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Elastocaloric polymers, whose performance typically relies on phase transformation between amorphous chains and crystalline domains, offer a promising alternative to traditional refrigeration technologies. While engineering polymer‐network architecture has shown the potential to boost elastocaloric performance, the role of topological defects remains unexplored despite their prevalence in real polymers. This study reports a defect‐engineering approach in end‐linked star polymers (ELSPs) that enables an adiabatic temperature change of up to 8.14 ± 1.76 °C at an ambient temperature above 65 °C, showing an enhancement of 39% compared to ELSPs with negligible defects. This defect‐regulated solid‐state cooling is attributed to two competing effects of dangling‐chain defects on strain‐induced crystallization (SIC) and temperature‐induced crystallization (TIC), synergistically regulating the adiabatic temperature change. Specifically, increasing dangling‐chain defects monotonically lowers ELSPs’ mechanical performance at high temperatures due to suppressed SIC, but nonmonotonically impacts the mechanical performance at low temperatures due to the competition between suppressed SIC and enhanced TIC. This work reports a defect‐engineering strategy that enables a record‐high adiabatic temperature change of up to 8.14 ± 1.76 °C in elastomers at an elevated temperature above 65 °C. Combined experimental and theoretical efforts reveal that increasing dangling‐chain defects nonmonotonically impacts the elastocaloric cooling performance of polymers due to the competition between suppressed strain‐induced crystallization and enhanced temperature‐induced crystallization.

This work investigates the effect of nanoclay addition—specifically natural montmorillonite (MMT) and organo-modified montmorillonite (O-MMT)—on the elastocaloric performance of natural rubber (NR), a promising material for solid-state cooling due to its non-toxicity, low cost, and ability to exhibit large adiabatic temperature changes under moderate stress (~a few MPa). Despite these advantages, the cooling efficiency of NR remains lower than that of conventional vapor-compression systems. Therefore, improving the cooling capacity of NR is essential for the development of solid-state cooling technologies competitive with existing ones. To address this, two series of NR-based nanocomposites, containing 1, 3, and 5 phr nanofiller, were prepared by melt compounding and hot pressing and characterized in terms of morphology, thermal, mechanical, and elastocaloric properties. The results highlighted that the better dispersion of the organoclays within the rubber matrix promoted not only a better mechanical behavior (in terms of stiffness and strength), but also a significantly enhanced cooling performance compared to MMT nanofilled systems. Moreover, NR/O-MMT samples demonstrated up to a ~45% increase in heat extracted per refrigeration cycle compared to the unfilled NR, with a coefficient of performance (COP) up to 3, approaching the COP of conventional vapor-compression systems, typically ranging between 3 and 6. The heat extracted per refrigeration cycle of NR/O-MMT systems resulted in approx. 16 J/cm3, higher with respect to the values reported in the literature for NR-based systems (ranging between 5 and 12 J/cm3). These findings emphasize the potential of organoclays in enhancing the refrigeration potential of NR for novel state cooling applications.

Barocaloric cooling is classified as environmentally friendly because of the employment of solid-state materials as refrigerants. The reference and well-established processes are based on the active barocaloric regenerative refrigeration cycle, where the solid-state material acts both as refrigerant and regenerator; an auxiliary fluid (generally water of water/glycol mixtures) is used to transfer the heat fluxes with the final purpose of subtracting heat from the cold heat exchanger coupled with the cold cell. In this paper, we numerically investigate the effect on heat transfer of working with nanofluids as auxiliary fluids in an active barocaloric refrigerator operating with a vulcanizing rubber. The results reveal that, as a general trend, adding 10% of copper nanoparticles in the water/ethylene-glycol mixture carries to +30% as medium heat transfer enhancement.

In this paper, the application of solid-state cooling based on the barocaloric effect in the cold food supply chain is investigated. Barocaloric solid-state technology is applied to the final links of the cold food supply chain regarding the steps of retail and domestic conservation. In this context, effective barocaloric cooling entails the refrigeration of food at 5 °C (273 K) and as such is a promising cooling technology due to its energy efficiency and environmental friendliness. The categories of food involved in this investigation are meat and fresh food products like soft cheese, yogurt, and milk. The energy performance of the barocaloric system is analyzed and compared with a commercial vapor compression refrigerator of a similar size, both operating using R600a under the same working conditions. Based on the results of this comparison, it is concluded that barocaloric cooling is a favorable technology for application in the final links of the cold food supply chain if the system operates in an ABR cycle at frequencies between 1.25 and 1.50 Hz with a regenerator comprising acetoxy silicone rubber as the solid-state refrigerant and a 50%EG–50% water mixture as the heat transfer fluid flowing at an optimal velocity of 0.15 m s−1. Thus, an appropriate tradeoff between the temperature span, cooling power, and coefficient of performance is guaranteed. Under these conditions, the barocaloric system outperforms the domestic vapor compression cooler operating using R600a.

We report on the design and characterization of a demonstrator device for miniature-scale elastocaloric (eC) cooling using a series of natural rubber (NR) foil specimens of 9 × 26.5 mm2 lateral size and thicknesses in the range of 290–900 μm. NR has the potential to meet the various challenges associated with eC cooling, as it exhibits a large adiabatic temperature change in the order of 20 K and high fatigue resistance under dynamic load, while loading forces are low. Owing to the large surface-to-volume ratio of rubber-based foils, heat transfer to heat sink and source elements is accomplished by mechanical contact enabling compact designs. Two actuators are implemented to control the performance in loading direction independent from the performance of mechanical contacting. The study of operation parameters is complemented by lumped-element modeling to understand the cycle frequency-dependent dynamics of heat transfer and resulting cooling capacity. The single-stage device operates in the strain range of 300%–700% and exhibits a temperature span up to 4.1 K, while the specific cooling power reaches 1.1 Wg−1 and the absolute cooling power 123 mW. The performance metrics show a pronounced dependence on foil thickness and heat transfer coefficient indicating a path toward future device optimization.

Elastocaloric cooling is recognized as a promising alternative to modern vapor-compression cooling systems, which often rely on environmentally hazardous refrigerants. Natural rubber (NR), a well-known renewable resource, stands out among elastomers exhibiting elastocaloric behavior due to a peculiar combination of nontoxicity, low cost, softness, long-life fatigue and high caloric power. Despite these properties, research on the refrigeration potential of NR is still in its early stages, and several aspects require attention. This work investigates, for the first time, the effect of crosslinking density on the elastocaloric properties of NR. Samples with three different crosslinking densities (2.9, 4.0 and 5.2 mol·10−4/cm3) were produced by internal compounding and hot pressing, and thermo-mechanically characterized. The assessment of the elastocaloric effect of the produced samples revealed that reducing the crosslinking degree significantly enhanced the elastocaloric properties. To compare the cooling capacity of the samples, a qualitative coefficient of performance (COPmat) was evaluated as the ratio between extracted thermal energy and deformational work per unit volume. The results highlight that the least crosslinked sample achieved the higher COPmat, equal to 2.4. These results underscore the significance of crosslinking density as one of the primary factors to be considered to enhance the refrigeration potential of NR.

Pulse-magnetron-sputtered long-term superhydrophilic coatings have been synthesized to functionalize the surfaces of solid-state cooling devices, e.g., electrocaloric heat pumps, where not only a complete wetting of the surface by a fluid is intended, but also fast wetting and dewetting processes are required. The coatings consist of a (Ti,Si)O2 outer layer that provides lasting hydrophilicity thanks to the mesoporous structure, followed by an intermediate WO3 film that enables the reactivation of the wettability through visible light irradiation, and a W underlayer which can work as a top electrode of the electrocaloric components thanks to its suitable electrical and thermal conductivity properties. Process parameter optimization for each layer of the stack as well as the influence of the microstructure and composition on the wetting properties are presented. Finally, water contact angle measurements, surface energy evaluations, and a contact line dynamics assessment of evaporating drops on the coatings demonstrate that their enhanced wetting performance is attributed not only to their intrinsic hydrophilic nature but also to their porous microstructure, which promotes wicking and spreading at the nanometric scale.

Elastocaloric is a promising cooling technique that offers a solid-state alternative to vapor compression. The elastoCaloric Effect (eCE) refers to the reversible changes in temperature and entropy that occur in Shape Memory Alloy (SMA) when loaded/unloaded by an external mechanical load. The research introduced in this paper compares various Ni–Ti-based SMAs to determine the optimal one to be exploited in an experimental air conditioner. The device can lodge 600 SMA wires in the space stacked by two cylinders concentrically arranged, with inner/outer diameter of 250/280 mm. Tests are performed while the device rotates at variable frequencies ranging from 0.3 Hz to 0.7 Hz. A rotary meshing two-dimensional tool has been developed and used to perform the test campaign under variable working conditions and NiTi-based SMAs. The energy performances are evaluated and (Ni 50 Mn 31.5 Ti 18.5 ) 99.8 B 0.2 resulted in the most suitable SMA showing 2.13 kW as peak of cooling power (at a cycle frequency of 0.6 Hz and a utilization factor of 0.7) and a maximum COP of 8.35 (at 0.3 Hz and 0.7 as utilization factor). This work demonstrates that the use of the (Ni 50 Mn 31.5 Ti 18.5 ) 99.8 B 0.2 alloy can enable the device to achieve performances superior to vapor compression-based devices.

Barocaloric is a solid-state not-in-kind technology, for cooling and heat pumping, rising as an alternative to the vapor compression systems. The former is based on solid-state refrigerants and the latter on fluid ones. The reference thermodynamical cycle is called active barocaloric regenerative refrigeration (or heat pumping cycle). The main advantage of this technology is to not employ greenhouse gases, which can be toxic or damaging for the environment and that can contribute to increasing global warming. In this paper, the environmental impact of barocaloric technology was evaluated through a Total Equivalent Warming Impact (TEWI) analysis carried out with the help of a numerical 2D model solved through a finite element method. Specifically, we propose a wide investigation on the environmental impact of barocaloric technology in terms of TEWI index, also making a comparison with a vapor compression plant. The analysis focuses on both the cooling and heat pump operation modes, under different working conditions and auxiliary fluids. The results revealed that a barocaloric system based on ABR cycle could provide a reduction of the environmental impact with respect to a vapor compression system. The addition of nanofluids contributes in reducing the environmental impact up to −62%.

Rare-earth-free magnetostructural MnNiSi-based solid solutions are considered as promising candidates for solid-state cooling applications. In this paper, we use density functional theory calculations to study the energetics, variations in atomic displacements and bond length, and magnetic properties of high-entropic, intermetallic MnNi-X (X = Si0.2Ge0.2Sn0.2Al0.2Ga0.2) magnet in both the low-symmetry Pnma and high-symmetry P63/mmc structures, where we confine the large configurational entropy to the non-magnetic X-site of the compound. Our calculations reveal that the high-entropic chemical substitution of Si0.2Ge0.2Sn0.2Al0.2Ga0.2 in the X-site carry fingerprints that favor a reduction in magnetostructural transition temperature with minimal impact of total magnetization. These results motivate a promising path of high-entropic X-site substitutions to tune the magnetostructural properties of MnNiSi-based solid solutions.