Lamar University Solar Splash Team

Transcription

1 Lamar University Solar Splash Team Technical Report Boat #14 7 May 2018 Team Members David Shifflett Sam Blackshear Scott Girdwood Rovin Jaime Jancy Varghese William Villa Shanna Walker Advisors Dr. Kendrick Aung Dr. Jenny Zhou

2 I. Executive Summary For the very first time, a team from Lamar University has decided to participate in the 2018 Solar Splash competition. The goal of this year is to be competitive with the numerous veteran groups entered this year. The team consists of seven senior mechanical engineering students who are excited to take on the challenge of incorporating solar power to an electric watercraft. As this is their first year, the team has had many decisions to make based off of a limited amount of data. The primary source of this data would be the technical reports from previous Solar Splash competitions. Reading through the technical reports gave the team enough information to start forming a plan. The decision was made to treat this year s event as a learning experience and to gather as much information as we could for next year s team. The team conducted an evaluation of different hull designs and propulsion systems and settled on using a commercially available square stern canoe with a modified outboard motor. Since we planned to exceed the manufacturer s recommended motor size for the canoe, an aluminum tube frame was constructed and mounted in the canoe. This frame also served as a means to mount the necessary batteries, electronics, and solar panels. The motor was made by removing the gasoline engine from a Suzuki outboard motor, generously donated by one of our sponsors, and replacing it with an electric motor. As it is with most rookie teams, funding was one of the largest challenges that the team faced. Since Lamar University is a smaller school, funding for senior design project is limited. This meant the team needed to raise the majority of the money to finish the project on their own. The team was able to raise enough money through a variety of fundraisers and sponsor donations. In the end, the team managed to reach their intended goals for the project. The challenges they faced completing the project have provided them with some experience to what engineers face on a daily basis in the real world and they look forward to attending the competition. 1

3 II. TABLE OF CONTENTS I. EXECUTIVE SUMMARY...1 II. TABLE OF CONTENTS...2 III. PROJECT OBJECTIVES...3 IV. CURRENT DESIGN...3 A. Solar System...3 B. Electrical System...4 C. Power Electronics...5 D. Hull Design...6 E. Drivetrain and Steering...8 F. Data Acquisition...8 V. PROJECT MANAGEMENT...9 A. Team Members and Roles...9 B. Project Planning and Schedule...9 C. Financial and Fundraising...9 D. Continuity and Sustainability...10 E. Self-Evaluation VI. CONCLUSIONS AND RECOMMENDATIONS...10 A. Strengths..10 B. Weaknesses..11 C. Future Work.11 D. Recommendations VII. BIBLIOGRAPHY...12 VIII. APPENDIX A. Battery Documentation...13 B. Flotation Calculations..32 C. Proof of Insurance...34 D. Roster...34 E. Center of Gravity Analysis..35 2

4 III. Project Objectives Since this is the first year for Lamar University to attend Solar Splash, the team decided to go for a balance approach. The overall goal was to produce a boat that would perform well in every category. The team evaluated the results of last year s competition and aimed for the middle of the pack. This approach is a modest one, but it allowed the team to stay in their budget while still producing a reliable and safe watercraft and enjoying the experience of doing so. The project goals for this year were to reach a top speed of 10 mph (4.47 m/s) for the sprint and to travel a distance of 8 miles (12.87 km) for the endurance portion of the competition. IV. Current Design The Lamar University solar splash team for 2018 is a rookie team that has not competed in the Solar Splash competition for a few years. For this reason there were numerous obstacles that had to be overcome without the aid from previous team tips and what to expect at the competition such as; Solar System, Electrical System, Power Electronics, Hull Design, and other important design criteria that had to be considered. Other parameters that had to be considered were the rules and regulation that must be met for the competition for example; battery weight, boat length and the combined voltage that the solar panels are rated for. A. Solar System 1.) Current Design: To stay within the Solar Splash rules five solar panels will be used in the competition, of these four were donated from Grape Solar at a rated output of 100 watts and the fifth one was purchased and is rated at 80 watts. The final layout of the solar panels is shown Figure 1 with the smaller 80 watt panel oriented sideways at the very back of the boat. For 2018 the team agreed to mount two solar panels in the front and rest of them behind the skipper to have the center of gravity closer to the middle of the boat. Not knowing how this layout will do against the other teams we can only learn and advice the 2019 team on where to mount the solar panels and where to put the skipper for better performance. Figure 1: Solar Panel Layout 3

5 2.) Analysis of Design Components: One of the downside of the current design of the solar panels is the size and the weight. Each 100 watt panels weigh approximately 20 lbs. and 15 lbs for the 80 watt solar panel making a total of 95 lbs. For next years team it would be advice to find more compact solar panels which would make the boat lighter and have less air resistance. The panels are connected to a charge control in order to regulate and monitor voltage to the batteries. 3.) Design Testing and Evaluation: The solar panels were successfully tested a few times in order to insure that the voltage that they produce was under the competition regulation. The solar panel configuration was also tested in cloudy weather in order to insure that the panels will produce good enough voltage during the competition if there is cloudy weather during one of the races. B. Electrical System 1.) Current Design The current charging design features a 36v solar charge source array. This is passed and filtered through charge controllers to provide a usable 24v for charging the lead acid battery array. The electrical powertrain then proceeds as follows: 24v from the battery array is augmented by a DC-DC step up converter to 48v, which is then passed to the motor controller subsystem. The motor control subsystem consists of the throttle, digital readout, and throttle output for the motor. Alternatively, a 36v battery array configuration will be used for the sprint section, as it is capable of producing more power on demand than the 24v configuration. 2.) Analysis of Design Components Below in Figure 2 is a graphical representation of battery life forecast under optimal conditions. This assumes full 480W directed onto the solar array, and a 10% total system inefficiency. As observed, an average throttle setting of 40-50% will allow maximum extraction of energy during the endurance race. Figure 2: Battery Life Estimation 4

6 3.) Design Testing and Evaluation Initial testing of the solar array and charging apparatus provided needed data to optimize the system. This was carried out by using lower gauge power wire to carry the requisite current. Also it appears that a greater efficiency can be achieved by charging the system at 12v rather than the 24v currently used. C. Power Electronics 1.) Current Design An overview of the entire power electronics system is given below in Figure 3. Figure 3: Electrical Diagram From this figure the major components are the electric motor kit, converter, and batteries. The solar panels and charge controllers have been discussed in Section A above. The circuit starts with our 24 or 36v battery pack and then goes into a Zahn electronics set up converter which will have an output of 48v, the max allowed per the rulebook. From here the current will go to the contactor, controller and then motor. A keyed switch is attached to the dashboard of the boat and wired in series to the deadman s switch to allow the system to be energized or de-energized depending on the situation. A throttle and display are wired to the controller to accurately control and monitor the electric motor. For ease of manufacturing this team chose, from the start, to use an electric motor kit that would include all major components; motor, controller, contactor, throttle, display, key switch, and wiring harness. After extensive research it appeared that the best option was to use a comprehensive kit from Thunderstruck Motors, specifically one that used a DC electric motor. The kit chosen was the 10kW brushless sailboat kit with the Curtis ET-134 throttle and Sevcon Clearview instrumentation. This electric motor kit uses a Motenergy ME1115 brushless DC motor and Sevcon Gen-4 controller. Due to the restrictions in the Solar Splash 2018 rule book of lead acid batteries, weighing no more than 100 lbs total, and no more than 36v out of the battery pack, and our budget, required a lot of research and ingenuity to come up with an appropriate battery and voltage delivery system. After an exhaustive search Sigmas Tek SP12-22HR batteries were chosen. These batteries are 12v with 22 AH each and weigh in at a svelte lbs each. Six batteries will be used, wired in a combination of series and parallel, for a total weight of lbs and either 24v and 72 AH or 36v and 50 AH depending on the event. The Sevcon Gen-4 controller 5

7 requires a minimum of 48v this makes it necessary to use a Zahn Electric DCDC24/48/5000 step up converter to deliver the needed 48v to the motor controller. 2.) Analysis of Design Components Thunderstruck Motors offers three sailboat kits, a 5 kw, 10 kw and 12.5 kw kit. From the start of this competition the design goal was a top speed of 10 mph or 8.6 knots, using Equation 1 below we calculated what the theoretical top speed for the different motor kits with our boat configuration would be. Knots= (10.665/(weight/shaft hp)^(⅓))*sqrt(length of water line) [1] Once this calculation was done Equation 2 was used to approximate what the run time would be under full load with the 24v battery configuration. The runtime was of primary importance to the endurance event and a much smaller factor in the sprint and slalom events. Run time = ((battery amp hours)*0.8)/(electric motor amp draw) [2] The data from these two equations is surmised below in Table 1. Table 1: Electric Motor Analysis Motor Kit 5 kw 10 kw 12.5 kw Theoretical Speed 10.7 mph 12.6 mph 14.6 mph Amp Draw 80 amp 120 amp 180 amp Estimated Run Time 43 minutes 34 minutes 20 minutes From this table the 10 kw kit was used to allow for frictional losses in the outboard as well as deficiencies in the hydrodynamic performance of the boat. While the 12.5 kw kit would have made the boat enjoyable to run in the sprint and slalom events the 20 minute run time would have been a severe hindrance during the endurance competition. 3.) Design Testing and Evaluation Testing of the electrical system with a simple voltmeter shows a little over 24 or 36v coming out of the battery pack, depending on which configuration it is, and a little over 48v coming out of the Zahn electronics step up converter. Testing the boat in water, with a handheld gps, an approximate top speed of 10 mph was recorded and out of water testing shows that the batteries will be discharged after 30 minutes of full throttle operations in the 24v configuration. These values highlight some of the inefficiencies we have in our outboard and hull design that were expected. Future teams should take note of this and choose more efficient designs. 6

8 D. Hull Design 1.) Current Design For the hull of the boat the team elected to go with a commercially available boat as the base of of our build. The model we have selected is a Sun Dolphin 15.6 Mackinaw SS. The Mackinaw SS is a canoe constructed of High-Density Polyethylene (HDPE) which will provide a lightweight, rigid shell to mount the equipment that will be needed for the competition. Another reason this model was selected was because of its shape, unlike other canoes that taper to a point at the back this model has a transom that will allow for the mounting of an outboard motor. 2.) Analysis of Design Components According to the manufacturer's recommendation, the canoe is limited to a maximum weight of 800 lbs and a maximum motor size of 2 hp. Since a 2 hp motor would not provide sufficient thrust for the boat to achieve our desired speeds, an aluminum frame was designed and fabricated. A force analysis of the frame was conducted using ANSYS and shown below in Figure 4. Figure 4: Force Analysis of Frame The results of the analysis estimates that the maximum stress and displacement will result from the pressure of the motor on the frame. With a max stress of 28.3 MPa and a max displacement of 0.07 mm at a pressure of 345 kpa, we are confident that the frame will be able to handle both the force of the motor and the weight of the equipment. 3.) Design Testing and Evaluation The boat performs well in regards to flotation, with a full load and a pilot at the maximum weight to remain under the safety factor, 6 to 8 inches of the hull stay above the water line. However, this type of boat was not designed to travel at the speeds we are attempting to reach. There are two areas of concern with the hull. The first can be seen as the boat begins to 7

9 accelerate over approximately 5 mph. The change in contour at the back of the boat causes the flowing water around the sides of the boat to become turbulent. As the boat increases speed, the height of the turbulent water rises to the point that some of the water splashes into the boat. The second is when the boat reaches approximately 7 mph; there is a noticeable wave at the front of the boat that quickly becomes high enough to enter the boat. Based on these observations, the team is still confident they will be able to complete the events of the competition, but have advised next year s team to find a better solution. E. Drivetrain and Steering 1.) Current Design The drivetrain and steering systems of the boat are primarily commercially available systems, with the exception of the motor which is a modified Suzuki DF15 outboard. With the decision to use a canoe for the hull, the team decided to use an outboard motor instead of an inboard system. Thanks to one of our sponsors, we were able to secure a used outboard motor that we could modify by replacing the gasoline motor with an electric motor. To facilitate the modification, a mounting plate was fabricated out of steel plate. 2.) Analysis of Design Components With this model of outboard, the crankshaft of the gasoline engine was fitted directly over the driveshaft and had a rotation speed of between 5,000 and 6,000 rpm. The electric motor we used has a max rotation speed of 3,000 rpm. The team decided to use a chain drive with sprockets in a 1:2 ratio in order to maintain a higher rotation speed. Due to the high rotational speeds of the system, a 530 series motorcycle chain was selected due to compatibility with ANSI 50 series industrial chain sprockets. The steering system consists of a SeaStar Solutions Safe-T Quick Connect rotary helm mounted to the dash and connected to steering cable. The steering cable, also from SeaStar Solutions, runs from the dash down the length of the boat and mounts to the clamp bracket of the motor. The end of the steering able has a stainless steel tube the runs through the clamp bracket and mounts to the swivel bracket via a link arm. 3.) Design Testing and Evaluation The current model tests well, achieving the desired top speed and mobility goal that were set for the project. There were some issues early on when the team attempted to use a propeller that was donated by a sponsor. The donated propeller had a pitch of 9 inches which was too aggressive for the motor in use and would cause the motor to draw too many amps which would trigger a built in safety mechanism in the controller and shut off the system. This was quickly fixed by replacing the propeller with the appropriate pitch of 7 inches which had been calculated by a member of the team. F. Data Acquisition 1.) Current Design The installation of the solar charge controller and gage allowed for the automatic numerical values of the amperage draw and source voltage. Real time speed was recorded via a GPS distance and location application. 8

10 2.) Analysis of Design Components The solar charge controller array converts the unsteady voltage from the solar array into a usable voltage to charge the battery bank. These are necessary because in the configuration chosen, two sections of two 100W panels are in series, and the last 80W panel is on its own circuit. The solar panels produce 36v and 18v, respectfully. For this reason, two charge controllers were necessary to hold a steady 24v to charge the batteries. One cannot simply connect solar power directly to the batteries because overcharging of the batteries can potentially cause a fire and release of hydrogen gas. The gage allowed for real time data of the power consumption of the motor. This data is useful for the skipper to avoid over-amping the controller and forcing a thermal shutdown of the system. 3.) Design Testing and Evaluation Throughout the testing period constant monitoring of battery voltage and current draw allowed the skipper to be in complete control of every subsystem. V. Project Management A. Team Members and Roles Lamar University's Solar Splash team is made up of seven senior mechanical engineering students. Initially, there were several sub teams that made up the group but it was quickly learned that having everyone work together reduced the number of mistakes. The areas that the responsibilities were separated into were as follows: Research and Development Electrical System Solar System Power Electronics Fabrication B. Project Planning and Schedule The team was assembled in August of 2017 which is when the delegation of positions and responsibilities occurred. Every week since then, a weekly meeting has been held to help keep all members on track and all questions answered. Each week goals were made for the following week to make sure that everyone stayed accountable. The months of August- December (the first semester of senior year) were dedicated to designing all components and ordering parts. January-April (second semester) was focused on fundraising for the final necessary components and the actual build stage. The testing of the boat was planned for mid- April and early May to allow for any last minute changes. The team assembled a Gantt chart to have a visual representation of the goals and be able to easily communicate to the advisors where the project stood. C. Financial and Fundraising As a rookie team at a smaller school, it was known that one of the biggest challenges was going to be making the most of the given budget. From the beginning, fundraising was the main 9

11 focus for certain team members to help the project along as much as possible. To raise money a couple of link sales were hosted and turned out to be successful. Companies and friends that were interested in the project were contacted and sent a fundraising letter which included the details of the project and what the funds would be put toward. Several donations were received which greatly helped the advancement of the boat and keeping it on schedule. Because of the restricted budget, the order of the components were purchased had the be thought out. The most essential and expensive parts were ordered first which was the boat, solar panels, batteries, and step-up converter. D. Continuity and Sustainability The success of the project this year can be attributed to organization and communication. The group had to greatly rely on each other and the ability to learn new skills due to the fact that this is a rookie team with no prior knowledge of the competition. Apart from the obvious reasons to want to be successful, a different goal was mentioned. Another objective was to do well enough to where the next year s team could do well with less financial strain and general stress. Having to buy all new electronics and wiring was quite the feat; the hope for the future is that they can reuse all of these brand new components and fabricate a new and more appropriate hull. All documentation is saved and prepared to be handed down as well as having members being willing to answer any questions that the next team might have. E. Self-Evaluation As to be expected from any group project, communication can always be worked on. Most of the time everyone was on the same page but there were a few situations where it was important to portray ideas and plans clearly, yet they weren t. This sometimes led to unnecessary calculations to be made or incorrect (but small) components purchased but the only negative that came from them was a small amount of time wasted. There were also small problems with inequality in work load. In the beginning, the division of roles seemed fair and suitable to each member s talents but as time progressed, it was apparent that certain people were doing more than others. This affected the boat s development and should have been more thought out. A. Strengths VI. CONCLUSIONS AND RECOMMENDATIONS Reached our initial design goal of top speed at 10 mph The duration of the design and building phase has allowed each team member to work together as a unit for the completion of this project Installation of the batteries, motor, step-up converter, bilge pump and various electrical components without injury Completed the construction of the canoe according to competition regulation with limited school funding 10

12 B. Weaknesses With no previous Solar Splash competitors from Lamar University, the team had no previous foundation to begin the design and construction of our design project. The boat was built with various manufactured components, from the square stern canoe to the electric motor kit and the step-up converter and are not up to par with solar splash competitors Drag on the hull and uneven weight distribution limiting the maximum speed C. Future Work Our team wanted to invest in the modification of the square stern hull, in order to minimize drag and the amount of water being taken in during operation. An even distribution of the weigh within the canoe will be addressed in order to prevent the square stern from dipping too far into the water. Maximize speed and endurance and minimize drag and overall weight Modify the drive train to enhance smooth operation for the skipper D. Recommendations Engineer hull to reduce drag Modify motor and electrical configuration to maximize current output Fundraising from the beginning of design phase is critical to finance the progression of the construction phase Evenly distribute workload to work effectively and efficiently as a team 11

13 VII. BIBLIOGRAPHY Gerr, Dave. Propeller Handbook: The Complete Reference for Choosing Installing, and Understanding Boat Propellers. International Marine, Rexnord. Chain Drive Design. Power Transmission Solutions, Rexnord Corporation, 2018, MacPherson, Steve. Prop Calculator. Vicprop - Prop Calculator for Displacement and Semi-Displacement Hulls, Victoria Propeller Ltd., 2015, vicprop.com/displacement_size.php. Sailboat Kits and Accessories. Inspiring and Enabling the EV Community, Thunderstruck Motors, LLC, 2018, 12

14 Appendix A: Battery Documentation VIII. APPENDIX Competition Batteries - (6 12 VDC batteries) Sigmas Tek SP12-22HR MSDS attached - nominal weight 13.4 lbs Auxiliary Batteries - (1 12 VDC battery) Johnson Controls Optima MSDS attached 13

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33 Appendix B: Flotation Calculations Using the following formulas, the flotation requirement for the boat were calculated and summarized in the tables below. Since the same air bag will be used for both sprint and endurance configurations, the air bag will be filled to occupy the full space of its current location, approximately 4 ft^3, which is greater than the amount of flotation required for the endurance configuration. Net Force = V (ρ Water ρ Component ) Total Net Force + 20% Safety Factor = 1.2 Net Force Flotation Required = Total Net Force + 20% Safety Factor ρ Water Components Table B1. Flotation for Sprint Configuration Weight (lbf) Volume (ft^3) Average Density (lbf/ft^3) Net Force (lbf) Batteries Boat Hull Motor Electronics Total Flotation required

34 Air bag Air bag % fill 0.20 Components Table B2. Flotation for Endurance Configuration Weight (lbf) Volume (ft^3) Average Density (lbf/ft^3) Force Net (lbf) Batteries Boat Hull Motor Solar Panels Electronics Total Flotation required 2.92 Air bag Air bag % fill

35 Appendix C: Proof of Insurance We are working with the university to obtain this at this time and will send it over as soon as it is received. We have been asking them for weeks and they are just now getting close to giving us an answer. Appendix D: Team Roster Name Major Year Role David Shifflett Mechanical Engineering Senior Power Electronics Shanna Walker Mechanical Engineering Senior Electrical System Jancy Varghese Mechanical Engineering Senior Research and Development Scott Girdwood Mechanical Engineering Senior Electrical System Rovin Jaime Mechanical Engineering Senior Solar System Samuel Blackshear Mechanical Engineering Senior Fabrication William Villa Mechanical Engineering Senior Research and Development 34

36 Appendix E: Center of Gravity Analysis A center of gravity analysis was conducted on the two configurations of the boat for the competition. Since all of the components were mounted toward the center of the boat, the focus of the analysis was along the length of the boat and only includes the major components. Table E1. Center of Gravity Analysis of Sprint Configuration Item Weight (lb) Distance from transom (ft) Moment Hull and Frame Motor Skipper Batteries Auxiliary Battery Sum of Moment Center of Gravity (ft from transom) 7.0 Table E2. Center of Gravity Analysis of Endurance Configuration Item Weight (lb) Distance from transom (ft) Moment Hull and Frame Motor Solar Panel # Solar Panel #3 & #

37 Skipper Solar Panel #1 & # Batteries Auxiliary Battery Sum of Moment Center of Gravity (ft from transom)