Highly Efficient Vertical Axis Wind Turbine for Low-Moderate Speed ...

Highly Efficient Vertical Axis Wind Turbine for
Low-Moderate Speed Wind
Farhang Pourboghrat, Professor
Mechanical Engineering Department
Indo-US Research in Renewable Energy
Symposium on Bio-fuels & Wind Energy, 7 th & 8 th December, 2010, New Delhi, India

Presentation Outline
Introduction & Motivations
MSU Wind Energy Research Team
Design of Highly Efficient VAWT
Continuous Variable Transmission (CVT)
Blade Materials and Manufacturing
Testing of FRP Composites
FEA of FRP Composite Forming
..
Ideas for Collaboration

Motivating Factors:
Introduction
Reduce Dependence on Petroleum to Generate Electricity
Generate Electricity From Clean, Renewable Wind
US Statistics:
Total US Electric Capacity in 2007 – 1 TW
Available Resources From Wind in the US – 5.5 TW
Generation of Electricity From Wind - 2% of Total US
Energy
DOE Goal for Generating Electricity From Wind By 2030 -
20%
Prevalent Type of Wind Turbine in the US – HAWT
HAWTs Generate kWatt-MWatt Range of Power
VAWTs Generate Watt-kWatt Range of Power
VAWTs Are Rated to Be Less Efficient Than HAWTs

World Wind Map

US Wind Map

Michigan Wind Map
MSU

NREL Chart of Efficiency for Various
Types of Wind Turbines

Advantages
Disadvantages
Advantages
Disadvantages
VAWT vs. HAWT
Horizontal Axis Wind Turbine (HAWT)
Higher efficiency due to variable blade pitch.
Consistent wind loading over the course of a rotation reduces vibration and noise.
Established manufacturing know-how and market acceptability.
Increased costs of transporting tall towers and long blades.
Installation requires very tall and expensive cranes and skilled operators.
Massive tower and heavy foundation to support blades, gearbox, and generator.
Complex design of twisted blades is difficult and expensive to fabricate.
Large size may disrupt the landscape and create local opposition.
Requires yaw control to turn the blades and nacelle toward the wind.
A distance of 5 rotor diameters siting is needed in order to minimize wake effects.
Difficult, expensive, and frequent maintenance required.
Vertical Axis Wind Turbine (VAWT)
Smaller tower structure, since lower bearings are mounted near the ground.
The generator and gearbox are installed near the ground.
Suitable for low speed winds, due to lower wind startup speed.
May be built at locations where taller structures are prohibited.
Can take advantage of locations where landscape increases wind speed near the ground.
May have a lower noise signature.
Needs less space than HAWT to generate the same amount of power.
Straight blades are much easier and economical to fabricate or extrude.
Lower overall maintenance and transportation costs.
Lower aerodynamic efficiency compared to HAWT.
Blade fatigue failure due to change in stress sign during each revolution.
May require dismantling the entire structure to fix the generator or gearbox.

GOAL: Develop Lighter, Stronger, Reliable,
Highly Efficient Straight-Blade VAWT
V
w
(Steady/Unsteady,
Low Speed Wind)
Blade Orientation
Mechanism
Central
Shaft
(Load,
Vibration)
Gearbox, CVT
Electric
Generator
(Optimum Tip
Velocity Ratio)
Airfoil
(Shape,
Lift/Drag)
Blade
(Orientation,
Material,
Sensors)
(Efficiency, Reliability,
RPM, Storage Type)

Industrial Partners
MSU
Wind
Energy
Team
University and
Research Lab
Partners
Develop Efficient, and
Reliable Transmission
Systems, Including CVT for
Variable Wind Conditions
Pourboghrat, Feeney

On-Going Projects..
Experimental Research Wind Turbine (W/T):
The W/T is Comprised of a Variable Speed Motor to
Simulate Variable Wind Conditions; a CVT; an
Induction Generator; and a Battery.
The Set Up Will be Used to Verify Computational
Modeling.
The CVT will Control RPM and Tip Speed Ratio (TSR),
to Insure that Generator’s Output Remains at 60 Hz.
Lightweight Composite Blades Will be Added Later.
Developing a FAST/Simulink Model of W/T with CVT to
Optimize Power Output and Mitigate Vibration Loads.
Pressure Sensors for Real Time Monitoring of Blades.
Finite Element Analysis of Vibration Loads in Gear Train
Systems (Using Romax software)..
Fabricating a High Efficiency VAWT with Blade Pitch
Control Mechanism.

Grid
t
g
Air
Wind Turbine:
1
2
3
Power t g Air CP V A
Drivetrain Efficiency
Generator Efficiency
AirDenisty 1.2 Kg m
C Power Coefficient ( Betz Limit, Max 0.59)
P
50 Hz
Inverter
Asynchronous
Generator
3
Fixed
Gear
Problem Areas
Rotor
V D
D Rotor Diameter m
V Wind Velocity m s
1 2 2
A Sweep Area D ( m )
4

Grid
60 Hz
1. Wind Turbine with CVT
NuVinci CVT
Inverter
Asynchronous
Generator
Variable
Gear
(CVT)
BENEFITS:
•Maximum efficiency even with sudden changes in wind speed.
• The generator produces electric current at a constant frequency.
• Improved output, efficiency, and reduced vibrations.
Fixed
Gear
Rotor
V D

NuVinci CVT

Experimental Set Up Representing W/T
Motor
Controller
CVT
• NuVinci CVT gear ratios range between 0.5:1.75 (350%)
• The CVT will control the “tip-speed ratio” for optimum W/T performance.
V T
V
“tip-speed ratio”: . D 2V
V
D .
2
Generator

PID Control of HAWT + CVT with FAST/Simulink*
The control objective is to track the ideal tip-speed ratio.
Simulation of the system’s performance in response to five turbulent wind
conditions show an improvement in the electric energy output compared with
the standard fixed-speed operation ranging from 3.9% to 29.8%.
A mitigation of fatigue loading is also possible but not done.
Control scheme can be optimized to take full advantage of CVT capabilities.
*Andrew H. Rex and Kathryn E. Johnson, Journal of Solar Energy Engineering, 2009.

FAST/Simulink Modeling of HAWT/VAWT with CVT
Rotor
Gear
train
CVT
Aerodynamics Dynamics Dynamics &
Controls
Apply SISO/MIMO Controls Strategies to
both mitigate load and improve efficiency
Simulink®
Induction
Generator
Electromagnetics

Objective
2. Nonlinear Dynamic Loading and Responses for
Wind Turbine Reliability
Brian Feeny, Michigan State University, Award # CBET-0933292
Understanding of wind turbine blade
dynamics, and how dynamic loading
affects gearbox reliability.
Issues
• Cyclic gravitational force F
• Direct cyclic component
• Parametric cyclic component
• Aerodynamic forces (e.g. distributed f a)
• Cyclic via wind shear, shadowing
• Self excitation (flutter)
• Responses cause gearbox loadings
Collaboration: MSU, Romax Tech., NREL
Gearbox Reliability Collaborative. Modal
analysis of gearbox housing. FEM of
gearbox, under vibration loading.
f a
F p
F d
F = mg
wind

Nonlinear Dynamic Loading and Responses for
Wind Turbine Reliability
Brian Feeny, Michigan State University, Award # CBET-0933292
Loaded Romax Model:
NREL Gearbox
HS
LS
Contact stress, outer race HS
shaft bearing
FEM Modal Analysis on
Housing
Contact stress, HS shaft
pinion gear tooth

3. Blade Material Options
Light Weight, Strong, Impact Resistant, Durable, Inexpensive
Matrix Choices:
Thermoplastic (Polypropylene, Polyethylene,..)
Thermoset (Polyester,..)
Biobased (Polyurethane, PLA, PHBV,..)
Non-Renewable Fiber Reinforcement Choices:
Glass and Carbon Fibers
Hybrid of Glass/Carbon Fibers (applied to select areas)
Graphene nano-platelets
Renewable Fiber Reinforcement Choices:
Straw Bio-Fibers (Corn/Wheat/Rice)
Non-Wood Bio-Fibers (Kenaf/Sisel/Henequen/Coir)
Wood Bio-Fibers
Nano-Whiskers

E (BTUs)/1 lb. fiber
U.S. Cents/lb.
120
100
80
60
40
20
0
30,000
25,000
20,000
15,000
10,000
5,000
0
Why Bio Fibers for Blades?
Cost comparison
70
23,500
Energy savings
6,500
Glass Kenaf
- Mechanical PERFORMANCE
- Biodegradable and Recyclable
- CO 2 Neutral & Sequesterization
25
Glass Biofiber
Density, g/cm3
4
3
2
1
0
2.6
Weight savings
1.3
Glass Biofiber
Biodegradable
Materials

Specific Modulus (E-Modulus/Density)
60
50
40
30
20
10
0
Comparison of Specific Modulus for Various
Fibers
Kenaf
Hemp
Modulus/Cost
Comparison
1 Sisal Coir E-Glass
Modulus/Cost (E-Modulus/($/kg))
160
140
120
100
80
60
40
20
0
Mechanical
Performance:
Modulus
Comparison
Comparison of Modulus Per Cost for Various
Fibers
1
Kenaf Sisal Coir E-Glass
Ref.: Zampaloni, M., Pourboghrat, F., Yankovich, S. A., Rodgers, B. N., James Moore, Misra, M.,
Mohanty, A. K., and Drzal, L. T., Composite A, 2007

Flexural Strength (MPa)
80
40
0
Flex Strength (MPa)
Flex Modulus (GPa)
34
46
1.7 1.5
Ref.: A. K. Mohanty, S. Desai, P.
Mulukutla, M. Misra, L. T. Drzal, 2004
6.2
37
PHB PP PHB + 30%
KENAF
Impact
Strength
PHB +30% Kenaf
superior to PP +
30%Glass
35
3.5
36
3.8
Impact Strength (J/m)
80
70
60
50
40
30
20
10
0
67
5.4
Kenaf HENQ Glass
PHB +
30% HENQ
PHB +
30% PALF
PP + 30%
GLASS
24
5.8
35
PHB + 30%
GLASS
9
6
3
0
PHB+ 30%Henequen
comparable to PP+30%Glass
48
36
PHB PP PHB + 30%
KENAF
Flexural Modulus (GPa)
Natural Fibers +
Biocomposites:
58
Kenaf HENQ
PHB + 30%
HENQ
Flexural
Modulus
29
PHB +
30%PALF
65
Glass
PP + 30%
GLASS
46
PHB + 30%
GLASS

Effect of Fiber Length and Volume Fraction:
Modulus (MPa)
12
9
6
3
0
2.9
3
4.6
5.9
6.2
A B C D E F
11
A= 30% kenaf 6mm fiber/ soy composites injection molding
B= 33% Kenaf 6mm fiber/ soy compression molding
C= 55% Kenaf 2mm fiber/ soy compression molding
D= 56% Kenaf 6mm fiber/ soy compression molding
E= 57% Kenaf 2 inch fiber /soy compression molding
F= 54% Kenaf long fiber/ soy compression molding
Impact strength (J/m)
400
350
300
250
200
150
100
50
0
Impact strength
Fiber length on impact surface
50
0.2
92
0.8
125
0.7
184
1.2
289
2.0
A B C D E F
370
2.7
3
2.5
2
1.5
1
0.5
0
Fiber length on Impact
surface (mm)

CNT Nanoparticle
Modification of CF
Surface
CNT - high modulus, high strength,
high electrical conductivity etc.
Expected CFRP properties
a. Fiber direction
- tensile strength
- compressive strength (-> OHC)
b. Transverse direction
- interlaminar fracture toughness (->
CAI)
- electrical conductivities
(-> lightning striking resistance)
c. Others
- damping property
Additional Improvements:
Exfoliated graphene Nanoplatelets at 5wt%
functionalized with a CTBN toughening agent increased
the unnotched impact strength by 238% of the base
vinyl ester resin without any loss of modulus.
MWCNT at 0.5 wt% coated on the CF surface increased
the Mode II fracture toughness by 7% without loss of
modulus or strength.
Compressive strength
CF CNT
preventing fiber buckling by
enhancement of modulus
and yield strength of matrix
Interlaminar fracture toughness
stopping crack propagation
by bridging effect

[MPa] [MPa] [MPa]
[MPa] [MPa] [MPa] [MPa]
200
180
160
140
120
100
80
60
40
20
14000
12000
10000
6000
4000
Flexural Strength
0
0 5 10 15
[Vol%]
20 25 30
Flexural Modulus
Flexural Modulus Of
1um Graphite
Nylon 66 15um Reinforced
Graphite
In-situ
CF
With Up VGCF To 20 v%
CB
8000 Nanofillers.
Flexural Modulus
[MPa]
14000
12000
10000
8000
6000
4000
2000
0
1um Graphite
15um Graphite
In-situ
CF
VGCF
CB
Flexural Modulus
1um Graphite
15um Graphite
In-situ
CF
VGCF
CB
Flexural Strength Of
Nylon 66 Reinforced
With Up To 20 v%
Nanofillers.
Flexural Modulus
0 5 10 15 20 25
[Vol%]

4. Experimental Testing of FRP Laminate
Glass mat fiber reinforced thermoplastic
Continuous fiber reinforcement (40% glass)
Long, chopped fiber reinforcement (32% glass)
“long” -> 50-100 mm in length
Polypropylene resin matrix
Processing at 0-30 psi Pressure

Glass Mat
207 kPa (30 psi)
0 kPa
Glass Mat
Delamination

Squeeze Flow Test –
A Method to Measure Anisotropy
Metal Plates
Preferred fiber orientation determination
Fiber Reinforced Sample
Heated Platens

Distance from center (in)
4.2
4.1
4
3.9
3.8
3.7
3.6
3.5
3.4
3.3
3.2
3.1
3
Determining the Preferred Fiber Orientations from Compression Tests for R401-B01
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360
Angle along part (deg)
Chopped Fiber
Length (in)
4
3.75
3.5
3.25
3
2.75
2.5
Continuous Fiber
Determining the Preferred Fiber Orientations using the Distance from the
Center Point after Compression Testing for C321- Chopped Fiber Mat
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360
Degrees from Zero (deg)

Stress (kPa)
140000
120000
100000
80000
60000
40000
20000
0
Stress-Strain Curve for R401-B01, Continuous Fiber Mat, 60 Degree Direction
Ef = 6.95 Gpa (1008 ksi)
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13
Strain (mm/mm)
Stress-Strain Curve
for a sample along
the 30 o Direction
Stress (kPa)
60000
50000
40000
30000
20000
10000
0
Uniaxial Tension Test Specimen
Stress-Strain Curve
for a sample along
the 60 o Direction
Stress-Strain Plot for C321-B01, Chopped Fiber Mat Thermoplastic,
30 Degree Direction
E f = 3.56 Gpa (516 ksi)
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11
Strain (mm/mm)

5. Finite Element Modeling of FRP
Initial
configuration
Final
configuration

Constitutive Relationship for
Multiple Preferred Fiber
Multiple Preferred
Fiber Orientations
Orientations
1-Fiber
Direction
2-Fiber
Direction
t 1 2
...
n
jk jk jk jk
Q Q Q Q
Q
t
jk
3-Fiber
Direction
Stresses and Strains based on rotated material frame
n-Fiber
Directions

Components of the Stiffness
Q E
Matrix
11 11 12 21
Q E
22 22 12 21
Q E
12 12 11 12 21
Q G
33 12
13 31 23 32
21 12
/(1 )
/(1 )
/(1 )
Q Q Q Q
Q Q
Material properties defined along the fiber directions
0

Material Properties Needed as
Model Input
Input parameters
Young’s modulus of the fiber (E f)
Young’s modulus of the resin (E m)
Poisson’s ratio for the fiber ( f)
Poisson’s ratio for the resin ( m)
Shear modulus for the fiber (G f)
Shear modulus for the resin (G m)
Initial volume fraction (V fo)

Input Parameters for
Constitutive Model - Glass Fiber
Continuous Fiber Mat Chopped Fiber Mat
E f, 0 5.15 GPa E f, 30 3.56 GPa
E f, 60 6.95 GPa E f, 105 6.5 GPa
E f, 90 6.69 GPa E f, 120 4.9 GPa
E m, all 1.5 GPa E f, 150 3.95 GPa
f, all 0.361 E m, all 1.5 GPa
m, all 0.1 f, all 0.317
G f, all 29.9 GPa m, all 0.1
G m, all 0.2 MPa G f, all 29.9 GPa
G m, all
0.2 MPa

Deformed Shape
Experiment: U.Mohammed et al., Composites Part A, p.1414, 2000

Continuous Glass Fiber Mat

Pressure Effect (on Fiber Angle)
Without pressure With pressure
Fluid Pressure Reduces Fiber Rotation.

Pressure Effect (on Shape)
Without Fluid Pressure 137 kPa (20 psi)
274 kPa (40 psi) 689 kPa (100 psi)

6. Composite Hydroforming*
Prepregs
Processing Steps:
1. Heat Thermoplastic Sheet (in the die).
2. Close Die, Fluid Fill, Pressurization.
3. Displace Punch, Control Pressure.
4. Cool Punch and Part. Remove Part.
1 2
3 4
* Farhang Pourboghrat, Zampaloni, M., and Benard, A., “Hydroforming of
Composite Materials”, US Patent No. 6,631,630, October 14, 2003.

Woven
Glass
Kenaf
Fiber

7. FRP Composite Blade Manufacturing
1) Design Blade Cross Section (Airfoil) For Maximum Lift:
Vorticity Contours over SD7003 Airfoil as obtained
by Large Eddy Simulation.
2) Split The Blade Into Two Halves (Asymmetric):
Top Half
Bottom Half
VAWT Blade

Blade Manufacturing Process
Stamping Process Stamping Process
(a)
Compression Molded Flat Composite Panel
Stamped Flat Panels Forming; (a) Bottom Half, and (b) Top Half.
Adhesively Glued Halves Form the Blade
(b)

Remove
Mold
Adhesive
Pressurized
Medium
Trim Excess
Material
Adhesive
Hybrid
Thermoplastic
Sandwich Sheet
Final
Blade

VAWT with Lightweight
CFPP Blades

8. Effect of Blade Orientation
Adjustment Strategy During the
Rotation on the Efficiency of VAWT
Table 1. Computed Effect of Blade Orientation Adjustment Strategy on VAWT Efficiency
FREQUENCY OF
BLADE
ORIENTATION
ADJUSTMENT
Every 1/2 o
Every 4 o
Every 8 o
WIND
VELOCITY,
V (M/S)
w
TIP SPEED
RATIO,
R V
w
TORQUE,
T (N.M)
POWER,
(WATT)
P T
EFFICIENCY,
C P P
p wind
5.0 1.0 35.3 176.5 47.5%
7.5 1.0 79.5 596.3 47.5%
5.0 1.0 18.8 94 25.3%
7.5 1.0 42.2 316.5 25.3%
5.0 0.81 6.53 26.4 7.1%
7.5 0.81 14.7 89.1 7.1%

Cascade Model Prediction of Power
Generated by High Efficiency VAWT
with Pitched Blade
Table – Numbers and Sizes of VAWTs Needed to Generate 30 MWh Energy per month
WIND
CATEGORY
AND
LOCATION
HEIGHT
FROM
GROUND,
H (M)
VAWT
DIAMETER,
D, AND
BLADE
HEIGHT, H
(M)
WIND
VELOCITY,
V (M/S)
POWER
(KW)
ENERGY
(MWH/MONTH)
NUMBER
OF WIND
TURBINES
3 (Lansing) 10 10, 12 4.71 3.54 2.55 12
3 (Lansing) 30 10, 12 5.62 6.0 4.32 7
3 (Lansing) 50 10, 12 6.09 7.67 5.52 6
3 (Lansing) 30 16,18 5.62 13.89 10.0 3
3 (Lansing) 50 14,16 6.09 13.89 10.0 3
5 (Shore) 50 14, 16 8.8 41.7 30.0 1
6 (Shore) 50 12, 14 9.6 41.7 30.0 1

Areas of Collaboration
Wind Tunnel Testing of Medium Size Highly Efficient VAWT.
Construction and Field Testing of Highly Efficient VAWT in Low-Moderate Speed
Wind Regions.
Scaling Up of the Highly Efficient VAWT.
Mechanisms for Pitching W/T Blades for Optimum Performance.
Blade Shape Morphing Mechanisms, Materials and Related Technologies.
Computational Model Development
Multi-Scale Computational Models to Predict Mechanical, Electrical, Thermal,
Electromagnetic Properties of Nano-Platelet Reinforced Polymer Composites.
Failure Models for Nano-Platelet Reinforced Polymer Composites.
Fatigue Failure Models for Various Wind Turbine Components.
Computationally Efficient Fluid-Solid Interaction Strategies/Model for Blade
Aerodynamics Simulation.
Integration of Simulink with Aerodynamics, Gear Train, CVT, and Generator
Models.
Robust Controls Strategies for Optimization of Wind Turbines System.
Etc.
Sensor Development for Real-Time Health Monitoring of Wind Turbine System.
Land Policy and Supply Chain Management Issues in India.

Thank You!
Questions?

U.S. Wind Map

4. Fabrication of Flat Laminated Composites
(a)
(a)
50 wt % PLA /50 wt % Kenaf fiber mat laminated composite: (a) before and
(b) after the Compression Molding.
Hybrid laminated composite (PLA/Glass mat/PLA/Kenaf fiber /PLA/Kenaf fiber
/PLA/Glass mat/PLA) : (a) before and (b) after the Compression Molding.
(b)
(b)