P12441: Thermoelectric Power Pack Andrew Phillips Colin McCune Lauren Cummings Xiaolong Zhang

Customer Needs Importance Scale: 1 - Low, 2 - Moderate, 3 - High NeedsImportanceDescriptionComments/Status 13Cheap cost of systemComponent cost 215 year life span (3x use per day) 32No user interaction for system protectionShould be handled by system 43User-friendly operationMinimal user interaction 52Operational in harsh environmentsExposure to moisture/salinity 61Ability to charge auxiliary device 73Plan to apply to team 12442’s stove 82Fan runs at start-upMultiple start/restart cycles 93Safe to operate 101System must be transportable 113Thermoelectric use 121Package shall be 3’’ x 3’’ x 1.5’’ and 3 lbs 133Rugged designSurvive crush test and drop test

Engineering Specifications SpecDescriptionImportanceUnitsMarginalTargetComments/Status 1Component Cost3$10 2Product Life Span2Years15Assume 2 hr/use and 3 uses/day 3Battery Lifespan1Years15 4Aux charging2Wh17Being able to charge ~2 cell phones per use. 5Fan Battery size3Wh12.5Energy required for 5 product start- ups 6Weight1lb0.53Include battery packs 7Volume1in.5x.5x.53x3x1.5Include battery packs 8User actions during operational cycle 1#20 Importance Scale: 1 - Low, 2 - Moderate, 3 - High

Engineering Specs Customer Needs Component Cost Product Lifespan Battery Lifespan Aux Charging Fan Battery Size Weight Volume User Interaction During Cycle Cheap Cost of System 5 Year Lifespan No Interaction for System Protection User Friendly Operation Endure Harsh Environments Charge Auxiliary Device Apply to P12442’s Stove Fan Runs at Start-up Safe to Operate Transportable Thermoelectric Use Size Req. (3x3x1.5), Under 3lbs Rugged Design

Monitor TE Output Run Fan Charge Fan Storage Run Aux Charge Aux Storage Manage TE Power Control Power to System MPPT Monitor Open Circuit Voltage Control Voltage Control Fan State Control Voltage Control Current Monitor Storage Level Limit Current Turn Off Current Control Voltage Control Current Monitor Device Storage Level Limit Current Turn Off Current Control Voltage Control Current Monitor Storage Level Limit Current Turn Off Current Functional Decomposition Of TEG Power

Enclose System House system Under a certain size Under a certain weight Protect system Protect from environment Protect from dropping Protect from crushing Provide connections Connect to fanConnect to TE Connect to AUX Function Decomposition Enclose System

Block Diagram

Comparison of Old and New Systems P11461 Purely analog system, “dumb”. Power intensive system Did not understand how the TEG operated until late in the project. P12441 Utilize microcontrollers to make “smart” system. Utilize MPPT technology to guarantee maximum power is delivered to system. Utilizing knowledge from previous project.

Moving Power Point Tracking (MPPT) Equations of Operation

Perturb and Observe (P&O) Samples the output voltage, then calculates the derivative of the IV curve. Very effective, easy to implement, but can oscillate under rapidly changing conditions. Incremental Conductance (INC) Very similar to the P&O method, but this measures the incremental conductance of the PSU to calculate the derivative of the IV curve. More Accurate than P&O, but can still oscillate and is more difficult to implement. Constant Voltage Method Estimates the maximum power point voltage to the OC voltage at 76%. 76% is normally a good estimate, but can easily vary. Very easy to implement. wastes energy taking measurements and the peak might not be at 76%.

Power from TEG with a 75 Degree Temperature Difference

Power from TEG with a 175 Degree Temperature Difference

Power from TEG with a 225 Degree Temperature Difference

Power Management Using the MPPT, maximum power can be harvested from the TEG. When maintaining a 200 degree temperature difference across the TEG, 4V at 1.25 A can be obtained. This voltage can then be boosted to a voltage that can be used by the fan and auxiliary output. The boost converters must be designed to allow for a range of input voltages.

Boost Converters When the switch is closed current in passed through the inductor. The capacitor supplies the output voltage to the load. When the switch is opened the inductor maintains that current and the current loop passes through the diode charging the capacitor and powering the load

Boost Converter Operations

Top 10 Risks (Part 1) Importance Scale: 1 - Low, 2 - Moderate, 3 - High ID Risk ItemEffectCauseLikelihoodSeverityImportanceAction to Minimize RiskOwner 1 Exceeding target cost per unit - Other features of the end product may be not included - Component cost - Manufacturing cost Minimize the amount of components - Increase the functionality of existing components(ex: have more tasks run within the uC) All Team 2 Device requires too much power - Unit will not have full functionality - Unstable behavior when operated - Poor design and component selection Design to be as power efficient as possible - Utilize MPPT functions - Using the uC as much as possible All Team 3 System cannot power fan during "warm up" - The stove will take longer to heat up - Take longer for the TEG to provide full power - Component failure - Bug in the code in the uC - Improper design/part selection Design the unit to operate on battery power - Ensure the uC operates correctly All Team 4 Going over development budget - Difficult to be able to fund further development - Poor planning133 - Track spending - Ordering correct parts - Proper testing All Team

Top 10 Risks (Part 2) IDRisk ItemEffectCauseLikelihoodSeverityImportanceAction to Minimize RiskOwner 5 Complexity of operation - Sell less units - Improper use - Reduce system lifetime - Poor Design133 - Minimize user interaction - Make simple to operate All Team 6 Decreased Reliability - Fewer sales - Unit will get damaged more often - Poor part selection - Poor fabrication - Poor design Design the unit to be as robust as possible - Choose high-lifetime components All Team 7 End of lifetime disposal - Pollution - Battery chemicals - Heavy metals with the PCB Use ROHS parts; use less batteries/heavy metal components - Increase total lifetime of the unit All Team 8 Power storage capacity - System startup failure - Cannot charge devices without a fire - Poor system design - Poor system storage capacity Use high-capacity storage to meet customer specs Battery Team 9ESD - Electronics failure - More replacement parts will be necessary - Poor grounding - Poor ESD prevention in the labs Follow ESD prevention measures - Ensure proper grounding All Team 10 Prototype construction time - Less time for de- bugging - Failure to deliver on time - Poor planning, - Complex system - Poor testing procedures - Unforeseen circumstances Strict scheduling milestones - Effective and reachable deadlines - Component delivery time - Ordering parts early enough All Team

MSD I 10 Weeks MSD I 10 Weeks Week One Week Two Week Three Project Assignment TEG Unit Testing Functional Decomposition Customer/Engineering Needs Project Risks Winter Break, Three Weeks uC Development MPPT Selection/Coding Charging Circuit/Converter Investigation Week Four Week Five Week Six Week Seven Week Eight Week Nine Week Ten Software Team Further uC Work Interface with HW Develop MPPT Code Hardware Team Charging Circuit Design Interfaces to the uC, Fan, and User Interaction Team Re-Group, Report Vacation Results System Design Presentation

MSD II 10 Weeks MSD II 10 Weeks Week One Week Two Week Three Week Four Week Five Week Six Week Seven Week Eight Week Nine Week Ten Software Team Full Functionality with HW Team, Further Optimized Code Hardware Team Full Functionality with uC Team, PCB Fabrication/Construction Software Team Optimized MPPT Code Successful Interface with HW Team Hardware Team Successful Battery Charging and Fan Control, Interface with uC Team, PCB Layout Software Team Preliminary Demonstration of working MPPT Code Hardware Team Stable DC-DC Voltage Conversion Circuitry Successful Final Demonstration/Project Delivery