Endoreversible Stirling cycles: plasma engines at maximal power

TL;DR

This paper demonstrates that endoreversible Stirling engines using plasma as the working medium operate at maximal power with Curzon-Ahlborn efficiency, generalizing to various plasma types due to their linear caloric equations of state.

Contribution

It reveals that plasma Stirling engines reach maximal power at Curzon-Ahlborn efficiency due to linear caloric relations, extending applicability beyond ideal gases.

Findings

Plasma Stirling engines operate at Curzon-Ahlborn efficiency at maximal power.

Efficiency drops significantly for plasmas with photonic equations of state.

Results generalize to a broad class of plasma-based engines.

Abstract

Endoreversible engine cycles are a cornerstone of finite-time thermodynamics. We show that endoreversible Stirling engines operating with a one-component plasma as working medium run at maximal power output with the Curzon-Ahlborn efficiency. As a main result, we elucidate that this is actually a consequence of the fact that the caloric equation of state depends only linearly on temperature and only additively on volume. In particular, neither the exact form of the mechanical equation of state, nor the full fundamental relation are required. Thus, our findings immediately generalize to a larger class of working plasmas, far beyond simple ideal gases. In addition, we show that for plasmas described by the photonic equation of state the efficiency is significantly lower. This is in stark contrast to endoreversible Otto cycles, for which photonic engines have an efficiency larger than the Curzon-Ahlborn efficiency.