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• The countercurrent hollow fiber membrane module is proposed for cold water generation. • A 3-D numerical model is developed accounting for irregular fiber filling. • Channeling effect and flow dead zones degrade the heat and moisture transport. • Irregular fiber filling increases the air side heat transfer resistance by >158 %. • Irregular fiber filling offers the potential to improve energy efficiency under certain conditions. The countercurrent hollow fiber membrane-based evaporative water cooler (MEWC) offers an eco-friendly and compact solution for cold water generation. This study introduces a random sequential addition algorithm to model the real-world irregular fiber filling within the MEWC. Inspired by the honeycomb structure, the developed 3-D numerical model adopts a calculation unit featuring a hexagonal prism comprising multiple fibers. Validation against experimental data reveals an average relative error of 2.81 % concerning outlet water temperature. The effects of fiber filling patterns (regular layout and random layout) on the velocity and temperature fields of the MEWC are investigated. Comparisons of outlet water temperature, cooling efficiency, consumptive electric power ratio, and heat and mass transfer resistance composition between these layouts under various operating conditions are conducted. The results indicate that the random layout fosters severe channeling effect and large flow dead zones, impairing air side heat and moisture transfer. The random layout exhibits over 15.9 % reduction in cooling efficiency and 36.3 % decrease in consumptive electric power ratio compared to the regular layout. Irregular fiber filling leads to a notable 158.6 % increase in air side heat transfer resistance and a 35.9 % rise in mass transfer resistance. Although irregular filling compromises the cooling performance, it demonstrates potential for energy savings under certain conditions. Design schemes should be carefully tailored to meet specific application requirements by considering these trade-offs. [ABSTRACT FROM AUTHOR]

Isobutane (R600a) is the most used refrigerant for low-capacity refrigeration systems, as it combines excellent environmental properties and offers good energy performance. A real possibility to increase the efficiency of these systems is using new refrigerant mixtures offering energy improvements (being compatible with existing systems). This work, from an experimental perspective, proposes mixtures of dimethyl ether and butane (RE170/R600) as potential drop-in refrigerants of R600a systems. For a given operating condition, the energy performance of RE170/R600 mixtures with maximum proportion of 27.5 % of RE170 has been tested using a water-to-water single-stage compression cycle, measuring COP increments from 10.1 to 17.6 % in relation to R600a. Then, the blend RE170/R600 (15/85 %), considered as the potential drop-in fluid of R600a, has been tested in a wide range of operating conditions, concluding that it offers the same cooling capacity than R600a but with COP increments from 12.6 % to 17.6 %. [ABSTRACT FROM AUTHOR]

Copyright of African & Mediterranean Journal of Architecture & Urbanism (AMJAU) is the property of Ecole Nationale d'Architecture and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Predicted power consumption and COP a chiller plant using XGBoost. • Quantified impacts of data intervals and data processing on the accuracy of models. • Improved the predictions compared to the baseline using data smoothing methods. • Demonstrated a guide to develop data-driven chiller power and COP models. In recent years, data-driven models have enabled accurate prediction of chiller power consumption and chiller coefficient of performance (COP). This study evaluates the usage of time series Extreme Gradient Boosting (XGBoost) models to predict chiller power consumption and chiller COP of a water-cooled chiller plant. The 10-second measured data used in this study are from the Intelligent Building Agents Laboratory (IBAL), which includes two water-cooled chillers. Preprocessing, data selection, noise analysis, and data smoothing methods influence the accuracy of these data-driven predictions. The data intervals were changed to 30 s, 60 s, and 180 s using down-sampling and averaging strategies to investigate the impact of data preprocessing methods and data resolutions on the accuracy of chiller COP and power consumption models. To overcome the effect of noise on the accuracy of the models of chiller power consumption and COP, two data smoothing methods, the moving average window strategy and the Savitzky-Golay (SG) filter, are applied. The results show that both methods improve the predictions compared to the baseline, with the SG filter slightly outperforming the moving average. Particularly, the mean absolute percentage error of the chiller COP and power consumption models improved from 4.8 to 4.9 for the baseline to 1.9 and 2.3 with the SG filter, respectively. Overall, this study provides a practical guide to developing XGBoost data-driven chiller power consumption and COP prediction models. [ABSTRACT FROM AUTHOR]

Spiral blast freezing is a common unit operation used in food processing facilities for rapidly freezing a variety of foodstuffs. The purpose of a blast freezer is to generate high velocity, low temperature air flow over food products being conveyed within refrigerated enclosures to accomplish the freezing process. However, air flow patterns observed within field operating blast freezers are often suboptimal, resulting in diminished system performance. This paper applies a Monte Carlo simulation technique to a food product freezing simulation in order to identify velocity profiles that optimize the freezing process. A one-dimensional food product model is used to evaluate the interplay between the time variation in the magnitude of the air velocity over food products conveyed through the freezing system and the resulting dwell time needed to achieve a target product core temperature at the blast freezer exit. Temporal heat transfer coefficients derived from field measurements made in a newly installed spiral blast freezer serve as a basis to calibrate the one-dimensional product model. The results of the Monte Carlo analysis show freezing system performance is improved when high and stable air velocities over the product are achieved early in the freezing process dwell time. Air flow patterns within a freezing system that result in high air velocity later in the freezing process dwell time are suboptimal. Field-measured data on a newly installed spiral blast freezer showed this suboptimal air flow pattern and the use of baffling within the spiral enables improved airflow leading to an estimated 10 % increase in production throughput. [ABSTRACT FROM AUTHOR]

• An enhanced ejector-subcooler CO 2 transcritical refrigeration cycle is presented. • A parametric analysis and optimization of the enhanced cycle and the baseline cycle are carried out. • The results suggest the integration of the proposed cycle could achieve more compact and reliable systems. • The maximum COP improvements are computed as 11.7%-17.5% when the gas cooler outlet temperature ranges from 35 °C to 50 °C and the evaporating temperature is -40 °C. The main drawback associated with CO 2 refrigeration systems is related to their performance reduction during transcritical operation at warm climate conditions, which may be compensated by better cycle architectures such as the split-cycle with subcooling or the flash-tank configuration, among others. Specifically, the use of standard gas-ejectors together with parallel compressors provides even better efficiency improvements, not being able to use them with low-temperature evaporators to prevent the triple point inside the ejector. This paper proposes an enhanced cycle with a gas ejector for two-stage compressor architectures with vapor injection from the flash-tank, which is able to operate at low evaporating temperatures and that provides a greater performance improvement the more severe the climate conditions are. The methodology conducted is based on a thermodynamic analysis that includes parametric evaluation and cycle optimization, comparing the results to a conventional CO 2 transcritical cycle with flash-tank and dynamic vapor injection architecture. The main results show that a maximum Coefficient of Performance improvement of 17.5% is achievable for transcritical operation at -40 °C evaporating temperature. The compressor displacement capacity required with the enhanced cycle is up to 9% lower for the same refrigeration demand, reducing the electrical consumption as well as the compressor expenditure. Moreover, greater vapor injection mass flow rates are obtained by the gas-ejector injection with discharge temperature reductions up to 18%, enhancing the system reliability. [ABSTRACT FROM AUTHOR]

• A novel variable stiffness valve based on PEEK and stainless steel was proposed. • Stress-strain behavior and operational characteristics of novel valve were studied. • Impacts of novel valve on compressor performance and noise experimentally. • Compressor performance improved by 2.6 % and noise reduced by 3–5 dB. Improving valve design is crucial for enhancing the performance of rolling piston type rotary compressor. A novel variable stiffness valve based on PEEK and stainless steel was proposed. The stress-strain behavior of the novel valve was studied, and its operational characteristics, including opening and closing angles and over-compression losses, were analyzed in a compressor. It is shown that opening and closing angle of the new-designed valve were advanced compared to that of the original cylinder by about 2∼3°, leading to a general reduction in over-compression losses, with a maximum decrease of 4.15 W. The impacts of new-designed valve on compressor performance were experimentally investigated. The cooling capacity and coefficient of performance of compressors equipped with new-designed compared to original valve were improved by 1.1–1.7 % and 1.1–2.6 %, respectively. In addition, the input electrical power required for the new valve was observed to be 0.9–1.3 % lower. The incorporation of high-damping material in the new valve design significantly reduced compressor noise by 3–5 dB at the critical frequency bands of 630–1250 Hz. These findings offer valuable insights for enhancing the energy efficiency and noise reduction in rolling piston type rotary compressors. [ABSTRACT FROM AUTHOR]

Résumé: De manière agrégée, les PME sont de grandes consommatrices d'énergie et ont des impacts environnementaux considérables au niveau mondial. Malgré cela, elles attirent encore peu l'attention des chercheurs et des responsables des politiques publiques. Pourtant, sans leur contribution, l'atteinte des cibles nationales en matière énergétique et environnementale est improbable. En ce sens, il devient essentiel de mieux comprendre ce qui les incite à devenir plus mature au niveau énergétique. La présente étude adopte une analyse multiniveau en considérant les aspects individuel, organisationnel, contextuel pour identifier les déterminants de la maturité énergétique des PME. Une étude menée auprès de 409 PME québécoises permet d'établir que ce sont les facteurs organisationnels intangibles qui sont les principaux déterminants de la maturité énergétique dans les PME québécoises. Les facteurs contextuels n'ont pas d'influence et un seul facteur individuel, l'âge du dirigeant, exerce une influence limitée. Cette reconnaissance de la prépondérance des facteurs organisationnels intangibles est un apport aux écrits sur le sujet qui ne font pas cette distinction lorsqu'ils considèrent les freins et accélérateurs des pratiques d'efficacité énergétique. Cela procure aussi un enseignement pratique important: l'acquisition de compétences et d'attitudes proactives dans les PME envers l'efficacité énergétique est un levier d'action à prioriser. In an aggregate manner, SMEs are very large consumers of energy and have significant environmental impacts worldwide. Nevertheless, they still attract little attention from researchers and public policymakers. Yet, without their contribution, the achievement of national energy and environmental targets is unlikely. In this sense, it becomes essential to better understand what motivates them to become more energetically mature. This study adopts a multi-level analysis that considers individual, organizational, contextual aspects to identify the determinants of SME energy maturity. A study of 409 Quebec SMEs shows that intangible organizational factors are determinants of energy maturity in Quebec SMEs. Contextual factors have no influence and only one individual factor, the age of the leader, has a limited influence. This recognition of the preponderance of intangible organizational factors is a contribution to the literature on the subject, which does not make this distinction when considering the obstacles and the accelerators of energy efficiency practices. It also provides an important practical lesson: the development of proactive skills and attitudes in SMEs towards energy efficiency is a lever of action to prioritize. [ABSTRACT FROM AUTHOR]

• A subcooler reduces the total mass flow rate for a given operation conditions. • Reduced evaporator superheat improves the evaporator heat transfer. • The coefficient of performance increases using a subcooling system. • Flash gas mass flow rate used to reduce the superheat at the compressor inlet. A new position of an internal heat exchanger within the thermodynamic cycle is proposed to improve the performance of CO 2 refrigeration systems in warm climates, specifically in supermarket applications. The proposed configuration uses the saturated vapor from the liquid receiver to recover the heat that is rejected by a subcooler positioned after the gas cooler. This system results in a reduced evaporator superheat. This configuration is compared with a reference system. The experimental study is conducted on a CO 2 laboratory cooling system reproducing a commercial plant. The cooling capacity of the system is 30 kW. The water inlet temperature in the gas cooler (hot source) varies from 15 °C to 35 °C, while the mono-ethylene glycol outlet temperature of the evaporator (cold source) is fixed at -8 °C. The setup is validated through an energy balance. Using a subcooler in this new position improves the coefficient of performance by 10.2 % under transcritical conditions and 6.3 % under subcritical conditions when compared with the reference system. [ABSTRACT FROM AUTHOR]

Separate sensible and latent cooling (SSLC) is a promising technology for enhancing the energy efficiency of space cooling systems. In this paper, we propose an SSLC configuration consisting of an indirect evaporative cooling (IEC) device and vapor compression cycle (VCC) for handling space sensible load, and a desiccant wheel for handling space latent load. The performance of the proposed configuration is investigated using physics-based or empirical models for each component. A year-round simulation study of the proposed SSLC system is performed for 12 different cities with diverse climatic conditions. This study considers electrical, thermal, or solar energy for desiccant wheel regeneration. Parameters governing the system performance such as the air flowrate ratio in the IEC and the DW, DW regeneration air temperature, and supply temperature are studied. The proposed SSLC configuration is superior to the conventional system in all cities. The enhancement of seasonal coefficient of performance (sCOP) ranges between 50 and 261 %, 67 and 387 %, and 60 and 2072 % with yearly electrical energy savings of 33 and 72 %, 40 and 79 %, and 38 and 95 % for electrical, thermal, and solar energy for regeneration of DW, respectively. [ABSTRACT FROM AUTHOR]

• Biogas energy assisted hybrid milk cooling system was experimentally investigated. • Energy consumption in the first and last milking is detected as 2.29 and 2.54 kWh. • Energy efficiency is 45.61% higher than conventional systems for the first milking. • It consumes 24.40% less energy than other hybrid systems for the last milking. Biogas energy assisted hybrid milk cooling system was investigated experimentally, in this study. The system operated in a cycle. Primarily, biogas was obtained from the residues of animals in the farm environment and an internal combustion gas engine is started with this gas. Then, the gas engine provided the power required for the compressor of the cooling system to operate. The main purpose of the study was to encounter the energy required for milk cooling only from the biomass potential of animal wastes and in this way, it was to bring a system with high energy efficiency for milk cooling process to the literature and industry. In experiments, 150 liters of milk in the first milking and 300 liters of milk in the last milking were cooled. It was determined that the energy consumption in the first and last milking is 2.29 kWh and 2.54 kWh. The results revealed that this developed system was 45.61% and 41.61% more advantageous for first and last milking, respectively, compared to conventional milk cooling systems in terms of energy consumption. When the system compared to other alternative energy source assisted milk cooling technologies with similar milk cooling capacity, It was observed that 14.55% and 24.40% more efficient with regards to energy consumption for the first and last milking. Additionally, experimental and Carnot COP values of the cooling system were determined as 4.29 and 8.26, respectively. These data revealed that the hybrid system had a higher performance of 38.4% compared to other milk cooling techniques. [ABSTRACT FROM AUTHOR]

• A novel CO 2 booster system for commercial refrigeration is presented. • The objective is to simplify ejector-supported booster systems keeping efficiency. • The system layout was experimentally validated and benchmarked. • Efficiency increased up to 40 % compared to conventional booster systems. • The novel configuration performed positively under all ambient conditions. The pernicious effects of synthetic refrigerants on different environmental aspects leave natural refrigerants as the only alternative for vapour compressions systems. Among natural refrigerants, CO 2 (R744) has become the preferred choice for commercial refrigeration at almost any location and climate. However, efficient R744 refrigeration systems for warm climates have a great level of complexity, implementing technologies such as mechanical subcooling or ejector that increase the investment costs. The goal of the novel hybrid configuration presented in this work is to simplify ejector-supported R744 commercial refrigeration systems while maintaining all the benefits of the ejector implementation in transcritical operation mode. Moreover, utilization of a low-pressure accumulator layout in the subcritical mode removes all the practical challenges related to the booster layout operating at low ambient temperatures. This solution is based on: (i) MT and LT compressor suction groups, (ii) non-superheated MT evaporation with increased evaporation temperature, and (iii) ejector utilization throughout the year. The ejector is actively operated as a high-pressure-control device at elevated ambient temperatures ('summer mode'), while it is passive and acts as a check-valve at lower ambient temperatures ('winter mode'). The experimental campaign performed proved that this novel system configuration is more energy efficient than booster systems with parallel compressors at any condition, improving the COP by around 40 % at the most extreme gas cooler outlet temperatures tested, i.e., 40 °C (summer mode) and 10 °C (winter mode). [ABSTRACT FROM AUTHOR]

This paper presents the design and application of a virtual sensor used in case of failure of the main physical sensor for temperature readings in automotive air conditioning. Using auxiliary temperature and pressure physical sensors combined with Support Vector Machine (SVM) Regression, the model of the virtual sensor is derived and prepared to be used as a redundant sensor until the broken physical sensor maintenance. Thus, enabling the system to operate continuously and maintaining its original power and thermal comfort features until the physical sensor replacement. In total, 32 h of training and test data involving different environmental conditions were used to generate the model that was further integrated. The designed virtual sensor presented a Mean Square Error (MSE) of 1 , 3 o C , a Mean Absolute Percentage Error (MAPE) of 3 , 6 % , and a Pearson Correlation Coefficient of 0,90. The results enabled the continuous and autonomous operation of the air conditioning plant respecting the designed thermal comfort guidelines even when under the physical sensor failure condition. [ABSTRACT FROM AUTHOR]

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Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A l’heure actuelle, le réchauffement climatique est devenu une problématique planétaire et une urgence incontestable à laquelle ondevrait impérativement y faire face. En effet, ce phénomène s’avère comme un enjeu majeur du développement durable. Car ses impacts ne se limitent pas seulement à des questions environnementales ; mais il pourrait entrainer de graves conséquences socio-économiques. Dès lors, une réflexion s’impose sur les actions à entreprendre afin de réduire la consommation énergétique et ainsi limiter les émissions de Gaz à Effet de Serre responsables du réchauffement climatique. Ceci nous rappelle la nécessaire mutation du secteur du bâtiment, notamment en matière d’habitat, étant donné qu’il est considéré comme premier consommateur d’énergie. Il serait donc temps de changer notre regard vers des habitats préconisant l’efficacité énergétique. De ce fait, l’objectif de cet article est d’évaluer l’impact de l’inertie thermique de l’enveloppe architecturale sur la consommation énergétique du bâtiment ; afin de contribuer au développement de solutions passives permettant de concevoir des bâtiments moins énergivores et plus durables. Pour ce faire, nous adoptons une approche analytique in vitro à travers une simulation numérique du bilan énergétique d’un prototype de bâtiment résidentiel de type collectif dans un climat méditerranéen à la ville de Constantine, et ce, à l’aide du logiciel TRNSYS. Les résultats de cette étude ont montré que le renforcement de l’inertie thermique, en l’occurrence, grâce à l’usage de la brique de terre cuite et du liège, a permis une réduction notable des besoins énergétiques ; permettant ainsi de consommer 84 % d’énergie en moins qu’un logement conventionnel contre un surcoût d’investissement de seulement 2 % compensé par une réduction conséquente des dépenses de fonctionnement.

• Main refrigeration systems in fishing vessels are based on R-22 and R-717. • There are significant developments in R-744 refrigeration systems. • The number of R-744 refrigeration units in fishing vessels has been increasing. • There is a lack of scientific efforts/studies on R-744 systems in fishing vessels. Globally, most fishing vessels still use the ozone-depleting and climate-harmful R-22 in their freezing and refrigerated seawater (RSW) systems. However, in some regions, the natural refrigerant ammonia is the preferred refrigerant. Another natural refrigerant, carbon dioxide (R-744), is becoming a viable option and is increasingly used onboard. This option will not exclude ammonia, but rather will be a good alternative to it to meet the demand for different cooling/freezing needs in post-R-22 systems. There are currently major developments in R-744 refrigeration technology that are widening the potential applications of R-744. These include compressors with larger capacities, more energy-efficient components, system designs with lower freezing temperatures and integration of heat recovery and thermal storage. This paper provides a review of the development of refrigeration systems with R-744 onboard fishing vessels. It includes a description of the commonly used cooling and freezing methods and of the development in R-744 refrigeration technology, especially within the system and component design, capacity and performance. It also includes the current status of R-744 refrigeration technologies in fishing vessels. Although there are limited publications on R-744 systems for fishing vessel applications, the review shows positive prospects of utilizing R-744 and further research and innovation within this topic is recommended. [ABSTRACT FROM AUTHOR]

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• We investigate R290/R600a mixtures in Vapor Compression Refrigeration System. • We present a test stand for household refrigerator compressors with small capacity. • We investigate the effect of compression ratio on the COP. • The optimum compressor speed is found close to 2100 rpm. • COP gain relative to R600a reaches up to 15 % using 60 % R290 mass weight in mixture. • 60 % of R290 mass weight exhibits a better volumetric and isentropic efficiency. This paper presents an experimental investigation of the effect of R290/R600a refrigerant mixtures on the performance of variable speed hermetic compressors used in household refrigeration. In this context, a small-capacity compressor test stand is introduced and four different compositions of R290/R600a mixtures are studied in detail. R290 composition in the refrigerant mixture varies between 40–70 % by mass weight. Performance outcomes of the mixtures are compared to baseline refrigerant R600a. The influence of R290 composition in refrigerant mixture over COP, refrigerant mass flow rate and power consumption rates are explored in the present study. Moreover, the effect of compressor speed, evaporation and condensation temperature on the compressor performance are studied via steady-state experimental tests. It has been concluded that increasing the mass weight of R290 in the mixture yields higher power consumption rates, yet it has brought a significant increase in the refrigerant mass flow rate, thus enabling a higher COP. The optimum compressor speed is found to be approximately 2100 rpm for the tested hermetic reciprocating compressor. The COP increases with the increments of evaporation temperature and decrements of the condensation temperature. The COP of the refrigeration cycle is 10–20 % greater than that of R600a depending on the composition of the refrigerant mixtures and operating conditions. [ABSTRACT FROM AUTHOR]

Access to energy is a key factor in the economic development of countries. We will first examine the evolution of different ways to access to energy and their correlations with world population and countries’ GDP. We will see that the objectives of reducing carbon dioxide emissions which require a profound transformation of our access to energy will be very difficult to achieve. We will also see that the thermal improvement of buildings, and in particular the renovation of existing housing, is one of the possible objective.

The combination of an ORC (Organic Rankine Cycle) with a VCC (Vapor Compression Cycle) is studied analytically. In this work, the two cycles use the same fluid and operate with a common condenser. Elementary transformations of the fluid between two consecutive points of the system are calculated using a one-dimensional thermodynamic approach considering real fluid properties, the pressure losses and irreversibilities present in the compressor, in the expander and in the pump. The performances and the recommended inlet and outlet diameters of the expander and the compressor are established for various operating conditions and 12 fluids. The system can produce a typical useful cooling capacity of 0.60 kW at 5.5 °C when using a 2 kW heating source at 65 °C and when the condenser temperature is 30 °C. The cooling capacity reaches 1.0 kW if the cold source temperature is 15.5 °C. Results show the required diameters ratios at inputs and outputs of the compressor and the expander. They indicate the situations for which the compressor is smaller than the expander and vice versa. They identify the particular cases in which the compressor and the expander have exactly the same inlet and outlet diameters. This particular case allows using two identical compressors, one working as a compressor, the second as an expander. [ABSTRACT FROM AUTHOR]

• Refrigerator modeling • Incremental capital and recurring cost of alternative designs • Energy efficient refrigerator design options • Energy efficiency – cost tradeoff • Lifecyle emissions reduction Domestic refrigeration appliances are ubiquitous consuming roughly 14% of the global residential electrical consumption. It is estimated that the global installed stock of domestic refrigerators is between 2 and 2.3 billion units. Furthermore, domestic refrigerators employ high global warming potential (GWP) refrigerants (e.g., R-134a). The global goal to limit the global warming to 1.5°C requires rapid reduction in CO 2 emissions and other greenhouse gases (GHGs). Transition towards cost-effective, efficient, and environmentally friendly refrigeration technologies is considered as one of the most effective measures to reduce GHG emissions. In this paper, we worked with 5 manufacturers in 4 developing countries to study energy efficiency (EE) design options and the associated incremental capital cost and incremental recurring cost (IRC). In our study, we have accounted for their product development capabilities, their productions volume, their relationship with original equipment manufacturers (OEMs), and the local product competition in their markets. Our detailed study showed that cost effective energy savings of 9.5 to 19.2% can be achieved while the maximum EE upgrades varied between 30.2 to 50%. Furthermore, the corresponding indirect emissions reduction varied by the local electricity production mix and the baseline technology. The cost-effective EE upgrades result in emission reduction of 65,145 to 612,959 metric tons of CO 2eq while the maximum EE upgrades result in emission reduction of 157,675 to 1,077,005 metric tons of CO 2eq. [ABSTRACT FROM AUTHOR]

Le secteur énergétique en Algérie a subi d'énormes transformations au cours des deux dernières décennies. L'un des changements majeurs qui ont été opéré est lié, particulièrement, à l'introduction des technologies de l'information et de la communication (TICs) dans la maitrise de la consommation énergétique. Parmi les réalisations les plus récentes, un projet pilote relatif à l’introduction de smart meters a été lancé dans le secteur résidentiel à Diar El Bahri situé dans la wilaya de Blida, à 47 km au sud-ouest de la capitale d’Algérie, Alger. Il s’agit de la première expérience en la matière dans le pays, marquant ainsi une étape majeure vers le développement de la Smart Grid. Malgré la volonté de mise en place d’un cadre communicationnel bidirectionnel de la maitrise de la consommation énergétique, le projet en question, qui était initialement programmé pour une période de (02) deux ans, n’a duré que (06) six mois. Par ailleurs, le nombre de foyers qui étaient censés bénéficier d’un raccordement aux smart meters n’a pas été respecté. L’objectif de cette recherche est de comprendre précisément le processus de mise en place dudit dispositif. Il s’agit d’effectuer une première évaluation, jamais conduite auparavant, de l’expérience Algérienne en matière de recours aux technologies de l’information et de la communication dans le cadre de la modernisation de la gestion et de maitrise énergétique. Cet article fait partie d'une recherche originale plus large qui vise à explorer les différentes voies à travers lesquelles les TICs peuvent être développées dans le secteur de l’habitat en Algérie de manière à accroître l'efficacité énergétique et créer des territoires numériques.

• EAHE system is combined with AHU to reduce the compressor power and annual cost. • Analytical model is built to evaluate the effect of different geometry parameters. • Optimum diameter is found to be 0.35 m and length depends on the number of pipes. • Maximum power saving is 44%, and the maximum cost reduction is 16.6%. • Payback period is ranged from 0.35–9.3 years depending on the number of pipes. This paper presents a thorough parametric analysis of an earth-air heat exchanger (EAHE) that reveals optimal parameters for minimizing the cost of central air conditioning in a hot and dry climate. A mathematical model with the aid of MATLAB is developed to optimize different parameters including length, diameter, and number of pipes. The performance of the selected cooling system is evaluated in terms of compressor power consumption, overall power savings, overall cost reduction, and payback period. As a case study for our analysis, a 25-TR air-conditioning system was chosen to cool an operation room in a hospital in Egypt. The maximum reduction in compressor power consumption is estimated to be 44%. Moreover, the reduction in the annual costs is estimated to be 16.6% with a payback period that increases as the number of pipes increases. [ABSTRACT FROM AUTHOR]

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Les progrès technologiques et les progrès techniques qui se développent constamment et rapidement ont eu un impact considérable sur la pratique de l’architecture dans le monde entier. Les architectes disposent désormais d'une large palette technique leur permettant une plus grande gamme d'expression utilisant des structures complexes avec des technologies de construction et des matériaux de pointe. Cette situation a conduit à produire des constructions spectaculaires et des bâtiments singuliers qui deviennent des "icônes" de l'architecture. Néanmoins, la question du développement durable et de l’efficacité énergétique s’impose aujourd’hui, comme une priorité à laquelle s’inscrivent également les architectures singulières. Cette question implique aussi le bâtiment singulier dans son interaction avec son milieu urbain. Le présent article traite de la conception d’un édifice au travers la combinaison des trois notions regroupées dans sa conception à savoir, la singularité de son architecture, le rapport à son milieu et son efficacité énergétique. Le choix s’est porté sur l’analyse de la tour Casablanca Finance City (CFC) du fait de la singularité de son architecture par rapport à son milieu et à son efficacité énergétique supposée. Une approche conceptuelle liée au paysage urbain et à l’environnement de la tour a été élaborée dans le cadre de l’analyse du site étudié par Morphosis Architects. Des outils de modélisation tridimensionnelle et de simulation thermique dynamique de quelques modèles de la tour, proposés par application de mesures d’efficacité énergétique, ont permis d’optimiser la consommation énergétique de la tour avec une réduction importante par rapport au modèle de référence, et assurer ainsi le confort des usagers d’ambiances intérieures de la tour.

Scientists advise limiting global warming to 1.5°C with substantial actions by 2030. Our viewpoint argues that climate response strategies in Canada have underemphasized and underestimated the potential contribution deep energy retrofits can make to greenhouse gas (GHG) emissions reductions, leading to inadequate responses in the building sector, and that Canada can (and should) be ambitious with building retrofits over the next decade. GHG savings from building retrofits can be realized more quickly than GHG reductions from other sectors, and either deliver net cost savings or are cost‐effective when compared to other mitigation measures. Retrofits can also provide social and economic benefits, such as improved health and comfort, and lower energy costs. This paper reviews energy use and building retrofits in Canada and argues the following should be implemented: (1) focus innovation on deep energy retrofit processes, not singular retrofit actions; (2) maximize both social and environmental benefits; (3) improve data gathering and availability for analysis and delivery; (4) innovate for a process of decisions and to avoid "dropouts" during the retrofit process; and (5) focus innovation on business models that maximize benefits. Key Messages: Greenhouse gas savings from deep energy building retrofits are cost‐effective and can be realized more quickly than reductions from other sectors.Program and policy design should prioritize the greatest social, economic, and environmental benefits.Innovation should focus on the retrofit process, financing, and delivery models, rather than solely on technology. [ABSTRACT FROM AUTHOR]

The energy sector in Algeria has undergone enormous transformations over the last couple of decades. One of the major changes that have taken place is related to the introduction of information and communication technologies (ICTs) in the control of energy consumption. In this regard, a pilot project of Smart Meters has been introduced in the residential sector in Diar El Bahri, which is located in the wilaya of Blida, at about 47 km southwest of the capital of Algeria, Algiers. This is the first experience in the country. Despite the will to set up a bidirectional communication framework for the control of energy consumption, the project, which was initially expected to last for a period of two (02) years, was carried, in fact, for only six (06) months. Besides, the number of households that were supposed to be connected to Smart Meters was not respected. The objective of this research is to understand precisely the process of setting up this system. The project is the first Algerian experience in terms of use of ICTs for the purpose of modernising energy management and control. The study aims to understand the reasons why the objectives that were initially set for the project were not reached. This paper is part of a larger original research project, which aspires to explore the different ways in which ICTs can be developed in the housing sector in Algeria in order to increase energy efficiency and create digital territories. [ABSTRACT FROM AUTHOR]

• The dynamic behavior of an adjustable jet-ejector refrigeration system is assessed. • A thermal storage system is considered to cope with variable solar irradiation. • The influence of two different jet-ejector architectures is evaluated using R1234yf. • The transient response is computed under real climatic conditions. In the present paper, the mid-term performance of two different architectures of a solar-driven jet-ejector refrigeration system is numerically compared: the first one is fitted with a fixed-geometry jet-ejector while the second one is equipped with an adjustable spindle that modifies the jet-ejector area ratio. The jet-ejector behavior has been predicted with a validated computational fluid dynamics approach and the dynamic response of the overall system accounts for transient effects in a small parabolic trough collector and a hot thermal storage tank. The investigation shows that the adjustable jet-ejector allows for continuous and smooth operation in a much wider range of outdoor conditions. Additionally, it enables more efficient management of the thermal level in the hot storage system. As a result, the adjustable refrigeration system improves the performance indicators in all the warm months of the typical meteorological year under evaluation. The maximum improvement potential is found in May; the fixed-geometry system provides an average C O P th of 0.34 while the adjustable system reaches an average C O P th of 0.48 considering the same boundary conditions in both cases. [ABSTRACT FROM AUTHOR]

Le présent travail vise à évaluer la quantité d’énergie électrique qui peut potentiellement être économisée dans le secteur du bâtiment au Niger. Le cas du site de l’Institut Universitaire de Technologie de l’Université Dan Dicko Dankoulodo a été étudié. Le site a été réparti en six blocs et les appareils électriques en cinq (05) postes de consommation. Les puissances nominales et les temps d’utilisation de l’ensemble des équipements électriques ont permis d’estimer la consommation électrique par blocs et par poste de consommation. Le profil de la consommation électrique montre une forte consommation en période de chaleur, mais aussi en période de forte activité (avril et mai). La faible différence entre la consommation totale obtenue à base des factures électriques et celle estimée a montré la fiabilité des données collectés sur le site. L’éclairage et la climatisation (climatiseurs et ventilateurs) représentent les postes de plus grandes consommation avec 40 % et 32 % respectivement. Une baisse de 31 % de la consommation totale d’énergie électrique a été estimée suite aux différentes propositions d’amélioration des performances des équipements électrique. Cette importante baisse de la consommation est due principalement à la proposition d’un système d’éclairage efficace à base des lampes LED. Les propositions de climatiseurs adaptés et efficaces et des ventilateurs moins énergivore sont également concernée. Ceci démontre la nécessité pour le Niger d’élaborer et d’appliquer une politique d’efficacité énergétique dans le secteur du Bâtiment.

The prerequisite for the exploration and exploitation of natural gas hydrate (NGH) is ensuring that the hydrate sample does not decompose during the sampling process. In order to solve this problem, the hole-bottom freezing sampling technique (HBFS) method was proposed, which uses a cold-alcohol to reduce the temperature of the hydrate sample and prevent its decomposition. However, the low heat exchange between the cold-alcohol and the hydrate sample results in a large loss of energy, and the sample cannot be frozen to the required temperature due to the size limitations of the sampler. In this study, three different heat transfer modes were used to increase the energy efficiency, namely heat conduction (cold-alcohol), phase change heat transfer (liquid nitrogen), phase change convection (alcohol-dry ice mixture). The test results show that the freezing efficiency of the alcohol and dry-ice mixture is 11.38%, which is the highest. The alcohol-dry ice mixture can cool the average temperature of the sample from approximately -17.81 to -23.37 °C, in which the hydrate sample does not decompose rapidly under normal pressure. The alcohol–dry ice mixture is more suitable as a coolant for the HBFS. [ABSTRACT FROM AUTHOR]

• Ejector and parallel compression configurations are proposed for high temperature heat pumps. • Internal heat exchanger analysis is included in the proposed configurations. • Alternative sustainable refrigerant assessment is performed to replace HFC-245fa. • Multi-objective analysis evaluates the compromise between volumetric heating capacity and COP. • Advanced high temperature heat pump configurations are promoted. Climate change evolution urges us to take action to reduce greenhouse gas emissions. As one of the main contributors, the industrial sector requires cleaner methods of heat production, such as high temperature heat pumps (HTHP) with the highest energy efficiency. Facing this challenge, this paper provides a performance comparison of the ejector and economizer with parallel compression configurations in HTHPs for low-grade waste heat recovery. A single-stage cycle has been used as a reference configuration to compare the proposed options. The internal heat exchanger (IHX) is included in all the configurations to extend the analysis and illustrate the influence of this component in high temperature applications. Moreover, alternative low-GWP refrigerants have been analyzed in order to replace the reference working fluid HFC-245fa. Ejector and economizer with parallel compression configurations with IHX provide a coefficient of performance (COP) improvement of up to 36% and 72.5%, respectively, using HFC-245fa for a heating temperature production of 140 °C. Moreover, the volumetric heating capacity (VHC) increases around 36% for the ejector cycle and 80% for the economizer with parallel compression cycle with IHX. HC-601, HFO-1336mzz(Z), and R-514 have the most significant COP improvement compared to HFC-245fa, along with the highest VHC drop. Multi-objective evaluation illustrates that single-stage and ejector configurations with IHX have similar results, whereas the economizer with parallel compression cycle with IHX presents a significant COP and VHC improvement. HCFO-1233zd(E) and HCFO-1224yd(Z) presents the proper trade-off between COP and VHC. [ABSTRACT FROM AUTHOR]

• Dehumidifier with PEM is suitable for the humidity control in refrigerators. • Performance of PEM dehumidifier under -10~10°C conditions was experimentally investigated. • The dehumidifier has a starting voltage, which is higher at lower air temperatures. • With the increase in applied voltage, the operating current first increases and then drops. • Performance changing rate with operating parameters is much lower under sub-zero temperatures, due to possible icing and swelling inside the membrane. • The low temperature performance is not as good as normal, but the efficiency is still competitive. Dehumidifier with Polymer electrolyte membrane (PEM) is suitable for high-accuracy, limited-space humidity control in refrigerators. This study experimentally investigated the performance of PEM-based dehumidifier under the temperature range of -10~10°C. Empirical equations of PEM water content at refrigerator temperatures were developed. Results showed that although the low-temperature performance of electrolytic dehumidifier is not as good as that of room temperature, the efficiency (~1.3 × 10−2 g·J−1·m−2) is still competitive to desiccant or electrochemical methods. The dehumidifier has a starting voltage, and the voltage is higher at lower air temperatures (i.e. 1.3V for 26.1°C and 2.3 V for -3.9°C). During dehumidification, the operating current first increases significantly and then drops as the applied voltage increases, leading to a first increase and then steady dehumidification rate. The peak of current occurs at a smaller voltage as the air temperature decreases, i.e. 1.8V for 0°C and 2.5V for 26°C. Furthermore, the dehumidification rate increases as the air temperature and flow rate increases, while the changing rate with operating conditions was lower at sub-zero temperatures. Dehumidification has little effect on the oxygen concentration or temperature increment of the supply air. Characterizations also indicated that there was no obvious physical change on the PEM surface after operating at low temperatures. However, there exists a starting temperature for the dehumidifier, i.e. -9.5°C for the 3V applied voltage, which is due to the possible icing and swelling problem within the membrane. This study provided a new method, and proved its feasibility for dehumidifying at refrigerator temperatures. [ABSTRACT FROM AUTHOR]

• A novel GEHP facility for cooling and domestic hot water is developed. • A novel condenser and three thermostatic expansion valves are used in the system. • The novel GEHP facility is able to maintain expected high performance. Heat pump technologies have been widely used in air conditioning and hot water application. However, most of the heat pump systems adopt an expansion valve to complete the cooling and heating modes currently. The flaw is that as the four-way valve is switched, the expansion valve cannot be guaranteed to be very close to the inlet of the evaporator in both modes, making the performance of the cooling or heating mode worse. In addition, for gas-engine-driven heat pump (GEHP), the utilization of engine waste heat is insufficient. Based on the above two shortcomings, a novel GEHP unit with an advanced finned tube heat exchanger and three thermostatic expansion valves was built in this work. The performance was evaluated under an experimental operating range of engine speed from 1300 rpm to 2000 rpm, air temperature from 23.8°C to 27.7°C, and evaporator water inlet temperature from 13.2°C to 22.4°C. Experimental results showed that when the engine speed and ambient temperature increased, the compression ratio increased, whereas the coefficient of performance (COP), primary energy ratio with heat recovery (PER 1), and primary energy ratio without heat recovery (PER 2) of the system decreased linearly. As the evaporator water inlet temperature increased from 13.2°C to 22.4°C, the COP, PER 1 , and PER 2 had an improvement of 23.6%, 20.8%, and 27.6%, respectively. The averages of COP, PER 1 and PER 2 were 3.67, 1.57 and 0.96, respectively. The results indicated that the novel GEHP unit was able to maintain expected high performance. [ABSTRACT FROM AUTHOR]

Ammonia is a high energy efficiency refrigerant with wide-ranging utilization in industry. It is a natural refrigerant that causes no ozone depletion or global warming. The refrigerated warehouse industry has been dealing with a difficult and growing challenge due to thousands of pounds of ammonia contained within their facilities. Since ammonia is toxic and flammable in large concentrations, it is subject to numerous federal, state and local safety regulations. The current work evaluates a distributed ultra-low ammonia charge (ULC) refrigeration package that greatly reduces ammonia quantity in comparison to centralized engine room system typical in existing facilities. Using closed coupled components in a compact refrigeration package, and electronic refrigerant injection control technology, facility ammonia charge is reduced by more than 98%, and worst case release scenario reduced to less than a hundred pounds. This evaluation compares initial costs, energy efficiency, water usage, operating and maintenance costs of ULC configuration against equivalent central engine room baseline. The analysis is based on typical medium sized industrial cold storage warehouse in Sacramento, CA with freezer, cooler and dock areas. The ULC configuration shows 7% reduction in energy (kWh) and 3% reduction in water (Gal) usage. The reduction in energy and water costs, combined with other operational and maintenance related savings show that investment in ULC technology will provide a payback within 3 years. The study demonstrates ULC systems as a promising replacement technology for industrial warehouse refrigeration in terms of overall cost of ownership, human safety and environmental benefits. [ABSTRACT FROM AUTHOR]

• Current state of expanders in vapour compression refrigeration systems is reviewed. • The highest reported COP improvement in a transcritical CO 2 refrigeration system was 30%. • The highest reported COP improvement in a conventional refrigeration system was 10%. • The highest measured expander efficiency was 83%. • Knowledge gaps and challenges are identified. • Recommendations for future work are provided. This paper reviews progress reported in the open literature of the use of expanders to recover expansion power to improve the energy efficiency of vapour compression refrigeration systems. Pioneering works in the field are first discussed, and then a variety of expander mechanisms, including reciprocating piston, rolling piston, rotary vane, scroll, screw and turbine are reviewed together with their reported performance. Most of the reported works have been for transcritical CO 2 refrigeration systems, which have reported improvements in the coefficient of performance (COP) of up to 30%. In a non-CO 2 system, the maximum reported increase in the COP was 10%. The maximum reported expander efficiency (i.e. the ratio of measured power to the power available from an isentropic expansion) was 83%, obtained with a scroll expander in a CO 2 refrigeration cycle. Other expander issues including heat transfer, expansion process, internal leakage, irreversibility, control strategies, installation issues and economic analysis are also reviewed. It is noted that there are a limited number of studies in these areas. Finally, challenges and recommendations for future research in the area of refrigeration expander technology is presented. [ABSTRACT FROM AUTHOR]

• Coggins and modified coordinate descent algorithms are presented for optimization. • The optimization of mixed fluid cascade LNG process is successfully performed. • Exergy analysis is performed successfully. • The overall exergy loss is minimized to 35.91% with 25.4% energy savings. • LNG can be produced on the expense of 0.2197 kWh/kg. The mixed fluid cascade (MFC) process is considered one of the most promising candidates for producing liquefied natural gas (LNG) at onshore sites, mainly owing to its high capacity and relatively high potential energy efficiency. The MFC process involves three refrigeration cycles for natural gas precooling, liquefaction, and subcooling, making its operation more complex and sensitive. Each refrigeration cycle consists of a different mixed refrigerant, which must be optimized to change feed and ambient conditions to operate efficiently. Any sub-optimal solution can lead to high exergy losses, ultimately reducing the process energy efficiency. Operating optimally is a challenging task, mainly owing to the non-linear interactions between the constrained decision (design) variables and complex thermodynamics involved in MFC refrigeration cycles. In this context, we employ a multivariate Coggins step-up approach to reduce the exergy losses associated with the MFC process. This study reveals that the overall exergy losses can be minimized to 35.91%; resulting in 25.4% overall energy savings compared to sub-optimal MFC processes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Integrated hybrid system combining CO 2 vapour compression cycle and adsorption chiller. • Efficient low temperature refrigeration using natural refrigerants only. • Dynamic optimisation of design and control to achieve maximum efficiency. • Energy savings up to 35% at high ambient temperatures and annual energy savings up to 22%. Sustainable refrigeration systems are of great importance to reduce greenhouse gas emissions. In particular, CO 2 vapour compression cycles are very promising due to their environmentally friendly, natural refrigerant. However, a major challenge for implementing CO 2 cycles is the low efficiency at high ambient temperatures resulting from high exergy losses in transcritical operation. To increase the efficiency, we present a hybrid system concept integrating an adsorption chiller into the CO 2 cycle. The adsorption chiller employs the natural refrigerant water and is driven by waste heat from the CO 2 cycle. The additional cooling generated by the adsorption chiller is integrated into the CO 2 cycle to increase the efficiency of the overall hybrid system. Compared to a stand-alone CO 2 cycle, we show by dynamic modelling and optimisation that the hybrid system leads to annual energy savings of 22% for a warm climate in Athens and of 16% for a moderate climate in Cologne. The results highlight the high potential of the hybrid system concept to efficiently provide refrigeration using environmentally friendly refrigerants. [ABSTRACT FROM AUTHOR]

Highlight • Our developing numerical simulation model can reproduce static and dynamic characteristics of variable refrigerant flow (VRF) systems precisely. • Our simulation model can be estimated dynamic characteristics quantitatively and can be analyzed the cause of response time difference of manipulated variables. • Interference from mutual indoor units affects the supply air temperature and superheating temperature largely, in case of manipulated each expansion valves especially. • This simulation results is expected to be applied to another VRF systems. Abstract In commercial and office buildings, it has recently become popular to install variable refrigerant flow (VRF) compression-type heat pump systems. In particular, VRF systems with multiple indoor units are being installed in large buildings because such systems have large adjustment capacity. On the other hand, because users of VRF systems can freely choose the number of indoor units to install and can turn indoor units on and off independently, operating conditions are not predictable and it is difficult to find adequate control parameters under wide changes in load. With this background, we are developing a new numerical simulation model based on the laws of physics. Because this model can easily add and delete system elements, we believe that it will be useful for VRF system analysis. In this study, we utilize a numerical simulation model to evaluate both steady and unsteady conditions in VRF systems. In this paper, we focus on the connection between manipulated variables (the expansion valve's open pulse and fan rotational speed) and controlled variables (supply air temperature and the degree of superheating at the evaporator outlet). Moreover, we compare the difference between the performance of a single indoor unit and that of multiple indoor units operating simultaneously. As a result, we can evaluate the dynamic characteristics of manipulated variables and the effect of changing the number of active indoor units, each of which has their own VRF characteristics. [ABSTRACT FROM AUTHOR]

Highlights • 2D numerical model of a device with an active electrocaloric regenerator is presented. • Material hysteresis greatly impacts the efficiency of the cooling device. • A system for energy recovery can increase the device efficiency by ten times. • The electrocaloric cooling device has a maximum specific cooling power of 16 W kg−1. Abstract This paper reports on the research and development of a cooling device with an active electrocaloric regenerator (AER) based on the bulk ceramic material (1-x)Pb(Mg 1/3 Nb 2/3)O 3 –xPbTiO 3 (PMN-100xPT). For the purposes of the study a 2D transient numerical model of the AER was developed. This model makes it possible to investigate the cooling characteristics of a device with an AER while considering the effect of the hysteresis of the electrocaloric material and the effect of the electric-energy recovery related to the polarization/depolarization process. The results of the numerical analyses show that the degree of electric energy recovery has a major impact on the efficiency of the device. By considering an idealised system for electric-energy recovery the energy efficiency (expressed by the coefficient of performance) of the device could be increased by up to ten times. A validation of the numerical model was performed through the design, construction and experiments on an improved AER cooling device. The results revealed a maximum specific cooling power of 16 W kg−1 and a maximum temperature span of 3.1 K for the new device. [ABSTRACT FROM AUTHOR]

Copyright of Matériaux et Techniques is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)