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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

Transcript of Magister Technologiae: Engineering: Mechanicaldougbanks.co.za/resources/documents/Opperman...

Page 1: Magister Technologiae: Engineering: Mechanicaldougbanks.co.za/resources/documents/Opperman M-Tech... · Magister Technologiae: Engineering: Mechanical BY: Adriaan Jacobus Opperman

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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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.

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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

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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)

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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

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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)

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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).

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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)

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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)

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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)

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Figure 8: Undershot Paddlewheel near Kakamas

Figure 7: Undershot Paddlewheel near Kakamas

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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

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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.