1. The design of cost-
effective pico-propeller
turbines for developing
countries
Dr Robert Simpson, Dr Arthur Williams
Nottingham Trent University, UK

2. Project overview
Aim: “to provide an accurate design and design
method for the cost-effective manufacture of
pico-propeller turbines (<5kW) in developing
countries that is scaleable for a range of
hydrological conditions”
Project partner: Practical Action Peru
(formerly known as Intermediate Technology
Development Group)
Funded by the Leverhulme Trust (UK trust
organisation)

3. Motivation
Low head hydro sites (2 to 10m)
have great potential for providing
electricity in rural areas of
developing countries BUT
progress appears to be hampered
by the lack of a cost-effective
reliable turbine design that is
appropriate for local manufacture in
developing countries
Much is known about the design of
large Kaplan and propeller turbines
but there is little published
regarding the design of very small
propeller turbines

4. Objectives
Understand fully the design scale effects for pico-propeller
turbines using CFD modeling, laboratory experiments and
field testing
Investigate, make and test design simplifications and
improvements to be implemented in the field and laboratory
Produce a design manual and simple computer program that
can be used by local manufacturers and engineers
Disseminate the information and results of the project which
will be made freely available

5. Stage One
Specify a prototype turbine design based on current
knowledge
Turbine manufacture, installation and field testing
(conducted with Practical Action Peru)
Analysis of the turbine performance and investigation
of possible improvements using Computational Fluid
Dynamics
Make modifications to the turbine and compare the
field test data to CFD simulations

6. The turbine site
(Magdalena, Peru)
Civil Works: silt basin, concrete channel,
pipe and forebay tank
Powerhouse: Tailrace water is returned
to irrigation channel

7. Turbine layout
Horizontal shaft
single stage V-belt pulley
driving a 5.6kW Induction
Generator as Motor
(IMAG) with Induction
Generator Controller (IGC)
Spiral casing with six fixed
guide vanes
90º elbow draft tube
Site specifications
Head = 4m
Flow rate = 180-220 l/s
The prototype turbine
(general layout)

8. Original rotor design
Diameter: 290mm
Blades fabricated from flat
plate steel (6mm thick)
Blade profile created by
bending and twisting the
plate to produce camber
and twist
no nose cone
Non-contact seal, with
water allowed to leak during
operation
The prototype turbine
(Rotor design)

9. Initial operation of turbine
Reported problems:
During initial operation water emptied from the forebay tank
The turbine was not producing sufficient power to get the
generator up to operating voltage
Redesign options:
Manufacture a new turbine with different diameter including
spiral casing, rotor and draft tube
Manufacture a new rotor (preferred option due to cost)
Decision:
Use ANSYS CFX to analyse the existing turbine performance and
determine how the turbine could be modified and put into full
operation

10. Spiral casing simulations
Total head loss for spiral casing and guide vanes estimated to be 0.43m at
180 l/s flow rate. Or approximately 11% of gross head at 4 metres.
Fluid angle varied between 22 and 30 degrees from the tangential direction.

11. Full turbine simulations

12. CFD Results
(original rotor)
0
1
2
3
4
5
6
200 210 220 230 240 250 260 270 280 290
Flow rate (l/s)
Head(m)&Power(kW)
0
10
20
30
40
50
60
Efficiency(%)
Head (600 rpm) Power (600 rpm) Efficiency (600 rpm)

13. Comparison of blade
geometry
Radius (m) 0.145 0.116 0.087 0.058
Blade angle (degrees) 17 21 27.5 37.5
Radius (m) 0.145 0.116 0.087 0.058
Blade angle (degrees) 38 46 57 72
Original rotor Redesigned rotor

14. CFD Results for rotors
(power and flow rate)

15. Redesigned rotor
Manufactured locally in Lima, Peru by bending and twisting flat sheet metal
into the required blade angles
Side effect: Slight S-shape in blade shape due to the twisting at the tip
Nose cone included in new design

16. Field testing in Peru
(experimental technique)
Torque: friction brake
Speed: handheld
optical tachometer
Flow rate: measured
from a flume
constructed
downstream of the
turbine
Head: height markings
measured using water
level

17. Revised CFD Simulations
Improvements made:
The S-shape geometry of the blade was modeled
The penstock volume was included
Changes to the geometry of the spiral casing and guide vane
angles were made based on measurements taken onsite
A 3 mm tip gap (3.5% of span length) was modeled
Ongoing research into:
Roughness effects
Leakage through the hydrodynamic seal
Transient simulations
Various turbulence models
Cavitation modeling

18. Blade to Blade view
(at mid-span)
Pressure contours in
blade to blade view
Possible area of cavitation

19. Comparison to field tests:
(power and flow rate)

20. CFD Results:
turbine component losses
Percentage of Gross Head (4 metres)
(speed=800rpm)
Power output
75%
Losses
25%
Tailrace
4%
Rotor
5%
Spiral casing
and guide vanes
11%
Penstock
1%
Draft Tube
4%

21. Scheme costs
Cost
US$
Electromechanical 3610
Civil Works 10500
Electrical Wiring 500
Installation 1000
Total 15610
Output Power 4 kW
Total Cost per kW 3902.5 $/kW
Turbine Cost per kW 902.5 $/kW

22. Conclusions and Future Work
Conclusions
CFD analysis has been used to identify operational problems with the prototype turbine
and has proved to be a useful tool for analysing new rotor geometries.
The CFD simulations give a reasonable predicted performance for power output until
the maximum power point, however, the flow rate is under predicted resulting in an
over estimation of the turbine efficiency by 10%.
Future Work
Further investigation into producing a profiled rotor with better cavitation performance
as well as improvements to the CFD models.
Detailed laboratory testing will be used to complement the CFD results and field tests
Miniature perspex turbine (200W) for a detailed investigation with Laser Doppler Anemometry
Spiral casing propeller turbine of similar construction to the Peruvian prototype (1kW)
Axial flow pump as turbine (approx. 1-2 kW)

23. Video

24. Transient CFD Animation