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Research Papers

# Solid-State Refrigeration Based on the Electrocaloric Effect for Electronics Cooling

[+] Author and Article Information
Y. Sungtaek Ju

Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095-1597just@seas.ucla.edu

J. Electron. Packag 132(4), 041004 (Nov 23, 2010) (6 pages) doi:10.1115/1.4002896 History: Received July 13, 2010; Revised September 01, 2010; Published November 23, 2010; Online November 23, 2010

## Abstract

Subambient temperature operations of advanced semiconductor devices offer many benefits, including improved reliability, reduced leakage currents, and enhanced signal to noise ratios. We discuss a new design concept for compact solid-state refrigerators based on the electrocaloric (EC) effect. The EC refrigerators are attractive because they may approach the Carnot efficiency more closely than Peltier coolers, which involve intrinsically irreversible processes. To address parasitic losses and other practical considerations that limit the actual performance of EC coolers, we incorporate laterally interdigitated electrode arrays with high effective thermal conductivity and switchable thermal interfaces with high switching ratios and high off-state thermal resistance. Numerical simulations are used to quantify the impact of various design parameters and the expected performance of the module, focusing in particular on the heat diffusion time and $RC$ thermal time constant. Based on the material properties reported in the literature, we project that cooling power densities $>10 W/cm2$ may be achieved across $ΔT$ of the order of 10 K at $coefficient of performance (COP)>10$. The present work motivates further experimental studies to develop advanced electrocaloric materials and fabricate/test cooling modules to assess the feasibility of their practical application.

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## Figures

Figure 6

The predicted cooling power density as a function of τht for different electrode assembly thicknesses

Figure 5

The predicted cooling power density as a function of the electrode assembly thickness for two different values of the heat transfer step duration τht. The effective thermal conductivity of the electrode assembly is assumed to be 1 W/m K, comparable to that of thick ceramic films without interdigitated electrodes.

Figure 7

Temperature distribution across the EC electrode assembly at the completion of the heat transfer steps for different values of τht

Figure 8

The predicted cooling power density as a function of the heat transfer duration τht for different values of the effective thermal conductivity of the electrode assembly

Figure 9

The predicted cooling power density as a function of the on-state resistance of the switchable thermal interface

Figure 10

The predicted cooling power density as a function of the cooling temperature differential (temperature of the heat sink—temperature of the electronic device to be cooled)

Figure 4

Laterally interdigitated electrode array: (a) top view, (b) cut angled view, and (c) after filling with an EC material

Figure 3

Cross-sectional views of the μECM (not to scale) illustrating its operation. The center mass (interdigitated electrode array infiltrated with the EC material, see Fig. 4) is suspended via silicon mechanical flexures and actuated up and down to make alternate thermal contacts with the cold side (device to be cooled) and the heat sink side: (a) polarization step (EC material heats up), (b) heat rejection step, (c) depolarization step (EC material cools down), and (d) heat absorption step.

Figure 2

T-S diagram of one potential thermodynamic cycle for EC refrigeration

Figure 1

Conceptual macroscale illustration of the mechanism of the electrocaloric cooling effect

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