Phase change material selection for two innovative compact energy storage systems in residential buildings

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2019Suggested citation
Zsembinszki, Gabriel;
Gasia, Jaume;
Oró Prim, Eduard;
Cabeza, Luisa F.;
.
(2019)
.
Phase change material selection for two innovative compact energy storage systems in residential buildings.
XI National and II International Engineering Thermodynamics Congress, June 12 to 14, 2019, Albacete. Proceedings book. Ediciones de la Universidad de Castilla-La Mancha. ISBN: 978-84-09-11635-5. p. 207-216.
Ediciones de la Universidad de Castilla-La Mancha.
http://hdl.handle.net/10459.1/69749.
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Within the framework of HYBUILD, an EU Horizon 2020-funded project, two innovative compact
hybrid electrical/thermal storage systems for stand-alone and district connected residential buildings
will be developed and tested in three demos located in Spain, France, and Cyprus. One of the innovative
systems is aimed to be placed in buildings located in Mediterranean climate regions, where cooling loads
are dominant, while the other system is intended for Continental climate regions, where the heating
demand is dominant. Each system will include, among others components such as a sorption storage
system and domestic hot water tanks, a latent thermal energy storage (LTES) system that will be
connected to a heat pump through an innovative heat exchanger made of aluminium and filled with
phase change material (PCM). In both cases, the heat pump works with electricity provided by a
photovoltaic system that is, at the same time, connected to an electrical storage battery. The aim of using
the LTES system is to enhance the use of solar energy, which will be translated into a reduction of the
building energy consumption and related costs. This study focuses on the selection of the most suitable
PCM to be used in each system. On the one hand, the LTES system of the Mediterranean system will
be used to store cold to reduce the cooling demand. Taking into account that, according to the design
parameters, the heat pump will require a refrigerant evaporation temperature around 2 ºC, and the
building cooling system will require water supply in the range from 7 ºC to 12 ºC, the PCM melting
temperature range should be within 0 ºC and 7 ºC. On the other hand, the LTES system of the Continental
system will be used to store heat to reduce the domestic hot water (DHW) demand. The LTES will be
located at the compressor outlet and will be charged by the hot refrigerant that exits the compressor at
temperatures as high as 120 ºC. During the discharge process, the heat stored in the LTES will be
supplied to the DHW at a temperature in the range between 50 ºC to 55 ºC. As a consequence, the range
for the PCM melting temperature investigated in this case should be between 62 ºC and 68 ºC. Besides
the melting temperature, other selection criteria considered include the PCM melting enthalpy and
melting range, maximum allowed working temperature, density, thermal conductivity, availability, cost,
and compatibility with aluminium. To decide the ideal PCM candidate for each system, a decision matrix
was defined and used, by applying a weighted score to the selection criteria items according to their
importance. The preliminary results indicate that for the Mediterranean system the best candidate is the
commercial savE OM3 PCM, while for the Continental system, another commercial product PureTemp
63 is the most adequate option.