Optimizing thermoelectric waste heat recovery from an automotive cooling system

The potential for thermoelectric (TE) power generation (via automotive waste heat recovery) to displace alternators and/or provide additional charging to hybrid electric vehicles has increased with recent advances in thermoelectric materials. While previous studies have focused on exhaust-based waste heat recovery, this study optimizes thermoelectric waste heat recovery from an engine cooling system with the goal of providing insight into the feasibility and potential of increasing automotive fuel efficiency.; The study creates a MATLAB-based steady-state numerical model for a cross-flow heat exchanger, where industry-provided operation data validate the heat transfer and pressure drop correlations. Using distinct attributes of an automotive cooling system, the model simulates the cross-flow heat exchanger as an automotive radiator. The study integrates the thermoelectrics into the radiator model and then incorporates this model into an optimization scheme to maximize the average net power output of the TE radiator on a systems level for a range of coolant flows and temperatures. Simple experiments validate the thermoelectric governing equations. The optimization scheme developed for the task is a hybrid algorithm combining the local search speed of gradient-based methods with the global search superiority of genetic algorithms. Feasibility robustness is also incorporated to study the impact of variation and uncertainty in design variables and parameters.; The study transforms the steady-state model into a dynamic model to evaluate the transient response of the optimal TE waste heat recovery system over three different driving cycles. The transient model provides a more complete picture of the potential of an optimized thermoelectric waste heat recovery system and its benefits relating to automotive fuel efficiency. Transient results show that radiator configurations with advanced TE devices used during aggressive driving cycles can recover over 2 kW in net power with 150 seconds of sustained recovery of over 1 kW. Replacing the alternator with the TE radiator for standard drive cycles can achieve fuel efficiency gains of up to 3.3%. Using the multi-parameter optimization and transient evaluation techniques developed, the study concludes that with future research, TE waste heat recovery from the automotive cooling system can become a practical means of improving automotive fuel efficiency.