KGCOE MSD Technical Review AgendaP12407- Clean, Self-Sustained Photovoltaic Energy Harvesting SystemKGCOE MSD Page 1 of 1 Technical Review AgendaMeeting Purpose:

1. Overview of the project2. Confirm Engineering Specifications and Customer Needs3. Review concepts4. Propose a design approach and confirm its functionality5. Cross-disciplinary review: generate further ideas

Materials to be Reviewed1. Project Description2. Customer Needs3. Customer Specifications4. Solar Cells5. Phase I and II Diagrams 6. Concept Development and Proposed Design – Buck-boost converters7. Concept Development and Proposed Design – Battery charger8. Concept Development and Proposed Design – Power

monitoring/management9. Control Diagram 10. MSDI Plan11. Risk Assessment

Meeting Date: October 27th, 2011Meeting Location: Senior Design Lab, fourth floor of Building 9Meeting time: 4:00PM to 5:00PM

Meeting TimelineTime Topic of Review Required

Attendees10:00 Introduction to the project Dr. Lyshevski10:05 Customer Needs Dr. Lyshevski10:07 Customer Specifications Dr. Lyshevski10:12 Solar Cells Dr. Lyshevski10:14 Ascent Solar Panel Concerns Dr. Lyshevski10:20 Phase I and II Sketches Dr. Lyshevski10:23 Questions, Concerns, Ideas Dr. Lyshevski10:27 Concept Development and Proposed Design – Buck-

boost convertersDr. Lyshevski

10:30 Questions, Concerns, Ideas Dr. Lyshevski10:35 Concept Development and Proposed Design – Battery

chargerDr. Lyshevski

10:37 Questions, Concerns, Ideas Dr. Lyshevski10:42 Concept Development and Proposed Design – Power

monitoring/managementDr. Lyshevski

10:43 Control Diagram Dr. Lyshevski10:45 Questions, Concerns, Ideas Dr. Lyshevski10:48 Project Plan Dr. Lyshevski10:50 Questions, Concerns, Ideas Dr. Lyshevski10:55 Risk Assessment Dr. Lyshevski11:00 Questions, Concerns, Ideas Dr. Lyshevski

Project Description

Project Background:

A clean, self-sustained photovoltaic energy harvesting system is the focus of this project. Photovoltaics will be used to acquire the energy from light and this energy will then be sent through an energy management system to charge a battery or drive a load.

Problem Statement:

Properly manage energy from multiple sources to charge a battery and drive a load. The team shall establish and then guarantee efficiency parameters based on benchmark results. This will require the team to investigate various applied technologies, components, and modules to establish engineering specifications. System and individual module efficiencies shall approach that of benchmarked modules where feasible.

Objectives/ Scope:

1. Generate (average) ~5 W of energy (rated).2. Highly efficient photonic-to-electrical,

electrical-to-electrical and electrical-to-photonic energy conversions.

3. Superior light harvesting capabilities.4. Sufficient energy storage abilities. 5. Robust voltage stabilization and distribution.6. Energy management system with multiple

photovoltaic energy source types.

Deliverables: Highly efficient energy conversion that meets

customer needs A functioning portable prototype

Expected Project Benefits:

Produce a clean, self-sustained photovoltaic energy harvesting system from multiple input power sources.

Core Team Members:

Mike Grolling- EE- Energy Storage Josh Stephenson-EE- Power Conditioning Tom Praderio-EE- Power Management

Assumptions and Constraints:

The team must obtain a well-rounded understanding of energy management and harvesting. By using multiple inputs which have different loading capabilities, a system must be in place to isolate low voltage photovoltaics.

Issues & Risks:

Improper battery voltage regulation may lead to permanent battery damage, swelling, or explosions

Oversized solar cells may lead to excessive heat dissipation through the parts and result in shortened lifetimes or failure

Customer Needs

Customer Need # Importance Description Comments/Status

CN1 1 Design will include safety and component failure Example: Li-ion Batteries (place in a wooden box when testing)CN2 1 Ability to manage inputs from multiple power sources 3-5 solar panel inputs/ do not load low voltage panels

CN3 1Investigate and benchmark technologies, components and modules

CN4 1 Engineer multiple concepts. Perform tradeoff analysis Find efficient battery charging technologyCN5 1 System will integrate power management and load distribution.

CN6 1Establish highly efficient energy conversion parameters and design Efficiency is dependent on light conditions

CN7 1 System must manage energy source variability Example: clouds or night-timeCN8 1 Provide data acquisition points for future team's display design Data acquisition is performed by the microcontrollerCN9 1 System must be portable Ascent Solar competition requirement

CN10 1 System must include instructions for set-up and use Ascent Solar competition requirementCN11 1 System must utilize Ascent Solar’s flexible solar modules Ascent Solar competition requirementCN12 1 Adequate amount of energy storage

Project Specifications

Spec. # Importance Source Function Specification (metric) Unit of Measure

Marginal Value

Ideal Value Comments/Status

S1 1 CN11 Power Ability to generate ~5W of energy W 5 Average power

S2 1CN3,4,5,

7,8 V StabilityVoltage stabilization for battery charging (~15V ±0.05V) V

14.95V-15.05V 15 Needs clarification

S3 1 CN5,7 V out Output voltage to load of 10V V 10

S4 1 CN7 I outFull solar delivery, provide a max output current of 0.5A A 0.5

S5 1 CN1, 7 I out Peak output current will meet 5A max A N/A 5S6 1 CN12 Storage Battery capacity is ~5 A-h A-h N/A 5 Choose an appropriate battery

S7 1 Load/DisplayPower load to simulate future display device at a constant 5W W 5

S8 CN2 Input Multiple solar panels V/A

5V-36V / 0A-1A

S9 CN3 AllBenchmark given component's specifications

S10 CN4 All Weigh concepts for each function

S11 CN6 AllCalculate, design, measure each function Efficiencies

S12 CN8 All List DAQ pointsS13 CN9S14 CN10 User's manual N/A N/A N/AS15 CN6 Efficiencies for each function

Proposed Solution Diagrams

Figure 1: Single-source testing concept model

Figure 2: Multiple-source concept model

Rating Rating Rating+ - +- - +0 0 0+ 0 ++ - -

Adjustable outputNumber of cells supported

Effi ciency

Overall RankLoad bypass

Preset values4A

1 3Yes No

496%

No4

Max charge current

LTM4006 LM3420Notes Notes

20mA

Concept Selection - Battery charger

Selection Criteria

95%No

2

ADP3806Notes

3AYes

Table 1: Battery charging concept selection

Rating Rating Rating+ + 0- + +

- ++ 0 0

Overall Rank

Input voltage rangeOutput voltage range

Quiescent currentEffi ciency at 250mAOutput disconnect

LTM4607 ADP1111Notes Notes

Concept Selection - Buck Boost Converters

Selection Criteria4.5V-36V 2V-30V0.8-24V 3V-Vin

300uA85% (12V)

SM74301Notes6V-95V

2.5V-Vin

92% (15V)No

3Yes No

1 2

Table 2: Buck-boost converter concept selection

Rating Rating Rating+ + 00 + -- + 0- 0 -

SM72441 Microconroller ADC (voltage division) ADM1276Selection Criteria Notes Notes Notes

Concept Selection - Power Management

0 to DC supply Depends on division resistors 2V to 20V8 24 1

Voltage sense maximumSensor channels per chip

50mW on the order of uWComplicated Passive components needed One chip needed per sense line

Power consumptionSystem complexity

2 1 3Overall Rank

Table 3: Power Management concept selection

Figure 3: Buck Boost Converter Application diagram

Figure 4: Battery Charger Application diagram

Note: Thermistors used as a precautionary measure against battery overheating

NC

NC

Figure 5: Microcontroller application diagram

Note: All BBC lines will be duplicated for each buck-boost converter in the final design. The MSP430 will support up to eight BBC’s.

Data Acquisition Points

Output of each photovoltaic panelo Voltage and current are measured internally by each buck-boost convertero Data is reported to the microcontroller via an SPI serial bus

Output of each buck-boost convertero Current is measured by a LTC6102 current sense amplifiero Voltage is measured by a high-impedance simple voltage dividero Data is reported to the microcontroller via an ADC channel

Battery charger outputo Measured internally by the battery chargero Data is reported to the microcontroller via an ADC channel

System output/loado Current is measured by a LTC6102 current sense amplifiero Voltage is measured by a high-impedance simple voltage dividero Data is reported to the microcontroller via an ADC channel

Figure 6: Microcontroller software algorithm for photovoltaic power management

Figure 7: Current Sensing solution application diagram

Action Item Week 8 Week 9 Week 10 Week 11 Fall BreakLearn PCB ExpressSystem Design ReviewOrder SamplesTI Competition AppChoose devicesDesign Passive CompCadence SchematicPsuedo CodingBOMDetailed ReviewUpdate BOMOrder PartsContact Ascent SolarTest Samples

Table 4: Senior Design I Time Line

Risk Assessment

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

Follow timeline and manage weekly updates

2 Parts arrive late Schedule is delayed Unreliable 2 3 6 Constant

vendor communication with Vendor

3Prototype draws too much power or is inefficient

Poor battery life/does not meet customer spec

Poor choice of technology 1 3 3 Choose low power/high

efficiency electronics

4

Photovoltaics produce insuffient/minimum power

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/ambient temp too high

Electronics overheat; inefficient

Poor choice of electronics or casing; unrealistic goals

2 2 4Choose low power electronics with wide operating temp range

7Internal 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

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

11Inability 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

12Getting 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

14Microcontroller not fast enough to manage power

Power management will be ineffective

Poor part selection 2 2 5

Microcontroller selected with appropriate speed

15Microcontroller code does execute properly

Power management will be ineffective Poor coding 4 7 8 Code will be thoroughly

tested and debugged