Efficient Solar Powered Electrolysis Device

1. Efficient Solar Powered Electrolysis Device ECE 345 Group 32 Justin Boike Johnny Bui TA – Marty Cantzler

2. Motivation • Past Projects in Heart Murmur Detector • Experience in analog circuit design • Desire to learn more about power circuits and conversion techniques • Environmentally friendly project

3. Introduction • Utilize solar power to perform electrolysis • Efficiently convert solar energy to controlled electrical signals • Use these electrical signals to “release” hydrogen from water • Create a prototype for large scale use

4. Objective • Maintain efficient power conversion • Battery operated control system • Self sufficient device

5. Objective (cont’d) • Step down various voltage levels through buck converters • Provide feedback to regulate variants in input

6. Final Design

7. Solar Panel Setup

8. Solar Panel Characteristics

9. Power Curve for Solar Panel

10. Goals for Circuit Design • Solar Panel output ~ 10  40 Volts • Chose maximum power point at 20 Volts • Converter 1: 20  15 Volts • Converter 2: 12.85  3.7 Volts • Converter 3: 20  3.7 Volts

11. Circuitry on the Protoboard

12. Basic Buck Converter

13. Buck Converter Design • Duty Cycle: D = Vout / Vin • Let frequency be determined by Lcritical • Freq = (2*Lcritical)/(Ro*(1-D) • Prevented making large toroids • Find Capacitance • C = T*(1-D)/Lcritical

14. Pulse Width Modulator • Motorola - MC34060A • Selected RT*CT = Operating Freq (0 – 500K) • Adjustable Duty Cycle 92-0% range • Built in Transistor

15. Duty Cycle Waveforms Buck 1 ~75% Duty Cycle

16. Duty Cycle Waveforms Buck 2 ~29% Duty Cycle

17. Duty Cycle Waveforms Buck 3 ~19% Duty Cycle

18. Feedback For Steady Output • Duty Cycle - merely percentage of input as output…magnitude independent • Add feedback to maintain maximum output • Feedback controls additional MOS transistor

19. Feedback Circuit Design

20. Feedback Theory • Op amp compares Vout • Op amp output triggers MOS accordingly • Duty Cycle adjusted if input exceeds preset limit

21. Goals for Charge Control Design • Battery Charging Circuit • Pulls input “charging” voltage from Buck #1 – 15V. • Hysteresis – 12.85 +/- 1 Volt • Lower Limit  ~11.85 Volts – signals the battery is low, and charges it. • Upper Limit  ~13.85 Volts – signals the battery is nearly overcharged, and stops charging.

22. Battery Charging Circuit Design

23. Charging Circuit Part 1 • We used a 2.5V reference for the Op-amp inputs • [R2/(R1+R2)] * Vbat = VA- = 2.5 V • Vbat = 12.85V R2/(R1+R2) = 2.5/12.85 • R1(actual) = 19.38 kW R2(actual) = 5.1 kW

24. Charging Circuit Part 2 • Not Charging the Battery • Battery Voltage has passed 13.85V • 12.85V/13.85V = X/2.5V X = 2.3V • R5/(R4+R5) * 2.5V = 2.3V - R5/(R4+R5) = .92 • R4(actual) = 4.62 kW R5(actual) = 56 kW

25. Charging Circuit Part 3 • Charging the Battery • Battery Voltage has gone below 11.85V • 12.85V/11.85V = X/2.5V X = 2.71V • (V1high - 2.5V)/R4 + (V1high - 12.85V)/(R5 + R6) = 0V • (2.71-2.5V)/4.62kW + (2.71-12.85V)/(56kW+R6) = 0V • R6(actual) = 131.86 kW • R7(actual) = 8.2 MW– pulls voltage for Op-Amp output • R3(actual) = 10.01 kW– used to pull current to the reference diode

26. Function Testing • Tested Converters and Overall Design

27. Accomplishments • Operational while charging • Over charge prevention • Functional outputs • Learned a great deal about power circuits • Understand developmental process

28. Future Recommendations • Adjustable circuitry to max power point • User defined for different outputs • Reduce energy loss in resistors

29. Acknowledgments • Special thanks to: • Marty • Course instructors • Parts and ECE store staff • Sunwize Technologies

30. Appendix

31. Appendix

32. Appendix Buck 1

33. Appendix Buck 2

34. Appendix Buck 3