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
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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