Thermodynamic Efficiency at Maximum Power

We show by general arguments from linear irreversible thermodynamics that for a heat engine, operating between reservoirs at temperatures $T_0$ and $T_1$, $T_0\ge T_1$, the efficiency at maximum power is bounded from above by $1-\sqrt{T_1/T_0}$.

Figure 1

(a) Generic setup for the conversion of a heat flow $\dot{Q}$ into a work flow $\dot{W}$; (b) cascade construction with a continuum of auxiliary heat baths; (c) tandem construction with one intermediate heat bath.