%0 Journal Article
%A Azcondo, M. Teresa
%A Orfila, María
%A Linares, María
%A Molina, Raul
%A Marugán, Javier
%A Amador, Ulises
%A Boulahya, Khalid
%A Botas, Juan Ángel
%A Sanz, Raul
%T Thermochemical Energy Storage Using the Phase Transitions Brownmillerite -2H Perovskite - Cubic Perovskite in the Ca xSr1−xCoO3−δ (x = 0 and 0.5) System
%D 2021
%U https://hdl.handle.net/20.500.14352/124417
%X The oxides Ca0.5Sr0.5CoO3−δ and SrCoO3−δ, which present perovskite or perovskite-related phases in different temperature domains, have been tested as materials for thermochemical energy storage. The first one, Ca0.5Sr0.5CoO3−δ, experiences a reversible phase transition upon consecutive cycles under an airflow at a maximum operating temperature of 1196 K. Unfortunately, the heat stored in this process, associated with an oxygen loss/gain and a structural phase transition, is very small, hindering its use for thermochemical heat storage. The as-prepared oxide SrCoO3−δ, which displays a brownmillerite structure like the Ca-containing compound, in the first heating step irreversibly segregates some Co3O4 at 823 K to yield a 2H hexagonal perovskite. This phase reversibly transforms at 1073 K into a cubic perovskite. These 2H ⇄ C transitions occur from the 2nd to, at least, 30th cycle. The average absorbed and released heat is ∼104.1 ± 0.06 and ∼68.8 ± 1.8 J/g, respectively, and therefore, SrCoO3−δ presents a high exo/endo ratio. The exergy efficiency is, on average for the 30 cycles performed, as high as 63.9 ± 1.2%. The mechanism of the phase 2H ⇄ C transition of SrCoO3−δ explains the good performance of this material for thermochemical energy storage.
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