Alternative Energy Tools: Harnessing Solar Power for Everyday Use

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Alternative Energy ToolsHarnessing Solar Power
for Everyday Use

• Andrew Just
• Adam Greenfield
• December 3, 2003

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Reasons for Choosing this Project

• Related coursework
• Clean, reusable energy
• Opportunity to learn
• Educate future engineers

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Objectives

• Track maximum power point
• Utilize alternative energy (i.e. solar, wind)
  to run household devices
• Charge Battery
• Present functional design in elementary schools

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Maximum Power Point
Point where product of current and voltage is at
a maximum
Brightness
?
Temperature
?
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Charge Battery

• Convert source voltage to 14.7 V
• Prevent overcharging

Operate Electronic Devices

• Step battery voltage down to power devices (i.e.
  lamp, portable CD player, etc.)

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Converter Design

• Two Low Pass Filters
• Two switches
• Steps down panel voltage to battery voltage

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Converter Design

• Determine duty cycle, D1
• Choose an operating frequency
• Find critical inductance
• Calculate capacitance
• Modify values for practical use

• D1 Vo/Vi
• 20 kHz
• Lcrit ROT(1-D1)/2
• C TD1/Lcrit

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Pulse Width Modulator

• MC34060A
• Internal Oscillator
• Internal Reference Voltage, 5V
• Output enabled if
• V5 gt V4, V3
• Creates duty cycle
• Controls PMOS

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Battery Charger Design

• Prevent overcharging of the battery through
  hysteresis

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Battery Charger Design

• Case 1 Not-Charging the Battery (VA- gt VA)

VA V1L 2.3V R5 / (R4 R5) 2.5V
2.3V R5 55kW, R4 5.1kW
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Battery Charger Design

• Case 2 Charging the Battery (VA- lt VA)

VA V1H 2.7V (V1H - 2.5V) / R4 (V1H -
12.7V) / (R5 R6) 0V (2.7V - 2.5V) /
5.1kW (2.7V - 12.7V) / (55kW R6) 0V R6
200kW
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Building the Circuit

• Parts Utilized

Actions Done

• MC34060A PWM
• LM393 Comparator
• LM336BZ-2.5 Zener
• MTP8P10 PMOS
• LCR components
• Panel, battery, loads

• Order parts from vendors, shop
• Toroids, toroids, toroids, toroids

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Functionality Testing

• Performed voltage testing on PWM, PMOS, and
  comparator components
• Tested current at all inputs/outputs

  Voltage V Current mA Power W Efficiency
Input 21.77 29.8 0.67 N/A
Battery 12.66 24.0 0.31 46.1
Converter 1 11.35 24.0 0.36 54.7
Converter 2 5.30 160.0 0.85 23.4
Converter 3 11.30 284.0 3.21 88.4
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Panel and Ripple Tests

• Observations
• Current independent of panels distance from
  light
• Ripple at Converter 3 0.19V (1.6)
• Ripple at Converter 2 0.12V (2.0)

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Accomplishments

• Functional Outputs
• Proper Conversion
• Battery Charging
• Overcharging Prevention
• Operation while Charging

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Shortcomings and Recommendations

• Current vs. Voltage Control
• Efficiency
• Maximum Power Point Tracking
• Only Solar Power Implementation
• Limited Prior Course Experience

Voltage Control
Current Control

• Add feedback
• Reduce of resistors
• Add windmill

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Very Special Thanks to
Professor Krein
Jonathan Kimball
Mark Wiegert
Resources
Elements of Power Electronics, Krein.
Modern DC-to-DC Switchmode Power Converter
Circuits, Severns and Bloom.