P12407- Clean, Self-Sustained Photovoltaic Energy Harvesting System
Josh Stephenson
Mike Grolling
Thomas Praderio
KGCOE MSD TECHNICAL REVIEW
PROJECT OBJECTIVEUtilize and properly manage energy from multiple sources to drive a load or charge a battery with high
efficiency for portable applications
CUSTOMER REQUIREMENTS • Design will include safety and component failure
• Ability to manage inputs from multiple power sources
• Investigate and benchmark technologies, components and modules
• System will integrate power management and load distribution.
• Establish highly efficient energy conversion parameters and design
• System must manage energy source variability
• Provide data acquisition points for future team's display design
• System must be portable
• System must include instructions for set-up and use
PROJECT SPECIFICATIONS• Ability to generate ~5W of power
• Voltage stabilization for battery charging (~15V ±0.05V)
• Output voltage of 10V
• Full solar delivery, provide a max output current of 0.5A
• Energy Storage is ~5 A-h
• Multiple solar panels
• Benchmark given component's specifications
• Calculate, design, measure each function
• List DAQ points
• Efficiencies for each function
PHASE 1: PRELIMINARY DESIGN
• Incorporates single energy source
(INITIAL) FINAL DESIGN
FINAL DESIGN
MAXIMUM POWER POINT TRACKING (MPPT)
SPV1020 MPPT IC
STANDARD BBC CONFIGURATION
STANDARD BATTERY CHARGER CONFIGURATION
STANDARD POWER MANAGEMENT CONFIGURATION
LITHIUM-ION BATTERIES
RISK MANAGEMENTID Risk Item Effect Cause Likelihood Severity Importance Action to
Minimize Risk
1 Team runs out of time Project doesn't get finished
Poor project planning 2 5 10 Good plan
2 Parts arrive late Schedule is delayed Unreliable vendor 2 3 6 Constant communication with Vendor
3 Prototype draws too much power
Poor battery life Poor choice of technology
1 3 3 Choose low power electronics
4 Photovoltaic produce insufficient/minimum voltage
Very low efficiency and power generation
Poor pairing of solar cells with DC/DC Conv.
2 5 9 Examine energy curves for different solar cells
5 Buck Boost converter incapable of blocking reverse bias conditions
reverse currents will drastically lower efficiency and may compromise operation or damage solar cells
Poor isolation of energy sources
1 7 8 Place diode across each solar cell to dissipate reverse emf
6 Internal electronics produce too much heat
Electronics overheat; inefficient
Poor choice of electronics or casing; unrealistic goals
2 2 4 Choose low power electronics
7 Internal electronics do not produce acceptable signals
Redesign/ project goals not met
Low margins of safety/ high-risk technology
2 3 6 Work with electronics that are acceptable
RISK MANAGEMENTID Risk Item Effect Cause Likelihood Severity Importance Action to Minimize
Risk
8 Requirements change during the project
Project will not be able to change in time
Redesign required 1 5 5 Verify deliverables with customer
9 Teammates do not do assigned work
Team will need to do the work for the teammate
Laziness/ not enough time
1 3 6 Ask for help with needed
10 Teammates do not arrive prepared
Team will be delayed and work will be postponed
Laziness/ not enough time
2 2 4 Assign tasks that have a high likelihood of being completed
11 Inability to contact the customer or guide
May miss vital information and requirements
Poor Communication 2 2 4 Keep constant info flow with the customer and guide
12 Getting wrong information from customer
Lead to solving an issue that doesn't exist
Poor Communication 2 3 6 Set up meeting s and communicate often
13 Arguments between teammates Will hurt team morale and cause conflict between members
Poor Communication 2 2 4 Have group focused and group leader aware
14 Microcontroller not fast enough to manage power
Power management will be ineffective
Poor part selection 2 2 5 Microcontroller selected with appropriate speed
15 Fractional gain op-amps use too much power
Battery life will decrease
Bad amplifier design 2 6 5 Select appropriately high-ohm feedback resistors and low-leakage op-amps
16 Microcontroller code does execute properly
Power management will be ineffective
Poor coding 4 7 8 Code will be thoroughly tested and debugged
CHALLENGES• Winter in Rochester– Forced to rely on artificial light
• Batteries used during experimentation were 12 years old and
• did not hold charge very long
• Flexible PV panels did not supply enough power
• Buck/Boost did not maintain required voltage while charging
• Learning curve on PCB layout software
• Scheduling with PCB ordering during the Chinese New Year
• Working with BGA footprint
CHALLENGES CONTINUED• Express PCB or Eagle CAD?
• Proprietary vs. open standards
• Licensing and version issues
• Finding vendor footprints
• Finding LGA footprints for the buck-boost
• Board house selection
• Price, capabilities, scheduling (Chinese new year)
• Final decisions:
• Eagle 5.7 for schematic and board layout
• MyRo PCB for fabrication
MICROCONTROLLER MSP430 DETAIL VIEW
FRACTIONAL GAIN AMPLIFIER FOR VOLTAGE SENSING
𝐴2=−𝑅 𝑓𝑏
𝑅𝑖𝑛
=− 750𝑘Ω9.1𝑀 Ω
=−0.0824𝑉 /𝑉𝐴1=−𝑅 𝑓𝑏
𝑅𝑖𝑛
=− 9.1𝑀 Ω9.1𝑀 Ω
=−1
𝐴𝑡𝑜𝑡𝑎𝑙=𝐴1∗ 𝐴2=−1∗−0.0824=0.0824𝑉 /𝑉
Both op amps are powered with a 3V button-cell CR2032
CURRENT SHUNT MONITOR INA193
PCB LAYOUT
RESULTS
0
0.5
1
1.5
2
2.5
3
3.5 3.28
2.352.15
Power at Each Stage
Pow
er (W
atts
)
MPPT Output
Buck-BoostOutput
Battery Charging
Power
RESULTS CONTINUED
0 5 10 15 20 25 300
1
2
3
4
5
6
Power at Each Stage Vs. Time
MPPT outputBB outputBattery
Time (Minutes)
Pow
er (W
atts
)
FUTURE CONSIDERATIONS• Troubleshoot analysis on PCB
• Added display for real-time data capture
• New batteries
QUESTIONS?