Senior Design Final Presentation

1. Stevens Institute of Technology Mechanical Engineering Dept. Senior Design 2005~06 Wave Energy Power Generator Senior Design Final Presentation Date: December 14th, 2005 Advisor: Dr. Kishore Pochiraju Group 10: Biruk Assefa, Lazaro Cosma, Josh Ottinger, Yukinori Sato

2. Agenda • Project Objective • Progress Feedback • Mathematical Model • Device Assembly • Component Designs • Cost & Weight Budget • Conclusion

3. Selected Conceptual Design Project Objective • Project Description • Design, develop, prototype and test a device that harnesses wave energy to generate electrical power on a buoy • Off-shore location requires buoy to be self-sustaining • Power output in the 100’s of Watts range • Objectives • Functional wave power generator which meet initial requirements

4. Progress Feedback • Identify losses in system • Mechanical Components  Mechanical Losses • Need for low number of components • Necessity of proper lubrication • Gearbox issues • Using gearbox to increase speed affects inertia by the ratio squared • As will be seen, ↑ Ratio: • Increases torque losses • Reach a point where the system is unable to overcome inertia • Impact of Model on the Design • Aid in sizing of several parameters: Buoy diameter, Reel radius, spring constant, gear ratio • How each variable affects overall system • Sensitivity of each variable

5. Mathematical Model • Systems Approach to Mathematical Model • Divided overall simulation into 6 subsystems • Identified by system components • Within each subsystem includes detailed modeling of the governing equations • Simulation is solved by the simultaneous computation of each equation • To simplify the analysis the “engaged” case was analyzed

6. Device Assembly

7. Device Assembly

8. Buoy Design • Buoyant force is the main driving force • Other forces: resistance from other components, weight, & damping force • Damping force is a function of buoy velocity • Buoy height (yellow) vs. Wave height (pink)

9. Buoy Mold Buoy Design • Diameter of 6 feet • Height of 25 inches • Buoy Fabrication • Commercially unavailable / Expensive • Using low density urethane foam • Laminated with fiber class for added strength • Mold Options: • Manufactured at machine shop / sheet metal • Purchase kiddy pool

10. Spring Operated Reel Function: Convert linear buoy motion into rotational shaft motion Design Aim: Maximize angular velocity of input shaft

11. Spring Operated Reel

12. Spring Housing Side plate Shaft connection Cable Guide Stand Cable Spring Operated Reel Design Variables used Wave Amplitude: 6 inches Wave Period: 7 seconds Reel Diameter: 3 inches Spring Constant: 10 inch pounds Preload length: 60 inches Buoy Diameter: 6 feet Reel Torque Reel shaft angular velocity

13. Shaft Design • Maximum torque located at reel output • Worst case scenario • Full submersion • Locked shaft • Torque on the shaft can be expressed as • Factor of safety: 1.2

14. Mechanical Rectifier • Design constraints • 1:1 ratio for CW & CCW rotation • Center distance relationship for gears: • Keeping effective inertia low • Design Issues • Engaged vs. Disengaged • Model simulation focuses on Engaged state • Testing will focus on Disengaged state

15. Mechanical Rectifier

16. Gear Box • Function: Speed up rotational shaft motion • Design Aim: Minimize gear ratio

17. Input Shaft Output Shaft Gear Box Angular velocity of Reel vs. Gear Box Design Variables used Reel Diameter: 3 inches Spring Constant: 10 inch pounds Preload length: 60 inches Buoy Diameter: 6 feet Gear Ratio: 10 Gearbox Torque

18. Flywheel Function: Maintain high RPM for Alternator Design Approach: • Size the flywheel by iteratively testing the prototype with flywheels with various moment of inertia

19. Alternator Function: Produce electrical power Design Approach: • Low inertia, high efficiency at low RPM, and variable torque preferred • Test for Torque vs. RPM and Efficiency vs. RPM curves

20. Alternator • Permanent Magnet Alternator • Wind industry • High efficiency at low RPM (~300RPM) • Variable EMF Alternator is chosen • Car Alternator will be used for prototype testing: • Inexpensive • Low efficiency at low RPM

21. Typical alternator regulator Encoder setup at Flywheel Method of Control • Purpose: To maintain high power output by maintaining high RPM • Microcontroller – provides programmable, digital control • Monitor two inputs (voltage and RPM) • Use PWM to adjust effective rotor EMF • Use encoder to monitor RPM • Will be limited to basic control (such as P-control) in this project

22. Battery Subsystem • Car battery: provide large amount of current for a short period • Deep cycle battery: provide steady current over a long period • Frequent charging and discharging capable • Optimal for the case of renewable energy generation • Regulate charging voltage • Utilize regulator placed between alternator & battery • Keep charging at consistent rate during the wave profile

23. Predicted Power Output Power Output • The Mathematical Model was run with determined design variables • Efficiency of alternator assumed to be 50% • Higher average power expected with Flywheel

24. Cost & Weight Budget

25. Conclusion • What we learned from ME 423: • Necessity for Project Management • Importance of detailed design • ME 423 & E 421: • Connect Product design, marketing, & sales • Basic understanding of intellectual property • Initial plan to purchase COTS • Need to custom make several components • Focus in ME 424: • Purchasing / Fabrication • Final Assembly • Testing Phase

26. Questions and Comments? ? THANK YOU FOR LISTENING! SEE YOU NEXT SEMESTER