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?