Modeling and Analysis of a Wind Turbine Blade with

Active Profile Control Using a Shape

Memory Alloy

By: Jeffrey Mensch

Background from: http://www.peaceenergy.ca/releases/PEC_press_release_04_07_07/Wind%20Turbine.jpg

Project Description

Development of triple rotor blade wind turbine:

• 10-100 kW range• Choose blade design• Use active profile control• Choose shape memory alloy (SMA)• Compare efficiency of new model with

current designs

Tasks to Be Performed

• Literature search (√)

• Development of design (√)

• Calculations

• Construction of models

• Testing and analysis

Current Blades

• Made out of graphite coated with epoxy• Lightweight• Somewhat flexible• Can be up to 60 meters long• Over time/due to strong gusts, can be

damaged (blade fatigue)– Blades stall– Wind turbine loses efficiency

Active Control - SMA

• Wind still deforms blade

• Strain gauges attached to blades

• Heating via resistor coils will occur when strain reaches certain level

• SMA blades would go back to original shape

Active Control – Pitch Control

• Default pitch: about 5°

• Wind speed measured by anemometer

• Pitch can be changed for optimal power output for given wind speed

Blade Design

NREL S809 foil chosen (type of Grumman Wind Stream blade) - is in common use for wind turbines

Source: http://www.nasg.com/afdb/show-airfoil-e.phtml?id=1188

SMAProperty Ni-Ti Cu-Al-Ni Cu-Zn-Al

% of each element

49-51%Ni, 49-51% Ti 13-14.5%Al, 3-4.5%Ni, 81-84%Cu 5-10% Al, 10-30%Zn, 65-80%Cu

Critical Temperature -50 to 110 deg. C -140 to 100 deg. C <120 deg. C

Density approx. 6.45 g/cc approx 7.64 g/cc approx 7.12 g/cc

Hysteresis (deg. C) approx. 30 deg. C approx 35 deg. C 15-25 deg. C

Problems

High reactivity of Ti during preparation (can be averted by preparing in inert atmosphere); high hysteresis (can be lowered by adding Cu); expensive

As ages, loses shape memory properties; can't withstand prolonged high temperatures; after long time as martensite, has aging induced martensite stabilization effect

Needs solution heat treatment to retain shape memory, which can lead to Zn evaporation; As ages, loses shape memory properties; can't withstand prolonged high temperatures; after long time as martensite, has aging induced martensite stabilization effect

Pros Large pseudoelasticity, can be reused thousands of times, stronger than other SMAs

Rank 1 2 3

Pros and Cons of SMA Blades

• Pros– Lasts longer than current blades– More efficient over time

• Cons– More expensive– About 3x heavier (this can partially be avoided

by only making the “skin” of the airfoil out of SMA)

Calculations

• Power Output– Defined by ½*CpρAV3

• Cp is the power coefficient (maximum is about .593 according to Betz limit)

• ρ is the air density

• A is the area swept by the wind turbine’s blades

• V is the wind velocity

Computer Programs Used

• Winfoil

• MATLAB

Acknowledgements

• Stevens Institute of Technology

• Dr. Siva Thangam

• Joseph Miles

• GISS

• NASA SHARP

• MTSI