Cycling Tames Power Fluctuations near Optimum Efficiency

Area of Science:

• Thermodynamics
• Statistical Mechanics
• Non-equilibrium Physics

Background:

• The Carnot cycle defines the theoretical limit for heat engine efficiency.
• Practical heat engines face a trade-off between high efficiency and significant power output.
• Thermodynamic uncertainty relations suggest high-power Carnot efficiency leads to large fluctuations and unreliability in steady-state engines.

Purpose of the Study:

• To demonstrate a method for achieving Carnot efficiency at large power output without compromising reliability.
• To resolve the apparent conflict between high-efficiency, high-power operation and thermodynamic uncertainty relations.
• To investigate the nature of work in cyclic versus quasistatic heat engines.

Main Methods:

• Theoretical analysis of heat engines operating under cyclic quasistatic conditions.
• Utilizing an exactly solvable model of an overdamped Brownian heat engine.
• Analyzing stochastic processes associated with work extraction in different engine regimes.

Main Results:

• A design strategy is presented to overcome the efficiency-power-fluctuation trade-off.
• Cyclic quasistatic operation allows for Carnot efficiency at large power with reduced fluctuations.
• Work in cyclic heat engines and quasistatic heat engines are shown to be distinct stochastic processes.

Conclusions:

• It is possible to achieve high efficiency and high power simultaneously in heat engines by operating cyclically under quasistatic conditions.
• This approach circumvents the limitations imposed by thermodynamic uncertainty relations for steady-state engines.
• The findings offer a new perspective on the fundamental nature of work and thermodynamics in cyclic processes.