its continuous rising cost of it and due to growing concern to reduce the effects

of climate change, such as global warming, generated by extensive and deliberate use of fossil fuels,

mainly in the electric power generating plants and transport. Global warming will continue unless

dependence on fossil is reduced, thus the Wind power has a key role in reducing greenhouse gas

emissions.

An attempt has been made to develop a twisted blade for its use in Savonius wind turbine rotors. The

objective is to reduce the negative torque and the self-starting characteristics of a single stacked rotor

system while maintaining a high rotational speed so that such a rotor system can be used for

electricity generation. Tests have been carried out of semicircular (curved) and twisted blades both in

a three bladed rotor system. Aerodynamic performance of these blades have been evaluated in a low

speed wind tunnel on the basis of starting torque, power output and rotational speed at various setting

angles and gap widths. Experimental investigation shows the potential of the twisted bladed rotor in

terms of smooth running, higher coefficient of performance and self-starting capability as compared

to that of the semicircular bladed rotor. (A. S. Grinspan et al, 2004). The plastic composite material

blades which have less cost and light weight than carbon fiber and balsa wood are designed and

fabricated. Proper aerofoil shape and manufacturing technique gives more lift and further more

power generation. The objective of this VAWT is to generate electricity in remote areas with less

setup cost. (Hemant Pathade et al, 2016). Summarization of the work done at the National

Aeronautical Labo- ratory (NAL) between 1975 and 1977 on the development of vertical axis wind

turbines based on the Darrieus rotor. On the analytical side, a performance analysis was developed

1st International Conference on New Scientific Creations in Engineering and Technology (ICNSCET-19)

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which permits the estimation of the characteristics of such machines. A 5 m high wind turbine using

curved wooden blades was designed, fabricated and tested. Both the theory and initial tests

confirmed the low starting torque of the turbine. Wind tunnel tests were performed on model

Savonius rotors to determine optimum starter bucket configurations. Finally a straight-bladed turbine

was designed and constructed. It is concluded from our experience that Darrieus turbines are likely to

be useful in large systems used to generate electrical power for the grid; for direct water pumping

purposes, however, these turbines are unlikely to be suitable. (P N Shankar, 1979). Savonius type

vertical axis wind turbine and its potential to generate power is designed and fabricated using the

locally available materials. Then the actual power is measured at different wind speeds and finally

the power coefficient is determined. The blade shape is taken as spiral involute. (Abubakkar A et al,

2016). Savonius vertical axis wind turbine can be better option as it operate in low wind condition

also. The choice for this model is to showcase its efficiency in varying wind conditions as compared

to the traditional horizontal axis wind turbine and contribute to its steady growing popularity for the

purpose of mass utilization in the near future as a reliable source of power generation. (Ashwin

Dhote et al, 2015). Pw – Wind power (watt), and Power produced by the turbine Pt has been

calculated using m – Mass flow rate (kg/s), Swept area of the windfall ,V- Velocity of the wind, Θ-

Angular position of turbine, T- Torque obtained by wind, Pt- Shaft power , Cp- Power coefficient

,Ct- Torque co-efficient , μ – Tip speed ratio , r – Radius of rotor , d- Diameter of rotor ,w- Angular

speed of rotor. They have mentioned Various operations involved in fabrication process and

characteristics & specifications of wind turbine. (P. L. N. V. Aashrith et al, 2014). An experimental

investigations to study the performance of a Savonius rotor as well as a Savonius- Darrieus machine.

They designed and fabricated two types of models, one Savonius rotor and the other Savonius-

Darrieus machine was carried out. The Savonius rotor was a two- bladed system having 8 cm bucket

diameter and 20 cm in height with provision for overlap variation. For the Savonius- Darrieus

machine, in the upper part, there was a two-bladed Savonius rotor having bucket diameter of 8 cm

and height of 10 cm and in the lower side, there was Darrieus machine having three curved blades of

dimension of 10 cm in height and 4 cm in radius. The overlap variation was made in the upper part.

These were tested in a subsonic wind tunnel and it was observed that there was an improvement in

the power coefficient for Savonius- Darrieus machine compared to only Savonius rotor under the

same test conditions. (R. Gupta et al, 2006).

2. VERTICAL AXIS WIND TURBINES (VAWT)

The rotational axis is perpendicular to the wind direction or the mounting surface. The main

advantage is that the generator is on ground level so they are more accessible and thus don’t need a

yaw system. Because of its proximity to ground, wind speeds available are lower. It is a vertical axis

machine, very simple from the standpoint of constructive and operational.

Besides simplicity, has the advantage of being very robust and have a strong starting torque,

that possible the starting even with very weak winds. But can be used only with reduced powers and

that the turbine works well with light winds, while its yield decreases with high winds and even

becomes vulnerable, so their size cannot exceed certain limits.

3 AERODYNAMICS AND PERFORMANCE ANALYSIS OF VAWT BLADES

Achieving success in harvesting the power of wind requires a detailed understanding of the

physics of the interaction between the moving air and wind turbine rotor blades. An optimum power

production depends on perfect interaction between both blade and wind.

The wind consists of a combination of the mean flow as well as turbulent fluctuations about

that mean flow. These are very complicated and time consuming for the analysis, and they can only





be predicted by understanding the aerodynamics of steady state operation. An idealized wind turbine

rotor will be examined along with the airflow around the generator rotor and wind turbine blade.

3.1 Aerodynamics Theory and Performance Characteristics

The aerodynamic analysis of VAWTs is complicated due to their orientation to the oncoming

wind. The VAWTs have a rotational axis perpendicular to the oncoming airflow. This accounts for

aerodynamics that is more complicated as compared to a conventional HAWT. However, the

configuration has an independence of wind direction. The main shortfalls of this are the high local

angles of attack and the wake coming from the blades in the upwind part and axis. This disadvantage

is more pronounced with VAWTs. Understanding the aerodynamics of the pure drag type of VAWT

will give important insight for improving the lift coefficient, and designing this turbine for better and

more efficient harnessing of the wind power.

3.1.1 Lift Force

The lift force is one of the major force components exerted on an airfoil blade section

inserted in a moving fluid. It acts normal to the fluid flow direction. This force is a consequence of

the uneven pressure distribution between the upper and lower blade surfaces.

3.1.2 Drag force

The drag force acts in the direction of the fluid flowing. Drag occurs due to the viscous

friction forces on the airfoil surfaces, and the unequal pressure on surfaces of the airfoil. Drag is a

function of the relative wind velocity at the rotor surface, which is the difference between the wind

speed and the speed of the surface, The lift and drag coefficient values are usually obtained

experimentally and correlated against the Reynolds number for analysis purpose.

This thesis uses a CFD code to predict these coefficient values over a range of operating

conditions. The amount of power generated by the vertical axis wind turbine will be analyzed

through code.

4 WIND TURBINE

Wind turbine is used to change wind energy into mechanical energy (such as wind mill and

moving height) and generate electricity. The turbines are classified to two categories, horizontal axis

wind turbines (HAWTs) as shown in Fig.1 and vertical axis wind turbines (VAWTs). If HAWT has a

horizontal axis of rotation, then VAWT has a vertical axis of rotation. VAWT has more simple

structure and installation than that HAWT. The generator of VAWT is placed at the bottom of

central shaft on the ground and they tower do not need to support it. The turbines are useful in

different speed and direction of wind. In contrast, VAWTs have low pressure coefficient, therefore

the scope for major research on VAWT rotors is to improve their performance. VAWT rotors have

different types, such as Savonius rotor, and (eggbeater) Darriues, or H-Darrieus rotor as shown in

Fig. 2. Savonius type (as shown in Fig.3) wind turbine, also called S-rotor, was originally invented

and patented by Finnish engineer, Sigurd J. Savonius in 1931. The turbine made of two halves

cylinder and then moving the two semi cylinder surfaces sideways along the cutting plane like the

letter S. The two semicircular surfaces, called blades or buckets, are mounted on a vertical axis

perpendicular to the wind direction with the gap at the axis between the blades or the overlap. It is a

simple in structure, has good starting characteristics, relatively low operating speeds, and an ability

to capture wind from any direction. But it has a low aerodynamic efficiency.





Fig. 1 HAWTs

Fig. 2 H.Darries

Fig. 3 Savonius Rotor

5. COMPONENTS

5.1 Wind Blade

Savonius wind turbines or wind blade as shown in Fig. 4. Wind turbines are a type of vertical

axis wind turbine (VAWT), used for converting the force of the wind into torque on a rotating shaft.





Fig. 4 Savonius blade

5.2 Shaft

When the rotor spins, the shaft also rotates which transfers the mechanical energy into

rotational energy.

5.3 Hub

The hub is the centre of the rotor to which the rotor blades are attached. Cast iron or Cast

steel is most often used. In VAWT there are two hibs upper and lower because blades are attached at

two points.

5.4 Bearing

A bearing is a machine element that constrains relative motion to only the desired motion,

and reduces friction between moving parts.

5.5 Chain and Sprocket

A chain and sprocket drive is a type of power transmission in which a roller chain engages

with two or more toothed wheels or sprocket, used in wind as a drive from shaft to dynamo. A chain

and Sprocket drive is one way of conveying power to the wheels of a vehicle.

5.6 Dynamo A dynamo is an electrical generator that produces direct current with the use of a

commutator.

5.7 Battery

An electric battery is a device consisting of one or more electrochemical cells with external

connections provided to power electrical devices such as flash flight, etc.,

6. DESIGN & FABRICATION

The blades are designed in Auto CAD. The two blades are of semi circular type which

resembles the Savonious type wind blade. The fig. 5 shows the drawing of the proposed wind turbine

blades.

Fig. 5 Blade

6.1 Fabrication

The blades are fabricated as per the design and specifications. The blades are joined together

with the hollow shaft by welding. The blades are accurately joined so that the air flow can induce

maximum torque to give rotation to the wind blades according to the wind velocity. A base is made

for withstanding the forces acting on the blades while the wind strikes the blades. The wind turbine

shaft is connected to the dynamo shaft through chain bracket.





6.2 Working

When the wind strikes the blades, the turbine shaft rotates according to the wind speed

fluctuations. The dynamo shaft connected to the turbine shaft also rotated by which the kinetic

energy of wind is converted into mechanical energy which is further converted into electrical energy.

The electrical energy from dynamo can be stored in a battery from which it can be further utilized for

electricity purpose.

Fig. 6 Chain Drive arrangement

Fig. 7 Savonius Wind Turbine

7. CONCLUSION

The efficiency of the fabricated wind turbine would be better with variance at different

velocities of the wind. Though the efficiency seems quite low but it can be seen as usable power

generated. These turbines have a great advantage over horizontal axis wind turbine that they can





work on low height thus these turbines can be installed on individual house for their particular use.

The power generated from the turbine can be stored or used to charge a device and then the storage

device can be used as a continuous power source.

REFERENCES

[1] A. S. Grinspan, U. K. Saha and P. Mahanta, “Experimental Investigation of Twisted Bladed Savonius Wind

Turbine Rotor”, ‘International Energy Journal’, Vol. 5, No. 1, June 2004.

[2] Hemant Pathade, Prasad Pandhare2, Rahul saskar3, Rohit Chaudhari4, Prakash Bairagi5, “Design and Fabrication

of Vertical Axis Wind Turbine (VAWT)”, ‘International Journal of Advanced Engineering Research and

Technology (IJAERT)’, Volume 4 Issue 5, May 2016, ISSN No.: 2348 – 8190.

[3] P N Shankar, “Development of vertical axis wind turbines”, ‘Proc. Indian Acad. Sci.’, Vol. C 2, Pt. 1, March

1979, pp. 49-66.

[4] Abubakkar A, T Ravisankar , M.Makeshkumar, “Design and Fabrication of Micro wind Turbine”, ‘International

Journal of Science, Engineering and Technology Research (IJSETR) Volume 5, Issue 5, ISSN: 2278 – 7798, May

2016.

[5] Ashwin Dhote, Prof. Vaibhav Bankar, “Design, Analysis and Fabrication of Savonius Vertical Axis Wind

Turbine”, ‘International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056, Volume:

02 Issue: 03 | Jun-2015. p-ISSN: 2395-0072.

[6] P. L. N. V. Aashrith, Ch.Vikranth, “Design and Fabrication of Savonious Wind Mill”, ‘Int. Journal of Engineering

Research and Applications’, ISSN: 2248-9622, Vol. 4, Issue 6 (Version 1), June 2014, pp.70-79.

[7] R. Gupta, R. Das & K.K. Sharma, “Experimental Study of a Savonius- Darrieus Wind Machine”, ‘Proceedings of

the International Conference on Renewable Energy for Developing Countries-2006’.

Design and Fabrication of Savonius Vertical Axis Windmill · Design and Fabrication of Savonius...

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