Vapor Compression Technology Research Articles

Synthesis, Characterization, and Magnetocaloric Properties of the Ternary Boride Fe2AlB2 for Caloric Applications.

The ternary transition metal boride Fe2AlB2 is a unique ferromagnetic "MAB" phase that demonstrates a sizable magnetocaloric effect near room temperature-a feature that renders this material suitable for magnetic heat pump devices (MHP), a promising alternative to conventional vapor compression technology. Here, we provide a comprehensive review of the material properties of Fe2AlB2 (magnetofunctional response, transport properties, and mechanical stability) and discuss alloy synthesis from the perspective of shaping these materials as porous active magnetic regenerators in MHPs. Salient aspects of the coupled magnetic and structural phase transitions are critically assessed to elucidate the fundamental origin of the functional response. The goal is to provide insight into strategies to tune the magnetofunctional response via elemental substitution and microstructure optimization. Finally, outstanding challenges that reduce the commercial viability of Fe2AlB2 are discussed, and opportunities for further developments in this field are identified.

Techno-economic analysis and fuel applicability study of a novel gasifier-SOFC distributed energy system with CO2 capture and freshwater production

This study employs the water-gas-shift membrane reactor and multi-effect distillation with thermal vapor compression technologies to facilitate low-energy carbon capture and large-scale freshwater production in gasifier-solid oxide fuel cell (SOFC) systems. The supercritical CO2 Brayton cycle and double-effect absorption refrigeration cycle are introduced to achieve waste heat cascade recovery. This work expands the fuel selection to 12 biomasses to explore the fuel adaptability and application scenarios of the system, and selects four representative cases to reveal their thermodynamic and economic attributes. The base scheme produces 21,635 ton/year freshwater and 1333 ton/year CO2, and achieves energy and exergy efficiencies of 70.68 % and 30.60 % with total cost rate of 23.21 $/h and levelized cost of products of 43.55 $/GJ. The gasifier and SOFC effort contributes to over 60 % of total irreversibility. Larch wood is preferred in resource-rich regions while wood residue, switch grass and wood chip are also prioritized; rice straw, rice husk, cotton stem and algal biomass are suitable for water-scarce areas. As key parameters change, Case-II consistently excels in power output, efficiencies and economic aspects, but lags in cooling capacity compared with other cases. This work provides a reference for low-carbon transition in the energy sector and large-scale freshwater production.

Enhanced Elastocaloric Effects in γ-Graphyne.

The global emphasis on sustainable technologies has become a paramount concern for nations worldwide. Specifically, numerous sustainable methods are being explored as promising alternatives to the well-established vapor-compression technologies in cooling and heating devices. One such avenue gaining traction within the scientific community is the elastocaloric (eC) effect. This phenomenon holds promise for efficient cooling and heating processes without causing environmental harm. Studies carried out at the nanoscale have demonstrated the efficiency of the eC effect, proving to be comparable to that of state-of-the-art macroscopic systems. In this study, we used classical molecular dynamics simulations to investigate the elastocaloric effect for the recently synthesized γ-graphyne. Our analysis goes beyond obtaining changes in eC temperature and the coefficient of performance (COP) for two species of γ-graphyne nanoribbons (armchair and zigzag). We also explore their dependence on various conditions, including whether they are deposited on a substrate or prestrained. Our findings reveal a substantial enhancement in the elastocaloric effect for γ-graphyne nanoribbons when subjected to prestrain, amplifying it by at least 1 order of magnitude. Under certain conditions, the changes in the eC temperature and the COP of the structures reach expressive values as high as 224 K and 14, respectively. We discuss the implications of these results by examining the shape and behavior of the carbon-carbon bond lengths within the structures.

Continuous operating elastocaloric air-cooling device

<p>Elastocaloric cooling has shown significant potential as an alternative to traditional vapor-compression technology because it relies on nonflammable, non-toxic, and zero-global warming potential solid refrigerants (usually NiTi and TiNi-based shape memory alloys). However, the uniaxial loading mode commonly used in existing elastocaloric cooling devices is often accompanied by a lower operating frequency. Additionally, using water as the heat exchange medium presents challenges in further cooling the air with cold water. These issues will hinder the application of this type of refrigerators in space cooling scenarios. Here, we report a continuous operating tension-based elastocaloric air-cooling device that utilizes the bundles of NiTi wires. The driving mode based on the cam structure realizes the alternating loading-unloading cycle of multiple NiTi bundles, facilitating continuous the cooling process. Our air-cooling device achieves a temperature decrease of 4.4 �� in continuous air flow and provides a cooling power of 21 W. These results demonstrate the possibility of applying elastocaloric technology in space cooling and provide a technical reference for designing household air conditioners using this technology.</p>

Effect of inactive section on cooling performance of compressive elastocaloric refrigeration prototype

Elastocaloric (eC) cooling using shape memory alloy (SMA) with zero direct carbon emission is a promising alternative of traditional vapor-compression technology. Compressive eC refrigeration prototype (ERP) performs high fatigue life but suffers from the limited cooling performance. Many studies focus on enhancing the heat transfer property of compressive eC regenerators to improve the specific cooling power (SCP). However, reducing the SCP loss is also essential for developing high-cooling-performance compressive ERPs but has not been given sufficient attention. In this study, we revealed that the force holder widely used in compressive ERPs works as an inactive section that dramatically reduce the SCP produced by the NiTi SMA active section. Numerical heat transfer simulations and experiments were conducted to study the impact of the inactive section on the SCP at varied operation parameters. Nondimensionalized governing equations of the numerical model revealed that the volume ratio (Volnon) of the fluid channel of the inactive section to that of the active section is the determinant geometric parameter for the SCP decrease. Numerical results show that, larger operation frequency fERP, smaller dimensionless fluid velocity V* and system temperature span (∆Tspan) lead to more pronounced decreases in SCPnon (ratio of the SCP to ideal SCPideal at Volnon = 0) as the Volnon increases. It also indicates that the Volnon should be minimized to better < 0.08 for achieving excellent SCPnon > 0.95. Experiments validate that the regenerator with a reduced Volnon = 0.08 exhibits a notable increase of 30.8% and 66.7% in zero-∆TspanSCP and no-load ∆Tspan respectively, in comparison to the regenerator with Volnon = 0.5. Therefore, minimizing the Volnon of the inactive section via reducing the length and diameter of the fluid channel inside the force holder is necessary and highly recommended for developing high-performance compressive ERPs.

Effect of aspect ratio on the elastocaloric effect and its cyclic stability of nanocrystalline NiTi shape memory alloy

NiTi shape memory alloy (SMA) has been suggested as an environmentally friendly solid-state refrigerant that is expected to replace the traditional vapor compression technology. However, its various refrigeration indicators still need to be further explored and enhanced. Nanocrystalline NiTi SMA has significant advantages in terms of elastocaloric effect (eCE) and cyclic stability compared with traditional coarse-grained NiTi SMA. In this work, the influence of aspect ratio (L/W, where L and W are the gauge length and width of the samples, respectively) on the eCE and its cyclic stability of nanocrystalline NiTi SMA was investigated experimentally. The in-situ cyclic tensile tests were performed to observe the axial strain field and temperature field on the surface of the specimens with different aspect ratios. Some microscopic observations were also carried out to clarify the internal mechanism. The experimental results show that as the aspect ratio decreases, the adiabatic temperature change ΔTad (elasocaloric cooling capacity) of the nanocrystalline NiTi SMA gradually decreases, while the coefficient of the performance of material (COPmat) increases, and the cyclic stability of eCE was enhanced. However, the dependence of eCE and its cyclic stability on the aspect ratio is gradually weakened when L/W > 4. The eCE and its cyclic stability of nanocrystalline NiTi SMA are not related to the dislocation slipping but rather attributed to the cyclically accumulated residual martensite. This work can provide valuable reference for designing efficient and reliable nanocrystalline NiTi SMA based solid-state refrigeration devices.

Parametric analysis of fatigue-resistant elastocaloric regenerators: Tensile vs. compressive loading

Elastocaloric cooling has recently shown high potential as an environmentally friendly alternative to vapor-compression technology. Here, we have studied and analyzed the geometric characteristics of two active elastocaloric regenerators (AeCRs) that were proved to have high application potential, i.e., a shell-and-tube AeCR loaded in compression and a parallel-plate AeCR loaded in tension, with the goal of maximizing their cooling performance. For this purpose, a previously developed and experimentally verified 1D numerical model was used. We focused only on the geometries and operating conditions that allow for durable, i.e., buckling-free operation in compression and fatigue-resistant operation in tension. The results show that although the applied strain of the parallel-plate AeCR loaded in tension needs to be limited (below 2%) to ensure fatigue-resistant operation, it outperforms (in terms of cooling power and COP at 15 K of temperature span) the shell-and-tube AeCR, which due to buckling issues suffers from a poorer heat-transfer geometry, but can withstand higher strains due to compressive loading. At the maximum strain of 2%, the optimum parallel-plate AeCR can generate a maximum cooling power of 1825 W (corresponding to 7075 W kg−1 of elastocaloric material) and a COP of 9.15 at a zero-temperature span. On the other hand, due to a higher applied strain (3%) the optimum shell-and-tube AeCR can generate a higher maximum temperature span at zero cooling power (up to 50 K) but has limited cooling performance at lower temperature spans. In addition, the layering of the shell-and-tube AeCR was investigated for the first time to improve its performance. This study shows the crucial impact of the heat-transfer geometry (heat-transfer area and hydraulic diameter), which needs to be further improved in compression-loaded AeCRs to improve their efficiencies (without compromising the buckling stability). The study also shows the importance of the applied strain, which needs to be at least 2% or more to achieve a high cooling performance of the AeCR. The obtained results should serve as guidelines for designing powerful and efficient AeCRs in the future.

Membrane and vapor compression technologies use in the two-stage dehumidifying scheme of the rocket launch complex thermal regulation system

Membrane and vapor compression technologies use in the two-stage dehumidifying scheme of the rocket launch complex thermal regulation system

Comprehensive characterization of the adiabatic temperature change and (convection) heat transfer coefficient of a NiTi tube elastocaloric refrigerant

Elastocaloric cooling without global warming substance emission is a promising alternative to the vapor-compression technology. Comprehensive and precise characterization of the adiabatic temperature change of the elastocaloric refrigerant and the heat transfer coefficient between the elastocaloric refrigerant and the surrounding heat transfer fluid/solid is significant for the structural design of elastocaloric coolers. In this article, an analytical solution of the volume-averaged temperature variation in a tubular shape memory alloy elastocaloric refrigerant under cyclic compression was derived using lumped analysis, and a method of comprehensive characterization of the adiabatic temperature change (∆Tad) and (convection) heat transfer coefficient h for the elastocaloric refrigerant based on the analytical solution was proposed. A dimensionless number Ch was defined as the ratio of the latent heat release/absorption rate to the (convection) heat transfer rate, with which the characterization procedure including a series of nonlinear least-square regression tests and data selection criteria were established. The method proposed is applicable to any cross section geometry under both tension and compression, and it was validated using experimental data on a NiTi tube under sinusoidal force-controlled and reverse Brayton cyclic compressions and using existing experimental data of NiTi-based films, strips, and pillars under tension and compression in the literature. The ∆Tad characterized using the proposed method agreed with that using the reverse Brayton cyclic loading method within 5% (absolute value of 1 K). The effect of data selection sequence on the characterization of ∆Tad and h was investigated, and the results showed that proper starting points were significant for the convergence of ∆Tad and h.

Superelasticity and elastocaloric effect in a textured Ti-Nb-Zr-Ta alloy with narrow stress hysteresis

Recently, elastocaloric cooling has been authoritatively regarded as the most promising alternative for replacing conventional vapor compression technology, yet obstacles like structural/functional fatigue and high processing cost still exist, which boost the investigation of new elastocaloric materials. In this paper, we investigated the superelasticity (SE) as well as the elastocaloric effect (eCE) in a textured Ti-22 Nb-4Zr-2Ta alloy prepared by cold rolling of 97% in thickness and subsequent annealing at 973 K for 30 min. The strong texture is in favor of harmonizing the superelastic critical stress and enhancing transformation homogeneity. As a result, superelasticity with narrow stress hysteresis of ∼47 MPa at ambient temperature and outstanding homogeneous eCE has been confirmed elaborately through observing strain together with temperature distribution during a superelastic cycle. The standard deviations (Sdev) of the strain distribution during superelastic deformation was in the range of 0.17%− 0.37% accompanying with temperature change (ΔTadi) of ∼4.4 K and ∼3.9 K during loading and unloading processes, respectively. Moreover, the narrow superelastic hysteresis and homogenous transformation behavior allowed for a coefficient of performance (COP) value of 13.2 and little degradation after 240 elastocaloric cycles. As eCE homogeneity and SE hysteresis correlate closely with functional fatigue behavior, the present Ti-22 Nb-4Zr-2Ta alloy may act as potential working materials for stable solid-state refrigeration.

Simulation and optimum control of a two-stage compression air source heat pump system: A comparison of two kinds of variable volume approaches

Two-stage vapor compression technology can effectively improve the performance of an air source heat pump, and a staged compression system with two separate compressors has a highly flexible modulation capacity. However, the effect of different volume modulation approaches on the heating COP requires further analysis. In this study, a Modelica-based dynamic simulation model of a two-stage air-source heat pump was developed and verified with experimental data. A numerical optimization method was used to obtain the optimum frequencies and low- or high-stage cylinder volumes of the compressors that maximize the COP. The results show that the three optimization approaches have different effects. At lower ambient temperatures, varying the high-stage compressor cylinder volume can yield the maximum COP among the three optimization methods, followed by varying the low-stage compressor cylinder volume and compressor frequencies. At higher ambient temperatures, varying low-stage cylinder volume can yield the maximum COP, followed by varying the compressor frequencies and high-stage cylinder volume. The further the working condition deviates from the design point, the greater the improvement in the COP. The maximum improvements in the COP achieved with optimization in this study were 8.23%, 6.39% and 5.39% by varying the high-stage cylinder volume, low-stage cylinder volume, and frequencies, respectively.

Magnetic cooling with thin Peltier modules as thermal switches

Magnetic refrigeration is a promising alternative to the existing vapor-compression technology. The refrigerant of magnetic cooling is the magnetocaloric material whose temperature is controlled by applying/removing the magnetic field during the cooling cycle. In this work we consider the scenario where thin Peltier modules are used to control the heat flow in the magnetic cooling device. A phenomenological 3-parameter model is adopted to describe the Peltier modules, based on which we develop a simple numerical procedure to simulate the cooling device that includes both magnetocaloric materials and Peltier modules. Using coefficient of performance as the performance metric, we find that the inclusion of Peltier modules can greatly reduce the design complexity, particularly to simplify the pumping and valving systems of the working fluid. The same design concept can be applied to the cooling systems using solid refrigerants.

Numerical Modeling of Shell-and-Tube-like Elastocaloric Regenerator

Elastocaloric cooling is considered an environmentally friendly future alternative to vapor-compression technology. Recently, a shell-and-tube-like elastocaloric regenerator loaded in compression has demonstrated record-breaking heat-pumping performance and fatigue-resistant operation. The aim of this work is thus to present a new 1D numerical model to simulate and optimize the operation of an elastocaloric regenerator with a shell-and-tube-like design. In the first part of this work, the superelastic and elastocaloric properties of a single NiTi tube, which serve as input data for the numerical model, were determined through experimental characterization and phenomenological modeling. In the second part, the results of the numerical model were compared with the experimentally obtained results. Relatively good agreement was found regarding the temperature span, cooling and heating power, and COP values, which indicates that the developed numerical model could be used for accurate optimization of shell-and-tube-like elastocaloric regenerators. Finally, the effects of operating conditions and hysteresis losses on the performance of the shell-and-tube-like elastocaloric regenerator are modeled and discussed. This work shows that the shell-and-tube-like elastocaloric regenerator with this configuration can achieve a maximum temperature span of more than 50 K at zero-thermal-load conditions and a maximum cooling/heating power of up to 4000 W·kg−1 and COP of about 4 (at zero temperature span).

From the elastocaloric effect towards an efficient thermodynamic cycle

In recent years, elastocaloric cooling technology has been considered as one of the most promising alternatives to vapor compression technology. Given that elastocaloric technology is only in the early stages of development, a uniform method for evaluating the elastocaloric effect has not yet been established, and the thermodynamics of different elastocaloric cooling cycles have not yet been studied in detail. Therefore, the main goal of this work is to investigate these two important areas. Here, multiple thermodynamic cycles were studied, focusing on the parameters of the holding period of the cycle, which is essential for heat transfer between the elastocaloric material and the heat sink/source. The cycles were applied to commercially available superelastic thin-walled NiTi tubes under compressive loading and a thin NiTi wire under tensile loading. Isostress cycles with constant stress throughout the holding period, isostrain cycles with constant strain throughout the holding period and no-hold cycles (without a holding period) were studied across multiple stress/strain ranges. Based on the experimental results, a previously developed phenomenological model was applied to better understand and further evaluate the different cycles. The results revealed that the applied thermodynamic cycle significantly affects the thermomechanical response and thus the cooling/heating efficiency of the elastocaloric material. We show that by using isostress cycles and partial transformations, a Carnot-like thermodynamic cycle with improved heating/cooling efficiency can be generated. By applying the isostress cycles, an adiabatic temperature change of 30.2 K was measured, which is among the largest directly measured reproducible adiabatic temperature changes reported for any caloric material to date. Ultimately, this study intends to serve as a basis for establishing a uniform method for evaluating the elastocaloric effect in different materials that would allow for reliable and accurate one-to-one comparison of the reported results in the rapidly growing field of elastocalorics.

Sustainable Cooling in a Warming World: Technologies, Cultures, and Circularity

Cooling is fundamental to quality of life in a warming world, but its growth trajectory is leading to a substantial increase in energy use and greenhouse gas emissions. The world is currently locked into vapor-compression air conditioning as the aspirational means of staying cool, yet billions of people cannot access or afford this technology. Non–vapor compression technologies exist but have low Technological Readiness Levels. Important alternatives are passive cooling measures that reduce mechanical cooling requirements and often have long histories of local use. Equally, behavioral and cultural approaches to cooling play a vital role. Although policies for a circular economy for cooling, such as production and waste, recovery of refrigerants, and disposal of appliances, are in development, more efforts are needed across the cooling life cycle. This article discusses the knowledge base for sustainable cooling in the built environment and its significant, interconnected, and coordinated technical, social, economic, and policy approaches.

Experimental study on silica gel/ethanol adsorption characteristics for low-grade thermal driven adsorption refrigeration systems

• Silica gel/ethanol adsorption pair is promising for EVs and PV/T applications. • Ethanol is highly attracted to silica gel through chemical adsorption. • The silica gel/ethanol presents minor hysteresis owing to condensation. • The theoretical cyclic performance of silica gel/ethanol were calculated 0.97. There has been an increasing interest in adsorption cooling and heat pumps as the most feasible green alternative to the widespread vapor compression technology. Recent developments in adsorption cooling highlighted the need for cost-efficient adsorption pairs of advanced adsorption characteristics. In response, this article experimentally investigates and models silica gel/ethanol pair adsorption characteristics that can utilize low-temperature heat sources, such as those available in the emerging electric vehicles and PV/T systems. The investigated characteristics are the porous structure stability, isosteric heat of adsorption, adsorption diffusion energy, adsorption isotherm, and adsorption kinetic under extended operating conditions 15–55 °C. The results showed the high affinity of silica gel towards ethanol to provide sub-zero cooling. Silica gel showed no structure deterioration during the repetitive adsorption/desorption cycles of net 22 % cyclic ethanol uptake. The chemical adsorption of silica gel/ethanol showed a high level of adsorption/desorption reversibility with minimal hysteresis, which the Langmuir model best simulated. The heat of adsorption was determined to be 4.49 × 10 4 J/mol, which was higher than the diffusion energy of 1.80 × 10 4 J/mol due to the slow physical mobility of ethanol molecules inside silica gel pores. The Elovich kinetic model was the most suitable for simulating the chemical adsorption/desorption processes. The material level cyclic analysis showed the potential of 22 kJ/kg ads cooling effect and 0.97 coefficient of performance by utilizing a 55 °C heat source, widely available in PV/T systems and electric vehicles.

Experimental investigation of buckling stability of superelastic Ni-Ti tubes under cyclic compressive loading: Towards defining functionally stable tubes for elastocaloric cooling

Elastocaloric cooling technology recently attracted significant attention as an environmental friendly alternative to vapor-compression technology. It is based on the elastocaloric effect, which occurs in superelastic shape memory alloys (SMAs) during stress-induced martensitic transformation. To date, several proof-of-concept devices (mostly based on tensile loading) have been developed, but limited fatigue life was shown to be one of the major issues. Compressive loading improves the fatigue life of such devices significantly, but in return buckling of SMA structure might occur. To overcome this challenge, it is crucial to understand the buckling phenomena of SMA structures, especially for thin-walled tubes that seem to be ideal candidates for application in elastocaloric cooling devices. Here, we experimentally investigated the effects of the diameter-to-thickness ratio (Dout/t) and slenderness (λ) on buckling stability of Ni-Ti tubes that were subjected to cyclic compressive loading. In total, 161 superelastic Ni-Ti tubes with outer diameter (Dout) ranging from 2 mm to 3 mm, Dout/t ranging from 5 to 25 and gauge lengths (Lg) ranging from 6 to 20 mm were tested. The loading procedure consisted of 3 parts: (I) 1 isothermal full-transformation loading cycle, (II) 50 training cycles, and (III) 20 adiabatic cycles to simulate loading conditions in elastocaloric device. We constructed experimental phase diagrams of buckling modes in λ - Dout/t space for constant Dout and in λ - Dout space for constant Dout/t ratio. Marked areas of functionally stable tubes in these phase diagrams give the design guidance for future developments of durable and efficient elastocaloric devices and other applications, e.g. actuators and dampers.

Heat management and losses of electrocaloric cooling devices based on electrostatic thermal switches

Electrocaloric cooling is a promising technology that could replace existing vapor-compression technology with lighter and more efficient solid state based devices. Among those, electrocaloric coolers using electrostatic actuation are rising; therefore harnessing their advantages and understanding their shortcomings is still a work in progress. In this paper, we pin down two limitations that stem from a commonly used device design, and we propose a model that takes them into account. The first is due to the displacement of the film, which moves the air around and causes losses. We estimate the air losses through a Poiseuille flow model. The second is related to the non-ideal Brayton cycle the device performs and which results in generating a heat flow opposite to cooling. We estimated the effect of this back-flow on the cold flux using a 2D thermal diffusion model. Ultimately, our results point at several possible improvements for further designs. Among them, a slight reduction of the air pressure in the device looks as a promising solution to reduce air losses. • Air losses in an electrocaloric cooler using electrostatic actuation are modeled. • The heat transfer in the material and at the interface are simulated. • Increasing the cycling frequency of the cooler increases the cold power. • At high frequency, air losses prevent the device from working efficiently. • To achieve high cooling temperature span, the air losses should be mitigated.

Colossal barocaloric effects with ultralow hysteresis in two-dimensional metal–halide perovskites

Pressure-induced thermal changes in solids—barocaloric effects—can be used to drive cooling cycles that offer a promising alternative to traditional vapor-compression technologies. Efficient barocaloric cooling requires materials that undergo reversible phase transitions with large entropy changes, high sensitivity to hydrostatic pressure, and minimal hysteresis, the combination of which has been challenging to achieve in existing barocaloric materials. Here, we report a new mechanism for achieving colossal barocaloric effects that leverages the large volume and conformational entropy changes of hydrocarbon order–disorder transitions within the organic bilayers of select two-dimensional metal–halide perovskites. Significantly, we show how the confined nature of these order–disorder phase transitions and the synthetic tunability of layered perovskites can be leveraged to reduce phase transition hysteresis through careful control over the inorganic–organic interface. The combination of ultralow hysteresis and high pressure sensitivity leads to colossal reversible isothermal entropy changes (>200 J kg−1 K−1) at record-low pressures (<300 bar).

Screening of Cooling Technologies in Europe: Alternatives to Vapour Compression and Possible Market Developments

The aim of this study is to investigate, review, and assess the recent advances of alternative cooling technologies using traditional vapor compression (VC) systems as a baseline. Around 99% of the final energy consumption used for cooling in the current European market (European Union plus the United Kingdom (EU27 + UK) is supplied by VC technologies. In comparison, the remaining 1% is produced by thermally driven heat pumps (TDHPs). This study focuses on providing a complete taxonomy of cooling technologies. While the EU heating sector is broadly explored in scientific literature, a significant lack of data and information is present in the cooling sector. This study highlights technologies that can potentially compete and eventually replace VC systems within the decade (2030). Among others, the most promising of these are membrane heat pump, transcritical cycle, Reverse Brayton (Bell Coleman cycle), and absorption cooling. However, the latter mentioned technologies still need further research and development (R&amp;D) to become fully competitive with VC technologies. Notably, there are no alternative cooling technologies characterized by higher efficiency and less cost than VC technologies in the EU market.