General Figures of Merit ZQ for Thermoelectric Generators Under Constant Heat‐In Flux Boundary

Abstract

The thermoelectric figure of merit ZT bridges the efficiency and material parameters for a thermoelectric device operating under constant temperature of the hot‐ and cold‐source thermal boundary (Type‐I TB). However, many application scenarios fall under the constant heat‐in flux (qh) and constant cold‐source temperature (Tc) thermal boundary (Type‐II TB), for which a figure of merit is absent for more than half a century. This study aims to fill this gap and propose a figure of merit ZQD for the thermoelectric devices under the Type‐II TB condition, defined as , where Z, h, and κ are the traditional figure of merit, leg height, and thermal conductivity, respectively. The effectiveness of ZQD is verified through both numerical calculations and experiments, which are more accurate and practical than ZT. Furthermore, a system‐level figure of merit ZQS is suggested after considering the external thermal resistance. Finally, optimization strategies for thermoelectric systems based on ZQS are proposed, showing a 30% enhancement in the efficiency. ZQD and ZQS are expected to be widely used in the thermoelectric field.

Lattice Architectures for Thermoelectric Energy Harvesting

“…For thermoelectric systems under constant heat-in flux, the power generation efficiency is proportional to zT/κ eff . 40 As zT is proportional to 1/κ eff , efficiency is thus proportional to 1/κ eff 2 . As such, the significant decrease in κ eff through lattice legs proves to be an effective strategy for improved power generation efficiency and enhanced specific output power.…”

“…This is approximately 6 times the power generated for every 1 kg of Bi 2 Te 3 used in a TEG. For thermoelectric systems under constant heat-in flux, the power generation efficiency is proportional to zT /κ eff . As zT is proportional to 1/κ eff , efficiency is thus proportional to 1/κ eff 2 .…”

Recent advances of 2D conductive metal–organic frameworks in thermoelectrics

“…37–46 Big progress has been achieved in inorganic TE materials in the past years. 47–64 He et al enhanced the ZT to 2.7 at 750 K in germanium telluride-based high-entropy materials and realized a high experimental conversion efficiency of 13.3% by high-entropy concept tuning electron and phonon decoupling. 53 Zhao and coworkers developed a lattice plainification strategy for defect engineering to weaken defect scattering and boost carrier mobility, leading to a ZT of ∼1.5 at 300 K. 54 However, traditional inorganic TE materials are often composed of transition metals, such as Pb, Te, Bi, etc.…”