Active Peltier Coolers Based on Correlated and Magnon-Drag Metals

Active cooling systems use electrical work to bring a hot device (such as an integrated circuit) down to near ambient temperature by draining heat from the hot area of the device to a passive heat sink. Commercial thermoelectric modules are optimized for refrigeration, and are not ideal for active cooling. Refrigeration maintains a temperature that is below the ambient temperature in a device (such as a kitchen refrigerator) by pumping heat from the cold area of the device to a heat sink. The thermoelectric figure of merit zT is used traditionally to evaluate the performance of thermoelectric modules, including refrigeration modules. But it is not a good indicator of the performance of active cooling materials. Here, we describe an efficient, all-solid-state active cooler based on the Peltier effect in metals with high thermoelectric power factor due to electron correlation effects (${\mathrm{Ce}\mathrm{Pd}}_3$) or magnon drag ($\mathrm{Co}$) and high passive thermal conductivity. We show theoretically and experimentally that the effective thermal conductance under applied current can exceed the limits imposed by Fourier’s heat conduction law. The designed device measures an effective thermal conductance that is an order of magnitude larger than the passive thermal conductance at ΔT = 1 K with the dynamic response of 4 s.

Figure 1

Schematic drawings show (a) the difference between active cooling and refrigeration, and (b)–(d) the use of Peltier couples in various modes of heat conduction: (b) passive mode, (c) refrigeration mode, (d) active cooling mode.

Figure 2

Calculated values of effective thermal conductivity. The red lines represent the κ_eff of $\mathrm{Co}$ and black dashes represent that of ${\mathrm{Ce}\mathrm{Pd}}_3$ (a) for ΔT = 1 K and (b) for ΔT = 10 K.

Figure 3

Data measured on a $\mathrm{Co}\text{−}{\mathrm{Ce}\mathrm{Pd}}_3$ TE couple cooler under a Peltier current I_S. (a) The temperature difference as a function of the heat load; the slope of these lines gives the thermal conductance. (b) The time dependence of the temperature drop after I_S is switched on.

Figure 4

Effective thermal conductivity of the $\mathrm{Co}\text{−}{\mathrm{Ce}\mathrm{Pd}}_3$ TE couple cooler for two values of I_S. In the bottom frame, the symbols represent measured points and lines represent theory. The top frame (the same colors identify I_S as in the bottom frame) shows the deviation between theory and experiment to be less than 10% for the same currents as are used in the bottom frame.