windpower engineering webinar - vortex generators on wind turbines

Copyright 2013 UpWind Solutions, Inc and SMART BLADE GmbH 1

Partnership Profiles

Smart Blade GmbHGerman engineering firm established in 2009, specializing in wind turbine aerodynamics & blade design

UpWind Solutions, Inc.North American O&M provider established in 2007, offering full range of O&M services and performance services


Blade Aerodynamics

Root section

Outer section


Design Compromises # 1– Blade Twist


Angle of Attack

Angle of Attack

Drag

Lift

Aerodynamic Stall

Aerodynamic Stall


Real shape ->

Best Compromise

Desirable (th

eoretical) shape

Betz optimization

Design Compromise # 2 – Chord Width


Design Compromise # 2 – Chord Width


Stall Effects and Cross Flow


Recapturing Lost Energy with VGs

Vortex generators re-energize areas of the blade that have stalled out

The flow remains attached for higher inflow angles (stall delay)

Dual benefits: Lift Increase and drag reduction


Designing the Perfect VG

Development of the optimal VG design and spacing for high lift-to-drag ratio using wind tunnel testing

Laser sheet

VG Test Units


Designing the Perfect VG

Analysis of the aerodynamic behavior of VGs for pre-stall and post-stall conditions

Vortex Cores

Particle Image Velocimetry Results Wind Tunnel Force Balance Results


Every Blade is Unique

Identifying the exact areas where stall effects are occurring on the blade at various rotor speeds is essential to maximum ROI with a VG installation. A one-size-fits all solution will result in lower PAEY (Production Annual Energy Yield) increases


Modeling Blade Characteristics


Design – Flow Characteristics

Any VG installation that isn‘t based on a complete understanding of the flow characteristics of the blade is missing valuable power gains


Optimized Installation Design

The flow separation line of a blade isn‘t straight, neither should a VG installation

If the orientation of the VGs don‘t change along the path of the install to account for cross flow, the quality of vorticies suffer and drag is increased


VG Design – VG Plastics

Plastic must be proven to survive in UV rich, highly dynamic environments for 10 + years

The VG should be impact resistant to allow for the installation to endure:

• Blade access for repair and inspection• Ice • Flying debris


VG Design - Adhesives

Adhesive must provide superior durability to match lifetimes of VG materials

Large climatic (humidity and temperature) installation envelope necessary for large scale installation efficiency

Minimum application temp = 40° F / 5° CAdhesive strength is retained even when installed in light rain


Installation Using Rope Access

Quality control essential to ensure long lifetime for the install and long-term returns on investment

UpWind utilizes a 35 point quality checklist with photo documentation of key steps


Installation Using Rope Access

Highly accurate placement ensures aerodynamic balance of rotor set

Repeatable installation process with proven 2-10 millimeter accuracy


Proving ROI – Design of Experiment

Turbine A Turbine BRef. Turbine (A)

VG Turbine (B)

Annual Energy Production (AEP) Comparison BEFORE

VG installation

AEP Comparison AFTERVG installation


Data Post Processing

Turbine A

Turbine B

BEFORE VGs AFTER VGs

Turbine B

Turbine A


AEP Increases

Wind speeddistribution

Turbine A vs Turbine B

Turbine C vs Turbine D

- Based on site specific wind distribution data, the AEP before and after VGs is computed- Values of AEP increase of 2-3% after a SMART BLADE/ UpWind VG installation are typical for wind turbines in good condition


Increased Loading Due to VGs?

Unsteady wind turbine loads occur during normal wind turbine operation

The installation of VGs:• Avoids stall and reduces the load

variability• Brings the blade operation closer to

the optimum performance for which it was designed


Increased Loading Due to VGs?

A full FEA (finite element analysis) based on reference materials and lamination plan confirmed theoretical hypothesis that VGs result in an insignificant increase in the operational loads of the turbine.


Additional Benefits – Noise Reduction

Stall Noise Significant noise source

VGs can reduce noise via stall delay


Additional Benefits – Noise Reduction

Aeroacoustic wind tunnel tests performed at various angles and speedsshowed a noise reduction due to VGs


Conclusion – Problem & Solution

Current Turbine Blade Challenges• Blade aerodynamics (design compromise)• Aerodynamic stall• Cross flow dynamics• Stall and wake losses (separated flow)

Solution – Improved Vortex Generators• Delay stall• Increase AEP 2-3%• Reduce loads during volatile wind speeds• Corrects for leading edge degradation• Noise reduction


Conclusion – Customized Process

Process Feature Significance/Value

Non-linear installation contour Accurately traces flow separation line for optimized performance

Varying VG orientation Correctly oriented VGs minimize drag and produce highest quality vortices

Fixed and repeatable measurement points and use of installation templates

Optimal and accurate placement of the VGs to ensure aerodynamic balance

Self-adhesive tape application Large climatic installation envelope and technician proof process with reduced margin for errors


Conclusion

After installing VGs and operating turbines on multiple wind farms, we have seen an AEP increase between 2-3%, providing a strong ROI in a short amount of time for owners

Every day you wait to install VGs, you lose out on production and ROI

Retail Price: $9,900 per WTG, volume pricing available for site and fleet wide installations

windpower engineering webinar - vortex generators on wind turbines

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