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The effectiveness of a hybrid cooling system consisting of flat heat pipes (HP) and a heat sink of phase change material (PCM) for the temperature regulation of the photocell (PV) is studied. The system is mathematically modeled and numerically solved by using MatLab software. The impact of the type of PCM (RT25, RT35, and RT42) in summer on the performance of the hybrid photocell cooling system is analyzed. Results prove that the HP-PCM cooling system performs better than the natural photocell cooling. PCM with a low melting point is more efficient for electric performance than a high melting point. For a given PCM thickness of 4 cm, the maximum temperature of the photocell is reduced by 8.7 °C when PCM RT25 is used as a heat sink compared to 7.5 °C and 7.3 °C for RT35 and RT42, respectively. RT25-based PV/HP-PCM system outperformed a conventionally cooled photocell in terms of electrical efficiency by 5.3%. In comparison, RT35 and RT42 yield incremental gains of 5% and 4.5 %, respectively. As the PCM melting point is lowered, the hourly thermal efficiency increases with a peak of 48.9% for RT25, 33.7% for RT35, and 32.2% for RT42, respectively.

Powering thermal desalination technologies by renewable energy is believed to be a viable solution to overcome the worldwide freshwater scarcity problem without causing more damage to the environment. In this paper, a multi-effect distillation system (MED) with mechanical vapor compression is powered by the generated electrical power of photovoltaic/thermal collectors and assisted by the by-product thermal power generated. The system is sized according to thermal power needed and designed for small-scale application and weather conditions of Alexandria, Egypt. Excess electricity is injected into the grid and hot water storage tank is used as a back-up to compensate low and fluctuating radiation. Results show that, at a saturation temperature of MED’s heating steam of 55 °C, freshwater production is 11.1 m3/day in 10 hours of operation, system specific power consumption is 9.72 kWh/m3, specific area is 317.04 m2s/kg, and performance ratios of the desalination unit is 3.33 and 6.97 for the overall system. However, at T = 65 °C the system’s electrical energy is totally absorbed by the compressor, and the system’s performance decreases.

Air conditioning unit performance, coupled with new configurations of phase change material as thermal energy storage, is investigated in hot climates. During the daytime, the warm exterior air temperature is cooled when flowing over the phase change material structure that was previously solidified by the night ambient air. A theoretical transient model is constructed and solved numerically for the proposed design in plate and cylinder configurations. This model is studied at different inlet hot ambient air temperatures and phase change material types (SP24E and SP26E) without and with inclusion of hybrid nanoparticles. The results affirm that the discharging and charging duration for the cylinder is minimal compared to the plate configuration. Raising the inflow air temperature lowers the exit air temperature and air conditioning coefficient of performance and power-saving but shortens the cooling time. Using phase change material with a relatively low melting temperature increases the melting time and exit air temperature but reduces the charging time. Mixing hybrid nanoparticles with phase change material has a short-term positive influence on air conditioning performance. The maximum power saving for 2 h of working is 16.4% for the cylinder, while for 10 h of working, it is 6.4% for the plate.

In this work, a hybrid system is comprised of wind turbines (WT) and photovoltaic (PV) panels to generate green Hydrogen via water electrolysis. Consideration is given to the influence of five electrical power generation scenarios on system performance and Hydrogen production cost. This study adopts the solar radiation, wind speed, and ambient temperature for Mersa-Matruh in Egypt. The system performance is studied using MATLAB-Simulink over one year. The winter months have high wind speed and low sun radiation compared to other months, whereas additional months have high solar radiation and lower wind speed than the winter months. The findings show that the amount of Hydrogen produced for all scenarios varies from 12,340 m3 to 13,748 m3 per year. The system efficiency and LCOH are 7.974% and 3.67$/kg, 9.56%, and 3.97$/kg, 10.7% and 4.12 $/kg, 12.08%, and 4.3$/kg, and 16.23% and 4.69$/kg for scenarios1 to 5, respectively. Finally, the introduced system can reduce CO2 emissions by 345 tons over the lifetime and gain about 13,806$.

Hydrogen energy, as clean and efficient energy, is considered significant support for the construction of a sustainable society in the face of global climate change and the looming energy revolution. Hydrogen is one of the most important chemical substances on earth and can be obtained through various techniques using renewable and nonrenewable energy sources. However, the necessity for a gradual transition to renewable energy sources significantly hampers efforts to identify and implement green hydrogen production paths. Therefore, this paper’s objective is to provide a technological review of the systems of hydrogen production from solar and wind energy utilizing several types of water electrolyzers. The current paper starts with a short brief about the different production techniques. A detailed comparison between water electrolyzer types and a complete illustration of hydrogen production techniques using solar and wind are presented with examples, after which an economic assessment of green hydrogen production by comparing the costs of the discussed renewable sources with other production methods. Finally, the challenges that face the mentioned production methods are illuminated in the current review.

Hybrid vapor compression systems based on adsorption are recognized as a viable alternative to traditional energy-intensive compression systems. Solar-powered hybrid adsorption-compression refrigeration systems feature a solar-powered silica gel/water-based adsorption cooling system paired with a traditional compression system that utilizes R134a as a refrigerant. Herein, the system feasibility of a solar-operated hybrid adsorption-compression refrigeration system has been evaluated theoretically using typical climatic data of Alexandria, Egypt. Mathematical modeling is generated and compared to the most relevant experimental data. PVT collectors are exploited to drive both the adsorption and the compression units. Simulation results suggest that using a three-to-one system size ratio between the adsorption and compression subsystems might considerably raise the COP from 2.9 to 5 for the compression system. It is observed that at an ideal size ratio of 7, the proposed system can considerably deliver an energy saving of 30.8 percent, compared to the hybrid system of the size ratio of 3, which attains only energy savings of 22.1 percent. Furthermore, the utilization of PVT collectors might feed the hybrid system by 3.474 kWh and augment the electric grid by 100 kWh, at an ideal size ratio of 7. Overall, investigating hybrid adsorption-compression systems might offer unique insight on optimizing the performance of conventional counterparts.

Nowadays freshwater needs were covered by fossil fuel-based desalination systems in many areas over the world. However, fossil fuels’ excessive burning results in rapid depletion and pollution of the local environment as well as threat to life sustainability. Therefore, through the last few decades the scientific community focused on the systems relying on solar energy in seawater desalination as a clean alternative. Stepped solar stills, which convert solar energy to the required heat for producing freshwater in seawater desalination, are paid much attention. This article provides a comprehensive analysis of stepped solar stills’ development. Performance enhancement techniques, desalinated water production, efficiency and maximum theatrical production are discussed. This work aims to keep researchers and concerned scientific community abreast of stepped solar stills’ improvements. Such stills of low construction and running costs can meet the freshwater daily needs for small communities in coastal areas, islands and rural areas especially in Mideast. In conclusion, this review clarified that the stepped type solar stills still need multiple improvements to enhance their production efficiency and freshwater quantity. Further attention should be paid to the design of modified stills to attain better and efficient solar heat absorption as well as evaporation of seawater.

Enhancing the performance of anode supported honeycomb solid-oxide fuel cells via operating at higher temperatures is of great interest. However, working at a higher temperature leads to a significant rise in thermal stresses over the allowable limit. Thus, in the current study, functionally graded electrodes are considered to avoid cell failure due to higher thermal stresses. To assess the cell performance and thermal stress distribution, a theoretical investigation of a solid-oxide fuel cell with a honeycomb configuration using functionally graded electrode compositions is conducted through a comprehensive 3D model. The developed model includes the charge transport, mass and momentum transport, energy conservation, electrochemical reaction kinetics, and elastic stress. The model is numerically simulated and validated with the available experimental data. Results indicate that using functionally graded electrodes with grading index m = 1 significantly improves the fuel cell's performance, with an improvement in power density reaching around 60%. In addition, the most beneficial improvement is to reduce thermal stresses at elevated temperatures, for which the maximum value of equivalent stress is reduced to 85% less than the conventional electrode at a temperature of 1150 °C. Accordingly, the fuel cell's maximum power density can be obtained by operating at elevated temperatures with safe thermal stresses. These improvements are particularly attractive for applications requiring compact, reliable, and high-power devices based on fuel cell technology.

Numerical simulation of blood flow modeling in cardiovascular system has been one of the most efficient tools in understanding and diagnosing many diseases in the recent few decades. Recent studies have been performed to investigate the effect of the external magnetic fields on the biomagnetic fluids such as blood. There are many applications of magnetic field which are closely related to hemodynamics such as the magnetic resonance imaging (MRI) devices, magnetic drug targeting (MDT) and cell separation. These applications have a direct connection with hemodynamics parameters such as the wall shear stress, pressure drop and recirculation zones. In this study, numerical simulation of blood flow in an abdominal aortic aneurysm under an external magnetic field is performed. Blood is considered as a non-Newtonian fluid with shear-thinning properties, in which the blood viscosity is a function of both shear rate and hematocrits using the Casson model. The three-dimensional axisymmetric flow is considered in the arterial segment. Results at different flow conditions such as the strength of the magnetic field, different inlet velocities and different hematocrits are estimated. The results indicate the significant effect of the magnetic strength on the wall shear stress and the pressure drop which reached 200 % and 600 %, respectively.

Numerical simulation of cellular blood flow modeling has attracted many studies in the few recent years due to its importance in determining many macroscopic properties of blood. Additionally, the accurate modeling of blood flow, and hence the diagnosing of many cardiovascular diseases requires a detailed description of the dynamical behavior of individual cells. The aim of this study is to simulate the blood flow in the cellular level to have a better understanding and accurate modeling of blood flow in some cases that are not intensively examined in literature such as the dense suspension of flowing RBCs in microvessel with different degrees of stenosis. The present study is based on an open-source code, Hemocell for modeling blood flow in the cellular level. The lattice Boltzmann method coupled with the immersed boundary method are used to capture the cell deformation and the interaction between plasma forces and cell membrane. The distributions of the RBCs in both radial and axial directions are obtained. The deformation of the cells due to passing through the vessel especially the throat is studied for two cases of stenosis. It is found that the deformation of the cells at the center of the stenosis is higher than the deformation in other regions. Additionally, the increase of the stenosis degree increases the average deformation of the cells. It is observed that a longer time is required for the simulation in the case of 80 % reduction in the diameter.

Coronary artery disease (CAD) is the abnormal contraction of heart supply blood vessel. This contraction in the blood vessels limits the flow of oxygenated blood to the heart. Thus, diagnosing its severity helps physicians to select the appropriate treatment plan. Most of the commonly diagnostic methods are qualitative. They depend on the physicians’ experience and judgement to specify the severity of the stenoses. Fractional flow reserve is one of the quantitative diagnostic tools used while coronary catheterization is being performed. Fractional flow reserve measures the pressure gradient from the proximal to the distal sides of a coronary artery stenosis; this helps in deciding whether the stenosis limits the oxygenated blood flow. Resent models of vascular hemodynamics consider physiologic blood flow to be laminar. Transition to turbulence is considered as a driving factor for numerous diseases such as stenosis and aneurysm. As the value of Reynolds number does not exceed 2000, the flow is laminar. Several researchers stated that the flow might be turbulent at critical Reynolds number value less than 2000. Hence, the aim of this study is to investigate the most accurate turbulence flow model compared to the available experimental data. It is important to replicate the experimental model. Accordingly, the same non-Newtonian blood flow model and pulsatile flow boundary conditions were used. The stenosed simple geometry with a centered fractional flow reserve guidewire is constructed based on the same dimensions of the experimental setup. The numerical models were simulated with laminar flow and K-ε, and large eddy simulation (LES) turbulence modelling. The predicted results are compared with the actual available experimental measurements to investigate the most accurate numerical model of the blood flow in the stenosed coronary artery. Based on the predicted results, pressure drop coefficient (CDP), Pressure recovery coefficient (CPR), and the pressure recovery factor η are investigated in the coronary stenosis with and without fractional flow reserve guidewire. For the severe 89% stenosis, it was found that the error in CDP before and during the guidewire insertion is small. The error in CDP before inserting the guidewire reached −7%, −7%, and −12% for laminar, turbulent K-ε, and LES models, respectively and −11%, −11%, and −4% for laminar, turbulent K-ε, and LES models, respectively during inserting the guidewire. Accordingly, it can be concluded that the laminar and LES modelling represent better performance in simulating the blood flow rather than the turbulence model.

This study investigates the utilization of petrochemical and domestic wastewater (PCW and DW) for dual biogas and biochar production, focusing on the economic and sustainable development criteria. Biogas yield by anaerobic co-digestion of a 0:1 (PCW:DW) feed was 306.4±11.8 mL per g chemical oxygen demand (COD) removed, which dropped by 12.7% with changing PCW:DW to 1:0. The results indicated that increasing the DW fraction in the feed encouraged the conversion of COD into more biogas and sludge amounts. The anaerobic sludge was subjected to pyrolysis to generate biochar with a yield of 0.6 g/g dry sludge. The delivered biochar showed appropriate surface morphology, elemental composition, physical properties, and surface functional groups, as demonstrated by SEM/EDX, XRD, and FTIR characterizations. The COD mass balance estimation of the anaerobic digestion system, with biochar yield, was used to determine the economic feasibility of treating 30 m3/day of wastewater. The 1:0 (PCW:DW) condition provided the most feasible scenario, with profits of 3340, 192, and 2819 USD/year for energy income, biochar selling, and pollution reduction, respectively. This economic benefit was equivalent to a payback period of 5.38 years. The fulfillment of multiple sustainable development goals (SDGs) related to clean and renewable energy production, human health protection, and economic growth was highlighted. Graphical abstract

The concentrator photovoltaic (CPV) systems commonly endure high cell temperatures, which affect their overall performance. Besides, the high cell temperature could lead to physical damages within the whole system due to the induced thermal stresses. Therefore, an efficient cooling is mandatory to achieve a higher net output power from the CPV and safe operation. The current work's main purpose is to investigate the integration of double-layered microchannel heat sink (DL-MCHS) with CPV cell as thermal management device. A three-dimensional (3D) model is presented to investigate the performance of a CPV cooled by the DL-MCHS to figure out the ability to handle the effective heat dissipation under different terrestrial conditions. The parallel flow (PF) and counter flow (CF) cooling orientations were studied. Ethanol coolant is used to cool the CPV under different concentration ratios (CR) of 5, 10, 15, and 20 suns. The results show that the temperatures remarkably decreases with the inlet flowrate is increased. The counter flow operation (CF) achieved the best temperature uniformity index ( T uni ) when the coolant mass flowrate (V) ranged between 200 and 1200 ml/hr. Especially at CR 5 suns, the temperature uniformity index, T uni , enhanced to 99.87% at 1200 ml/hr.

The present study introduces an innovative method for fresh water and electricity generation in the isolated regions. This proposed system couples a concentrated photovoltaic (CPV) unit with a membrane distillation (MD) unit. The CPV unit converts solar energy into electrical energy with conversion efficiency of about 40%. The rest is converted to thermal energy, which may cause cells degradation if temperature exceeds manufacturer limits. An intermediate fluid is used as a coolant which transfers the excess energy to the feed of the MD unit through a heat exchanger. The generated thermal energy in the HCPV cells is used as the driving force for the distillation phenomena in the MD unit. Numerical models were built to simulate the hybrid system. It was found that, at a solar radiation concentration ratio of 1000 suns, the coolant flow rate should exceed 150 g/min for a maximum cell temperature less than 349 K. This arrangement should produce 177 W electric power, and 308 W thermal heat transferred to the coolant. At these conditions, the feed inlet temperature reaches about 323 K, at which, the MD unit produces about 5.88 kg/m2.h of pure water, thus allowing the system to simultaneously produce electricity and pure water for isolated coastal regions.

This work investigates the incorporation of a flat plate solar collector into an air gap membrane distillation (AGMD) system to produce pure water from water wells in Egypt. First, it considers the metrological data for Borg El Arab city, which is located at the north of the western desert in Egypt. A three-dimensional AGMD numerical model is established and solved using ANSYS 2019 commercial software, after setting suitable boundary conditions. Once the pure water flux is predicted at certain feed water inlet and outlet temperatures, a thermal analysis of the flat plate solar collector is introduced to estimate the required solar collector area to produce the required pure water flux.

In this paper, theoretical investigation of an integrated solar-powered cooling system consisting of commercial photovoltaic/thermal (PVT) collectors and an adsorption chiller is performed. The performance is investigated under different climate conditions of the Middle East such as Alexandria in Egypt, Dubai in United Arab Emirates and Riyadh in Saudi Arabia. System performance parameters including cooling capacities, chiller COP, solar COP, generated electric power and total system efficiency have been investigated. The results of the study for the month of July show that the maximum generated electric power is about 12.55 kW in Alexandria, while the maximum cooling capacity and COP are 8.1 kW and 0.43, respectively in Dubai. Furthermore, the average total system efficiency in a typical day in July is about 0.248, 0.288 and 0.275 in Alexandria, Dubai and Riyadh, respectively.

In this study, a novel interrelationship between the ventilation rate and the solar chimney design parameters, EAHE geometrical specifications, pressure drop, and climatic conditions in the hot arid area was presented based on experimental and numerical comprehensive investigations. This new correlation simplified designing and optimizing of the passive cooling/heating and ventilation system. Moreover, this correlation was used in a case study of passive cooling/heating and ventilation of a two-stories residential building in Egypt by TRNSYS simulation. The indoor operative air temperatures, heating and cooling loads, thermal comfort conditions, energy consumptions/savings, and CO2 emission savings were calculated and analyzed. Two cases were simulated and compared with the basic-case. In case 1, the basic-case combined with the solar chimney and EAHE. Case 2 had a hybrid passive and active ventilation, which included case 1 equipped with electrical fans that continued operating for 24 h. Finally, an economic study was conducted to calculate the payback period and discount payback period for the construction of such a system using the local Egyptian market equipment. The basic case results show that the zonal temperature was more than the ambient temperature yearly, and in summer, the indoor temperature exceeded the surrounding temperature by 5–6 °C. Using the proposed system in case 1 and case 2 attained a zonal temperature around 5 °C and 9 °C less than the ambient temperature in the summer season, respectively. However, the total annual electrical energy and CO2 emission savings were 42.9 kWh/m2/year and 4.545 tons/year, respectively, in case 2. Finally, the simple payback period was 5.4 years, and the discount payback period was 6.8 years.

This paper presents the state-of-the-art of the integration of adsorption chillers into different configurations of combined cooling, heating, and power (CCHP) systems. Adsorption chillers, as a thermally-activated cooling system, provide a great solution to the utilization of low-temperature waste heat, thus help to increase the efficiency of the existing power generating systems, and to reduce the greenhouse gasses emissions including the chlorofluorocarbons (CFC) that is used in traditional electric-powered chillers. In this study, a brief introduction to CCHP systems and the thermally-driven cooling systems is presented, and the working scheme of the adsorption cooling cycle is illustrated. The paper also focuses on the CCHP systems integrated with adsorption chillers that are driven by solar thermal energy via different solar collectors. Furthermore, multigeneration systems driven by internal combustion engines, gas turbines and fuel cells are highlighted. Finally, the integration of adsorption chillers in hybrid cooling systems and with Organic Rankine Cycles (ORC) is also presented.

The dense solar radiation received by a high concentration photovoltaic module (HCPVM) causes a high cell temperature. In this module, multiple solar cells were electrically connected in both series and parallel. The higher temperature of the solar cell in the series string limits the generated power for the whole string. Therefore, it is crucial to employ a uniform cooling mechanism for higher electrical performance along with a longer lifespan. The uniform cooling is required to attain safe operating temperature and prevent the hot spot formation. Hence, in the current work, a four-compartment microchannel heat sink is proposed for the thermal management of HCPVM under high solar concentration of 1000 suns (1 sun = 1000 W/m2). A three-dimensional (3D) conjugate heat transfer model with exergy analysis is developed and validated. This model was used to investigate the effect of inlet and outlet orientation of four quadrants microchannel heat sink as a cooling method for HCPVM. Eight different orientations of parallel-flow and counter-flow conditions were investigated and compared in terms of temperature non-uniformity, module power, and exergy performance. The results showed that the inlet and outlet orientation was a key role affecting the module temperature non-uniformity. For the counter-flow operated heat sinks, the HCPVM can be operated under a temperature non-uniformity of 3.1 °C at total inlet module mass flowrate of 350 g/min and solar concentration ratio of 1000 suns. In addition, the attained HCPVM electrical, thermal, and overall exergy efficiency were 37.2%, 8.2%, and 45.4% respectively at the same conditions.

This paper investigates microwave drying effect as a pretreatment method on the kinetic parameters of four torrefied biomasses. The considered biomasses are rice straw, rice husk, sugarcane, and cotton stalks. Dried samples (microwave or oven-dried) were then torrefied under isothermal conditions in a thermogravimetric analyzer (TGA) at two different temperatures of (250 and 300 °C). Two simple kinetics methods were applied including direct Arrhenius (DA) and Coats and Redfern (CR). The physical structure of rice straw and cotton stalks as a function of drying method and torrefaction temperature has been studied using Brunauer–Emmett–Teller (BET) surface area technique. Results revealed that microwave drying increased both the activation energy and the pre-exponential factor for both rice straw and sugarcane regardless of the torrefaction temperature, while the opposite occurred for rice husk. In the case of cotton stalks, microwave drying increased the kinetic parameters at 250 °C and decreased them at 300 °C. The activation energy and pre-exponential factor values obtained from CR method were larger than the ones from DA method. The 300 °C torrefied, conventionally dried rice straw has the lowest activation energy and pre-exponential factor and the largest peak width indicating wide range of reactivity. While microwave dried sugarcane, torrefied at 250 °C, is the hardest one to react. All microwave dried samples require more heat to decompose regardless of the torrefaction temperature. Microwave drying increased the surface area, mean pore diameter, and pore volume for rice straw, while the opposite occurred for cotton stalks due to its woody nature.

In the current study, three-dimensional theoretical model of the photovoltaic (PV) panel coupled with a heat spreader is carried out. A thermal model is constructed and solved mathematically by using ANSYS software. The effect of coupling the heat spreader with the PV and the heat spreader dimensions on the PV cooling and performance is studied. Also, the effect of solar radiation intensity and weather conditions (wind speed and ambient temperature) on the performance of PV with heat spreader system is considered. The model is validated with the previous results found in the literature. Moreover, the temperature distribution of the PV with the heat spreader is presented. The results show that the optimum thickness and cross sectional area of the heat spreader for PV dimensions of 125 × 125 mm are 10 mm and 0.3 m2. The cell temperature is decreased by 15 °C when the heat spreader is used with the PV. Also the average power output and efficiency of the PV module are increased by 9% when the heat spreader is used.

Inspired by the tubercles on the pectoral flipper leading-edge of the humpback whale, the most acrobatic of baleen whales, sinusoidal leading-edge have been used as a passive flow control method to enhance the stall characteristics of lifting surfaces in different applications. They are supposed to reduce the lift gradually during the stall with an increase in the post-stall lift, however, their enhancement ability in pre- and post-stall is highly dependent on the geometrical parameters and the flow regime. Two different design schemes: nonlinear shear transformation design scheme (NLST) and channelled-like scheme, of the sinusoidal leading edge of the high lift airfoil S1223 are tested and compared with the unmodified airfoil at angles of attack of −6 to 30 degrees experimentally inside a wind tunnel at low Reynolds number Re = 100,000. Experimental data show that Tubercles implemented on S1223 at such a flow regime with either design scheme enhance the post-stall characteristics as much as a 42% increase in lift at some angles for NLST with pre-stall lift penalties. NLST, compared with baseline and channelled models, exhibit a significant increase in aerodynamic efficiency which make it more preferable for wind turbines applications.