Electricity from Excess Heat Group 22 Sung Hoon Bae (BME) Daniel Rim (ChBE) Chris Zachara (ChBE) Owen Graduate School of Management Bae, Rim, Zachara BME 273: Oral Report #4http:// Third World Electric Generator

Problem Statement Bangladesh  Large population/high poverty rate Population: 162 Million – 7 th GDP (PPP): $1,500 per capita – 153 rd

Problem Statement Only 30% electricity distribution (2002)  25% in urban and 10% in rural (2000)  79% of population in rural (1999) Government efforts  30% to 38% distribution from  Slow 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 Symbol  Needed for reading (above all else)

Objective Generate electricity  Household scale generator  “Reasonable” retail price  Sufficient output electricity  Utilize thermoelectric generator (TEG)

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 CostDurabilityUser FriendlyEfficiencyQualityPortabilityFlexibilityTotal Cost Durability User Friendly Efficiency Quality Portability Flexibility

Determining Source of Light. Source of Energy Gas LampElectricityManual (Shake) CriteriaWeightValueProductValueProductValueProduct Cost Durability User Friendly Efficiency Quality Portability Flexibility Total

Brainstorming Electric Generation Turbine system Thermoelectric generation Solar panel Manual Stirling generator Efficient only in large scale Expensive Emerging Technology Well understood Low efficiency Keeps improving Relatively expensive Great flexibility Unlimited energy source Sun as energy source Weather dependent Expensive Cheap Uses any kind of heat Expensive Complicated 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 parts  No 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 cooled  Cold side is just mm’s away from heat source

Possible Heat Sources Biogas Lamps  Efficiency only lm/W  Consume 120 to 150 L Biogas daily  Rely on incandescent metals heated to °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 voltage  More current compared to other batteries  Various capacity available Safety Issues  Careful 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 QE dV/dt E E E E Light L

Initial Design: Overall LED Heat Source Control Battery Heatsink Generating Unit Storage Unit Thermal Grease Rechargeable Portable Convection

Initial Design: Generating Unit Heat 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 Q max = 29.3W (TH=25°C) I max = 14.0 A (TH=25°C) V max = 3.5V (TH=25°C) ΔT max = 67°C Price = 23.42$ ( )

Materials: Thermal Grease Product Name: Arctic Silver 5  Arctic Silver ® Thermal Conductance: >350,000W/m 2° 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)/16in 2  SA TEG = 900mm 2 = 1.4in 2  Per Unit Price ≥ 9.99$/16in 2 · 1.4in 2 = 0.87$/prototype

Initial Design: Storage Unit LED Control Battery Storage Unit Components  Batteries NiMH Batteries  Controllers Current controller  For powering the LED Voltage regulator  Charging batteries  LED

Materials: LED Product Model:LED DG WH (TheLEDLight.com) Emitted Color: White Luminous Intensity = 6000mcd max at I A =20mA Beam Angle = degrees Continuous forward current = 30mA Forward voltage = V Price = 6$/6LEDs

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)

Experiment Set-up ~5cm Heat source: candle 100kOhms LABVIEW

Result: Short Term Drift 0.9V max V max ~.61V V max ~.32V Rise time ~47sec 0.1V max ~2sec~49sec

Result: Short Term Drift (power) W max ~.0035mW

Result: Long Term Drift Peak Voltage ~ 0.625V 0.9V max 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: ~ $( X) /unit

Implementation Idea Collect Stove Top Steam Advantages  Consistent Temperature  Near TEG optimum (80 o C) Challenges  Heat Insulation  Moisture

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 revision. United Nations.. Retrieved "Bangladesh"