p12441: thermoelectric power pack for next generation stove

P12441: Thermoelectric Power Pack for Next Generation Stove

Andrew Phillips – Project ManagerColin McCune – Lead EngineerLauren Cummings – Electrical EngineerXiaolong Zhang – Cost Engineer

Background• 3 billion people use open fires and inefficient stoves

regularly• Requires large amounts of fuel

• Damage to ecosystem

Haiti• Deforestation

• Soil erosion• Decrease in agricultural yields• Landslides• Running out of fuel

• Need for more fuel-efficient stoves• Add oxygen to combustion

process

Haiti

Dominican Republic

Need for Power

• Haiti has a history of destructive earthquakes• No power grid and no landlines• Cell phones and radios for

communication• Difficult to charge

Needs Importance

Description Comments/Status

1 3* Fan runs the entire duration of cooking

2 3* Plan to couple to team 12442’s stove.

3 3 Cheap cost of system Component cost including PCB if applicable

4 3 User-friendly operation Minimal user interaction5 3 Safe to operate 6 2 Fan runs at start-up Multiple start/restart cycles7 2 Rugged design Survive crush and drop test8 2 Operational in Harsh Environments Exposure to Rain, Moisture, Heat

and Salinity9 2 Ability to charge USB device

10 1 System must be transportable 11 1 5 year life span (3x use per day)

Customer Needs

*Most important needsImportance Scale: 1 - Low Importance, 2 - Moderate Importance, 3 - High Importance

Spec Customer Need

Description Importance

Units Marginal

Target Comments/Status

1 1 Component Cost 3 $ 15 10 Including any PCB, for quantities of 1-10K.

2 2, 6, 8 Power supplied to fan

3 W .7 1.2

3 2, 6, 8 Voltage supplied to the fan

3 V 11 12 Converter needs to be adjustable.

4 8 Amount of startups that can be performed on battery power.

3 Start up 1 3 A system startup is the 20 minute period in

which the fan is powered by the battery

only.5 3 User interaction to

maintain proper system operation

3 Actions 1 0 The user shouldn’t need to perform

adjustments to properly operate electronics.

6 2 Electrical connections

provided to the stove.

3 Connections 6 4 2 input wires, 2 output wires

7 4, 7, 11 Survive drop test 2 Drops 2 20 Survive 20, 2 meter drops.

8 4, 7, 11 Survive crush test 2 PSI 2 5 Enclosure must survive being stepped on

9 4, 7, 11 Survive a rain test 2 hours 1 2 Put it in the shower.

Engineering Specifications


Spec Customer Need

Description Importance Units Marginal Target Comments/Status

10 4, 7, 11 Survive a humidity test

2 hours 1 5 Place the unit in an above 90% enclosed

area.11 5, 10 Enclosure surface

temperature2 °C 10 55 Surface of enclosure

may not exceed 55 °C during operation.

12 3, 5 User interaction to protect system

2 Actions 1 0 The user should not need to perform an action to protect the

system13 9 USB output power 2 W 2.375 2.5 Margin derived from

specs 15, and 1614 9 USB output voltage 2 V 4.75 5 From USB spec

15 9 USB output current 2 A .475 .5 From USB spec

16 9 Number of charges from battery

2 Charges 1 2

17 11 Product Life Span 2 Hours 1500 11,000 Assume 3 hours/use, 2 uses/day, for 5

years18 10 System Weight 1 lbs 6 3 Include battery packs

Engineering Specifications cont.


Spec Customer Need


Units Marginal


19 10 Enclosure Volume 1 In 5x5x5 3x3x1.5 Include battery packs

20 3 User actions duringoperation cycle

1 # 2 0

Engineering Specifications cont.


System Architecture

Maximum Power Point Tracker (MPPT)

Network Power Storage and

Distribution

MPPT

Maximum Power Point Tracker (MPPT)

Network

Maximum Power Point Tracker (MPPT)o Allows efficient power transfer from TEG to

system

Power Distribution

Power Storage and Distribution

0 50 100 150 200 250 3005

5.2

5.4

5.6

5.8

6

6.2

6.4

6.6

Battery Discharge Test

Battery B (Connected)

Battery B (Disconnected)

Battery A

Time (Minutes)

Volt

age

(V)

• The battery must always have enough power to run the system during start-up

• To prevent overdraw• First USB is disabled• Then fan is disconnected

• To prevent overcharging• System will stop charging

battery

Battery Management

Battery Protection SystemBattery disconnect from MPPT and TEG when terminal voltage reaches 6.4 V

USB and Fan disconnect from battery when terminal voltage reaches 5.8 V

The voltage at the terminal of the switch (yellow) and the voltage at the input to the switch (blue)

CAT ProcedureStep 1: Connect battery and power on circuit.

Step 2: Run system until USB is disabled.

Step 3: Run system until fan is disconnected.

Step 4: Attach power pack to TEG.

Step 5: Run system until powered by TEG,

Step 6: Run system until fan is reconnected.

Step 7: Run system until USB is re-enabled.

Step 8: Run system until battery is disconnected.

Step 9: Disconnect power pack from TEG.

Step 10: Connect cell phone to USB output.

Step 11: Charge cell phones until USB is disconnected.

Step 12: Power off power pack.

Customer Acceptance Test (CAT)Bench Setup

A A

A A

The output power of the various systems sinks and sources.

The voltages at the various voltage sources of the system

The currents of the various systems

Needs Importance

Description Comments/Status

1 3* Fan runs the entire duration of cooking

2 3* Plan to couple to team 12442’s stove.

3 3 Cheap cost of system Component cost including PCB if applicable

4 3 User-friendly operation Minimal user interaction5 3 Safe to operate 6 2 Fan runs at start-up Multiple start/restart cycles7 2 Rugged design Survive crush and drop test8 2 Operational in Harsh Environments Exposure to Rain, Moisture, Heat

and Salinity9 2 Ability to charge USB device

10 1 System must be transportable 11 1 5 year life span (3x use per day)

Project Status


Spec Customer Need


Units Marginal


1 1 Component Cost 3 $ 15 10 Including any PCB, for quantities of 1-10K.

2 2, 6, 8 Power supplied to fan

3 W .7 1.2

3 2, 6, 8 Voltage supplied to the fan

3 V 11 12 Converter needs to be adjustable.

4 8 Amount of startups that can be performed on battery power.

3 Start up 1 3 A system startup is the 20 minute period in

which the fan is powered by the battery

only.5 3 User interaction to

maintain proper system operation

3 Actions 1 0 The user shouldn’t need to perform

adjustments to properly operate electronics.

6 2 Electrical connections

provided to the stove.

3 Connections 6 4 2 input wires, 2 output wires

7 4, 7, 11 Survive drop test 2 Drops 2 20 Survive 20, 2 meter drops.

8 4, 7, 11 Survive crush test 2 PSI 2 5 Enclosure must survive being stepped on

10 4, 7, 11 Survive a rain test 2 hours 1 2 Put it in the shower.

Project Status cont.


Spec Customer Need

Description Importance Units Marginal Target Comments/Status

12 5, 10 Enclosure surface temperature

2 °C 10 55 Surface of enclosure may

not exceed 55 °C during operation.

13 3, 5 User interaction to protect system

2 Actions 1 0 The user should not need to perform an

action to protect the system

14 9 USB output power 2 W 2.375 2.5 Margin derived from specs 15,

and 1615 9 USB output voltage 2 V 4.75 5 From USB spec

16 9 USB output current 2 A .475 .5 From USB spec

17 9 Number of charges from battery

2 Charges 1 2

18 11 Product Life Span 2 Hours 1500 11,000 Assume 3 hours/use, 2

uses/day, for 5 years

19 10 System Weight 1 lbs 6 3 Include battery packs




Spec Customer Need


Units Marginal



20 3 User actions duringoperation cycle

1 # 2 0



• Complete design and implementation of the MPPT.

• Decrease system cost.• Increase the efficiency of

the DC-DC converters.• Complete system PCB

layout, and have PCB layout.

• Manufacture and test enclosure.

• Send system to Haiti for field testing.

Future Work

Questions?

p12441: thermoelectric power pack for next generation stove

Documents

low importance

moderate importance

battery power

power haiti

usb output voltage2v4

system2actions10the

usb device101system

output wires74