Generating Unit TEG (TEC ) - V max = 16.4V; Q max = 57W Heat sink Thermal grease (Arctic Silver) - Maximizes contact area Storage Unit NiMH Battery (Sanyo Electric) - Voltage = 1.2V - Capacity = 2000mAh Controllers -Voltage regulator -Charging controller LED (Figure 4) - V forward = 2.4V; I forward = 20mA - R = 1.8Ohms - Luminous = 6000mcd Sung Hoon Bae 1, Daniel Rim 2, Chris Zachara 2 Advisor: David Owens 3 Dept. of 1 Biomedical, 2 Chemical Engineering, 3 Owen Graduate School of Management, Vanderbilt University, Nashville, TN Third World Electric Generator: Electricity from Excess Heat System Verification Problem Statement Third world countries, though some of the most populated regions on earth, suffer from abysmal electricity distribution Manure-to-biogas digesters are a great source of renewable fuel for families off the grid, but use of biogas is largely inefficient Design Approach Utilize excess heat wasted by gas appliances Stored electricity is needed for its portability and ease of use Thermoelectric Generation (TEG) Temperature difference creates electric potential described by: where and are Seebeck coefficients and and are temperatures at junctions (Figure 1) Typical application is thermoelectric cooling (TEC) - Theoretically reversible process Specially doped semiconductors (ex. Bismuth Telluride) Current technology: only 10% energy efficient Nickel Metal Hydride (NiMH) Battery Relatively constant discharged voltage (Figure 2) More current compared to other batteries Various capacities available IntroductionIntroduction Future Directions Further investigate ways to increase output voltage and power Experiment with larger TEG’s and TEG’s in series Analyze performance of various TEG’s from multiple manufacturers Investigate advanced cooling methods, like fluid or fan cooling Finalize method of implementation and develop housing. Assess feasibility of market success Generating Unit Short-term drift and long-term drift Characterized actual specifications Heat source: boiling water (100°C) Storage Unit Monitored charging process over time Design Performance (continued) Design Components Storage Unit Not enough power was generated to charge the batteries Unrealistic theoretical charging time with given performance Cost Analysis Cost of the prototype = 57.86$/unit Battery life is approximately 4 years (limiting factor) Visible monetary benefit in 6 years at most Design a household scale electric generator Integrate with biogas systems Utilize thermoelectric technology to recover energy from excess heat Power 6 LED lights for 2 hours per day Incorporate a battery charging system for portable electricity Achieve low selling price, ideally between $40 and $60 Project Goals Table 3 Material cost of the prototype I without economic scale AcknowledgementsAcknowledgements We would like to thank the Dr. King, Dr. Bonds, Dr. Walker, Alex Makowski, Kurt Hogan, Stephen Songy, and the ME mechanics shop for making this project possible. Design Criteria Must be easy to use and require no training Must be portable for flexible uses Must be economically feasible No additional energy should be used to generate electricity Should effectively use excess heat to generate electricity Charging process should be safely and automatically monitored Figure 3 Overall design of the prototype Table 4 Expected savings by usage years for different energy consumptions (Eq.1), Design Performance Generating Unit (Figure 6 and Table 1) Steady electric generation after ~50 seconds Higher electric generation from prototype I (~2.5V) Prototype I withstood ~30 minutes of operating period Not enough power was generated for both prototypes ConclusionsConclusions Thermoelectric cooling (TEC) and thermoelectric generating processes are not completely reversible Current prototype cannot provide sufficient power to charge 2 NiMH batteries or light 6 LED lights Failed to meet the required product specifications under the price constraints (mainly due to quality of TEG) Figure 1 Diagram showing Seebeck effect Figure 6 Short-term (left) and long-term (right) drift measurements of prototype I (blue) and prototype II (red) Table 1 Various specifications of prototypes I and II. *To charge NiMH batteries. Table 2 Required charging time for each various usages hours (1,2,3, and 4) Figure 5 Experiment set up Figure 4 Circuit diagram of LED component Figure 2 Discharging graph of a NiMH battery ComponentUnit Price ($/unit) TEG5.50 Heat sink NiMH Batteries14.99 Thermal Grease LED lights6.00 Miscelleneous6.50 Total57.86 Average Money Spent for Lighting Year1.00$/mo1.50$/mo2.00$/mo Type Rise TimeFalling TimeAvg. Amp.Power GeneratedPower Needed* I47 sec30 min2.50 V6.25 mW500 mW II46 sec11 min0.62 V0.38 mW500 mW Usage Hours 1 hour2 hours3 hours4 hours Energy used (mAh) % Capacity Used Expected Charging Time (hrs)