THEORETICAL ANALYSIS OF PYROELECTRIC HARVESTING OF LOW-GRADE EXHAUST WASTE HEAT

Efficient and cost-effective harvesting of exhaust waste heat represents significant opportunities for improving the overall energy efficiency of combined heat and power cycles, transportation vehicles, and industrial processes. Pyroelectric thermal energy harvesting is interesting for its potentially high efficiency. We report a design concept and related thermal models for harvesting of exhaust waste heat based on the pyroelectric effect. The design concept utilizes switchable thermal interfaces formed on duct walls of exhaust gas and liquid coolants to achieve temporal thermal cycling of pyroelectric materials. Our thermal model explicitly accounts for spatial variations in the exhaust gas and coolant temperatures for practical waste heat harvesting systems, for example, those that can be incorporated into micro-CHP (combined heat and power) units. Model prediction results for example cases are presented to illustrate the impact of design parameters, including the heat capacity rate and the convective heat transfer coefficients.