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Sustainable Push Cart for Reduction of Postharvest Loss

Sustainable Push Cart for Reduction of Postharvest Loss. Harikrishna Patel, James Rey, Stu Almeleh. Group 34 May 2, 2014. Introduction. Reduce the postharvest loss of a push cart through the utilization of renewable energy sources and creative refrigeration techniques .

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Sustainable Push Cart for Reduction of Postharvest Loss

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  1. Sustainable Push Cart for Reduction of Postharvest Loss Harikrishna Patel, James Rey, Stu Almeleh Group 34 May 2, 2014

  2. Introduction Reduce the postharvest loss of a push cart through the utilization of renewable energy sources and creative refrigeration techniques

  3. Functional Objectives Convert solar energy to battery power Create an evaporative cooling environment using a misting fan Power a cooler overnight via battery

  4. Overall Block Diagram Solar Panel Control Circuitry Misting Fan Battery Converter Misting Converter Battery Cooler Blue arrows indicate power flow. Orange arrows indicate duty cycle adjustment.

  5. Battery Converter Description Buck converter Maintain 14.5 V output +/- 0.3 V Input/Output: Solar panel  battery Efficiently charges battery during daylight hours

  6. Battery Converter Picture

  7. Battery Converter Schematic

  8. Battery Converter Requirements & Verification

  9. Battery Charging

  10. Battery Charging

  11. Thermoelectriccooler Picture

  12. Thermoelectric Cooler Requirements & Verifications Requirement: Temperature Inside Cooler 40-45 degrees less than surrounding environment Verification: connected battery to cooler and used a temperature probe

  13. Cooler Usage

  14. Cooler Usage

  15. Misting Converter Description Inverter and flyback converter Converts 12 VDC to 120 VAC +/- 5% Input/Output: Battery  Misting fan Allows misting fan to run during daylight hours

  16. Misting Converter Picture

  17. Misting Converter Schematic

  18. Misting Converter Schematic Continued

  19. Misting Converter Requirements & Verification

  20. Misting Fan Converter Inverter PWM Input Voltage (DC) Output Voltage (AC)

  21. Transformers Picture of Ferrite Core

  22. Transformers Possible Failures Initially searched for DC-DC transformers Couldn’t find 1:10 transformers Wound transformer was not magnetically coupled? – maybe should have wound it on a powdered iron core

  23. Control Circuitry Description Regulatory circuit to control output voltages Keeps battery input voltage in optimal charging range(14.5 V +/- 0.3 V) Keeps misting fan input voltage in optimal range (120 V +/- 6 V)

  24. Control Circuitry Algorithm for Battery Converter Start Value: D = 35 Sample Output Voltage Vout> 14.8V Yes Decrease D by 1 No Vout < 14.2V No Yes Increase D by 1 D has a range of 10 to 90

  25. Control Circuitry Requirements & Verification

  26. Control Circuitry Vin Vgs PWM Vout

  27. Control Circuitry

  28. Battery Charging In 45 min, the voltage increased from 12.606 to 12.732 V (ΔV = .126) 13.1 – 12.06 = 1.04 (1.04/.126) x 45 min = 6 hours 12 min

  29. Power Budget Solar Panel to Battery: 4 A x 40 V x 8 hr* 85% = 1088 Wh Cooler: 12 V x 4.25 A x 12 hr= 612 Wh Misting fan: 120 V x .65 A x 4 hrx 133% = 416 Wh 1088– 612 – 416 = 60 Wh excess

  30. Recommendations Higher efficiency – MPPT, snubber circuit, DC fan instead of misting fan Battery overcharge protection Enclosed PCB for both converters Snubber circuit

  31. Concerns Weight Excessive cloudy weather (monsoon season)

  32. Special Thanks To… Professor Carney Professor Singer Dennis Yuan Kevin Colravy Chris Barth SrikanthanSridharan

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