Efficiency at Maximum Power of Low-Dissipation Carnot Engines

Abstract

We study the efficiency at maximum power, ${\eta }^{*}$, of engines performing finite-time Carnot cycles between a hot and a cold reservoir at temperatures $T_h$ and $T_c$, respectively. For engines reaching Carnot efficiency ${\eta }_C=1-T_c/T_h$ in the reversible limit (long cycle time, zero dissipation), we find in the limit of low dissipation that ${\eta }^{*}$ is bounded from above by ${\eta }_C/(2-{\eta }_C)$ and from below by ${\eta }_C/2$. These bounds are reached when the ratio of the dissipation during the cold and hot isothermal phases tend, respectively, to zero or infinity. For symmetric dissipation (ratio one) the Curzon-Ahlborn efficiency ${\eta }_{\mathrm{CA}}=1-\sqrt{T_c/T_h}$ is recovered. DOI: http://dx.doi.org/10.1103/PhysRevLett.105.150603 © 2010 The American Physical Society