AC 2010-828: SYSTEMS DESIGN OF A HYDRO-KINETIC TECHNOLOGY FORRURAL AREAS OF DEVELOPING COUNTRIES

Joshua Baumgartner, LeTourneau UniversityJoshua Baumgartner is a senior mechanical engineering student at LeTourneau University. ANational Merit Finalist and member of LeTourneau’s Honors Program, he advanced to the 2008ASME Student Design Contest International Finals with his sophomore design team. Joshua plansto return to his hometown of San Antonio to work in building design and become a professionalengineer. His other career interests include teaching engineering and designing for people withdisabilities.

Timothy Hewitt, LeTourneau UniversityTim Hewitt is currently studying for his Bachelors of Science in Mechanical Engineering atLeTourneau University in Longview Texas.

Edgar Licea, LeTourneau UniversityEdgar Licea is a student majoring in mechanical engineering at LeTourneau University,Longview. His goal is to take the experience and quality of education he receives from auniversity education and further society through technological innovation.

Nolan Willis, LeTourneau UniversityNolan Willis is a senior electrical engineering student at LeTourneau University. Originally fromAlaska, he spent much of his life working as a commercial salmon fisherman while performingnecessary mechanical work and preparations. More recently, Nolan has taken special interests inrenewable/alternative energy applications as well as power engineering. His career goals includebecoming a professional engineer and solving some of the world's most challenging energyproblems.

Matthew Green, LeTourneau UniversityDr. Matthew G. Green is an assistant professor of Mechanical Engineering at LeTourneauUniversity, Longview. His objective is to practice and promote engineering as a servingprofession, with special interest in improving the quality of life in developing countries. Focusareas include remote power generation, design methods for frontier environments, and assistivedevices for persons with disabilities. Contact: MatthewGreen@letu.edu. IMPORTANT NOTE:DUE TO COMPLICATIONS, THIS IS THE REVIEW VERSION OF THE PAPER. EMAILTHIS AUTHOR FOR THE SIGNIFICANTLY UPDATED FINAL VERSION.

© American Society for Engineering Education, 2010

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Systems Design of a Hydro-Kinetic Technology for Rural Areas of Developing Countries

 

Abstract

This paper presents a case study of a global service-learning project leading towards the implementation of renewable energy technology for remote electricity generation. A student team designed, prototyped, and tested a hydro-kinetic device as part of a project ultimately intended to provide 100 continuous watts of electrical power from river currents in remote regions. The final design must be portable, cost-effective, exceptionally robust, and readily adaptable for needs in the rural developing world. Additional sponsor requirements disallow major civil works or obstruction of river traffic. The design team’s primary sponsor HCJB seeks the system in rural applications where small amounts of power are needed for radio broadcasting, various tools, and medical equipment. This project builds on previously reported work1,2 investigating water-wheel technology, but the focus here is on below-water hydro-kinetic technology due to sponsor request.

The team defined the project scope based on needs interviews and a visit from HCJB engineers. Based on these needs and specifications the team is adapting a commercially available generator with a velocity-boosting shroud specifically designed for slow river speeds, a robust and portable anchoring system, and a suitable electrical system. Extensive testing equipment and methods are being developed to refine and verify the design locally. This paper describes the needs and requirements, design process, industry/organizational partners, final design, and testing results. Consideration is given to the implementation of such projects within an academic structure including funding, identifying knowledgeable sponsoring “customer” organizations, and field implementation of the results. Conclusions are drawn regarding the impact of such projects on student learning and career aspirations.

1 Introduction and Background

Many engineering schools are now employing a service-learning approach to globally-based humanitarian projects3,4,5. The importance of integrating both globalization and social needs into the engineering curriculum is acknowledged by the ABET criteria6, and human need is a clear priority of the engineering profession, as indicated in the NSPE creed*,7. However, the majority of North American engineering students are not familiar with the contexts in which vast needs exist, such as those among the physically disabled or the estimated 4 billion people living on less than $2 a day (PPP)8. These conditions represent a formidable “frontier design environment”, or environments outside the experience and expertise of most engineering students. Sufficiently understanding design needs is notoriously problematic in frontier environments where data and contextual experiences are not readily available.

From a global perspective, many remote areas have either unreliable electrical power or no power at all9. HCJB, an international humanitarian organization, recently requested a student team to design, prototype, and test a system to provide ~2.4kW-hr/day (before storage) of

* “As a Professional Engineer, I dedicate my professional knowledge and skill to the advancement and betterment of human welfare …”

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electrical power in remote areas, from a river with no dams or other significant elevation change. Creating a remote power module with minimal site works (e.g. no dams) will empower HCJB to fulfill their humanitarian objectives in several capacities in remote areas.

1.1 Why Pico-Hydro?

Two of the leading technologies for frontier power generation are fossil-fuel based generators and solar photovoltaic (PV) cells. These technologies are useful, but both have limitations that can affect their usefulness. Portable gasoline powered generators are useful because they can operate in almost any environment, can operate at any time or duration of time, are transportable, reasonably priced, and can have a large power output. The main disadvantages for such generators are fossil fuel reliance, noise emission, and maintenance requirements. The fuel requirement of generators creates reliance on operator intervention, recurring funding for fuel, and fuel availability. Likewise, the generator needs to be maintained regularly to ensure a long work-life.

Photovoltaic (PV) power generation is becoming more common due to ease of use and lower maintenance requirements. The advantage of photovoltaic generation is that once the cells and battery system have been installed, relatively little maintenance is required over years of usage. The disadvantages of photovoltaic generation stem from the reliance on sunlight and the limited life expectancy of the battery storage system. Sunlight is not always plentiful in the location and time most desirable for power generation.

As a result of the disadvantages of other technologies, pico-hydropower generation from flowing water is of great interest to HCJB due to their work in remote locations. The advantage of pico-hydro technology independent from civil works is that it could be brought to a remote location and be easily installed. Once installed, it would be able to generate power constantly and require little or no maintenance. The disadvantages of a pico-hydro solution would be a possibly higher initial expense and long-term maintenance such as battery replacement. Thus, in locations with flowing streams the pico-hydro solution could potentially offer both the continuous power availability of a gas generator (with smaller battery banks than PV) and the low operator intervention and recurring costs of photovoltaic power generation with the least amount of disadvantages.

1.2 Interdisciplinary Senior Design at LeTourneau University

Student involvement in interdisciplinary teams is not only an expectation of industry but also has become a required outcome of the ABET engineering criteria10. LeTourneau university offers a BSE in general engineering with concentrations in biomedical (BME), computer (CE), electrical (EE), mechanical (ME), materials joining (MJE), and recently in civil engineering (CVE). Much of the curriculum is interdisciplinary, with design projects in multiple courses. In parallel, the Department of Engineering Technology offers a bachelor of science degree in engineering technology, with concentrations in electrical (EET), mechanical (MET), and materials joining engineering technology (MJET).

An emphasis on design projects is a historical strength in the LeTourneau school of engineering, and has been developed especially well in the last 10 to 15 years as senior design projects have become more ambitious and have also expanded to include significant applied research projects. In addition, underclass courses have also embraced the project experience to a large degree. This

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project orientation is a defining strength of the program, providing a distinct educational advantage for students.

Senior design initially consisted of one-semester individual projects. These were changed to team projects in 1992 and, at the recommendation of an ABET visiting team, to two-semester team projects in 1997/98 school year. During the period from 2001 to 2006, three separate course tracks were offered – EE Design (including CE students) I and II, ME Design I and II (including BME students), and MJE Design I and II. All senior engineering students began meeting together once a week for most of the spring semester in 2003 in a seminar format to discuss issues of engineering ethics, standards, and professionalism.

It became apparent that students were not uniformly prepared for senior design, so in response a major curriculum enhancement was implemented in 2006-2007 to build upon the existing project-emphasis strength and further improve engineering design projects. The changes required no new faculty resources and did not change the credit hour requirements of any degree plans. A common interdisciplinary senior design experience was implemented in 2006-2007 for all students, in both engineering and engineering technology. The curriculum changes promise a higher quality senior design experience through improved student preparation throughout the curriculum, increased faculty supervision in senior design, and fully interdisciplinary projects.

The hydro-kinetic design team featured in this paper benefits extensively form the interdisciplinary mix of ME, MET, and EE students. The ME students bring strength in fluids and energy, the MET’s excel in prototyping and experimentation, and the EE student addresses needs in data acquisition, electricity generation, power transmission, and charging circuitry.

1.3 Design Project Team and Sponsoring Organizations HCJB Global requested our university conduct a student design project in support of their Micro-power project. Additionally I-TEC has agreed to co-sponsor the project by serving as a secondary customer, since the design work is in line with their mission. In 2007-08 five senior and three junior design students indicated the project as their first choice, and SPARC was born (Figure 1.) The project is continuing in 2009-10 with a new team (Figure 2) and a shift in focus towards under-water hydro-kinetic technology. Because both “sponsor” organizations are non-profit organizations, their contributions consist of lead-user needs definition and extensive technical expertise. The team is raising several thousand dollars from friends, family, and businesses to fund prototyping expenses. Additionally the world leader in small-scale hydro-kinetic technology, Ampair11®, has donated significant equipment and guidance to the team.

Figure 1: SPARC Logo (Supplying Power Alternatives for Remote Communities)

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Figure 2: The SPARC Senior Design Team 2009-10 Pictured L-R: Tim Hewitt, Joshua Baumgartner, Chris Sokolove (Lead), Nolan Willis,

Howard Record, Ned Funnell, Edgar Licea, Austin Williams, Dr. Matthew Green (Faculty Director), Dr. Ted Forringer (not pictured)

1.4 HCJB Global

HCJB was the first radio call name of what is now HCJB Global12 in Quito, Ecuador. HCJB has two main areas of focus: HCJB Voice, their media ministry and HCJB Hands, their medical ministry. Today, HCJB healthcare ministries and radio broadcasts impact more than 100 countries. The HCJB Micro-power project currently underway at the HCJB Global Technology Center13 in Elkhart, Indiana seeks remote power solutions in support of HCJB’s mission. HCJB desires to use pico-hydropower for medical, broadcasting, and office needs.

1.5 I-TEC (Indigenous peoples Technology and Education Center)

The Indigenous Peoples Technology and Education Center (I-TEC)14 works to empower indigenous peoples through technology and education. I-TEC was founded by Steve Saint15, son of legendary martyr Nate Saint16, to assist indigenous peoples like the Waodani Indians Steve grew up with. I-TEC’s past projects include visual training modules, backpack dental chairs, and powered-parachutes for transportation in frontier areas. I-TEC has developed and widely disseminated a thirty-five pound portable dental chair and dental drill. I-TEC is also developing “the Maverick,” a prototype off-road/aerial vehicle that can carry four passengers for use on short landing strips in remote areas. I-TEC desires to use electricity in remote areas for medical equipment, office equipment, and maintenance.

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2 Stream Selection and Placement

Research conducted by the team indicates that pico-hydro-kinetic technology is best suited for regions where electricity is not widely and cheaply available and where flat terrain or other factors (e.g., security, financial, or river use concerns) render more common potential-energy-based hydropower solutions impractical. Since the Amazon Basin is typical of such areas and is the proposed deployment location of the primary sponsor, team members conducted an extensive study of the region and its streams. This study confirmed the feasibility of the project, resulted in guidelines for stream selection, and informed the design of the anchoring system. Gradient, depth, tidal effects, river traffic, and proximity to population centers were the primary factors considered for stream selection guidelines. Steeper gradients in the small tributaries will provide better power output than the major rivers. Manageable depths and the lack of large-draft river traffic confirm the selection of smaller streams. Most of the rural population is within a few miles of major rivers; however, smaller rivers widen and slow immediately before emptying into the major rivers. Hydro-kinetic units should, thus, be deployed in small streams, near villages, generally between 0.5 and 3 km from major rivers.

Tidal effects and seasonal flooding pose additional problems. Twice daily, tidal bores reverse the flow of 600 miles of the lower Amazon and tributaries near the delta. Throughout the Amazon Basin, river depths vary considerably season to season.

Correct placement within a given stream dramatically affects hydro-kinetic performance. Flow is generally fastest just below the surface because locations near the bed and banks suffer from friction loss and turbulent effects. An optimal location, then, is as close to the surface as minor river traffic will permit and far enough away from the banks to avoid their effects.

3 Anchoring System Design

3.1 Preliminary Design Decisions for Anchoring System Concept A unit that rotates with changing stream flow direction due to tidal bore effects is more universally deployable, yet has several disadvantages that would increase cost and time to design. The unit would be mounted via a bearing on a support plate to which anchor lines would be attached. While a “weathervane” would be unnecessary due to the shape of the diffuser, the stability complications and the weight of the additional parts would increase the cost of several components. A design for uni-directional flows was selected in order to meet cost and time constraints.

Vertical support will be accomplished with a positively buoyant unit tied down to multiple anchors (Figure 3). This design was selected rather than one or more broad-based rigid supports because seasonal depth variations necessitate vertical adjustability. The system must be completely submerged, and adjusting rigid supports underwater is a potential safety hazard. The anchor lines will be routed through rings or pulley on their respective anchors and then tied down on the bank. This allows a user to adjust the vertical height of the unit by pulling in or releasing anchor line from the safety of the riverbank.

3.2 Anchoring System Design Details The drag force will be countered by a primary anchor upstream from the unit. A fluke anchor was selected for this purpose on account of its superior holding power in the soft mud beds

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common in deployment regions. As seen in Figure 3, the main anchor line will be routed through a pulley connected to a deadweight anchor and, by a near-horizontal chain, the fluke anchor. The fluke anchor can bear much more force at a small angle of elevation, so the deadweight anchor permits a smaller fluke anchor and increases stability by shortening the main anchor line. Downstream from the unit, smaller deadweight anchors will stabilize the unit against sideways motion and propeller-induced twisting. Since these secondary anchors need not counter much of the drag force, sandbag anchors may be used to simplify placement and removal and to reduce cost and transportation weight.

Figure 3: Concept of Anchoring System

3.3 Preliminary Flow Concentrator Design David Gaden’s master’s thesis17, “An Investigation of River Kinetic Turbines,” includes information on flow concentrating anchors. In a relatively stable channel, an anchor can double as a ramp to concentrate the stream flow (Figure 4).

Figure 4: Effect of Flow Concentrating Anchor17

Gaden’s experiments resulted in a maximum power increase of 40%. The power boost increased with the height of the anchor.

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Seasonal depth variations and the cost of a heavy, custom-designed deadweight anchor render a flow-concentrating anchor impractical for the overall design. However, a flow concentrator apart from the anchor could be integrated into the current design. A rigid sheet suspended from the main anchor line and the underside of the shroud opening would act as a partial nozzle, directing a larger flow toward the propeller (Figure 5).

Figure 5: Concept of Flow Concentrator – Side and Front Views

A future senior design team will evaluate whether the benefits of a flow concentrator are worth the detriment to the diffuser shroud’s effectiveness and significant increase in required buoyancy.

4 Preliminary Shroud Design

4.1 Shroud Concept Based on background research18,19,20 and awareness of the cubic power relationship of power in a flowing stream, the team determined velocity-concentrating technology such as a shroud would be needed to satisfy both power and cost requirements. Our objective was to analyze different designs based upon highest efficiency and optimize the involved parameters. Included in this design are considerations of construction and incorporation into other aspects of the project.

Early research found the Betz limit indicated the maximum theoretical efficiency possible with a turbine alone. A turbine removing energy from a flowing fluid creates a higher-pressure region in front, thus forcing a large amount of fluid to divert around the propeller. Therefore, a fundamental limitation is placed upon the maximum efficiency available from such a device, which Albert Betz determined to be 59.3%. In order to exceed the Betz Limit, the moving fluid must be constrained so that it cannot flow directly around the turbine due to the high-pressure region formed in front of the turbine.

4.2 Evaluation of a Diffuser vs. Nozzle-Diffuser for Velocity Increase Within the realm of shroud design, two possible solutions were considered. The first option was a combination of both a nozzle and a diffuser (Figure 6). The second option was to use just a

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diffuser (Figure 7). Research indicated that the diffuser possessed the advantage in removing stagnant water whose energy had been removed by the generator and that it alone was the best solution.

Figure 6: Nozzle-Diffuser Example Figure 7: Diffuser Example

4.3 Shroud Optimization via CFD Since the diffuser solution was a better option, the next step was to determine the variables in the design. The shroud inlet area was fixed to fit the Ampair® UW100 system, a readily available commercial system capable of satisfying project power requirements if a sufficient water velocity increase could be obtained with the shroud. This left the diffuser as a two degree of freedom system constrained by the change in area and the change in angle. The two parameters were optimized with a simplified CFD model and the results are shown below (Figure 8 and Figure 9).

To verify CFD results the team fabricated small-scale models for testing in a small pool known as a swimmer’s treadmill with pumps creating a continuous current. For two test configurations water velocity was measured using two pitot tubes measuring static and dynamic pressures so that velocity could be determined using Bernoulli’s equation. Water velocity inside each shroud was compared to the free stream velocity, which was determined the same way. The testing results were then compared with CFD models (Table 1). The results indicated CFD could be used to predict flow within a reasonable margin of error. Even though results were positive and had potential to be used for predicting actual velocity increase, our main interest was to only optimize shroud geometry with CFD.

Table 1: CFD Verification Results - %Velocity Increase

*36% at diffuser opening; 57% at ¼ diffuser length.

% velocity increase Testing results CFD Results % Error Nozzle/diffuser shroud 33.3% 31.17% 6.4%

Diffuser 48.3% 36 to 57%* +25 to -19%

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The next step was to optimize the two variables established earlier. Solid Works models were made to create CFD models keeping all variables constant except the one being optimized. Figure 8 and Figure 9 show the results of varying angle and area ratio, respectively. (These models do not account for the flow restriction and other effects created by a turbine.)

Figure 8: Angle Optimization Results

Figure 9: Area Optimization Results

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From these charts, conclusions were drawn that for a speed of 2.5 mph (1.2 m/s), the maximum velocity increase will come from a 25° angle and the largest feasible outlet area.

4.4 Preliminary Shroud Testing The current testing setup measures free stream velocity but not velocity within the shroud, so a direct assessment of velocity increase is not possible. However, testing does show increased power output from shrouded geometry that can be compared to unshrouded tests to determine and “effective” velocity to see what speed is necessary to produce the same power without a shroud.

To further confirm CFD predictions, three different shroud sizes were tested: 20°, 25°, and 30°. All had an outlet area to inlet area ratio of four. The 25° and 30° power-velocity curves were similar, allowing the team to conclude the best angle was somewhere between the two, which closely matches our prediction of about 25°.

Figure 10: Shroud Testing Results*

4.5 Final Shroud Design The final shroud design utilizes the diffuser concept and incorporates optimized parameters determined previously: 27.5° half angle and outlet area/inlet area ratio of 4.5. The shroud was constructed using 1/8” aluminum rolled into the desired cone shape and mounted with steel brackets. Effort was taken to maintain minimal clearance between turbine and shroud to eliminate water flowing past the tips of the blade.

* Power output here is less than the maximum system output, since currently only the shroud geometry is optimized.

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Figure 11: Design of Final Shroud Prototype

5 Debris Filter

To protect the Ampair® UW100 and maintain performance, a conical debris filter will be attached to the front of the shroud. A large ring (matching the diameter of the shroud opening) and a small ring (connecting to the main anchor line) will be connected with four load bearing bars (Figure 12). To filter smaller debris, Kevlar string will be routed longitudinally from ring to ring. Finite element analysis was used to validate the strength and stiffness of the debris filter.

Figure 12: Debris Filter Design

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6 Electrical System

This small-scale hydro-kinetic power system requires extremely efficient power transmission and a reliable means of conversion for storage in batteries.

6.1 Power Transmission The most practical and cost-effective approach to power transmission is to specify a source voltage as high as possible to reduce the required wire size. Within the context of this design project, an Ampair® UW100™ generator became the generator of choice. Since this generator would normally produce a nominal 12 or 24 volts AC, the team custom-ordered a unit to produce approximately 100 volts instead. This Ampair® unit produces two phases 30º apart and thus three conductors can be used instead of four by using a common ground for both phases. With this configuration, standard three conductor marine cable may be used for power transmission. Depending on distance, wire sizes from 16-12 AWG should be used.

6.2 Power Reception On the receiving end, the 100 volts AC used for transmission will need to be reduced to a usable level and converted to DC so that the recovered energy may be stored. Power transformers on each phase will step down the voltage and bridge rectifiers will convert the AC to DC. Once both phases have been stepped down to the desired level and rectified, both phases may be bridged in parallel to produce a common output (Figure 13).

Figure 13: Diagram of power transmission system drawn using National Instruments® Multisim™. (Note: load resistor holds place of voltage regulator and energy storage system).

Transformers do not perform well at below-design frequencies while operating at their full rated output because the cores saturate and heating results in efficiency loss. Therefore transformers must be oversized to compensate for low frequency operation according to the following equation:

Needed _ Transformer _ Rating(VA) Spec _ Frequency

Expected _ Frequency Power _ Load(VA)

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Once the Ampair® UW 100 is tested further evaluation will determine the exact transformer ratings needed.

6.3 Energy Storage and Charging Regulation The main sponsor wishes to use lead-acid batteries for energy storage. Charging regulation must use temperature compensation to prevent overcharging and accommodate the following battery maximum voltages:

13.6 volts for gel-cell batteries. 13.7 volts for Absorbed Glass Matrix (AGM) batteries. 13.8 volts for standard flooded cell batteries.

These requirements may be satisfied with a commercially available unit. Team research has indicated that charging systems with different voltage settings are readily available, and Ampair® informed the team that they have considered producing an adjustable regulator with temperature compensation. In summary, the electrical system design is as follows:

100 volts nominal output from the generator’s two phases. Power conversion on the receiving end using transformers and bridge rectifiers. Voltage regulation accomplished by means of a commercially available regulator. Energy storage using a lead-acid battery.

Such a scheme should be relatively cost-effective to implement while being robust enough to be used in developing countries with reasonable maintenance.

7 Testing

7.1 Testing Equipment The purpose of the fall semester testing was to provide a proof of concept and to determine whether the testing system will be sufficient for testing a shrouded Ampair® UW 100.

To test on a still body of water, a puller system moved a float bearing a generator, shroud, flow sensor, and DAQ. The puller is a gas-powered engine with a chain-driven cable drum. Its operation simulates a constant river flow.

An aluminum-framed floatation device with a vertically adjustable center bar acts as a mount to submerge the generator, the shroud, and the flow sensor (Figure 14). Existing pontoons from an earlier team were used, with the addition of enclosed sides to reduce turbulence.

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Figure 14: Float

Since the Ampair® UW 100 system was not received until January, a trolling motor served as a place holding generator for fall testing. A shroud was manufactured based on initial research to serve as a rough substitute until the final shroud was obtained.

Before taking data, the Swoffer Turbine21 flow sensor was first calibrated in a pool away from wind and debris so that speed was the only independent variable (Figure 15).

Figure 15: Flow Sensor Calibration

The data acquisition system (DAQ) must collect various forms of data during testing and display the data in a readable format. It also needs to be water resistant. Three hardware options were available. A wireless system would meet the water resistance requirement because it would be on land, but it was over budget. A wired system would require a long transmission cable, which would be difficult to protect from turbine blades and other hazards. The team chose to record the data on board as a self-contained system, using a Pelican® waterproof case to protect the equipment. Labview™ software was installed onto a netbook as the foundation for the DAQ, and National Instruments® DAQmx™ was used for sensor interface. A remote activation system was added later.

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7.2 Testing Plan and Locations Finding locations for testing was crucial. The testing plan required three types of locations: first, easily accessible still bodies of water; second, a still body of water large enough to create power from the turbine generator; and, third, a stream able to simulate actual river environments.

Two sites were readily available on campus: a pool and a pond. The flow sensor was calibrated by pulling it consistently across the pool. In the pond, the objective was to test the puller, float, flow sensor, and DAQ to find and correct problems before moving on to the next stage of testing. However, the float was being dragged into the water by the puller and the flow sensor was getting stuck with debris. The former problem was fixed by installing cones on the front of the float in order to have the nose of the float stay above water. The latter problem was a non-issue as the second stage of tests is being conducted in a lake relatively free of debris. The full system on the float, using the temporary shroud and trolling motor, was pulled across part of the lake by the puller. Further tests will be conducted in like manner with the Ampair® UW 100. The Sabine River in East Texas will meet the requirements of the third stage of testing. It provides both accessibility and situations that will be similar to that of the Amazon Basin (e.g., flood stages, presence of debris, continuous but variable stream flow, and similar average gradient).

7.3 Testing Results Figure 17 shows power-velocity curves generated in a preliminary test with a trolling motor in un-shrouded and shrouded conditions. The test was for verification of the experimental setup and a preliminary indication of the possibilities for power increase with a shroud. The same test setup was employed with the Ampair® UW 100 and an improved shroud (Figure 18). To increase the electrical efficiency, resistive loads of 80-400 Ohms were tested. An array of ten 40 Ohm power resistors in series was used to dissipate the power output from the UW 100. Velocity, voltage, current, and resistance were recorded with the remotely operated DAQ unit and results were compared (Figure 19 and Figure 2016). The 400 Ohm constant load performs the best at lower velocities. Currently 70 Watts can be achieved at 1.95m/s with a 400 Ohm resistor.

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Figure 17: Unshrouded vs. Shrouded Power-Velocity Curves (Trolling Motor)

Figure 18: Unshrouded vs. Shrouded Power-Velocity Curves (Ampair® UW100)

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Figure 19 : Power from varying Resistive Loads (Ampair® UW100), units in Ohms

Figure 20 : Power as a Function of Velocity and Resistance (Ampair® UW100)

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8 Student Learning

With minimal guidance the student team performed all the planning, design, and testing presented in this paper, in addition to maintaining relationships with customers and sponsoring organizations. Student comments on learning (Table 2) report growth in technical skills related to power conversion technologies, in addition to “softer” skills, such as effectively dealing with team dynamics, legal, and ethical concerns.

Table 2: (Adapted) Student Comments on the Project Learning

Power conversion 1. Various power conversion technologies, especially from flowing fluids 2. Propeller design 3. Characterizing a motor as a generator (RPM and Power_out vs. Torque_in) 4. Fluid dynamics

Teaming

1. Team building and management skills 2. Importance of collaborating among many individuals 3. Large-team dynamics pros and cons 4. Importance of clear goal-setting and prior planning according to goals 5. Potential harm of slipping a project timeline

Legal and Ethical

1. Negotiating and fulfilling ethical responsibilities such as protecting client IP 2. Legal paperwork such as NDA’s

Prioritizing customer needs with multiple invested customers.

Five students commented on how participation on the design team may influence future career decisions (Table 3). One student said the project confirmed a long-time interest in pursuing renewable energy, two students indicated the project increased their chances of being involved in similar projects as a hobby, and two students indicated the project has not changed their career aspirations.

Table 3: Student Comments on the Project’s Potential Impact on Future Career Aspirations (Raw)

I have been interested in renewable energy for a long time, and this has helped confirm some of my interests.

No, this project will not have any significance in my career path. It has, however, opened my eyes to the needs of third world countries.

Although my career aspirations at current have not been modified through this project, it has been and continues to be a desire of mine to pursue projects of this sort during my free time. Working on this project has furthered my knowledge of potential projects.

I don't think this has had much impact on my career [aspirations].

Working on this project has not significantly affected my career aspirations.

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9 Current Project Status and Future Plans

The design team’s overall objective for the fall semester was to estimate the kinetic energy in a flowing stream available for conversion through the use of velocity-boosting technologies coupled with hydro-kinetic technology. This was accomplished with research, design, fabrication, and testing. Significant progress has been made toward the spring semester objectives of a complete design and a deployment-ready prototype. Additional work is required, but the team is confident in its ability to meet its goals.

Acknowledgements: The team and faculty director sincerely thank Ampair11 for donation of the Ampair® UW100 unit and technical guidance, and thank HCJB engineers for technical guidance.

References

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Contextual Needs Assessment Case Study for Remote Power," Proceedings of the 2008 American Society for Engineering Education Annual Conference, Pittsburg, PA.

[2] Green, M.G. and P.R. Leiffer, "Enhancing International Humanitarian Design Projects: a Contextual Needs Assessment Case Study of Remote Power for Faith-Based Organizations," Proceedings of the 2008 Christian Engineering Education Conference, Beaver Falls, PA.

[3] Tsang, E., 2001, Projects That Matter: Concepts and Models for Service-Learning in Engineering, American Association for Higher Education.

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[13] HCJB Global Technology Center, 2007. HCJB Global Technology, www.hcjbtech.org [Accessed Mar. 2010].

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