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Nowadays about 20% of the worldwide energy consumption is attributable to refrigeration that is almost entirely based on vapor compression refrigeration. The elastocaloric refrigeration is being considered in the recent years as one of the most promising alternatives to vapour compression cooling technology. It is based on the latent heat associated with the transformation process of the martensitic phase, found in Shape Memory Alloys (SMA) when they are subjected to uniaxial stress cycles of loading and unloading. SMAs are characterized by the mechanical property of being able to return to the initial form once the uniaxial stress has been removed. Currently the prototypes of elastocaloric cooler developed in the world are less than ten units and they are not close to the industrialization and commercialization, yet. This contribution presents the design processes and the steps of development of the first Italian elastocaloric device: SSUSTAIN-EL. This research involves part of a bigger Italian project, called SUSSTAINEBLE, that involves three research institutes: University of Naples Federico II, University of Genoa and the National Research Council. The aim of research group is the developing of a demonstrative prototype of a continuously elastocaloric cooler, which can represent a fundamental step as "proof of concept".

Electrocaloric and magnetic refrigeration are two emerging, solid-state based technology, which could constitute a real chance to overcome vapor compression refrigeration limits. To underline the differences and the affinities concerning such solid-state techniques, in this paper electrocaloric and magnetic refrigeration are compared through some performance parameters. For this purpose, it has been introduced a two-dimensional model, capable to reproduce, in room temperature range, the behaviors of both AMR and AER parallel plates regenerator. AMR and AER are the acronyms of Active Magnetic/Electrocaloric Regenerative cycle, respectively, which are inverse Brayton based thermodynamical cycles. In the model have been tested as refrigerant the most promising magnetic and electrocaloric materials, like Gd, Gd5(SixGe1-x)4, LaFe11.384 Mn0.356Si1.26H1.52, LaFe11.05Co0.94Si1.10, as magnetocaloric, P(VDF-TrFE-CFE)/BSTs, 0.93PMN-0.07PT, PLZTs, as electrocaloric ones. Among them, the PLZT thin film class confers the best results, higher than every magnetocaloric material tested, conferring to electrocaloric refrigeration the real role of the environmental friendly technology of the future.

This paper describes a two-dimensional (2D) multiphysics model of a parallel plate active electrocaloric regenerator (AER) which operates as a refrigerant for an electric refrigerator at room temperature. Different electrocaloric materials have been tested with the model as refrigerants: (P(VDF–TrFE–CFE), P(VDF–TrFE–CFE)/BST, PST, PMN–PT, PLZT). The numerical results are presented in terms of temperature span, refrigeration energy, and coefficient of performance. The most promising to electrocaloric refrigeration are the compositionally graded structures of PLZT ceramics that give the maximum values in terms of temperature span (around 23 K), refrigeration power (with the best value of 893 W) and COP (with the best value of 11.2). With these materials, an AER cycle can successfully over-perform AMR and vapour compression cycles and can be an eco-friendly technology in chiller applications.

This paper reports the results of a comparative experimental analysis between HCF134a and HFO1234ze. The experimental apparatus consists of a domestic, commercial refrigerator operating with HCF134a and for which a drop-in substitution with HFO1234ze has been realized. A series of experimental trials have been taken out to evaluate: the pull-down time for the identification of the optimal charge of HFO1234ze and 1-day electric energy use. All the tests have been taken under sub-tropical conditions in conformity with the UNI-EN-ISO15502. The results show that the refrigeration cycle performance of HFO1234ze is as good as that of HFC134a. In particular, the cycle working with HFO134ze with the optimal charge shows an energy saving of 9%.

Magnetic Refrigeration (MR) is a novel refrigeration technique based on eco-friendly solid materials as refrigerants, whom react to the application of magnetic fields, with warming and cooling by magnetocaloric effect. The thermodynamical cycle which best suits the magnetic refrigeration is Active Magnetic Regenerator cycle (AMR). Regenerator is the core of a magnetic refrigerator, since that it plays a dual-role: it operates both as refrigerant and regenerator in an AMR cycle. An AMR cycle consists of two adiabatic stages and two isofield stage. In this paper an investigation is conducted about the magnetocaloric refrigerator design through two-dimensional multiphysics numerical models of two different magnetocaloric regenerators: (1) a packed bed and (2) a parallel plates magnetic regenerators made of gadolinium, operating at room temperature under a 1.5T magnetic field induction. Both models employ water as secondary fluid. The tests were performed with variable fluid flow rate at fixed AMR cycle frequency. The results obtained are presented in terms of temperature span, cooling power, coefficient of performance and mechanical power of the circulation pump, and they indicate under which operating conditions packed bed configuration is to be preferred to parallel plates and vice versa.

Solid-state refrigeration technologies are considered nowadays emerging alternative to vapor compression refrigeration. In this paper is introduced a two-dimensional model of solid-state refrigerator, which employs materials experiencing a combined electrocaloric-elastocaloric effect and it operates at room temperature. A numerical investigation is performed to explore the energetic performance of the refrigerators. The results reveal that PbTiO 3 as elastocaloric refrigerant confers the best performances in terms of COP; the highest cooling power estimated are proper of combined elastocaloric-electrocaloric effect, with increments around +65% than employing PbTiO 3 in single electrocaloric/elastocaloric refrigeration, on equal operative conditions.

Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magneto-caloric effect (MCE). The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative refrigeration). In order to demonstrate the potential of magnetic refrigeration to provide useful cooling in the near room temperature range, a novel Rotary Permanent Magnet Magnetic Refrigerator (RPMMR) is described in this paper. Gadolinium has been selected as magnetic refrigerant and demineralized water has been employed as regenerating fluid. The total mass of gadolinium (1.20 kg), shaped as packed bed spheres, is housed in 8 regenerators. A magnetic system, based on a double U configuration of permanent magnets, provides a magnetic flux density of 1.25 T with an air gap of 43 mm. A rotary vane pump forces the regenerating fluid through the regenerators. The operational principle of the magnetic refrigerator and initial experimental results are reported and analyzed.

Nowadays, the refrigeration is responsible of about 15% of the overall energy consumption all over the world. Actually most of the refrigerant fluids working in vapor compression plants (VCPs) are environmentally harmful, since they presents high GWP (Global Warming Potential), which leads to a substantial warming of both earth surface and atmosphere. Electrocaloric refrigeration (ER) is an innovative, emerging refrigeration technique based on solid state refrigerant that shows a great potential. It fits in the context of environment-friendly refrigeration systems, whom are spreading increasingly to replace VCPs. ER is founded on electrocaloric effect that is a physical phenomenon found in materials with dielectric properties, electrocaloric materials. The thermodynamical cycle that best is addressed to the electrocaloric refrigeration is Active Electrocaloric Regeneration cycle (AER) that consists of two adiabatic and two isofield stages. The core of an electrocaloric refrigerator is the regenerator whom operates both as refrigerant and regenerator in an AER cycle. In this paper, we compare the energetic performance of a commercial R134a refrigeration plant to that of an electrocaloric refrigerator working with an AER cycle. The comparison is performed in term of TEWI index (Total Equivalent Warming Impact) that includes both direct and indirect contributions to global warming.