ELECTROCALORICS
Giant temperature span in electrocaloric regenerator
A. Torelló1,2, P. Lheritier^1 , T. Usui^3 , Y. Nouchokgwe1,2, M. Gérard^1 ,
O. Bouton^1 , S. Hirose^3 , E. Defay^1
Cooling devices based on caloric materials have emerged as promising candidates to become the
next generation of coolers. Several electrocaloric (EC) heat exchangers have been proposed that use
different mechanisms and working principles. However, a prototype that demonstrates a competitive
temperature span has been missing. We developed a parallel-plate active EC regenerator based on lead
scandium tantalate multilayer capacitors. After optimizing the structural design by using finite element
modeling for guidance and to considerably improve insulation, we measured a maximum temperature
span of 13.0 kelvin. This temperature span breaks a crucial barrier and confirms that EC materials are
promising candidates for cooling applications.
T
he development of highly efficient and
environmentally friendly energy systems
is a primary concern for mitigating glob-
al warming and promoting a sustainable
use of natural resources. Approximate-
ly 20% of the world’s energy consumption is
used for refrigeration purposes, and the ab-
solute amount of air conditioning units is
predicted to double by 2040 ( 1 ). Current vapor-
compression–based refrigeration systems have
reached their thermodynamic limit after
100 years of advancements. They release green-
house effect gases into the atmosphere and are
typically noisy. Moreover, these systems are not
suitable for the sort of miniaturization needed
for several types of cooling applications.
Caloric materials undergo large entropy
changes when crossing phase transitions be-
cause of stimuli such as magnetic fields (mag-
netocalorics), electric fields [electrocalorics
(ECs)], uniaxial stress (elastocalorics), or pres-
sure (barocalorics) ( 2 – 5 ). These materials have
emerged as promising candidates for cool-
ing technologies because they do not suffer
from some of the disadvantages of the vapor-
compression systems. Their efficiency is alsopresumed to be higher ( 6 ). In comparison with
the other caloric materials, ECs are of partic-
ular interest because the coefficient of per-
formance (COP) can be enhanced with energy
recovery ( 7 ). Electric fields are cheaper and
easier to produce than magnetic fields, which
require permanent magnets for magneto-
calorics. EC materials fatigue less than elasto-
calorics, which require stress stimuli that
drives mechanical failure of these materials.
Nevertheless, EC prototypes have struggled to
maintain temperature spans comparable with
those of magnetocaloric or elastocaloric pro-
totypes, for which more than 10 K has been
repeatedly reported ( 8 – 13 ). The main reasons
are a modest intrinsic adiabatic EC temper-
ature change in most EC materials but also
low thermal conductivity and mandatory elec-
trical connections, both of which hinder heat
transfer.
The first EC prototype dates back to three
decades ago. Sinyavskyet al. proposed an
active EC regenerator (AER) based on leadSCIENCEsciencemag.org 2 OCTOBER 2020•VOL 370 ISSUE 6512 125
Fig. 1. Experimental design.(A) Schematic showing the experimental setup. (B) The operation principle for one cycle to stabilize the temperature gradient along
the regenerator. (C) The geometry of our simulated model using COMSOL Multiphysics 5.2a software. We applied adiabatic conditions at the exterior walls (red lines)
as a first approximation, whereas a no-slip boundary condition was set at the solid-fluid interface (blue lines).
(^1) Materials Research and Technology Department, Luxembourg
Institute of Science and Technology (LIST), 41 Rue du Brill,
Belvaux L-4422, Luxembourg.^2 University of Luxembourg, 2
Avenue de l’Université, Esch-sur-Alzette L-4365, Luxembourg.
(^3) Murata Manufacturing Co., Nagaokakyo, Kyoto 617-8555, Japan.
*Corresponding author. Email: [email protected]; emmanuel.
[email protected]
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