P08441:Thermoelectric Auto Exhaust Power Generation Project Introduction : The motivation for this project stems from an increasing need for highly efficient power generation in the transportation sector. Thermoelectric power generation is seen as a theoretical means for gaining efficiency fuel efficiency in an economical manner. Furthermore, motivation lies in the general understanding of the operation and feasibility of thermoelectric power recovery. P08441 will build upon two previous Senior Design projects by implementing integral testing equipment which has already been designed. The aim of the project will be to produce electrical energy from heat recovered from an auto exhaust system through the use of thermoelectric modules and a heat exchange system. Needs and Specifications: Design and build a thermoelectric power generation system that can produce 100 Watts of electrical energy. Be able to charge an automobile battery with thermoelectric system. Design must stay within budget. Overall system efficiency increase of 1%. Obtain hot side temperature of 200C under specified test conditions. Limit the pressure drop across the unit below 1100 Pascals. Test Conditions: Inlet Exhaust Temperature: 550K Exhaust Mass Flow Rate:.04kg/s Specifications will be verified on the thermoelectric test stand designed by previous teams. Basic Thermoelectric Operation Diagram From left to Right: Paul Gaylo (ME); Michael Rheinheimer (ME); Erin Crowley (ME); Joel Nelson (EE); Frank Trotto (EE); Stephen Byrne (ME) Our heat transfer model was verified using Finite Element Analysis software. The software concluded a hot side temperature of approximately 200C under our test conditions, which validates our analytical model. Our pressure drop model was verified using Computational Fluid Dynamics software. The results match well with our analytical model at around a 260 Pa pressure drop. Modeling Results: Governing Equations for Pressure Drop Governing Equations for Heat Transfer The governing equation for the pressure drop throughout the TEG unit takes into account the additional fluid friction associated with the unit and the entrance and exit losses from the unit exhaust transitions. The system of equations for the heat transfer are based on the calculated convective coefficients and thermal resistances between the various components. These equations allow us to calculate the amount of power generated from each thermoelectric. To increase the amount of heat flowing into the thermoelectric we want to decrease the thermal resistance as much as possible by adding internal fins all while taking into account the increase in back pressure associated with this. The graph shows the relation between thermal resistance and pressure drop. Concept: Design Considerations: Maximize temperature difference across thermoelectric i.e. Make hot side hot and cold side cold. Limit the pressure drop through the unit. Design that would accommodate many thermoelectrics. Current Design: Balances adequate heat transfer with acceptable pressure drop. Sufficiently cools the cold side of the thermoelectric in a cost effective and simple manner. Supplies adequate surface area for 48 thermoelectrics. Thermoelectric Generator Unit (TEG) Concept Results: Battery charging circuitry functional Design came in under $3,000 budget Pressure drop below 500 Pascals across unit Hot side temperature of 200C not met. Hit 180C. Maximum power output specification not met. Hot side downstream spec met. Met system efficiency specification of 1%. Conclusions: From the beginning of this project, the primary interest has been the study of thermoelectric performance. Project P08441 focused on waste heat recovery in an automotive exhaust stream. While the power generative performance of the resulting prototype was below the expectations of this project, the endeavor to seek further insight into the run-characteristics of thermoelectrics has certainly been achieved. There are clear improvements, inherent to a first-run prototype, that future teams could address with both mechanical, and electrical changes. All in all, project P08441 has accomplished a fair degree of success and even greater degree of knowledge and understanding of thermoelectric modules.