Perturbation Methods for Real-Time In Situ Evaluation of Hot-Side Thermal Resistances in Thermoelectric Energy Recovery Systems

Abstract

Thermoelectric (TE) power systems in high-temperature industrial, transportation, and military energy systems require high-performance hot-side and cold-side heat transfer to provide the critical temperature differential and transfer the required thermal energy to create the power output. Hot- and cold-side heat transfer performance is typically characterized by the hot-side and cold-side thermal resistance, Rh,th and Rc,th, respectively. This heat transfer performance determines the hot-side temperature, Th, and cold-side temperature, Tc, conditions when operating in energy recovery environments with available temperature differentials characterized by an external driving temperature, Tsrc, and ambient temperature, Tamb. It is crucial to monitor and track the hot-side thermal performance at all times during TE energy recovery system operation, thereby allowing one to track the system “health,” predict future expected system performance, and anticipate/prevent system failures. This paper describes the use of a perturbation methodology and a direct coupling between the TE current, voltage, and hot-side energy flow to extract a real-time in situ evaluation of hot-side thermal resistances. External measurable TE parameters, either system current or Tsrc, can be perturbed during system operation, and the resulting TE system response can then be coupled mathematically to the hot-side thermal transfer performance (i.e., thermal resistance). This paper discusses the mathematical formalism of this technique, and TE module experimental data showing successful application of real-time current perturbation. This technique provides a pathway for developing faster, real-time system monitoring and diagnostics to alleviate system performance degradation, or prevent system damage from dramatic changes in hot-side thermal transfer conditions in industrial, transportation, and spacecraft TE power systems.