Speed and Efficiency Limits of Multilevel Incoherent Heat Engines

TL;DR

This paper develops a comprehensive quantum-mechanical theory of heat engines with periodically-modulated energy levels, revealing fundamental limits on their speed, power, and efficiency under incoherent operation.

Contribution

It introduces a unified framework for analyzing multilevel heat engines, including new hybrid cycle forms, and determines their fundamental operational limits.

Findings

Identifies speed and efficiency limits for incoherent multilevel heat engines.

Discovers new hybrid cycle forms beyond traditional engine cycles.

Provides a theoretical basis for optimizing quantum heat engine performance.

Abstract

We present a comprehensive theory of heat engines (HE) based on a quantum-mechanical "working fluid" (WF) with periodically-modulated energy levels. The theory is valid for any periodicity of driving Hamiltonians that commute with themselves at all times and do not induce coherence in the WF. Continuous and stroke cycles arise in opposite limits of this theory, which encompasses hitherto unfamiliar cycle forms, dubbed here hybrid cycles. The theory allows us to discover the speed, power and efficiency limits attainable by incoherently-operating multilevel HE depending on the cycle form and the dynamical regimes.