Expanded-plane bilayer thermal concentrator for improving thermoelectric conversion efficiency

Thermoelectric devices are pivotal in the energy sector, with enhancing their conversion efficiency being a longstanding focal point. While progress has been made, overcoming the inherent low efficiency and heat management issues remains challenging. The advent of thermal metamaterials, particularly thermal concentrators, holds promise for improved thermoelectric efficiency. The concentrator has the potential to amplify the temperature gradient within the working region without altering the temperature gradient of the background, thereby enhancing thermoelectric conversion efficiency through this concentrating effect. Nevertheless, the efficacy of this effect is contingent upon the structural parameters of the concentrator. Systematically investigating the impact of metamaterials on thermoelectric conversion efficiency, particularly in terms of quantifying the enhancement, presents a significant challenge. Additionally, the intrinsic thermal conductivity of the material imposes constraints on the applicability of the concentrator in this regard. In this context, drawing inspiration from the recently proposed passive ultra-conductive heat transport scheme, we have devised expanded-plane bilayer thermal concentrators. We substantiate the prospective performance of our design through analytical demonstration, further validated through finite-element simulations and experiments. Notably, through direct calculation, we illustrate an efficiency improvement of about 38\% when utilizing the expanded-plane concentrator comparing with not using expanded-plane structure. The expanded-plane geometrical configuration of the outer layer can also attain large-scale value. These findings not only present a novel avenue for the functional transformation of thermal metamaterials but also hold significant implications for the field of thermoelectrics.