Piggott turbine design_code_dakar_presentation
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Transcript of Piggott turbine design_code_dakar_presentation
Piggott turbine modeling
Estimation of electricity production and blade/tower loads for Hugh Piggott designs, using BEM theory and simple PMG-battery charging model
Hanan Einav Levy
ScopeA BEM code with a battery charging generator model was written in matlab (also runs on the open source octave)This presentation shows the basics of the modelAnd comparison to measurementsThe code is open for any one to use!Also, a web page is being written, for allowing non octave savvy individuals to use this code, for designing and reviewing their Hugh Piggott turbinesThe model is made of two parts:
BEM - Blade Element MomentumBattery charging PMG model
Code algorithmGeometry
Chord twist profileat several point along the radius
Wind speed
RPM range
Blade power and thrust
coefficients
TSR = π60
RPM ·RVTSR = Tip Speed Ratio:
Part 1
Code algorithmBlade power and thrust
coefficients
Generator, Battery & system
parameters
+
Part 2
Test subject: WindAids’ 4 meter design
Are we using the best generator for these blades?How much will we gain by
modifying it?
BEM theoryPart 1
BEM theoryUsing conservation of momentum/energy/mass on annular rings of flow volume through the bladesUsing 2D blade section data - from measurements, or simulations (xfoil,JavaFoil )Results: prediction of Shaft power, and blade loads for every blade RPM and windspeed (usually - the combination of both through ,where R is the blade radius and V is the wind speed )
TSR = π60
RPM ·RV
BEM input 1: Blade geometry
BEM input 2: airfoil properties
NACA 4412
BEM input 2: airfoil properties
NACA4412 Re = 250K-750K
BEM output: force distribution at each TSR
BEM output: Power coefficients vs. TSR
Estimating the Power CurveBalance of power - Blade shaft power = generator shaft powerAll that’s missing is - a model for the generator shaft power vs. RPM, and generator electrical power vs. RPM
Part 2
Generator modelAxial flux Permanent Magnet Generator charging a battery
VPMG
RPMG
Rwire ΔVBR
VBatt
rBatt
I
Vd
KPMG - Voltage constantRPMG - stator resistance model parameters can be calculated based on Hugh Piggott’s model (from windpower workshop) Assuming 2 phases activeOr measured from the PMG
VPMG = KPMG ·RPM
KPMG = 12050
RPMvolt
⎡⎣⎢
⎤⎦⎥
VPMG
RPMG
Rwire ΔVBR
VBatt
rBatt
I
Vd
Generator modelAxial flux Permanent Magnet Generator charging a battery
Equations:
Where Vd was capped according to controller limitation (31V for a 24V machine)
I = KPMGRPM −Vbatt − ΔVBRRPMG + Rwire + rbatt
Vd = KPMGRPM − I(RPMG + Rwire )− ΔVBRPbatt =Vd ·IPShaft = KPMGRPM ·I
Sources:1 - Massachusetts Institute of TechnologyDepartment of Electrical Engineering and Computer Science 6.685 Electric MachinesClass Notes 6: DC (Commutator) and Permanent Magnet Machines2005 James L. Kirtley Jr.
2 - J. R. Bumby, N. Stannard and R. MartinA Permanent Magnet Generator for Small Scale Wind Turbines
VPMG
RPMG
Rwire ΔVBR
VBatt
rBatt
I
Vd
Generator modelAxial flux Permanent Magnet Generator charging a battery
PMGPermanent Magnet GeneratorVPMG
RPMG
Rwire ΔVBR
VBatt
rBatt
I
Vd
The generator model output Example of real PMG numbers
Missing: KPMG reduction and RPMG increase at high currents
Estimating the power curve - WA4Putting it together
Comparison to measurements is good (but not enough measurements)
Estimating the power curve - Piggott 3 mComparison to measurements is not very good - Section data from NACA 44XX
measurements , resulting in a wrong Cp vs TSR curve
Concluding remarksModel is sufficiently accurate
Can help decide if generator winding need changing
Quantify how to change best wind speed efficiency of turbine
Or to identify poor blade configuration
Concluding remarksNeeds improvement
Many possible measurement errors
Amp/volt measurement
wind measurement
Many possible modeling errors
Generator/Battery/wire resistance
Blade profile propertiesfor wooden blades
I’m working on a site for this program
At the moment at It’s at http://gs.playstix.net/piggott/
Will include an option to upload your blade geometry & generator parameters, and use the code to predict outputs, calibrate to measurements and see how changes in gen. parameters effect performance etc.
work is at an early stage… probably up and working by the middle of the year
Code is written in Octave, and is open-source - http://gitorious.org/piggott-turbine-design/piggott-turbine-design
That’s me. Wish I was here in Dakar!