ENHANCING THERMOELECTRIC ENERGY RECOVERY VIA MODULATIONS OF SOURCE TEMPERATURE FOR CYCLICAL HEAT LOADINGS

摘要

Very recent thermoelectric (TE) device materials improvements have pushed this technology to the cusp of usefulness in converting waste heat to electricity in a variety of applications - from automotive to aerospace. For applications where the heat loading is cyclical or non-constant, the effect of active control to maintain the source temperature at or near the peak allowable temperature while maximizing the temperature difference across a TE temporally on the overall thermoelectric efficiency is investigated. Efficiencies for constant heat loading applications that are not at near peak allowable temperatures are also investigated. The modulation of the source temperature would be achieved through the use of a 'thermal switch' or 'active thermal potentiometer' between the heat source and the thermoelectric device. Two methods are used to model the thermoelectric energy recovery system. First, an RC equivalent model is used to define the controlling factors for efficiency on a first order basis. Second, a numerical model is created to investigate the system in more detail. Both models demonstrate that maximizing the exergy of the source by maximizing its temperature during off-peak heat loadings is capable of improving the time-averaged efficiency of a thermoelectric device. For some conditions, improved time averaged efficiencies of more than 4 times are realized. Criteria defining the operation space where efficiency improvements are realized are also developed.