1. Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
K. Latoufis | Rural Electrification Research Group | www.rurerg.net
2nd
Wind Empowerment Conference | 3rd - 7th November 2014 | Athens
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab

2.  Reference design: Hugh Piggott (HP) small wind turbine recipe book
 Construction workshops: Undergraduate students of NTUA
 Test machines: 1.8m Neodymium SWT/grid tied, 2.4m Neodymium
SWT/direct battery connection, 2.4m Ferrite AFPM generator/direct battery
connection, 4.3m AFPM generator/grid tied
 Assessment: 2.4m NdFeB SWT / direct battery connection (48VDC) (2005
Piggott design manual) and 1.8m NdFeB SWT / grid tied (2009 Piggott
design manual), assessed for Performance and Robustness
1. Locally manufactured small wind turbine assessment
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab

3. 2. Generator test bench experiments (2.4m HP Batt 48V)
 Cut-in RPM: Found to be close to 210 RPM (depends on battery SOC)
 EMF vs RPM: EMF = 0.0976 x RPM + 0.0058
Terminal Voltage and Line Current against RPM for the 2.4m HP generator connected to batteries
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies

4. 2. Generator test bench experiments (4.3m AFPM Gen Grid)
 Phase difference: 119° - 120° between phase groups (OC operation)
Locally manufactured three phase star connected stator with 5 coils per phase group
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies

5. 2. Generator test bench experiments (2.4m HP Batt 48V)
 Efficiency: Maximum 0.88 at 260 RPM (low wind speeds)
 Torque vs Current: Torque = 3.4 x Line current – 0.73
Efficiency against RPM for the 2.4m HP generator connected to batteries
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies

6. 2. Generator test bench experiments (2.4m HP Batt 48V)
 Temperature: Maximum 85° Celsius after 15 min at rated power (800W)
Temperature against time for the 2.4m HP generator connected to batteries
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies

7. 2. Generator test bench experiments (2.4m HP Batt 48V)
 Power vs RPM: Length of power transmission wire influences RPM of rotor
Power against RPM for the 2.4m HP generator connected to batteries with different power transmission cable lengths
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies

8. 2. Generator test bench experiments (2.4m HP Batt 48V)
 Harmonic content: Due to uncontrolled diode bridge rectifier and direct
battery connection which produces 'humming' noise of generator
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Harmonics in the current waveform due to the three phase rectifier and current Fast Fourier Transform

9. 3. Blade rotor wind tunnel tests (1.2m HP on resistive load)
 Aerodynamic power coefficient (cp): Optimal TSR is 5.5 - 5.75 and
maximum cp is 0.38 - 0.40 at 9.5 m/s. At lower wind speeds cp is 0.35
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Aerodynamic power coefficient against tip speed ratio for wind speeds between 8m/s to 11 m/s

10. 4. Small wind turbine test site (2.4m HP Batt 48V/Cable 80m/4mm2)
 Power curve: Cut-in at 3m/s, rated power at 10.5m/s with 525W uncertainty
of +/-11.2W, furling system commences operation at 6.5m/s
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Power to batteries against wind speed using the method of bins

11. 4. Small wind turbine test site (2.4m HP Batt 48V/Cable 80m/4mm2)
 Power coefficient: System efficiency peaks at 0.31 at 5m/s, values of above
0.3 for wind speeds ranging from 5 to 6.5m/s, at 10m/s the system's efficiency
drops to 0.18 due to power regulation by the furling system
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Power coefficient against wind speed using the method of bins

12. 4. Small wind turbine test site (2.4m HP Batt 48V/Cable 80m/4mm2)
 Annual Energy Production: With 5m/s mean wind speed, the 2.4m HP
wind turbine would be expected to produce 1271kWh per year with an
uncertainty of +/- 111kWh, which would amount to an estimation of 106kWh
per month
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Estimation of the annual energy production according to the mean wind speed
Mean wind speed (m/s) AEP (kWh) Uncertainty (%)
4 751.61 9.9
5 1270.85 7.94
6 1747.85 6.76
7 2124.21 6.05
8 2392.87 5.62
9 2569.72 5.34
10 2673.97 5.13

13. 4. Small wind turbine test site (2.4m HP Batt 48V/Cable 80m/4mm2)
 Response time of furling tail: A power surge from 200W to 1.093kW
occurred in 5s with a wind gust surging from 6m/s to 13m/s
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Response time of furling tail during fast wind speed changes

14. 4. Small wind turbine test site (2.4m HP Batt 48V/Cable 80m/4mm2)
 Starting wind gust: A gust of 4.45 m/s is needed to move the rotor from
standstill to operation
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Response time of furling tail during fast wind speed changes

15. 4. Small wind turbine test site (2.4m HP Batt 48V/Cable 80m/4mm2)
 Furling operation: Tests on the operation of the furling system with 0, 1.5
and 3 extra kgrs
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Response time of furling tail with different weights

16. 4. Small wind turbine test site (2.4m HP Batt 48V/Cable 80m/4mm2)
 Operation in extreme weather conditions: Highest wind speed recorded
31m/s and corresponding power at 470W
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Power curve of 2.4m HP small wind turbine for up to 25m/s using the method of bins
during two days of extreme weather conditions (average wind speed 82km/h)

17. 4. Small wind turbine test site (1.8m HP Grid tied)
 Operation in highly corrosive environment: The test site is located next
to the sea in a highly corrosive environment. Polyester resin cracks in the
rotor allowed for corrosion of the back iron disks within the first year of
operation. The disks were galvanized and cast with vinyl ester resin and
corrosion has been avoided so far, for two more years of operation.
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Corroded back iron disk due to crack in polyester resin and sea water was galvanized and cast with vinyl ester resin

18. 5. Open source hardware research and development at the NTUA
 Ferrite magnetic materials: In order to avoid alloys of Neodymium
magnetic materials which are prone to corrosion, designs with ferrite
magnets have been developed
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
The rotor and stator of an AFPM generator usinf Ferrite magnets for a 2.4m rotor

19. 5. Open source hardware research and development at the NTUA
 Pico-hydroelectric: hybrid design between the AFPM generator described
by Hugh Piggott in the design manual ‘Small wind turbine recipe book’ and
the small hydro casing and turgo runner designs of Joseph Hartvigsen
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Pico-hydro experimental setupTurgo pico-hydro plant

20. latoufis@power.ece.ntua.gr
Thank you for your attention!
Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
Assessment of locally manufactured small wind turbines and
development on open source renewable energy technologies
Kostas Latoufis
neaguinea.org / rurerg.net
RurERG NTUA
SmartRUE research lab