Unified approach to power-efficiency trade-off relations of generic thermal machines

TL;DR

This paper introduces a unified framework for analyzing power-efficiency trade-offs in various thermal machines, revealing how interaction control influences efficiency and deriving new bounds for quantum Otto engines.

Contribution

It provides the first unified approach to power-efficiency relations across different thermal machines, including quantum engines, based on a general irreversibility scaling law.

Findings

Efficiency at maximum power approaches Carnot as interaction parameter increases

Recovers low-dissipation results when the irreversibility exponent is one

Derives the first power-efficiency trade-off for finite-time quantum Otto engines

Abstract

We present a general framework for determining the power-efficiency trade-off relations across arbitrary thermal machines, addressing the lack of unified optimization results stemming from their diverse functionalities (e.g., heat engines, refrigerators, and heat pumps). For time-dependent cycle irreversibility $A(\tau)$ following a $\tau^{-\alpha}$ power law, where $\alpha$ is an interaction-dependent parameter, we show that engineering the interactions between thermal machines and reservoirs enables control over the trade-off relations, with the efficiency at maximum power approaching Carnot efficiency as $\alpha$ increases. Setting $\alpha=1$ naturally recovers typical low-dissipation regime results. Additionally, we derive the first power-efficiency trade-off for finite-time quantum adiabatic Otto machines with $\tau^{-2}$-scaling. This work establishes a unified constraint for thermodynamic cycles across non-equilibrium regimes, facilitating consistent optimization of diverse thermal devices in practice.