Electricity from Excess HeatGroup 22Sung Hoon Bae (BME)Daniel Rim (ChBE)Chris Zachara (ChBE)Owen Graduate School of Management

Bae, Rim, Zachara http://www.bme.vanderbilt.edu/srdesign/2009/group22/ BME 273: Oral Report #4

Third World Electric Generator

Problem Statement Bangladesh

Large population/high poverty rate Population: 162 Million – 7th

GDP (PPP): $1,500 per capita – 153rd

http://upload.wikimedia.org/wikipedia/en/f/f2/Bangladesh_(orthographic_projection).svghttp://en.wikipedia.org/wiki/File:Flag_of_Bangladesh.svg

Problem Statement Only 30% electricity distribution (2002)

25% in urban and 10% in rural (2000)79% of population in rural (1999)

Government efforts30% to 38% distribution from 2002-2008Slow progression

Rural Bangladesh Families Average family has 6 members

Typically 4 children Total literacy is only 48%

Considerably lower in rural areas Poverty is major threat to primary

education Lighting is a Basic Need

Status SymbolNeeded for reading (above all else)

Objective Generate electricity

Household scale generator“Reasonable” retail priceSufficient output electricityUtilize thermoelectric generator (TEG)

http://www.odec.ca/projects/2007/sidd7g2/Images/appelectricty.gifhttp://image09.webshots.com/9/2/10/75/112721075ZEGbyv_fs.jpghttp://www.ct.gov/opapd/lib/opapd/newsletter-pics/dollar2520squeezed.jpg

Design Criteria• Cost – cheap product and source of energy• Durability – long lasting materials• User friendly – simple design and simple

operation• Efficiency – efficiency of converting source

energy into light energy• Quality – quality of energy source (higher score

for naturally occurring energy source)• Portability – device should be mobile• Flexibility – extent of dependency of the device

on external environment

Determining Weight Values Cost Durability User Friendly Efficiency Quality Portability Flexibility Total

Cost - 1 1 1 1 1 1 6

Durability 0 - 1 1 1 1 1 5

User Friendly 0 0 - 0 0 1 0 1

Efficiency 0 0 1 - 0 1 0 2

Quality 0 0 1 1 - 1 0 3

Portability 0 0 0 0 0 - 0 0

Flexibility 0 0 1 1 1 1 - 4

Determining Source of Light. Source of Energy

Gas Lamp Electricity Manual (Shake)

Criteria Weight Value Product Value Product Value Product

Cost 6 4 24 4 24 5 30

Durability 5 4 20 5 25 5 25

User Friendly 1 3 3 5 5 5 5

Efficiency 2 2 4 1 2 2 4

Quality 3 1 3 4 12 1 3

Portability 0 5 0 5 0 5 0

Flexibility 4 2 8 4 16 0 0

Total 62 84 67

Brainstorming

Electric Generation

Turbine system

Thermoelectric generation

Solar panel

Manual

Stirling generator

Efficient only in large scale Expensive

Emerging Technology

Well understoodLow efficiency

Keeps improving

Relatively expensive

Great flexibility

Unlimited energy source

Sun as energy source

Weather dependent

Expensive

Cheap

Uses any kind of heat

ExpensiveComplicated

Simple design

No moving parts

User friendly

No moving parts

But not user friendly

Simple design

User friendly

Complicated design

Thermoelectrics

Phenomenon: temperature difference creates electric potential or vice versa

Materials: specially doped semiconductors, most commonly made from Bismuth Telluride

Current Uses: portable refrigeration, electronics cooling

Equations:

Advantages of TEG Less Expensive than Turbine Technology Utilize Low Grade Heat Small Silent Reliable

No moving partsNo maintenance

Challenges of Using TEG TEG Only 10% Energy Efficient

Other design aspects will be very important Significant Heat Gradient Needed

The “cold side” must be cooledCold side is just mm’s away from heat source

Possible Heat Sources Biogas Lamps

Efficiency only 1.2-2.0 lm/W Consume 120 to 150 L Biogas daily Rely on incandescent metals heated to 1000-2000°C

Over 90% of energy emitted as heat 10% Efficient TEG could, theoretically, double performance

Biogas Stoves Can be quite efficient, but still produce excess heat

Heat-to-electricity unit would have no additional energy costs

LED light Commercial white LED light 65 lm/W

at 20mA 4 times as efficient as standard

incandescent Commercially available white LED light

are very cheap (exp. $6/6LEDs)

NiMH Batteries Advantages

Relatively constant discharged voltageMore current compared to other batteriesVarious capacity available

Safety IssuesCareful charging method is required

Timer controlled dT/dt detection dV/dt detection

Process Flow Chart

Heat Source TEG Voltage Regulator

Charging ControllerNiMH Batteries

Current Controller

LED

+

+

-

Q E

dV/dt

E

E

E

E

Light

L

Initial Design: Overall

LED

Heat Source

Control

Batte

ry

Heatsink

Generating Unit

Storage UnitThermal Grease

Rechargeable

Portable

Convection

Initial Design: Generating UnitHeat Source

Heatsink

Generating Unit

Thermal Grease: maximizes contact surface area between TEG and heatsink

Pressurized attachment

Coated with black color for maximum heat absorption?

Components• TEG• Heatsink• Thermal grease

Connecting joint

Materials: TEG (TEC) Product Model:CP2,31,06,L1,W4.5

Laird Technology

30mm x 30mm x 4.6mm Qmax = 29.3W (TH=25°C)

Imax = 14.0 A (TH=25°C)

Vmax = 3.5V (TH=25°C)

ΔTmax = 67°C Price = 23.42$ (http://www.mouser.com)

http://lairdtech.thomasnet.com/item/thermoelectric-modules-2/-series-peltier-solid-state-thermoelectric-coolers/pn-4059?&seo=110&bc=100|3001624|3001688|3001251

Materials: Thermal Grease Product Name: Arctic Silver 5

Arctic Silver ® Thermal Conductance: >350,000W/m2°C (0.001 in layer)

Thermal conductivity of air ~ 0.024W/m°C Thermal conductivity of silver ~ 429W/m°C

Temperature Limits Peak: -50 to 180°C Long term: –50°C to 130°C

Important Note Takes about 200hrs and several thermal cycles to achieve

maximum performance Price = 9.99$ (newegg.com)/16in2

SATEG = 900mm2 = 1.4in2

Per Unit Price ≥ 9.99$/16in2 · 1.4in2 = 0.87$/prototypehttp://arcticsilver.com/as5.htm http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Initial Design: Storage Unit

LED

Control

Batte

ry

Storage Unit

Components Batteries

NiMH Batteries Controllers

Current controller For powering the LED

Voltage regulator Charging batteries

LED

Materials: LED Product Model:LED5 40-50DG WH

(TheLEDLight.com) Emitted Color: White Luminous Intensity = 6000mcd max at IA=20mA Beam Angle = 40-50 degrees Continuous forward current = 30mA Forward voltage = 3.0-3.2V Price = 6$/6LEDs

http://www.theledlight.com/5mmwhleds.html

Materials: NiMH Batteries Product Name: Eneloop

Sanyo Electric Co., Ltd.

Voltage = 1.2V Capacity = 2000mAh Low self-discharging rate

~90% after 360days

Long life cycle ~1000 charges

Price: 11.99$/4units (Amazon.com)

http://www.eneloop.info/home/performance-details/self-discharge.html

Experiment Set-up

~5cm

Heat source: candle

100kOhms

LABVIEW

Voltage versus Time

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 10 20 30 40 50 60 70

Time (sec)

Am

plit

ude

(V)

Prototype IPrototype II

Result: Short Term Drift

0.9Vmax

Vmax~.61V

Vmax~.32V

Rise time ~47sec

0.1Vmax

~2sec ~49sec

Result: Short Term Drift (power)Power vs. time

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

0 10 20 30 40 50 60 70

Time (sec)

Pow

er (

mW

)

prototype IPrototype II

Wmax~.0035mW

Result: Long Term Drift

Peak Voltage ~ 0.625V 0.9Vmax

5minutes 40sec

Expected Cost and life span TEG: ~$20/~200,000hrs = 22.8yrs*

Depends on individual TEG device Heatsink: ~$20/indefinite Batteries: $11/~4years Voltage regulator ~ $0.5 (onsemi.com) Charging controller ~ $0.7 (onsemi.com) Current controller = $11.85 (theLEDlight.com) Thermal grease: 0.87$/prototype Total: ~ $(64.92+ X) /unit

Implementation Idea

Collect Stove Top Steam Advantages

Consistent TemperatureNear TEG optimum (80o C)

ChallengesHeat InsulationMoisture

Future Work Low voltage problem

Increase insulation to improve TEG performance Find more efficient TEG (look into more expensive

TEG) Extensive with more controlled setting

(controlled known temperature input) Finish building charging unit that can safely

charge NiMH Investigate Water Cooling Work on Implementation

References Department of Economic and Social Affairs Population Division (2009) (.PDF). World

Population Prospects, Table A.1. 2008 revision. United Nations. <http://www.un.org/esa/population/publications/wpp2008/wpp2008_text_tables.pdf>. Retrieved 2009-03-12.

"Bangladesh". <International Monetary Fund. http://www.imf.org/external/pubs/ft/weo/2009/02/weodata/weorept.aspx?sy=2006&ey=2009&scsm=1&ssd=1&sort=country&ds=.&br=1&c=513&s=NGDPD%2CNGDPDPC%2CPPPGDP%2CPPPPC%2CLP&grp=0&a=&pr.x=35&pr.y=9. Retrieved 2009-10-01>.

<http://web.worldbank.org/WBSITE/EXTERNAL/EXTABOUTUS/IDA/0,,contentMDK:21387765~menuPK:3266877~pagePK:51236175~piPK:437394~theSitePK:73154,00.html>.

<http://www.geni.org/globalenergy/library/national_energy_grid/bangladesh/index.shtml>. .

http://www.malmberg.se/module.asp?XModuleId=14085 http://www.stefanv.com/electronics/using_nimh.html http://www.tegpower.com/products.html