Fig. 4: Josephson–Stirling cycle.
Total work W and efficiency η or coefficient of performance (COP) as functions of the reservoir temperatures Te and Tb a, b without and c, d with parity constraints. In both cases, ES = 0.165Δ. The different operating modes of the cycle are indicated in panels a, c: for refrigerators, the cycle absorbs heat Qe from the cooled subsystem with temperature Te and releases heat Qb < 0 with ∣Qb∣ > Qe to the heat sink with temperature Tb. If Te < Tb, Qe < 0, and Qb < 0, the machine is a Joule pump that completely converts work into heat released to the reservoirs. On the other hand, if Te < Tb, Qe < 0, and W < 0, while Qb > 0, the machine acts as a cold pump transferring heat from the hot (T = Tb) to the cold reservoir (T = Te).
