KGCOE MSD TECHNICAL REVIEW
P12407- Clean, Self-Sustained Photovoltaic Energy
Harvesting System
Josh Stephenson
Mike Grolling
Thomas Praderio
PROJECT OBJECTIVE
Utilize 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 MANAGEMENT
ID
Risk Item
Effect
Cause
Likelihood
Severity
Importance
Poor project planning
2
5
10
Unreliable vendor
2
3
6
Poor choice of
technology
Poor pairing of solar
cells with DC/DC Conv.
1
3
3
2
5
9
Buck Boost converter
reverse currents will Poor isolation of
incapable of blocking reverse drastically lower
energy sources
bias conditions
efficiency and may
compromise operation
or damage solar cells
Internal electronics produce Electronics overheat; Poor choice of
too much heat
inefficient
electronics or casing;
unrealistic goals
Internal electronics do not Redesign/ project
Low margins of safety/
produce acceptable signals goals not met
high-risk technology
1
7
8
2
2
4
Choose low power
electronics
2
3
6
Work with
electronics that
are acceptable
1
Team runs out of time
2
Parts arrive late
3
Prototype draws too much Poor battery life
power
Photovoltaic produce
Very low efficiency
insufficient/minimum voltage and power generation
4
5
6
7
Project doesn't get
finished
Schedule is delayed
Action to
Minimize Risk
Good plan
Constant
communication
with Vendor
Choose low power
electronics
Examine energy
curves for
different solar
cells
Place diode across
each solar cell to
dissipate reverse
emf
RISK MANAGEMENT
ID
Risk Item
8
Requirements change during the
project
Teammates do not do assigned
work
9
10 Teammates do not arrive
prepared
11 Inability to contact the customer
or guide
12 Getting wrong information from
customer
13 Arguments between teammates
14 Microcontroller not fast enough
to manage power
Effect
Cause
Project will not be able Redesign required
to change in time
Team will need to do Laziness/ not enough
the work for the
time
teammate
Team will be delayed Laziness/ not enough
and work will be
time
postponed
May miss vital
Poor Communication
information and
requirements
Lead to solving an issue Poor Communication
that doesn't exist
Will hurt team morale Poor Communication
and cause conflict
between members
Power management Poor part selection
will be ineffective
Likelihood
Severity
Importance
1
5
5
1
3
6
2
2
4
2
2
4
2
3
6
2
2
4
2
2
5
15 Fractional gain op-amps use too Battery life will
much power
decrease
Bad amplifier design
2
6
5
16 Microcontroller code does
execute properly
Poor coding
4
7
8
Power management
will be ineffective
Action to Minimize
Risk
Verify deliverables
with customer
Ask for help with
needed
Assign tasks that have
a high likelihood of
being completed
Keep constant info
flow with the
customer and guide
Set up meeting s and
communicate often
Have group focused
and group leader
aware
Microcontroller
selected with
appropriate speed
Select appropriately
high-ohm feedback
resistors and lowleakage op-amps
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
𝐴1 = −
𝑅𝑓𝑏
9.1 𝑀Ω
=−
= −1
𝑅𝑖𝑛
9.1 𝑀Ω
𝑅𝑓𝑏
750 𝑘Ω
𝐴2 = −
=−
= −0.0824 𝑉/𝑉
𝑅𝑖𝑛
9.1 𝑀Ω
𝐴𝑡𝑜𝑡𝑎𝑙 = 𝐴1 ∗ 𝐴2 = −1 ∗ −0.0824 = 0.0824 𝑉/𝑉
Both op amps are powered with a 3V button-cell CR2032
CURRENT SHUNT MONITOR INA193
PCB LAYOUT
RESULTS
Power at Each Stage
3.5
3.28
Power (Watts)
3
2.35
2.5
2.15
2
1.5
1
0.5
0
MPPT Output
Buck-Boost
Output
Battery
Charging
Power
RESULTS CONTINUED
Power at Each Stage Vs. Time
6
5
Power (Watts)
4
MPPT output
3
BB output
Battery
2
1
0
0
5
10
15
Time (Minutes)
20
25
30
FUTURE CONSIDERATIONS
•
Troubleshoot analysis on PCB
•
Added display for real-time data capture
•
New batteries
QUESTIONS?