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RESEARCH PROPOSAL FOR:
Analysis of Factors Influencing the Performance of a Zero Head Hydro Energy
Harvester
SUBMITTED TO:
FACULTY OF ENGINEERING, THE BUILT ENVIRONMENT AND INFORMATION
TECHNOLOGY
OF THE
NELSON MANDELA METROPOLITAN UNIVERSITY
FOR THE PROPOSED RESEARCH PROGRAMME:
Magister Technologiae: Engineering: Mechanical
BY:
Adriaan Jacobus Opperman
Student Number: 207081055
Submitted:
Supervisor : Dr Russell Phillips
Co-supervisor : Prof. Danie Hattingh
1
1. Introduction
Since antiquity nature provided mankind with flowing water and one such
example is rivers. This flow of water is driven by a difference in height from the
start of the river to the end. This difference is also known as the head. Due to the
fact that the water is moving it has kinetic energy. The concept of harnessing this
hydrokinetic energy has been around for many years.
A number of devices exist that extract energy from flowing water. Most of these
devices utilize a differential water level (head). A well-known example of this is
the hydraulic ram (1). Extraction of hydrokinetic energy from flowing bodies of
water where no differential in level exists is also possible (2) however few
successful installations are currently in use in South Africa.
2. Objective
This research is to develop a Zero Head Hydro (ZHH) energy harvester with a
increased efficiency to conventional machines in use.
3. Problem Statement
Factors contributing to the performance of ZHH are not well documented. The
main variable needs to be identified and evaluated to determine optimum design
and installation conditions.
4. Sub Problems
4.1. Design of a working model that will be used for evaluation and optimisation.
4.2. Development of optimum shape of paddles or blades – evaluates, compare
and document performance.
4.3. The influence of augmentation devices to increase flow velocity.
4.4. Safety mechanism in case of flooding – dealing with debris and high water
levels.
2
5. Hypothesis
This research will identify critical variables for the ZHH platform optimisation
which will allow for increased efficiency. The main contributing factors would be
design optimisation and flow convergence.
6. Delimitation of the research
6.1. Three types of ZHH machines will be analysed.
6.1.1. Axial flow underwater type.
6.1.2. Cross flow underwater type.
6.1.3. Paddle wheel type.
6.2. Experiments will be only conducted in a 700mm wide controlled open
channel.
6.3. ZHH experimental platform with a max power output of less than 1kW will be
considered.
7. Significance of Research:
7.1. For agriculture and rural communities in South Africa
If energy can be extracted from flowing water such as rivers, it can be utilized
for pumping water or generating electricity. The availability of this cheap
renewable energy in areas without grid electricity will enhance agriculture as
well as the quality of life in rural communities and small farmers.
7.2. For NMMU
This project will enhance the NMMU’s focus on sustainable renewable
energy research and broaden the knowledge base in this field.
8. Preliminary Literature Review
8.1. Axial flow underwater turbine
An axial flow underwater turbine can be described as a turbine with the
rotational axis parallel to the incoming water stream utilizing lift or drag type
3
blades (3). An example of an inclined axis Garman axial flow water current
turbine is shown in Figure 1.
This particular configuration was installed by a company called Action Contre
la Faim (ACF) in the Nile near Juba a major Southern Sudan city. The
purpose of the installation was to supply drinking water to the local
population. A Gamin under water turbine can produce blade efficiencies of up
to 30% and power output of up to 3kW with a constant hydrofoil rotor blade
and pitch. To connect the rotor to the centrifugal pump a two stage belt drive
was used. This allowed the rotor to operate as close as possible to the most
efficient tip speed ratio over a wide range of water speeds (4). The
performance range is as follows.
1. The minimum viable river current speed is 0.6 m/s in which a turbine
with a 4m diameter rotor will deliver 2 l/s of water to a 4m static head or 100
W of electricity from a 240 V generator.
Figure 1: Inclined Garman Turbine (4)
4
2. At 1.2 m/s a 3.4 m rotor diameter machine would give an electrical
output of 820 W.
3. At 1.9 m/s the corresponding figures are 2.2 m diameter and 1750 W.
Above 2.0 m/s the rotor diameter would be sized to limit the system output to
about 2 kW.
To illustrate the figures above look at Graph 1. This graph compares the
actual power produced to the Bets limited power to the available kinetic
power from the flowing water.
The kinetic power available from flowing water is given by (5):
Were:
To calculate the power output from a rotor device such as the Garman the
following formula is used (5):
Were:
1 2 3
Actual Power Output (W) 100 820 1750
Ideal Power Output (W) 804.800 4651.744 7730.728
Kinetic Power Output (W) 1357.167 7844.425 13036.640
0
2000
4000
6000
8000
10000
12000
14000
Po
we
r (W
)
Power Comparison
Graph 1
5
According to Dixon (5) under ideal theoretical conditions the maximum value
of is 0.593. Therefore only 59.3% of the available kinetic power can be
used as output power under ideal conditions. This limitation is called the Betz
limit. Most well designed machines will have a of between 0.3 and 0.35.
The maximum pumping head is 25 m using a single turbine, but by installing
turbines side-by-side with their pumps in series, higher heads can be
generated. For electricity generation at 240 V, a three-phase induction motor
is used as a generator with an electronic controller and ballast load. For
battery charging, a permanent magnet alternator is used. On a 240 V system
operating in northern Sudan, both generator and pump are fitted to the
machine, allowing the farmer to pump during the day and have electricity at
night (4).
Figure 2: River current turbine on the Nile, Sudan, 1982 (8)
6
According to Khan (2), within a period of four years, a total of nine of these
Garman prototypes were built and tested in Juba, Sudan on the White Nile
totalling 15,500 running hours.
Figure 3 illiterates three installation possibilities to utilize the axial flow
underwater turbine configuration.
8.2. Cross flow underwater turbine
Cross flow underwater turbines can be horizontal or vertically orientated and
differs from the axial flow underwater turbine by having the rotational axis
perpendicular to the flowing stream of water (6). An advantage of the cross
Figure 3: Axial flow water turbines: (a) inclined axis, (b) float mooring; (c) rigid mooring (2).
7
flow under water turbine is that most of them rotate unidirectional even with
bidirectional fluid flow (7).
As mentioned above the cross flow turbines can be divided into two groups,
vertical and horizontal. In the vertical axis domain the use of H-Darrieus or
Squirrel Cage Darrieus is rather commonly used for power generation from
wind but nearly non-existent in hydropower production. The Gorlov turbine is
another member of the vertical axis family were the blades are of helical
structure. Savonious turbines are “semi drag type” devices that may consist
of straight or skewed blades. Some disadvantages of the vertical axis
turbines are: low starting torque, torque ripple and lower efficiency. These
turbines may not be self-starting therefore an external starting mechanism
may be needed (7).
Shown in Figure 4 are different vertical types cross flow underwater turbines.
Figure 4: (a) Darrieus, (b) H-Darrieus, (c) Savonious, (d) Gorlov (2)
8
Furthermore the horizontal cross flow turbines are mainly drag based devices
and said to be less efficient than their lift based counterparts. The large
amount of material usage can be another problem for such turbines. Axial
flow turbines are self-starting and the issue of start-up is not significant.
However, they come with a price of higher system cost owing to the use of
submerged generator or gearing equipment. Vertical axis turbines, especially
the H-Darrieus types with two or three blades are reasonably efficient and
simpler in design, but not self-starting. Mechanisms for starting these rotors
from a stalled state could be devised from mechanical or electromechanical
perspectives (7).
Shown in Figure 5 is the Atlantisstrom horizontal cross flow turbine designed
and tested by Braunschweig Technical University, Harzwasserwerke GmbH
and Volkswagen - Coaching GmbH in Bad Harzburg, Germany (6).
8.3. Paddle wheel type
The vertical paddle wheel can also be seen as a cross flow device since the
axis of rotational is perpendicular to the direction of flow. However the paddle
wheel is not submerged. According to Denny the maximum efficiencies of the
conventional overshot and undershot paddlewheels are 63% and 22%
respectively (8).
Figure 5: Atlantisstrom turbine (6)
9
Denny (8) goes on and explains why the undershot paddle wheel is still used
even though the efficiency is almost three times less than its overshot sibling.
To understand this, one must appreciate the importance of waterwheels in
Europe, at the beginning of the industrial revolution, prior to the widespread
availability of steam engines. The Domesday Book of 1086 recorded over
5000 mills in England. By 1820 France alone had 60 000 waterwheels. The
dense population of mills along early 19th century European rivers and
streams meant few hydro sites, so water head (height difference, and thus
potential energy) became a scarce and valuable resource. Overshot wheels
required a large head (2–10 m) and so were usually confined to hilly areas, or
required extensive and expensive auxiliary construction, such as mill races
(water flumes or sluices) that ran for hundreds of metres. Undershot wheels,
on the other hand, could operate with less than 2 m head and so could be
located on small streams in flat areas, nears to population centres.
Due to the lack of head the undershot paddle wheel was used near Kakamas
in the Northern Cape, South Africa to pump water and is shown in Figure
7&8.
Figure 6: (a) Overshot Paddlewheel, (b) Undershot Paddlewheel (7)
10
Figure 8: Undershot Paddlewheel near Kakamas
Figure 7: Undershot Paddlewheel near Kakamas
11
9. Research Methodology
9.1. Research on current ZHH devices.
9.2. Comprehensive literature study.
9.3. A solid model of the proposed research platform will be drawn up.
9.4. CFD analysis of flow augmentation.
9.5. Construction of model for testing.
9.6. Systematic modification and enhancements to model to optimize efficiency.
9.7. If desired performance is obtained with model a full scale prototype will be
built and tested in a river.
10. Budget (Estimates)
Manufacturing scale model R 5 000
Testing scale model R 5 000
Testing platform (Manufacturing & Equipment) R 20 000
Manufacturing full scale model R 10 000
Testing model (Transport & Modifications) R 5 000
Travelling R 5 000
Printing, binding and other consumables R 1 000
Total Budget R 51 000
11. Project Timeline
12. The Researchers Qualifications
National Diploma Mechanical Engineering, Nelson Mandela Metropolitan
University, 2009
Baccalaureus Technologiae Mechanical Engineering, Nelson Mandela
Metropolitan University, 2010
12
Bibliography
1. HowStuffWorks.com. [Online].; 2000 [cited 2011 05 05. Available from:
http://science.howstuffworks.com/transport/engines-equipment/question318.htm.
2. Khan MJ, Iqbal MT, Quaicoe JE. River current energy conversion systems:
Progress, prospects and challenges. Renewable and Sustainable Energy
Reviews. 2008; 12(8): p. 2177-2193.
3. Khan MJ, Bhuyan G, Iqbal MT, Quaicoe JE. Hydrokinetic energy conversion
systems and assessment of horizontal and vertical axis turbines for river and tidal
applications: A technology status review. Applied Energy. 2009; 86(10): p. 1823-
1835.
4. Water Current Turbines Pump Drinking Water. Technical. Oxfordshire: CADDET
Centre for Renewable Energy.
5. Dixon SL. Fluid Mechanics and Thermodynamics of Turbomachinery. 5th ed. Stein
J, editor. Oxford: Elsevier; 2005.
6. Atlantisstrom. [Online].; 2004 [cited 2011 June. Available from:
http://www.atlantisstrom.de/description.html.
7. Sornes K. Small-scale Water Current Turbines. Oslo: Zero Emissions Resource
Organisation (ZERO); 2010.
8. Denny M. The efficiency of overshot and undershot waterwheels. European
Journal of Physics. 2004; 25(2): p. 193-202.
9. Ainsworth D, Thake J. FINAL REPORT ON PRELIMINARY WORKS
ASSOCIATED WITH 1MW TIDAL TURBINE. Marine Current Turbines Ltd; 2006.