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Population growth, coupled with industrial and agricultural development, has resulted in increased demand for freshwater supply. For countries with scarce water resources, desalination constitutes the only viable solution to this problem. Reverse osmosis (RO) technology has become widely used as the membrane materials have been upgraded and the costs have been reduced. Nowadays, RO is the foremost technology for desalting different types of water such as seawater, brackish, and tap water. However, its design is critical since many parameters are involved in obtaining a good design. The high use of RO encourages the establishment of a procedure that facilitates the design process and helps in obtaining an optimum-performance RO desalination system. This paper presents a procedure divided into three parts: (1) classifying RO parameters; (2) choosing the parameters in a certain order and doing the calculation process through 12 steps; and (3) then inserting the selected parameters and the obtained values on RO System Analysis (ROSA) software. These points are then summarized by creating an algorithmic chart to follow during the design phase of the RO system using ROSA. An example on the proposed list is then taken to validate the procedure, and a comparison is conducted on choosing different values for the parameters. The results of this comparative study show that choosing different parameters affects the RO system productivity. Additionally, every design has a specific optimum set of parameters, which depends upon the design constraints set by the user.

The aim of this study is to combine renewable energy sources with heat pumps so that the usage of electricity needed to operate heat pumps is minimized along with associated fuel combustion. The aforementioned objective leads to reduce the energy consumption, the operational cost and the environmental impact of the heat pump. To minimize the usage of electricity, it is proposed that the heat pump (HP) system is combined by two renewable energy systems, a Solar Air Heater (SAH) and a Geothermal Well Water (G). To enrich this study, five prospective combinations of Heat Pump (HP), Solar Air Heater (SAH) placed Upstream (U) and Downstream (D) of the condenser, and Geothermal Water Well (G) were investigated. Hereafter, these five combinations are referred as HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D. The thermal modeling of the aforementioned combinations in addition to baseline HP were developed and examined using an in-house computational code. To ensure that the input data used in the computational code are reliable, experiments were conducted to validate that the geothermal water temperature is higher than the ambient temperature in winter, in addition to confirming the analytical thermal modeling of the solar air heater. Numerical analyses and associated parametric studies revealed that the combination of Solar Air Heater (SAH) and a Geothermal Well Water (G) can efficiently increase the performance of the system by reducing the power needed to operate the compressor of HP. The gain in COP was found to be 48, 43, 81, 105 and 191 % for HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D respectively. In addition, results revealed that the most efficient system is the (HP-G-S-D) for all simulated conditions and assumptions with a gain in COP that can reach up to 191 % in comparison to the baseline heat pump system.

Abstract The use of various kinds of magnetic resonance imaging (MRI) techniques for examining brain tissue has increased significantly in recent years, and manual investigation of each of the resulting images can be a time-consuming task. This paper presents an automatic brain-tumor diagnosis system that uses a CNN for detection, classification, and segmentation of glioblastomas; the latter stage seeks to segment tumors inside glioma MRI images. The structure of the developed multi-unit system consists of two stages. The first stage is responsible for tumor detection and classification by categorizing brain MRI images into normal, high-grade glioma (glioblastoma), and low-grade glioma. The uniqueness of the proposed network lies in its use of different levels of features, including local and global paths. The second stage is responsible for tumor segmentation, and skip connections and residual units are used during this step. Using 1800 images extracted from the BraTS 2017 dataset, the detection and classification stage was found to achieve a maximum accuracy of 99%. The segmentation stage was then evaluated using the Dice score, specificity, and sensitivity. The results showed that the suggested deep-learning-based system ranks highest among a variety of different strategies reported in the literature.

Electricity is a critical component of many everyday activities, demanding continuing research to create new or improved techniques for generating electrical power. Thermoelectric generators (TEGs), which work basically on the Seebeck effect can successfully transform input heat from numerous applications into valuable electrical energy, as well as power electronic devices and sensors on their own. However, obstacles include increasing the temperature difference and creating novel materials to improve electrical output and efficiency. Accordingly, this paper discusses these problems by providing a thorough examination of available strategies to enhance the thermoelectric performance. In this study, a variety of materials is presented, starting by the standard used conventional organic and inorganic thermoelectric (TE) materials. Organic materials, such as polyaniline and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT) composites, acquired ZT values ranging from 0.5 to 1.0, demonstrating their promise for versatile and low-cost applications. At extreme temperatures (∼500 K), inorganic materials such as bismuth telluride (Bi2Te3) and lead telluride (PbTe) achieved ZT values around 2.0, indicating great efficiency in power production. Bi2Te3/PEDOT, a hybrid material with organic and inorganic components, demonstrated improved performance with ZT values of 1.5–2.0 due to the synergistic effects of its constituents. Novel composite materials, such as Bi2Te3-carbon nanotube (CNT) composites and using graphene, developed to optimize thermal and electrical characteristics, enhanced device performance by up to 25% over standard materials, with ZT values ranging from 1.8 to 2.2. In addition, in the present study the new recent materials after applying enhancement methods will be presented. These new materials are developed by different methods and synthesis such as doping, superlattice and heterostructure materials and other methods will be discussed. The main findings indicate that the strategic use of these advanced materials may significantly increase the efficiency and output power of TEG devices, making them more practical for a wide variety of applications. As an examples, 2.8 for (GeTe)0.95(Sb2Te3)0.05 alloy, 2.4 for Chalcogenide, ZrS2, Bismuth telluride thin film (p-type Bi2Te3/Sb2Te3 superlattices) and 2.75 for Bismuth telluride thin film (Bi2Se1.2Te1.8). Finally, the present paper investigates on the newest technology and strategies that are applied in this research area in order to enhance the TEG performance enhancement.

Vortex generators are very effective tools in increasing heat transfer from one region to another, especially by convection, and appear to be a very promising concept to be coupled with heat recovery systems. On the other hand, Thermoelectric Generators (TEGs) are devices able to convert differences in temperature into electrical power using the Seebeck effect, the main advantage being working on high or even low differences in temperature. These TEG modules could be very effective tools in the hybridization of heat recovery systems. In this context, the present paper suggests an innovative system that couples three important energy axes together such as Heat recovery, TEGs, and Vortex generators. The current study employs a TEG in a rectangular channel to analyze the influence of the TEG on the flow and the effect of the effect of flow regime on producing electric power in order to assess the viability of this recently proposed concept. The investigation is conducted by varying the Reynolds number in a range of five values: 1000, 2000, 4000, 7000, and 10,000, applying six different configurations. Consequently, the results show that several factors affect the electrical power generated by TEG such as the emplacement, angle of attack, and absence/presence of vortex generators. On the other side, the heat recovered by the flow is affected by the TEG and Re, where the highest heat recovery is achieved at Re = 10,000 for configuration 4 with electrical power of 7.4 W, and for configuration 5 heat recovered by the flow of 1913 W. Besides, it was concluded that TEGs decreased the losses in both hot and cold sides by 1.42 times.

This paper introduces a novel empirical correlation designed to predict the overall heat transfer coefficient (U) in concentric tube heat exchangers. The study utilizes a comprehensive dataset of 2700 data points from CFD simulations, examining the impact of critical variables including hot and cold fluid Reynolds numbers (Reh, Rec), Prandtl numbers (Prh, Prc), and heat exchanger dimensions (tube hydraulic diameter Dh, annular space hydraulic diameter Dc, and overall length L). The analysis incorporates a range of fluid combinations in the tube and annular sections – air–air, air–water, water-air, and water–water – across Reynolds number ranges from 1000 to 20000, covering both laminar and turbulent flow regimes. The correlation was developed using the Adam optimizer to minimize the Weighted Mean Squared Error (WMSE), achieving an impressive convergence to an average prediction error of 6.7% compared to actual U values. The model categorizes flow into four distinct categories, each corresponding to a combination of flow patterns in the tube and annular spaces regimes – Laminar–Laminar, Laminar–Turbulent, Turbulent–Laminar, and Turbulent–Turbulent – integrating both hydrodynamic and thermal entry effects to enhance prediction accuracy. Rigorous error analysis revealed a median error of 5.18%, substantially outperforming existing models. Notably, 10% of the predictions deviate by less than 1%, with 90th percentile errors staying below 15%. Parameters were finely tuned through extensive numerical simulations, ensuring accurate application of the correlation across diverse operational conditions. The study concludes by highlighting the model’s potential to significantly enhance the design and efficiency of heat exchangers and proposes future enhancements to further improve its predictive accuracy.

This study delves into exploring and comparing various cooling technologies for PV panels, with a special focus on revealing the harmful effect of excessive heat absorption on solar energy efficiency. Effective temperature management and dissipation of excess heat are essential to protect the integrity of PV panels and improve power generation. With a strong emphasis on the importance of experimental setups, this comprehensive research examines the methodologies and cooling methods used across a wide range of experimental studies, illustrating the complexities of data collection and analysis. Supported by schematic illustrations depicting various experimental setups, this study demystifies the complexities inherent in distinct PV cooling methods. Furthermore, the research extends beyond experimentation to include a comprehensive examination of the energy and economic aspects associated with various cooling technologies, including the calculation and presentation of energy efficiency ratios. It is worth noting that the results confirm the superiority of passive cooling techniques, including heat sinks (43 %), PCM (25), evaporation techniques (36 %), and spray cooling systems (54 %), in contrast to active cooling methods, as indicated by their net energy efficiency ratios. Passive cooling is advantageous for its low maintenance and cost-effectiveness, whereas active cooling, though effective in hot climates and enhancing PV efficiency, incurs higher initial costs and maintenance requirements. The novelty of this research lies in its detailed classification of cooling techniques and the specific materials used for each method, coupled with a thorough examination of the measuring tools employed. Furthermore, this study includes a comprehensive comparative analysis based on energy and economic aspects, alongside the advantages and disadvantages of each cooling technique. These invaluable insights hold the potential to revolutionize the development of efficient and dependable cooling strategies for PV systems, thereby elevating the feasibility and sustainability of solar energy as a pivotal cornerstone in our future energy landscape.

This paper presents a simplified theoretical model for analyzing the temperature dynamics of photovoltaic (PV) modules. The model is built on an energy balance approach, considering solar irradiation as the primary energy input. It accounts for the conversion of solar power into electricity and the storage of thermal energy within the PV module, which subsequently increases the PV temperature leading to decay in its electrical efficiency. Heat loss from the top and bottom surfaces of the module, with variations for cooling techniques, is also included. The model is validated against three different experimental studies, demonstrating good agreement with the experimental temperature variations, with a maximum discrepancy ranging from 4 % to 16 %. This simplified model is then applied to two case studies: one representing typical daytime conditions and another simulating cold weather events. By comparing the PV temperature dynamics between the model and the experimental data, it is shown that the model accurately captures the dynamic response of the PV temperatures to changes in solar irradiation and ambient temperatures. Moreover, a parametric analysis is conducted to investigate the effects of key parameters on PV temperature and efficiency. Higher cooling rates from the bottom surface significantly boost electric power output, aligning closely with solar irradiance variations. Enhanced upper surface cooling, through increased convection, reduces PV temperature and thereby improves electric efficiency and power production. The PV temperature increases quasi-linearly with ambient temperature, especially at lower wind speeds, and decreases with higher wind speeds, eventually stabilizing at high values. Additionally, both ambient temperature and solar irradiance contribute to rising PV temperatures, with ambient temperature having a slightly greater effect. These findings underscore the critical role of cooling techniques in optimizing PV performance amidst varying environmental conditions.

In this work, the exact solutions of the (2+1)-dimensional generalized Hirota–Satsuma–Ito equation are reported by adopting the He’s variational direct technique (HVDT). The analytic findings of solutions were obtained by semi-inverse scheme, and six form of supposed studies reveal that the solutions belong to soliton groups. The modulation instability is considered. The tan(Π(ξ))\tan \left(\Pi \left(\xi )) scheme on the suggested model is employed to study new rational solutions. The investigated properties of solutions were determined by graphic studies, which shows significantly values of the parameters and susceptibility of abundant solutions. The obtained results in this work are expected to open new perspectives for the traveling wave theory. For the aforementioned wave solutions, we graphically describe their dynamical properties. It is worth mentioning that our results not only enable us to understand the dynamic properties of such equations more intuitively but also provide some ideas for researchers to facilitate more in depth exploration. It is important to mention that our proposed method is highly effective, consistent, and impacting and can be utilized to solve different physical models.

Cogeneration systems, exploiting waste heat sources, have emerged as crucial solutions in decreasing energy consumption and mitigating CO2 emissions across diverse industrial domains. This study delves into the innovative integration of multiple waste heat recovery (MWHR) mechanisms with thermoelectric generators (TEGs) within industrial contexts, with a specific emphasis on harnessing exhaust gas heat. Through meticulous investigation, six distinct configurations of TEG placement covering three unique systems were examined to expose their influence on overall system efficacy. Findings clarify a deep correlation between TEG positioning and system performance, with TEGs strategically positioned in close to heat sources, particularly along the inner walls of exhaust pipes, demonstrating the most auspicious outcomes in terms of power generation. Furthermore, the study reveals notable metrics, including a maximum power efficiency of 0.11 W per TEG and a water heat flow rate peaking at 5114 W. However, a comprehensive analysis underscores the imperative for interpreting the primary mechanisms governing TEG placement's impact on system performance, alongside defining the practical implications of the observed power efficiency and water heat flow rate. These empirical insights underscore the transformative potential of WHR-TEG interactions in optimizing energy utilization within industrial ecosystems, highlighting the request for further research actions aimed at implementation strategies and sustainability benchmarks.

In this paper, a unique method for using thermoelectric generators (TEGs) to generate electricity is introduced, a technique that makes use of a cold oil tank and hot exhaust gases from generators. A set of TEGs and an integrated cold oil tank are connected to the diesel generator as part of the suggested design. A pertinent thermal modeling was designed and a thorough parametric study was carried out to show the validity of this innovative concept. The parametric study has demonstrated that when the generator power and the thickness to thermal conductivity ratio of each TEG in the system are increased, the temperature differential in each TEG module and the power produced by the assembly of TEGs both exhibit linear increases. The length of the TEG plate and the height of the exhaust gas duct cause an exponential increase in the temperature differential across each TEG module. The TEG assembly's power output increases linearly with TEG surface length and decreases exponentially with exhaust gas duct height. Using an exhaust gas duct height of 0.05 m, and a TEGs plate length of 1 m, the parametric study showed that power generation of up to 2778 W is feasible under the predetermined circumstances of a diesel generator with an output of 125 kW. When compared to a conventional setup, the new hybrid generator in this scenario may be able to increase power generation by up to 2.22 %.

Our aim of this work is to present a review of solar photovoltaic (PV) systems and technologies. The principle of functioning of a PV system and its major components are first discussed. The types of PV systems are described regarding the connections and characteristics of each type. PV technology generations are demonstrated, including the types, properties, advantages and barriers of each generation. It was revealed that the first generation is the oldest among the three PV generations and the most commonly utilized due to its high efficiency in spite the high cost and complex fabrication process of silicon; the second generation is characterized by its low efficiency and cost and flexibility compared to other generations; and the third generation is not commercially proven yet in spite the fact that it has the highest efficiency and relatively low cost, its raw materials are easy to find and its fabrication process is easier than the other generations. It was shown that the target of all the conducted studies is to study the PV technology to enhance its performance and optimize the benefit from solar energy by reducing conventional energy dependence, mitigating CO2 emissions and promote the economic performance.

This work concerns a comparative experimental study of cooling PV panels by free and forced convection and using finned plates. To this end, four prototypes are considered: the first one with a PV panel alone without cooling techniques, the second one consists of a PV panel with a rectangular finned plate attached to its rear surface and cooled by free convection, a third prototype consists of a PV panel cooled by forced convection by three axial-flow fans and a fourth prototype consists of a PV panel with a rectangular finned plate attached to its rear surface and cooled by forced convection by three axial-flow fans. Results showed an increase of 3.01% in the efficiency of the PV panel with finned plate under forced convection, an increase of 2.55% in the efficiency of the PV panel with finned plate under free convection and an increase of 2.10% in the efficiency of the PV panel under forced convection. Economic and environmental studies are also conducted and estimations of savings per year and amount of carbon dioxide emission reductions are provided.

One of the most effective ways to deal with the effects of the current global energy crisis is to reduce energy consumption and rely energy management strategies. As a result, waste heat/energy recovery might be a helpful option for decreasing energy costs and environmental effect. It entails finding a practical way to apply any engineering system’s wasted heat where the percentage of wasted heat is too high in global. In this context, waste hot water is a rich source of wasted energy that, if recovered, can significantly cut down on the amount of electricity used worldwide. Within this framework, the present research paper provides a thorough analysis of Waste Water Heat Recovery Systems (WWHRS) in terms of performance, design, tools and applications. In addition, it is highlighting the key elements associated with WWHRS, including the wastewater sources and approaches used in the literature for waste water heat recovery. Moreover, the present paper demonstrates the effect of the heat recovery from the drain waste water on economically and discuss the technical barriers to using WWHRS. It will be demonstrated that the feasibility of recovering heat from waste water could decrease significantly the cost of energy consumption for residential or industrial application. In addition, the main tools that are used for heat recovery systems is the heat exchanger where various types are used and the thermal performance are strongly affected by the choice of heat exchangers. Moreover, based on the literature review, it is shown that the methods of studying the thermal performance of the heat recovery system are experimental and/or numerical and in some cases the study is performed analytically. Finally, all discussed and presented studies demonstrate that the WWHRS has a significant benefits and could be considered for new residential construction.

A new concept of power generation from thermoelectric generators TEGs using the hot exhaust gas of boilers and a cold oil tank is proposed. The suggested concept consists of a flow of exhaust gas of boilers and cold oil in a tank separated by a plate comprising several TEGs in series. The oil tank at the bottom of the system constitutes the cold convection condition for the TEG plate and the upper hot exhaust gas flow constitutes the hot convection condition. Accordingly, a temperature gradient is created across the thickness of the TEGs, which play the role of a separation plate, and converted to an electrical power. To justify the feasibility of this new concept, a suitable thermal modeling is developed and the associated parametric analysis is carried out. The parametric analysis reveals that powers up to 622 W can be generated with a system having a space heating load of 200 kW, an exhaust gas duct height of 0.05 m, and a TEG plate length of 1 m. The temperature difference across each TEG module decreases exponentially when the TEGs plate length increases and decreases exponentially when the exhaust gas duct height increases.

The global research community has increasingly focused on sustainable energy solutions to combat the environmental challenges posed by extensive fossil fuel consumption. This paper presents a new simple approach to enhance the electric efficiency of photovoltaic (PV) panels through efficient cooling techniques using simple parallel water pipes on the back of the PV panel. Additionally, the waste heat generated during this process is harnessed as a valuable heat source for residential hot water systems. Experimental measurements were conducted on both the reference PV panels without cooling and the PV/T system equipped with cooling pipes. A comprehensive energy analysis was performed to compare their performance. The results demonstrate that the cooled PV/T system exhibits consistently higher electric efficiency due to effective cooling by about 10%, resulting in surface temperature reduction and enhanced performance. The system also demonstrates a significant improvement in waste heat recovery, making it a practical and promising choice for sustainable energy applications.

The recovery and recycling/upcycling of plastics and polymer-based materials is needed in order to reduce plastic waste accumulated over decades. Mechanical recycling processes have made a great contribution to the circularity of plastic materials, contributing to 99% of recycled thermoplastics. Challenges facing this family of processes limit its outreach to 30% of plastic waste. Complementary pathways are needed to increase recycling rates. Chemical processes have the advantage of decomposing plastics into a variety of hydrocarbons that can cover a wide range of applications, such as monomers, lubricants, phase change materials, solvents, BTX (benzene, toluene, xylene), etc. The aim of the present work is to shed light on different chemical recycling pathways, with a special focus on thermochemicals. The study will cover the effects of feedstock, operating conditions, and processes used on the final products. Then, it will attempt to correlate these final products to some petrochemical feedstock being used today on a large scale.

The enhancement of energy systems in industrial zones is attracting the attention of researchers from all over the world. At the same time, optimization and advancement in heat recovery systems are now generating major interest in the energy sector. In this context, the present study suggests a new multiple heat recovery system should be applied to an industrial thermal peeling press machine. The new system consists of multiple sources of energy: the heat excess in the chimney, the exhaust gas of the chimney, and the exhaust gas of the boiler. To proceed with testing the potential of the suggested system, a hydraulic thermal peel press machine in the wood industry undergoes different tests to achieve the best configuration that will enable this machine to reach its operational temperature when heating. Five test configurations are proposed, designed, and applied experimentally on this machine. Many parameters were effective during the experimental tests, such as water flow rate, ambient air temperature, and initial water temperature. It was found that the application of the multiple heat recovery system increases the rate of heating from around 7 °C/min to around 13 °C/min. In terms of energy and economy, the “chimney + boiler only” configuration proved to be the best system to apply during the fall and winter seasons.

The increasing global demand for renewable energy sources underscores the significance of Solar Water Heating Systems (SWHS), emphasizing the need for thorough research and analysis in this domain. SWHS play a pivotal role in addressing energy efficiency and environmental sustainability, making it imperative to conduct in-depth studies on their utilization. Hence, this paper aims to provide a comprehensive overview of SWHS. It starts by explaining the principles behind these systems, including their components and classification. Moreover, this review consolidates various studies that have been conducted on SWHS to highlight both their advantages and disadvantages. Additionally, a case study is conducted in which it takes into consideration important economic and environmental factors. In particular, it focuses on several scenarios present in Lebanon such as family homes, schools, restaurants hotels and gyms to estimate potential cost savings achieved through implementing SWHS as opposed to relying solely on electric heaters. Furthermore, this investigation also examines the corresponding payback period associated with adopting SWHS along with assessing the significant reduction in carbon dioxide emissions possible if these systems were widely implemented. The findings of the study demonstrate that there is a direct correlation between the extent to which SWHS are utilized and both the payback period and reduction in CO2 emissions. It was observed that when SWHS are used more frequently, with a high percentage of time (Pr=0.9), significant advantages can be achieved. For instance, for different types of establishments such as family homes, schools, restaurants, hotels, and gyms, it was estimated that average payback periods would be 14.2 years, 4.6 years, 9.2 years, 4.4 years, and 5.3 years, respectively. These results indicate that adopting a greater dependency on SWHSs not only leads to quicker cost recovery but also significantly contributes towards reducing carbon dioxide emissions. The analysis reveals that the yearly decrease in carbon dioxide emissions per individual is 0.16 t within a household, 0.016 t per student in an educational institution, 0.04 t per customer within a dining establishment, 0.37 t for each occupied bed in a hotel accommodation, and 0.11 t per individual at a gym. This paper serves as guidelines to SWH community. Additionally, it adds a practical insights into economic and environmental issues relevant to both Lebanon and countries with similar climates.

This paper presents a heat recovery system (HRS) that exploits the chimney`s exhaust gasses to heat water. Optimization of a waste HRS called the ''multi tube tank,'' as suggested by Khaled et al., is performed through experimental means. The design is described in detail and constructed, after which it is tested. Investigation of the impact of altering the head shape on the performance of the system is performed by constructing two distinct heads, one cylindrical (Cyl) and one conical (Con). Results indicate that the conical head (ConH) outperforms the cylindrical head (CylH). Specifically, in 275 min, the water temperature increases to a maximum of 59 °C with the CylH, while the ConH can raise the water temperature to 68 °C. Moreover, in 400 min, the ConH system can augment the water temperature up to 80 °C. Furthermore, economic and environmental analyses are performed, which show that the ConH system can save approximately 16 $/month more than the CylH system when the system is exploited 140 times/month for 275 min. Additionally, the payback period for the ConH system is about half that of the CylH system (6 months). Finally, the ConH system can reduce emissions of CO2 gas by 2 tons/year more than the CylH system when utilized 140 times/month.

Utilizing a cooling technique can help prevent overheating, which can have a detrimental impact on the performance of solar panels. Instead of using a water cooling system that requires a pump, an alternative method uses the return air from a Heating, Ventilating, and Air Conditioning (HVAC) system often utilized in industrial settings. An air cooling system that uses the HVAC system's return air was previously recommended by the co-authors of the current study. Using numerical methods, they carried out a feasibility analysis and showed how a variety of parameters, such as the convection coefficient and the flow type (natural or forced), might affect the output power (efficiency) of the system. As a continuation of the previous study, the present study examines two cooling scenarios to further their past findings. Three different configurations for external flow were tested: cooling the upper and lower surfaces of the PV with exhaust air, installing a vortex generator at the leading edge of the lower surface while relying on natural convection for the upper part, and installing a vortex generator on both the upper and lower surfaces. The efficiency of the PV system increases from 11 % to 18 % with an increase in cooling demand from 0 to 160 kW with solar radiation of 500 W/m2. Efficiency was improved by generating turbulent flow at the leading edge of the panel. While using an internal flow on the bottom surface, the system's efficiency increased as the PV module's length increased.

Vortex generators (VGs) have been extensively studied and utilized in multifunctional heat exchangers/reactors due to their remarkable ability to create coherent flow structures and streamwise vortices. These characteristics significantly enhance the mixing and heat transfer performance in laminar and turbulent flow regimes. With the advancement of computational power, VG shape optimization has become feasible, leading to the discovery of various optimized shapes in the literature for different Reynolds numbers. In this paper, the response surface polynomial method is employed as a surrogate model to optimize the angle of attack and inclination angle of a delta winglet VG at a Reynolds number of 4,600. The potential applications of these optimized designs are diverse, particularly in scenarios that require cooling or heating. Some examples include photovoltaic (PV) panel cooling, waste heat recovery in hybrid PV/solar water heating systems, energy-efficient HVAC systems, and thermal management in electric vehicles. To achieve this objective, Computational Fluid Dynamics (CFD) simulations are conducted to compute the thermal performance factor of each VG design at various values of attack and inclination angles. By enhancing mixing and heat transfer capabilities, this design can have a substantial impact on various renewable energy applications, contributing to a greener and more sustainable future. The highest thermal enhancement factor of 1.15 is found to be achieved for an inclination angle of −45° and an angle of attack of 35°. This means that optimized VG enhances heat transfer by 15% compared to empty channel flow, while maintaining the same pumping power.

In light of the environmental concerns associated with the misuse of fossil fuels and the increasing consumption of energy, heat recovery systems have become an essential option for conserving energy. In this study, an innovative design that couples a highly efficient vortex generator-based heat exchanger with a new multi-drain water application for 48 accommodations is suggested. A numerical study is done by varying the flow rate and investigating the effect on the heat transfer, overall heat transfer, and thermal enhancement factor. Besides, the economic and environmental impacts of the system are studied to investigate its sustainability. Four types of input energy are studied: coal, diesel, gas, and electricity. Results show that the design provides a temperature increase of 3.5 to 7.5 °C of cold water, consequently, the daily environmental savings are up to 0.87 € (for gas), 1.74 € (for diesel), 4.63 € (for coal), 17.63 € (for electricity US) and 2.26 € (for electricity FR). Besides, the daily economical savings are up to 7.54 $, 8.63 $, 4.63 $, and 15.07 $ respectively with a payback period of around 0.61, 1.2, 1.42, and 2.89 years for gas, diesel, coal, and electricity respectively.

The present work aims at investigating laminar flow effects over bumped-surface circular cylinders at Reynolds number ≤ 200. Three bumpy cylinder surfaces are considered and studied, comprising square, triangular, and dimple surface shapes. The bumpy surfaces are placed on the upper surface of the cylinder and arranged between 0° and 90° from the front stagnation point of the cylinder. These angles include θ = 0○, 45○, and 90○. The flow characteristics, such as the lift and drag coefficients, as well as the Strouhal and Nusselt numbers, are evaluated. For all three examined bump shapes, it is demonstrated that when θ ≤ 45°, the amplitude of the drag coefficient is smaller than larger angles. It is also found that at θ = 90°, the magnitude of the drag coefficient is about 40% larger than test cases with θ ≤ 45°. It is found that the Nusselt number is dependent on the location of the bump on the leading surface of the cylinder. The critical angle of the bump's location is identified and introduced, which is θcm = 45°. While the minimum Nusselt number is obtained once the bump is located at θcm = 45°, the maximum Nusselt number is assessed at θ = 90° with approximately a 12% increment.

In response to escalating energy demands, intensifying climate change concerns, and growing environmental degradation, the incorporation of renewable energy sources has gained traction across diverse sectors and regions. Concomitantly, scientists and engineers have recognized the potential of heat recovery systems in mitigating energy consumption, fostering further investigations into their practical applications. This study introduces an innovative design, integrating vortex generators into a concentric tube heat exchanger for heat recovery from a multi-drain water system that serves 48 accommodations. The design's sustainability is assessed by evaluating its economic, and environmental implications when paired with various renewable energy sources. Specifically, the aim is to quantify both cost and environmental savings engendered by implementing this design in a multi-drain application for a building with 48 accommodations.A numerical investigation elucidates the effects of flow rate variations on heat transfer, overall heat transfer, and thermal enhancement factors. Four types of renewable energy input - solar, wind, biomass, and hydropower - along with one storage system (pumped storage) are analyzed. The study reveals that the design implementation results in an elevation of cold water temperature between 3.5 and 7.5 °C. Furthermore, daily environmental savings for solar, wind, biomass, hydropower, and pumped storage are estimated to be 0.783 €, 0.339 €, 0.141 €, 0.027 €, and 1.356 €, respectively. Conversely, daily economic savings are calculated to be 3.62 €, 2.49 €, 5.05 €, 3.62 €, and 6.70 € for each corresponding energy source. This research underscores the viability of the proposed design in fostering sustainability through both environmental preservation and economic efficiency.

The development of different renewable energy techniques has shown their ability in limiting the environmental crisis and meeting future needs. In recent years many efforts have been made in order to produce hybrid systems that work on integrating renewable energy systems with thermoelectric generators (TEGs) in order to increase energy efficiency. This review attempts to discuss and summarize different configurations of hybridizing TEGs with different renewable energy sources (solar, fuel cell, biomass) underlying the concepts and approaches used to reach these hybridizations. This review will give necessary information about this type of hybridization and encourage for future research due to its promising results.

Currently, the world is perceiving a change-over from its existing conventional energy sources to a future with optimized and inventive energy sources. Nowadays, the world is more and more oriented to the use of renewable energy sources to decrease the consumption form the conventional energy sources in particular the fuel energy. In addition, the use of renewable energy source decrease the impact of the conventional energy on the environment. For all these reasons, researchers are currently focusing on studies that implement and innovate methods for the purpose of optimizing and increasing the efficiency of existing renewable energy sources. Of the proposed methods are the hybrid systems. These systems are applicable in both residential and industrial sectors. However, hybrid systems can be applied to renewable energy, wind energy, fuel cell, Desalination, Heating, Ventilating, and Air Conditioning, Engines, Electric Vehicles, Heat Pump, Redrying, PV cells, Engines, Solar Cells, and many other systems. In this context, the aim of the present paper is to provide a short recent review focusing on the types and applications of hybrid renewable energy systems and hybrid recovery energy systems that are applied in industrial and residential sectors. Moreover, the environmental impact, cost and the efficiency will also be presented and discussed.

Reducing energy consumption has its direct impact on the worldwide environmental status. Smart energy processes must be adopted in order to enhance the reduction capacity of energy usage. In this view, both renewable energy as well as heat recovery strategy has been used in a wide range of engineering applications. With this in mind, hot wastewater is considered as a valuable source of energy that could be recovered. The present paper illustrates an overall review on the waste water heat recovery systems (WWHR). All systems can be classified based on their structural configuration and application. It has been shown that under some conditions a 50% energy could be stored or recovered using a heat recovery system. In addition, all systems are considered as an economic as well as environmental effective methods.

Phase change materials proved their capability of enhancing buildings’ thermal inertia and improving occupants’ thermal comfort. More attention was triggered by the scientific community as the use of thermal energy storage systems kept evolving in the building sector. Previous experimental investigations examined the effectiveness of enhanced macro-encapsulated coconut oil bio-based PCM integrated with underfloor water radiant heating system in two similar small-scale test facilities that are modular. The current study focuses on performing comparative energetic and economic analyses of the system performance in regards to: weather conditions, PCM application, PCM type and properties, and PCM plates position at the underfloor. Results highlighted the effectiveness of utilizing coconut oil PCM in active floor, and passive wall and roof as load shifting and energy savings were obtained. It was shown that with the combination of active and passive systems, annual savings of 227 USD can be achieved; and by placing the PCM underneath the heating system, energy saving of 393.5 kWh was achieved corresponding to 169 USD annual savings. However, 32 USD annual saving was achieved by the system integrated with paraffin wax compared to that integrated with cocoa-nut oil PCM. Finally, the PCM capability in cost savings was reflected with the payback periods being evaluated as follows: 6.82 years for experiment 2, 6.75 years for experiment 3 (both encountering load shifting), and 3.94 years for experiment 4 (encountering energy saving).

As the world deviates towards sustainability in buildings due to massive increase in energy demand, the effective integration of Phase Change Material (PCM) in buildings gained substantial attention. The capability of PCM in enhancing the thermal performance of buildings relies heavily on the encapsulation technique used as it is in direct link with enhancement techniques required for upgrading thermo-physical, chemical and environmental PCM properties. The current study reviews shortly recent literature involving PCM integration in buildings and highlights different encapsulation techniques used for their proper active and passive incorporation. It also summarizes recent methodologies of properties enhancements prior to encapsulation. Preliminary results reflect the importance of proper encapsulation using the five distinct techniques: direct mixing, imbibing, shape-stabilization, macro-encapsulation and micro-encapsulation. Commercialization of macro-encapsulated PCMs is dominant over other techniques, where micro/nano-encapsulation technique is still limited and requires further study being the most promising.

Photovoltaic panels play a pivotal role in the renewable energy sector, serving as a crucial component for generating environmentally friendly electricity from sunlight. However, a persistent challenge lies in the adverse effects of rising temperatures resulting from prolonged exposure to solar radiation. Consequently, this elevated temperature hinders the efficiency of photovoltaic panels and reduces power production, primarily due to changes in semiconductor properties within the solar cells. Given the depletion of limited fossil fuel resources and the urgent need to reduce carbon gas emissions, scientists and researchers are actively exploring innovative strategies to enhance photovoltaic panel efficiency through advanced cooling methods. This paper conducts a comprehensive review of various cooling technologies employed to enhance the performance of PV panels, encompassing water-based, air-based, and phase-change materials, alongside novel cooling approaches. This study collects and assesses data from recent studies on cooling the PV panel, considering both environmental and economic factors, illustrating the importance of cooling methods on photovoltaic panel efficiency. Among the investigated cooling methods, the thermoelectric cooling method emerges as a promising solution, demonstrating noteworthy improvements in energy efficiency and a positive environmental footprint while maintaining economic viability. As future work, studies should be made at the level of different periods of time throughout the years and for longer periods. This research contributes to the ongoing effort to identify effective cooling strategies, ultimately advancing electricity generation from photovoltaic panels and promoting the adoption of sustainable energy systems.

Sustained low-efficiency dialysis (SLED) is usually performed over 6–12 h among hemodynamically unstable patients. Conduction of 4-h SLED may spare time and manpower during hospitalization. Therefore, we conducted a retrospective observational study to explore the appropriateness and clinical outcomes of 4-h SLED among critically ill patients admitted to our center from 1/06/2016 to 1/06/2020. Renal parameters including blood urea nitrogen, serum creatinine, sodium, phosphorus, potassium, and bicarbonate were determined on the day of dialysis before SLED and within 24 h after SLED, and clinical outcomes including, acute kidney injury (AKI) recovery, in-hospital mortality, 30-day mortality, 180-day mortality, and re-admission with AKI, were evaluated. Of the 304 patients included, 69.4% were male. The majority of patients were from the Middle East (65.8%), followed by 28.6% from Asia. Four-hour SLED resulted in a significant improvement in the renal parameters. Recovery from AKI was observed in 25.4%, in-hospital mortality rate was 48.7%, while the 30- and 180-day mortality outcomes were 3.2 and 9.6%, respectively, and re-admission with AKI was observed in 16.9%. Our findings suggest that 4-h SLED significantly improved renal parameters and was associated with favorable clinical outcomes in terms of survival and AKI recovery, suggesting possible utilization of SLED shorter than 6 h in the acute settings to preserve time and manpower for procedures.

Air heating is currently an essential part in many industrial and residential applications. One of its disadvantages is the higher energy consumption. Therefore, the renewable energy sources present now different solutions in order to decrease the energy consumption and to enhance the performance of existing systems by the hybridization. For these reasons the energy management at all levels became one of the most important research. In this context, the present paper proposes a design for a solar air heater that could be applied in more than one application. A modelling and an experimental study are presented. The presented solar air heating system allows reducing the energy consumption by replacing completely or partially an electrical air heating system. In addition, an in-house code is developed in order to simulate the suggested solar air heater and to study its performance. The experimental setup is implemented and designed to validate the developed code. Accordingly, a relative error of the modelling is estimated and it varies between 4 and 14%. Finally, the system is evaluated economically and environmentally by assessing the effect of replacing the electrical heating system of a fruit dryer by the suggested solar heating. It has been shown that adopting such system allows to save up to $106 per year and to reduce about 2045 kg of carbon dioxide emission.

This paper presents a simulation model and parametric analysis of a parabolic trough thermoelectric hybrid system. The structure of the system under study mainly consists of a parabolic trough with a triangular receiver equipped with a photovoltaic layer and thermoelectric generators at its back. A thermal model of this system is described and simulated using MATLAB software. The thermal model is utilized to investigate the system performance by performing a parametric analysis. This analysis is conducted to analyze the influence of several parameters such as fluid and air velocities, fluid channel diameter, receiver side length, and the thermal conductivity of the thermoelectric generator on the performance of the system. The results reveal that the thermal efficiency increases noticeably by 6% and 21% when increasing the dimensionless tube diameter from 0.5 to 1 and the dimensionless receiver side length from 1.67 to 8.33, respectively. It decreases significantly by 23% when rising the air Reynolds number from 1.90 × 106 to 18.98 × 106, whereas the fluid velocity and thermoelectric generators thermal conductivity have a negligible effect on it. Furthermore, the electric efficiency is enhanced considerably by 36% and 14% when augmenting the dimensionless tube diameter from 0.5 to 1 and the fluid Reynolds number from 5982 to 19940 respectively. However, it is noticeably reduced by 13% when increasing the dimensionless receiver side length from 1.67 to 8.33, while it is affected negligibly when varying the air velocity (air Reynolds number) and the thermal conductivity of thermoelectric generators.

In this paper, a contemporary concept that is based on dividing, by means of multi-passages, the water flow rate of water-air cross flow heat exchangers (HXs) is proposed. The thermal performance of water-air cross flow heat exchangers varies through a rationale function when the water flow rate changes. The new concept is based on dividing high flow rates of water entering a water-flow heat exchanger into several passages. This fragmentation prevents keeping the thermal performance from being nearly constant at high flow rates which lead to increasing the thermal performance globally. The feasibility of this concept was examined and had been proven through calculations on a double passage heat exchanger using an in-house two-dimensional computational code that had been developed and validated to evaluate the thermal performance of Heat Exchangers (HX) using a prescribed set of parameters. It was observed that the thermal performance increases rapidly with the water flow rates at low flow rates and become nearly constant at high flow rates. Furthermore, results revealed that the implementation of the novel concept can increase the thermal performance of a standard water-air cross flow heat exchanger by up to 25.7 %. The enhancement is more significant at high mean air velocities and low water flow rates.

The type and quantity of municipal solid waste are important factors for determining how these wastes should be handled, managed, and valorised. This paper investigates the effect of different living styles on the type of generated municipal solid waste (MSW). It is also forecasting the amount and type of generated municipal solid waste. Al-basaten, a district at East-Cairo, Egypt was considered a case study due to the diversity of lifestyles. The Al-basaten area has three different zones depending on level styles: poor, social, and privileged zones. Solid waste was collected separately from each zone, sorted (as plastic, glass, paper, carton, and organic waste), gathered the same type of sorted solidwaste from each zone individually, and weighted. The analysis of distinguishing waste is discussed. The forecasting model by using a long short-term memory (LSTM) along with deep learning time series forecasting (DLTSF) network was used for Al-basaten MSW. The forecasting model was trained, validated, and tested on the real-life dataset of the sorted and weighted waste from each zone. The analyzed results provide the average solid waste was 0.42, 0.65, and 0.86 kg/person/day for poor, social, and privileged zones, respectively. The forecasting results indicated that the proposed model could effectively forecast the future series values of the plastic, glass, paper, carton, and organic waste for the poor, social, and privileged zones. The mean RMSE of DLTSF was 0.03371 for forecasting the total MSW. This analysis will help decision-makers maximize solidwaste recycling benefits.

Electricity plays a significant role in daily life and is the main component of countless applications. Thus, ongoing research is necessary to improve the existing approaches, or find new approaches, to enhancing power generation. The thermoelectric generator (TEG) is among the notable and widespread technologies used to produce electricity, and converts waste energy into electrical energy using the Seebeck effect. Due to the Seebeck effect, temperature change can be turned into electrical energy; hence, a TEG can be applied whenever there is a temperature difference. The present paper presents the theoretical background of the TEG, in addition to a comprehensive review of the TEG and its implementation in various fields. This paper also sheds light on the new technologies of the TEG and their related challenges. Notably, it was found that the TEG is efficient in hybrid heat recovery systems, such as the phase change material (PCM), heat pipe (HP), and proton exchange membrane (PEM), and the efficiency of the TEG has increased due to a set of improvements in the TEG’s materials. Moreover, results show that the TEG technology has been frequently applied in recent years, and all of the investigated papers agree that the TEG is a promising technology in power generation and heat recovery systems.

The present article is discussing the performance of heat transfer enhancement (HTE) using a trapezoidal vortex generator in a Concentric Tube Heat Exchanger (CTHE) through Computational Fluid Dynamics (CFD) code ANSYS Fluent. Heat transfer and fluid flow analysis are conducted for various Reynolds numbers inside the tube and annular. The effects of Vortex Generators (VGs) are studied as well, and the turbulence flow is simulated using the k-ꞷ model. The analysis was made on four designs, where the VGs are placed in three different locations as follows: (case 0) no VGs, (case 1) VGs inside the tube, (case 2) VGs on the interface between annular and tube, and (case 3) VGs on the outer wall of the annular part. Accordingly, the overall heat transfer, heat transfer ratio, and heat transfer/power of each of the three cases with VGs are normalized to case 0 to study the effect of VGs on the flow and heat transfer enhancement. Results show that VGs are effective in all locations and cases, however, the highest improvement was spotted in case 1 at Reynolds number of 8000 for the cold fluid and Reynolds number of 2000 for the hot water, where the enhancement of heat transfer ratio was 97% for case 1, 92% for case 2 and 56% for case 3, whereas the thermal enhancement factor was 210% for case 1, 180% for case 2 and 142% for case 3.

In order to reduce the energy bills and pollution of buildings due to the use of conventional cooling systems, the present paper presents a parametric analysis and a case study concerning a newly proposed Multi Geothermal Cooling System that uses the cold soil to precool or cool air of several residences simultaneously. For that purpose, a thermal modelling and a related in-house code are developed. The modelling allows to predict the temperature of the precooled (or cooled) air in function of the return air temperature (hot flow) and the mass flow rate. The effect of other governing parameters has been evaluated, like the depth in soil, the tubes length and diameter. Modelling results have been confronted to experimentation showing a worst case error of 1.9 °C in the precooled air temperature. The work doesn't stop here. The predicted air temperature has been used in a numerical study of a multi geothermal cooling system with air-conditioning systems and different scenarios were simulated. Energy savings and reduction in CO2 emission have been evaluated for different coefficients of performance. Results are promising and relevant recommendations were put on firm roots.

Due to global warming and environmental issues in recent times, the world's concern is oriented nowadays toward discovering new renewable energy sources and energy management methods. Particularly, researchers are emphasizing on heat recovery technologies and applications in both residential and industrial sectors. While there are plenty of review papers in the literature on the subject matter, there is always a necessity to update the literature with the new advancements in the field. In this context, the purpose of this paper is to present a recent and complete systematic comprehensive review along with critical analysis and potential recommendations related to waste heat recovery (WHR) methodologies and applications. In methodologies, heat exchangers, Rankine cycle and thermoelectric generators are studied. Moreover, applications of WHR are discussed in automotive, and in both residential and industrial zones. Studies show that the optimization of heat recovery systems lead to significant magnitudes of energy savings. On the other hand, hybrid heat recovery systems prove to be the most trending research subject nowadays. For future work, the negative effect of backpressure should be taken into consideration when recovering energy from exhaust gases of engines and power generators, and more importance should be given to hybrid systems.

The present study suggests a new concept of heat recovery applied to underhoods of vehicles parked in underground parkings. The advantages of this concept is twofold: (1) enabling cool the environment around the parked vehicle and under its hood (2) considering to use the excess of heat under the hood to heat/preheat water in use in public buildings. This system shows potential performance especially in car parking where a large number of vehicles is present such as supermarkets, universities, schools, etc. The feasibility of recovering energy from underhoods of parked vehicles is performed in the study. An experimental setup equipped with thermocouples, a heat exchanger and a fan is implemented. The engine is stopped after a certain period of operation then measurements are performed on two types of engines: V4 and V6. The temperature of the hot air aspirated by the V4 and V6 engine reached 40 °C and 54 °C respectively. The hot air is used for heating water using a finned-tube cross flow heat exchanger where the recovered heat rate reached around 500 W. In addition, a case study for the parking of the Lebanese International University along with an economic study are considered. From the study, 300 cars are assumed to be present daily in the parking, equipped by different engines (V4, V6 and V8). Consequently, the recovered energy obtained during the 80 min is estimated at 97 kWh, which permits to heat 4000 L of water from 20 °C to 40 °C.

Prediction of heat exchangers performance is primordial in the world of machine design especially when the industrial environment becomes demanding in terms of size reducing or price lowering. The most common adopted procedure for this kind of investigation is defining the exchanger's overall heat transfer coefficient with a purely empiric way using interpolations and mathematical operations missing physical senses in the modeling. The present work offers a first step in theoretically modeling the heat transfer coefficient and presents a semi-empirical method which allows expressing the latter in function of the Reynolds' numbers of the fluids' flows when the variations of the Prandtl numbers of the two fluids are small. The method consists in an iterative technique based on a single test approach and allows the prediction of the heat exchanger performance for a large range of flowrates. Experimental validation of the method is performed for a cross-flow heat exchanger with water and air as working fluids, showing a relative error less than 1.6%. The relative error of the mathematical methods applied is less than 1.7%.

The thermal performance of fin-and-tube heat exchangers (HX) is a crucial aspect in a multitude of applications and fields; several design and operational parameters influence this performance. This study focuses on the issue of flow maldistribution and its effect on the HX thermal performance. For this purpose, an experimental setup is designed and implemented to emulate the conditions under which an automotive heat exchanger operates in regard to the non-uniform upstream airflow velocity distribution over the HX surface. The setup allows obtaining various configurations of airflow velocity non-uniformity of some desired mean velocity and standard deviation. The experimental results reveal that a higher degree of non-uniformity (higher standard deviation of the velocity distribution) causes an increased deterioration of the HX thermal performance. For example, at a water flowrate of 200 L/h and a mean airflow velocity of 2 m/s, increasing the standard deviation from 0 to 2 m/s (i.e., moving from the lowest to highest degrees of non-uniformity) causes a total deterioration of 27% in the performance (3.78 to 2.75 kW, respectively), which can also be observed in the increased level of outlet water temperature (53.8 to 58.2 °C, respectively). The obtained results confirm the numerical results reported in the literature.

The automotive domain is a very good candidate for energy management, particularly due to the huge amounts of energy lost by heat through exhaust and water-cooling systems. This makes the optimization of vehicle cooling modules directly related to energy consumption and carbon dioxide emission. In this context, contemporary designs that employ diffusers between the forward-facing of an automobile and its heat exchanger subjected to airflow are presented in this work. The ultimate aim is to reduce the fuel consumption and carbon dioxide emissions of vehicles. Based on the aforementioned design, the intensity of the air velocity would be decreased but distributed over a larger exchanger surface. Consequently, the velocity non-uniformity of the airflow upstream would decrease and therefore, the thermal performance would increase. The above-mentioned conclusion is a result of parametric numerical analysis and its associated numerical results that disclosed the enhancement of water-air heat exchanger thermal performance. To perform a parametric numerical analysis of the heat exchanger thermal performance for the new suggested configurations, a computational code was developed and validated to estimate the thermal performance for a known set of parameters. It was shown that for an automobile, with engine power ranging from 100–200 kW that is utilized for three hours a day and equipped with a diffuser, reduction of up to 2.91 kg (3.89 L) of gasoline consumption and 9.51 kg of CO2 emission can be achieved per day. The originality of the present work resides in the use of diffusers in cooling modules of vehicles, the thermal modeling of heat exchanger’s thermal performance along with its associated code, and the parametric analysis performed to prove the potential enhancement related to the use of diffusers in the cooling modules.

The present work proposes the engagement of relatively cold air exhausted from Heating, Ventilating and Air Conditioning (HVAC) systems, that exist in structures such as residential commercial and industrial, to reduce the PV modules’ operational temperature. To proceed, a thermal resistance model in steady state is developed along with its corresponding iterative procedure and calculations which are carried out for different configurations and scenarios. The thermal modeling was validated by comparing it to experimental measurement found in the literature. It was revealed that the PV modules’ temperature can be reduced with increasing the mass flow rate of the exhaust air. However, the air mass flow rate depends on the cooling load need; which increases with increasing the cooling load. The efficiency of the PV has shown an increase from 11 to 18% when the cooling load increases from 0 to 160 kW for a solar radiation of 500 W/m2. Moreover, there is an optimum height for the exhaust air duct for each cooling load that must be determined.

This paper suggests a heat recovery concept that is based on preheating/precooling the cold/hot fresh outside air by means of the relatively hot/cold exhaust air in winter/summer weather conditions. To investigate the feasibility of such a concept, an experimental setup is established to simulate conditions similar to an All-Air HVAC system. The prototype consists of a 6.7-m3 air-conditioned chamber by means of a split unit of 5.3-kW capacity. The heat recovery module consists of a duct system that is used to reroute the exhaust air from a conditioned chamber to flow through the fin side of a fin-and-tube heat exchanger of crossflow type. At the same time, outside, fresh air is flowing through the tube side of the fin-and-tube heat exchanger. A parametric study is performed to assess the amount of heat that can be recovered by varying the mass flow rates on both the duct and heat exchanger sides. The results show that up to 200 W of power can be saved for an exhaust flow rate of 0.1 kg/s and a fresh, outdoor air flow rate of 0.05 kg/s. Environmentally speaking, this leads to a reduction in production of about 1 tons of CO2 per year when the system operates 24 h/day. From an economic point of view, the system is able to return its price after 1.5 years when it is used 24 h per day during hot days at 196-W thermal recovery, whereas it requires at least 6.3 years when it is used during cold days at a 60-W thermal recovery rate, which, in both cases, represents a duration less than the lifespan of an air conditioner.

The use of phase change material (PCM) as a thermal energy storage system integrated in new buildings, and as retrofits in old buildings, proved its merit as promising renewable energy source. Heating and cooling building applications of PCM have been studied by plenty of scientists, globally, on the basis of numerical and experimental analysis. The performed experiments have mainly focused on one application—active or passive—using permanent prototype design for a certain duration and weather condition. The current study is a new review that focuses on two complementary aspects: (1) Reviewing latest studies in PCM domain and assessing the thermal performance of implemented prototypes within the conducted PCM experimental studies, namely, the effect of the design on the number of acceptable variables and possible PCM applications; and (2) suggesting a new, advanced, flexible, and modular prototype designed to enable several applications of PCM to be adapted and combined within the model. It was implied that the new design allows different configurations that are lacking in the literature and serves for future PCM building applications of thermal analysis towards PCM integration optimization, as an attempt for transforming residential compartments into net zero energy buildings. The designed prototype overcomes the deficiencies found in previous reviewed experimental facilities.