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Alternative Energy Tools: Harnessing Solar Power for Everyday Use. Andrew Just Adam Greenfield December 3, 2003. Reasons for Choosing this Project. Related coursework Clean, reusable energy Opportunity to learn Educate future engineers. Objectives. Track maximum power point
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Alternative Energy Tools:Harnessing Solar Power for Everyday Use Andrew Just Adam Greenfield December 3, 2003
Reasons for Choosing this Project • Related coursework • Clean, reusable energy • Opportunity to learn • Educate future engineers
Objectives • Track maximum power point • Utilize alternative energy (i.e. solar, wind) to run household devices • Charge Battery • Present functional design in elementary schools
Maximum Power Point Point where product of current and voltage is at a maximum Brightness Temperature
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.)
Converter Design • Two Low Pass Filters • Two switches • Steps down panel voltage to battery voltage
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
Pulse Width Modulator • MC34060A • Internal Oscillator • Internal Reference Voltage, 5V • Output enabled if V5 > V4, V3 • Creates duty cycle • Controls PMOS
Battery Charger Design • Prevent overcharging of the battery through hysteresis
Battery Charger Design • Case 1: Not-Charging the Battery (VA- > VA+) VA+ = V1L = 2.3V [R5 / (R4 + R5)] * 2.5V = 2.3V R5 = 55kW, R4 = 5.1kW
Battery Charger Design • Case 2: Charging the Battery (VA- < 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
Building the Circuit Actions Done Parts Utilized • MC34060A – PWM • LM393 – Comparator • LM336BZ-2.5 – Zener • MTP8P10 – PMOS • LCR components • Panel, battery, loads • Order parts from vendors, shop • Toroids, toroids, toroids, toroids
Functionality Testing • Performed voltage testing on PWM, PMOS, and comparator components • Tested current at all inputs/outputs
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%)
Accomplishments • Functional Outputs • Proper Conversion • Battery Charging • Overcharging Prevention • Operation while Charging
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
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.