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Human Energy Storage for Off-Grid Use. ECE 445 Spring 2009 Project #5 Scott Aderhold Shruti Sharma Chris Graca. Introduction. Off-grid source of electricity Exercise with benefit of harnessing otherwise wasted energy. Power for on demand or stored for later use.

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human energy storage for off grid use

Human Energy Storage for Off-Grid Use

ECE 445

Spring 2009

Project #5

Scott Aderhold

Shruti Sharma

Chris Graca

introduction
Introduction
  • Off-grid source of electricity
  • Exercise with benefit of harnessing otherwise wasted energy.
  • Power for on demand or stored for later use.
  • Clean source of electricity
features
Features
  • Compatible with a variety of bicycles
  • Output:120V-AC, 60Hz
  • Simple Operation
  • Compact and Portable
  • Battery voltage display
generator
Generator

Currie Technologies

PMDC Motor

model no. XYD-6D

  • 24V DC
  • Rated Speed: 2600 RPM
  • Rated Current: 22 A
  • Rated Power: 350 W
bike stand
Bike Stand

Bell Motivator Mag Indoor Bicycle Trainer

  • Dual adjustment locking mechanism
  • Foldable and compact
  • Adjustment for varying wheel sizes
calculations
Calculations

Road bike circumference: 2.096m

Generator shaft circumference: 0.35908m

Generator speed: 800 RPM

calculations1
Calculations

Typical drivetrain losses= 5% Normal force= 70 N

Rolling resistance= 0.07 Number of tires=1

Generator efficiency= 95% Bike speed=3.44m/s

Generator output=95W

recommendations
Recommendations
  • Hook up motor to dynamometer to do better testing and get more motor characteristics.
buck boost converter theory
Buck-Boost ConverterTheory
  • Output voltage determined by duty ratio and input voltage
  • Transfer of Energy between inductor and capacitor
  • Switching frequency higher than time constant
  • Inverted Output voltage

Image from http://en.wikipedia.org/wiki/Buck-boost_converter

buck boost converter initial design and modifications
Buck-Boost ConverterInitial Design and Modifications
  • Correct Concept but with errors in chip selection and layout
    • Original PWM could not reach desired pulse widths
    • High Side switching not diagnosed as problem
  • Non-IC Design correct
buck boost converter modifications
Buck-Boost ConverterModifications
  • Changed PWM chip to UC2843
    • Allowed for pulse width to vary to desired ranges
  • Accounted for high side switching
  • Isolated grounds of PWM from the converter ground
buck boost converter end design
Buck-Boost ConverterEnd Design
  • Snubber Circuit
  • Additional Capacitors to
  • reduce ESR
  • Capacitor Across DC input
  • to reduce high frequency
  • ripple
  • PMOS to account for high
  • side switching problems
  • Inductor needed large
  • wiring in order to handle
  • Iout + Iin sized currents
buck boost converter results
Buck-Boost ConverterResults

Efficiency higher than 1 can be attributed to ripple current for 20 volt input

  • More tests should be done with varying
  • loads
    • Circuit
  • Tests should also be done with generator
  • Ripple was not measured and skews the
  • results
buck boost why high side switching can be bad
Buck-BoostWhy High Side switching can be bad
  • NMOSs create less losses (smaller capacitance and internal resistance)
  • Vgs > 2*Vth (In Power FETs)
  • Vgs > 10 + Vs (Rule of thumb)
  • High side can be very large, requiring Vg of up to 25 volts (in this design)
  • In PMOS, Vgs < Vs – 10 to turn off, allowing for lower Vgate
  • Vgs limits of volts Vgs
buck boost future work
Buck-BoostFuture Work
  • PMOS should be changed to NMOSs with high side gate drivers
  • Possible change to a Flyback or Push Pull converter.
    • Isolation available
    • No need for high side drivers
    • The transformer might get excessively large in order to handle large currents.
  • Implement feedback control
inverter theory
InverterTheory
  • Reverse of a full-wave rectifier
  • Uses switches to change polarity of voltage on load
  • Implemented with FETs and a PWM chip

Image from http://en.wikipedia.org/wiki/Buck-boost_converter

inverter initial design
InverterInitial Design
  • Design very similar to Stirling Engine group from last semester
  • Wiring was a little incorrect, but only slight modifications had to be made
inverter results
InverterResults
  • Problems with High side switching (Again)
  • Output of PWM was as expected (quasi sine wave)

Dead-time can be adjusted

inverter future work
InverterFuture Work
  • Implement High Side switches
  • Possible change to Flyback or push-pull converter to reduce transformer size
battery
Battery

Lead Acid battery

MODEL – PSH-1280 F2

12 Volts

8 Amp Hr.

36 Watts per Cell

Charge rate 600mA at 12V

Charging time = 8000/600

=13.33 hours

battery charger
Battery Charger
  • Three Stage process
  • STAGE 1 – BULK CHARGE
  • 10.5 Volts to 15 Volts
  • STAGE 2- ABSORPTION CHARGE
  • 14.2 Volts – 15.5 Volts
  • STAGE 3- FLOAT CHARGE
  • 13.02Volts – 13.2 Volts
charger schematic
Charger Schematic
  • Precision Voltage Source
  • Temperature Sensor with negative temperature Coefficient of -8mV per degree Celsius
  • Large Power Diode
  • LM350 – 3 pin Voltage Regulator
      • 1.2 V to 33 V output range
      • Adjust Pin function
testing and results3
Testing and Results
  • Applied different voltages ranging from 10V to 15V through the circuit
  • Charged for 14V and above
  • Input current 0.3 A
  • Output current 0.205 A
  • Power = VI
  • Input Power 4.2 Watts
  • Output Power 2.46 Watts
  • Efficiency 58.57%
display schematic
Display Schematic
  • Dot Mode
  • Input voltage of 12.65 V- Led 10 lights up
  • Led 1 lights up at 11.89 V
  • Entire circuit uses 10 mA
  • Led Brightness Adjustable
transformer
Transformer
  • Obtained core from the Power lab
  • Step Up Transformer
  • Toroid
  • Primary Side 12V
  • Secondary Side 120 V
  • Turns Ratio 1:10
  • Windings
testing and results4
Testing and Results
  • Open Circuit Test
    • Connected the low side of the transformer to a function generator
    • High side was left open
  • For 1.9 V it stepped to 13.6V
  • For 2.2 V it stepped to 38.4 V
  • Flow of Flux
recommendations1
Recommendations
  • Use a higher capacity battery for testing instead of a smaller battery.
  • Laminated Core for Transformer
  • Current Limiter Circuit
  • Numeric Display
  • Use PQ core instead of toroid geometry.
estimated overall efficiency
Estimated Overall Efficiency
  • Mechanical to Generator Electrical Output

77.4%

  • Buck-Boost Efficiency
    • Measured approximately 98% but actual is more likely to be lower, 80%
  • Battery Charger Efficiency

55%

  • Overall Efficiency: 77.4*80*55 = 34.5%
ethical considerations
Ethical Considerations
  • Safety is primary concern
    • High currents in Inductor
    • Overcharge protection is a must for Lead Acid batteries
    • Possible overheating if not more cooling added
summary
Summary
  • Overall efficiency of 34.5% to the battery
  • Use dynamometer for testing of motor
  • Implement high side switching
  • Feedback is a must on final design
  • Possibly switch to flyback or push-pull converter
  • Use a higher capacity battery for testing instead of a smaller battery.
  • Laminated Core for Transformer
  • Current Limiter Circuit
  • Numeric Display
  • Use PQ core instead of toroid geometry.
acknowledgments
Acknowledgments

A special thank you to:

  • Professor Gary R. Swenson
  • Professor Patrick Lyle Chapman
  • Professor Philip T. Krein
  • Professor Peter W Sauer
  • Kevin James Colravy
  • Ali Bazzi
  • Andy Friedl
  • Zuhaib Sheikh
buck boost calculations inductor and capacitance
Buck-Boost CalculationsInductor and Capacitance
  • Assumed 350W input and 24v max input
  • Voltage ripple of 1% (.148v)
  • Current ripple of 10% of Iout
  • Final equations:
flyback converter
Flyback Converter
  • Provides Isolation
  • Output is dependent on transformer turns ratio and Pulse width
  • Same function as buck boost
  • Provides Isolation from output and low side switching