Energy optimization of two-level quantum Otto machines

TL;DR

This paper analyzes the energy efficiency and optimization of a two-level quantum Otto machine functioning as a heat engine or refrigerator, deriving bounds and optimizing performance criteria.

Contribution

It introduces new optimization strategies for quantum Otto machines, deriving bounds for efficiency and performance metrics under various criteria.

Findings

Derived bounds for efficiency at maximum power and ecological function.

Optimized refrigerator coefficient of performance for different criteria.

Analyzed power loss during operation as heat engine and refrigerator.

Abstract

We present the spin quantum Otto machine under different optimization criterion when function either as a heat engine or a refrigerator. We examine the optimal performance of the heat engine and refrigerator depending on their efficiency, output power and maximum entropy production. For heat engine case, we obtain the expression for the upper and lower bounds efficiencies at maximum power and maximum ecological function. In addition, the spin quantum Otto refrigerator coefficient of performance is optimized for three different criterion -- cooling power, product of performance and power and ecological function. We further study the dimensionless power loss to the cold reservoir when the machine is operating as a heat engine as well as its counterpart for the refrigerator case. We find that the maximum operation of the heat engine (refrigerator) cycle is when optimized with respect to hot (cold) reservoir frequency.