Power Converter for Electrocaloric Refrigeration
Fig. 1 depict the typical thermal cycle of the electrocaloric refrigeration, where Q is charge, E is electrical field, T is temperature, S is entropy, and t is time. An electrical field is applied to the electrocaloric dielectric material on a time scale in which the heat flow from the material to the surrounding bath can be neglected. Under this circumstance, the total entropy of the whole system remains constant as an adiabatic process. Therefore, this adiabatically applied electric field results in an increase in the temperature of the material due to the lattice vibration entropy compensation of the reduction of the dipolar subsystem entropy. Similarly, removal of the electrical field causes a decrease of the temperature of the electrocaloric material.
It can be found from this process that the part of the work done to drive representative electrocaloric cycles does not pump heat, and may therefore be recovered to increase the system efficiency. This can be achieved by dual electrocaloric module system where two electrocaloric modules are charged and discharged out of the phase. A converter presented in Fig. 2 provide the desired function of the electrocaloric refrigeration system: providing power for system initialization, heat pumping, and loss compensation as well as recycling charge between two electrocaloric modules. The proposed design is experimentally verified with waveforms shown in Fig. 2.