Approaching Carnot efficiency at maximum power in linear response regime

TL;DR

This paper demonstrates a heat engine that surpasses traditional efficiency bounds at maximum power within the linear response regime by using a harmonic oscillator and shortcut techniques, approaching Carnot efficiency.

Contribution

It introduces a classical harmonic oscillator heat engine utilizing shortcuts to adiabaticity to achieve near-Carnot efficiency at maximum power in the linear response regime.

Findings

Efficiency at maximum power can approach Carnot efficiency.

Cycle duration is minimized to thermalization times.

Work performed is quasistatic and arbitrarily large.

Abstract

We construct an example of heat engine whose efficiency at maximum power breaks down the previously derived bounds in the linear response regime. Such example takes a classical harmonic oscillator as the working substance undergoing a finite-time Otto cycle. Using a specific kind of shortcut to adiabaticity, valid only in the linear response regime, quasistatic work is performed at arbitrarily short times. The cycle duration is then reduced to the sum of relaxation times during the thermalization strokes exclusively. Thus, power is maximum since the work is maximum (quasistatic work) and the cycle duration is minimum. Efficiency at maximum power can be made arbitrarily close to Carnot efficiency with an appropriate choice of the ratio between the temperatures of the two heat baths.