Experimental implementation of finite-time Carnot cycle

The Carnot cycle is a prototype of ideal heat engine to draw mechanical energy from the heat flux between two thermal baths with the maximum efficiency, dubbed as the Carnot efficiency \(\eta_{\mathrm{C}}\). Such efficiency can only be reached by thermodynamical equilibrium processes with infinite time, accompanied unavoidably with vanishing power - energy output per unit time. In real-world applications, the quest to acquire high power leads to an open question whether a fundamental maximum efficiency exists for finite-time heat engines with given power. We experimentally implement a finite-time Carnot cycle with sealed dry air as working substance and verify the existence of a tradeoff relation between power and efficiency. Efficiency up to \((0.524\pm0.034)\eta_{\mathrm{C}}\) is reached for the engine to generate the maximum power, consistent with the theoretical prediction \(\eta_{\mathrm{C}}/2\). Our results shall provide a new platform for studying finite-time thermodynamics consisting of nonequilibrium processes.