Diverging, but negligible power at Carnot efficiency: theory and experiment

TL;DR

This paper investigates the theoretical and experimental feasibility of achieving Carnot efficiency at nonzero power in various heat engine models, revealing that while possible, the power is always negligible compared to maximum attainable power.

Contribution

It provides a comprehensive analysis of different heat engine models showing that Carnot efficiency at finite power is practically negligible, and offers conditions and experimental tests for these phenomena.

Findings

Carnot efficiency can be approached at nonzero power in several models.

The power at Carnot efficiency is always negligible compared to maximum power.

Experimental verification is feasible with current micromanipulation techniques.

Abstract

We discuss the possibility of reaching the Carnot efficiency by heat engines (HEs) out of quasi-static conditions at nonzero power output. We focus on several models widely used to describe the performance of actual HEs. These models comprise quantum thermoelectric devices, linear irreversible HEs, minimally nonlinear irreversible HEs, HEs working in the regime of low dissipation, over-damped stochastic HEs and an under-damped stochastic HE. Although some of these HEs can reach the Carnot efficiency at nonzero and even diverging power, the magnitude of this power is always negligible compared to the maximum power attainable in these systems. We provide conditions for attaining the Carnot efficiency in the individual models and explain practical aspects connected with reaching the Carnot efficiency at large power output. Furthermore, we show how our findings can be tested in practice using a standard Brownian HE realizable with available micromanipulation techniques.