Heat management and losses of electrocaloric cooling devices based on electrostatic thermal switches

Abstract

Electrocaloric cooling is a promising technology that could replace existing vapor-compression technology with lighter and more efficient solid state based devices. Among those, electrocaloric coolers using electrostatic actuation are rising; therefore harnessing their advantages and understanding their shortcomings is still a work in progress. In this paper, we pin down two limitations that stem from a commonly used device design, and we propose a model that takes them into account. The first is due to the displacement of the film, which moves the air around and causes losses. We estimate the air losses through a Poiseuille flow model. The second is related to the non-ideal Brayton cycle the device performs and which results in generating a heat flow opposite to cooling. We estimated the effect of this back-flow on the cold flux using a 2D thermal diffusion model. Ultimately, our results point at several possible improvements for further designs. Among them, a slight reduction of the air pressure in the device looks as a promising solution to reduce air losses. • Air losses in an electrocaloric cooler using electrostatic actuation are modeled. • The heat transfer in the material and at the interface are simulated. • Increasing the cycling frequency of the cooler increases the cold power. • At high frequency, air losses prevent the device from working efficiently. • To achieve high cooling temperature span, the air losses should be mitigated.