Human Energy Storage for Off-Grid Use

1 / 43

# Human Energy Storage for Off-Grid Use - PowerPoint PPT Presentation

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.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Human Energy Storage for Off-Grid Use' - lavender

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Human Energy Storage for Off-Grid Use

ECE 445

Spring 2009

Project #5

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.
• Clean source of electricity
Features
• Compatible with a variety of bicycles
• Output:120V-AC, 60Hz
• Simple Operation
• Compact and Portable
• Battery voltage display
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

Bell Motivator Mag Indoor Bicycle Trainer

• Foldable and compact
• Adjustment for varying wheel sizes
Calculations

Generator shaft circumference: 0.35908m

Generator speed: 800 RPM

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
• Hook up motor to dynamometer to do better testing and get more motor characteristics.
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 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 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 ConverterEnd Design
• Snubber Circuit
• 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 ConverterResults

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

• More tests should be done with varying
• Circuit
• Tests should also be done with generator
• Ripple was not measured and skews the
• results
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-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
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

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
InverterResults
• Problems with High side switching (Again)
• Output of PWM was as expected (quasi sine wave)

InverterFuture Work
• Implement High Side switches
• Possible change to Flyback or push-pull converter to reduce transformer size
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
• 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
• 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
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
• 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
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 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
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
• 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
• 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
• 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

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 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
• 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