Modeling and Analysis of a Wind Turbine Blade with Active Profile Control Using a Shape Memory Alloy By: Jeffrey Mensch Background from:

Project Description Development of triple rotor blade wind turbine: 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:

SMA PropertyNi-TiCu-Al-NiCu-Zn-Al % of each element 49-51%Ni, 49-51% Ti %Al, 3-4.5%Ni, 81-84%Cu5-10% Al, 10-30%Zn, 65-80%Cu Critical Temperature-50 to 110 deg. C-140 to 100 deg. C<120 deg. C Densityapprox g/ccapprox 7.64 g/ccapprox 7.12 g/cc Hysteresis (deg. C)approx. 30 deg. Capprox 35 deg. C15-25 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 ProsLarge pseudoelasticity, can be reused thousands of times, stronger than other SMAs Rank123

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*C p ρAV 3 C p 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