Universality of Efficiency at Maximum Power

We investigate the efficiency of power generation by thermochemical engines. For strong coupling between the particle and heat flows and in the presence of a left-right symmetry in the system, we demonstrate that the efficiency at maximum power displays universality up to quadratic order in the deviation from equilibrium. A maser model is presented to illustrate our argument.

Figure 1

Illustration of the maser model.

Figure 2

(a) Efficiency at maximum power compared with Carnot efficiency (straight dashed line) and Curzon-Ahlborn efficiency (dotted line). (b) Scaled energies $x_l$ and $x_r$ and maximum power $\mathcal{P}$ (note that $x_l$ and $x_r$ depend only on the ratio ${\Gamma }_l/{\Gamma }_r$ but $\mathcal{P}$ does not).