Vertical Wind Energy Engineering Ian Duffett Jeff Perry Blaine Stockwood Jeremy Wiseman Design and Evaluation of a Twisted Savonius Wind Turbine

Vertical Wind Energy Engineering

Ian DuffettJeff PerryBlaine StockwoodJeremy Wiseman

Design and Evaluation of a Twisted Savonius Wind Turbine

Property of Vertical Wind Energy Engineering7April 2009


Outline• Problem Definition• Introduction• Concept Selection• Design• Fabrication• Testing• Results• Conclusions• Recommendations



Problem Definition

Design and test a vertical axis wind turbine (VAWT). This design should meet the following objectives:

• Design will be novel and untested• Design will be self-starting• Design will produce reliable power in harsh weather conditions



Wind Energy

• The conversion of wind energy into various other useful forms such as electricity is known as wind power

• Studying wind energy is desirable because:– Wind energy is renewable– There is ample supply of wind energy– Suitable wind patterns are available worldwide– Production costs of wind energy are declining– Wind energy produces minimal greenhouse gas emissions


Vertical Wind Energy EngineeringWind Turbines

Horizontal Axis Wind Turbines (HAWT)Advantages• Higher efficiency• Can furl out of the wind to reduce wind

speed seen by the blades• High towers reduce turbulence caused

by nearby structures Disadvantages• Tower mounting makes maintenance

more difficult• Requires large structures• Installation requires heavy equipment• Requires additional controls to furl and

rotate to orient blades in the wind direction

Vertical Axis Wind Turbines (VAWT)Advantages• Ground mounting makes

maintenance easier• Can be installed in areas of wind

funnelling and high wind speeds• Lower noise signature• Requires lower starting speedsDisadvantages• Lower efficiency• May require guys to support rotation

axis• Can create an inconsistent torque

(pulse)


Vertical Wind Energy EngineeringMajor Types of VAWT

1. Darrieus Wind Turbine– Uses lift to create

rotation– Good efficiency– Torque ripple– Not self-starting

2. Savonius Wind Turbine– Uses drag forces to

create rotation– Low efficiency– High reliability– Self-starting

A very large Darrieus wind turbine on the Gaspé peninsula, Quebec, Canada

Savonius wind turbine



Twisted Savonius

• Increases efficiency of standard savonius wind turbine

• Consistent torque created by symmetrical helical shape

• Rotates regardless of wind direction

• Self-starting



Concept Selection

Modified Twisted Savonius Turbine • Provides consistent torque• Will be self-starting• Will only rotate at the wind speed

allowing for greater reliability in high wind

• Design is untested– Closed around shaft



Independent Design Parameters:• Long Radius• Short Radius• Angle of Twist

Prototype Modelling

Long RadiusR

Short Radius r

180 °360 °

Bottom Plane

Top Plane

α

Short Radius r

RLong Radius

360 ° 180 °

Bottom Plane

Top Plane

α

Bottom Plane



CFD Analysis

• FloWorks simulation developed to test static torque on various foil designs:

→ Constant velocity air stream, 15m/s

→ Measure torque generated on shaft



Circular Foil Design• Maximum Torque @ 360° Twist Angle 0.47 N·m

Elliptical Foil Design• Maximum Torque @ 360° Twist Angle,

108.3 mm Long Radius 0.56 N·m

0 90 180 270 360 450 540 630 7200

0.5

Circular Foil Design

Angle of Twist (°)

Torq

ue (N

·m)

0 20 40 60 80 100 120 140 1600

0.5

1

Elliptical Foil Design

Long Radius (mm)

Torq

ue (N

·m)

CFD Analysis

0 90 180 270 360 450 540 630 7200

0.1

0.2

0.3

0.4

0.5

Circular Foil Design

Angle of Twist (°)

Torq

ue (N

·m)

0 20 40 60 80 100 120 140 1600

0.1

0.2

0.3

0.4

0.5

0.6

Elliptical Foil Design

Long Radius (mm))

Torq

ue (N

·m)


Vertical Wind Energy EngineeringPrototype Fabrication

Rapid Prototyping• Fused Deposition Modeling• Turns computer-aided design (CAD)

geometry into solid state structures.• Max Build Size 10” x 10”• Sectioned Prototype• Required Build time ~ 36 hours per

section• Two Section Shaft• $6300



Design Plan



Prototyping ChallengesPrototyper Size ConstraintsProblem: Limitations in nozzle movement

prevented achieving maximum cross-section

Solution: 5% Reduction in CAD Model SizeProblem: Damage to nozzle heads due to

overheating of material in the semi-liquid state

Solution: Reduced size (by height) of individual foil sections to decrease run time and prevent overheating



Prototype FabricationPrototyping ChallengesAssemblyProblem: Shrinkage of the material

during cooling from the semi-liquid state

Solution: Use of body filler during assemblage to create continuous foil surface

Problem: Rotational unbalance within the foil due to body filler and flexibility of shaft

Solution: Replacement of two shaft aluminum design with single steel shaft


Vertical Wind Energy EngineeringWind Tunnel Setup

Memorial University’s Wind Tunnel

- Wind Speed Range 1.2 m/s (Full Closed) to 10.6 m/s (Fully Open)- Rectangular test section 20.0 x 0.93 x 1.04 meters



• Setup 1• Installed centered and vertically in the wind tunnel with both ends of

the shaft extruding through the bottom and top of the tunnel(2 x Alum 1/2” OD x 36”, inserted at both ends)

• Low friction polyblock bearings• Setup 1 Problems

• Large vibrations during rotation of Blade• Not installed:

• Friction Brake Dynamometer• Anemometer• LED Tac



• Setup 2• Installed centered and vertically within the wind tunnel with a shorter

shaft (Steel 7/16” OD x 36”)• Low friction shaft bearings• Instrumentation setup:

• LED Tac / Handheld Tac• Friction Brake Dynamometer• Anemometer

• Setup 2 Problems• Vibration of Friction Brake Dynamometer

• Pulse loading on load cell• LED Tac sampling rate limited to 50 Hz

• Unable to capture flywheel rotations fast enough



• Setup 2 - Pictures



• Setup 3• Installed centered and vertically within the wind tunnel with a shorter

shaft (Steel 7/16” OD x 36”)• Low friction shaft bearings• Instrumentation setup:

• Handheld Tac• Friction Brake Dynamometer• Anemometer

• Setup 3 Problems• Vibration of Friction Brake Dynamometer

• Pulse loading on load cell



• Setup 3 - Pictures


Vertical Wind Energy EngineeringTesting Matrix

- Number of Tests -> 36


Vertical Wind Energy EngineeringTesting Predictions

Predicted ResultsTwo important design features are:

• Tip Speed Ratio (TSR or ) • Is the ratio between the rotational speed of

the tip of a blade and the actual velocity of the wind

• Power Coefficient (Cp)• The power coefficient tells how efficiently a

turbine converts wind energy into electricity


Vertical Wind Energy EngineeringCFD / Testing Comparison

FloWorks simulations were developed over a range of wind speed for static torque and compared to static test acquired throughout testing


Vertical Wind Energy EngineeringTesting Results

0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.0000.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

Cp vs. Tip Speed

TSR

Cp

4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.00.000

2.000

4.000

6.000

8.000

10.000

12.000

14.000

Power Output vs. Wind Speed

Wind Speed [m/s]

Pow

er O

utpu

t [W

atts]



Summary

•Successful test of novel design

•Design determined to be self starting under varying wind conditions

• Maximum 15% efficiency achieved

•Maximum Power Output of 13 Watts

•Cp vs. TSR Plot follows a similar profile of the predicted

• Power and torque output increases as wind speed increases



Plan Forward & Next Steps

• Improve testing set-up for more reliable results

• Use high frequency DAQ to accurately measure rotation speed

• Review friction brake design to measure more consistent loads

• Test under Newfoundland environmental conditions

• Icing and snow tests

• Higher wind speeds

• Longer term effect of sea spray and fog on system performance



Special Thanks to:

• Dr. Iqbal

• Steve Steel

• Matt Curtis

• Craig Mitchell

• Don Taylor



This Concludes our PresentationQuestions?

Thank you for your Attentionhttp://www.engr.mun.ca/~blaines/

http://www.engr.mun.ca/~blaines/

Documents

Vertical Wind Energy Engineering Ian Duffett Jeff Perry Blaine Stockwood Jeremy Wiseman Design and Evaluation of a Twisted Savonius Wind Turbine