KGCOE MSD TECHNICAL REVIEW

forestevanescentElectronics - Devices

Nov 2, 2013 (3 years and 8 months ago)

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P12407
-

Clean, Self
-
Sustained Photovoltaic Energy
Harvesting System


Josh Stephenson

Mike
Grolling


Thomas
Praderio

KGCOE MSD TECHNICAL REVIEW

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

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 MANAGEMENT

ID

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

𝐴
2
=

𝑅
𝑓
𝑅
𝑖
=

750

𝑘
Ω
9
.
1

𝑀
Ω
=

0
.
0824

𝑉
/
𝑉

𝐴
1
=

𝑅
𝑓
𝑅
𝑖
=

9
.
1

𝑀
Ω
9
.
1

𝑀
Ω
=

1

𝐴
𝑡𝑡 𝑙
=
𝐴
1

𝐴
2
=

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

3.2785

2.35125

2.1465

0
1
2
3
4
Power (Watts)

System Charging Efficiency

MPPT Output

Buck
-
Boost

Output

Battery

Charging

Power

3.28

2.35

2.15

0
0.5
1
1.5
2
2.5
3
3.5
Power (Watts)

Power at Each Stage

MPPT Output

Buck
-
Boost

Output

Battery

Charging

Power

RESULTS CONTINUED

0
1
2
3
4
5
6
0
5
10
15
20
25
30
Power (Watts)

Time (Minutes)

Power at Each Stage Vs. Time

MPPT output
BB output
Battery
FUTURE CONSIDERATIONS


Troubleshoot analysis on PCB


Added display for real
-
time data capture


New batteries


QUESTIONS?