Small Wind Turbine Blade Performance Measurement and Analysis Through Vehicle Test Procedure Kimon Silwal1, Sulav Shrestha1, Peter Freere2, Rakesh Sinha2, Pramod Ghimire2 Kathmandu Alternative Power and Energy Group, Nepal
[email protected]
2nd Global WE Conference: WeAthens2014
• Testing a locally fabricated wind turbine system often is a daunting task specially in absence of wind tunnel testing facility and before taking the prototype to far distant mountain location specially in context to country like Nepal. • Verification of the system performance in a short term basis has been possible through vehicle test procedure. • Essentially during the test, velocity of the vehicle is adjusted at certain time intervals to maintain the turbine at different rotating speed. The power curve can be plotted generally to maximum of 13m/s wind speed with the developed vehicle test set-up. Wind turbine and tower clamped to truck
Turbine Tail
Upper section holding pipes
Anemometer 1 (Data Logger)
Anemometer 2 (Manual data)
Figure 1: Fi^ng the components
Variables collecDon from vehicle test procedure • Ba9ery Voltage(V) • Current to ba9ery(A) • Frequency(Hz) • Wind speed(m/s)
Note: These variables can either be manually noted down or be saved in a flash drive using a 4 channel digital oscilloscope while driving the vehicle at different speed or be logged in a data logger.
Parameters measurement • Phase Resistance(R) • Voltage drop across the diodes in the bridge rec6fier
Note: Torque is calculated as func?on of rota?onal speed with and without coupling an unloaded generator.
To pulse channel
F
W
Figure 3: Methodology chart for performance analysis
150
500 400
100
200
50
100
DP1 Three Phase Bridge rectifier Unit
Resistances R1:3.3K R2: 6.8K R3:1.4K R4: 20k R5: 10K
Voltage Sensor Circuit R1 DP2
Current Sensor
0
0 3
4
R2
+12V
6
7 8 9 10 Wind speed (m/s)
11
12
13
14
Turbine Speed (RPM)
Figure 6: Ba9ery power and turbine speed as func6on of wind speed.
DP1: Differential Probe 1 (50x) DP2: Differential Probe 2 (50X)
-
5
Ba9ery Power (Wa9)
Capacitances C1: 20uF
-12V
F: Frequency C: Current V: Voltage W: Wind Speed
Cp and TSR
Dc Bus Bars
0.35
10 9 8 7 6 5 4 3 2 1 0
0.30 Battery Bank
0.25
2, 12V 200Ah Battery
DeterminaDon of l osses
• Using the following equa6ons Cp and TSR can be calculated. PW = 0.5*ρ*A*V3 wa9, ρ = density of air (1.29kg/m3) A = Area swept by the blade (m2) V = Wind velocity (m/s) Cp = PB/PW TSR = RPS*R/V R = radius of the blade (m) V = wind velocity (m/s)
-
V
The mechanical shaT power supplied by the blade can be calculated as PB = Po + Prec + Psta + PFW PB = Blade Power Po = Output Power to ba9ery Prec = Power lost in the rec6fier PFW = Power lost as fric6on and windage
700
300
+
DeterminaDon of Blade Power
+
C
Current Sensor Circuit
• Rec6fier loss(W): Rec6fier loss can simply be calculated as a product of measured current at different vehicle speed and voltage drop across the rec6fier. • Stator loss(W): Measured current from the vehicle test and phase resistance, stator loss can be calculated. • Fric6on and windage loss(W): The fric6on and windage torque can be calculated from eq1 mul6plied with rota6onal speed(RPS) will yield power loss as fric6on and windage.
200
600
R3
Calculate Cp and TSR
Figure 2: Test set-‐up at the back of the truck
7ah 12V battery for data logger Power supply
Frequency Sensor Circuit
Variable collecDon from lab test • Torque as func6on of generator speed TFW = A*Ω + B..eq1 (Ω is the generator angular velocity rads/s)
800
R5
Measuring variables and system p arameters
900
R4
Figure 4: CR1000 data logger and sensor set-‐up for KAPEG 2 rotor blade 12 volt system
The graphical plots presented below are generated with the computation technique mentioned as in method section through vehicle test procedure for KAPEG 2 rotor blade design. The measurements were recorded manually from oscilloscope during the test. Losses Graph
100 90 80 70 60 50 40 30 20 10 0 300
Fric6on Loss
Rec6fier loss
% loss(stator)
400 450 500 550 RotaDonal Speed (RPM) % loss(rec6fier)
0.15
0.05 0.00 2
3
4
5
6 7 8 9 10 11 12 13 14 Wind Speed (m/s)
Power Coefficient (Cp)
Series2
Figure 7: Cp and TSR as func6on of wind speed
CONCLUSION The vehicle test procedure could be a convenient way to determine the performance of small wind turbine prototypes where wind tunnel facility or field testing facility are not available. The testing procedure could be completed in 3 or 4 hours with all the preparations done before hand with generation of power curve slightly over the rated speed. Using data loggers allows analysis of large number of collected measurements with increased precision. But loggers would be quite expensive to buy.
Stator loss
350
0.20
0.10
VEHICLE TEST RESULTS FOR KAPEG 2 ROTOR BLADE DESIGN
Percentage of the total loss ( % )
INTRODUCTION
250
Rotaional Speed (RPM)
A simple set of test is required initially in a lab with simple test rig mainly to model generator’s friction and windage loss expression. The test could be run without a torque meter but then the drive in the test rig needs to be modelled. A 2.5m 3’’ tower is fitted at a back of a truck with a small wind turbine system under test along with anemometer and other measuring equipments. The vehicle is driven at different speed ranging from 10km/ hr to 45km/hr to collect various measurements required for turbine performance analysis.
Power and Blade Speed
Tip Speed RaDo (TSR)
Extracting performance curves for a small wind turbine system is often a challenging and comprehensive task. There are different ways of achieving performance curves such as from wind tunnel testing or directly from field testing. The paper present methodologies, tools and techniques and graphical analyses involved in producing characteristics curves of a small wind turbine blades through vehicle test procedure. The procedure of vehicle testing is elaborated both from manual data collection and through logging the data from Campbell Scientific data logger.
Power (WaQs)
METHOD
Cp
ABSTRACT
600
650
CONTACT
% loss(fric6on)
Figure 5: Different losses graph as func6on of turbine speed
Kimon Silwal :
[email protected]
