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Advancements in water electrolysis technologies are crucial for green hydrogen production. Proton exchange membrane water electrolysis (PEMWE) is characterized by its efficiency and environmental benefits. The prediction and optimization of hydrogen production rates (HPRs) in PEMWE systems is difficult and still challenging because of the complexity of the system as well as the operational parameters. The integration of artificial intelligence (AI) and machine learning (ML) appears to be effective in optimization within the energy sector. Hence, this work employs the artificial neural network (ANN) to develop a model that accurately predicts HPR in PEMWE setups. A novel approach is introduced by employing the Levenberg–Marquardt backpropagation (LMBP) algorithm for training the ANN. This model is designed to predict HPR based on critical operational parameters, including anode and cathode areas (mm2), cell voltage (V) and current (A), water flow rate (mL/min), power (W), and temperature (K). The optimized ANN configuration features an architecture with 7 input nodes, two hidden layers of 64 neurons each, and a single output node. The performance of the ANN model was evaluated against conventional regression models using key metrics: mean squared error (MSE), coefficient of determination (R2), and mean absolute error (MAE). The findings of this study reveal that the developed ANN model significantly outperforms traditional models, achieving an R2 value of 0.9989 and an MAE of 0.012. In comparison, random forest (R2 = 0.9795), linear regression (R2 = 0.9697), and support vector machines (R2 = − 0.4812) show lower predictive accuracy, underscoring the ANN model's superior performance. This work demonstrates the efficiency of the LMBP in enhancing hydrogen production forecasts and sets a foundation for future improvements in PEMWE efficiency. By enabling precise control and optimization of operational parameters, this study contributes to the broader goal of advancing green hydrogen production as a viable and scalable alternative to fossil fuels, offering both immediate and long-term benefits to sustainable energy initiatives.

Nanofluids, comprising nanoparticles and a base fluid, have captured substantial interest due to remarkable enhancements in thermal conductivity and other crucial thermophysical properties. These advancements facilitate diverse applications across various industrial processes, including biomedical and drug research. This review centers on non-Newtonian nanofluids, which diverge from Newton's law of viscosity, rendering them more adaptable and versatile. Through a comprehensive examination of the latest research, preparation methods, including both one-step and two-step techniques, and their formulations in oil-based, water-based, and ethylene glycol-based solutions are systematically explored. The study synthesizes findings that highlight significant improvements in heat transfer efficiency and introduces novel applications in sectors, such as biomedical engineering and energy systems. Furthermore, an in-depth characterization of non-Newtonian nanofluids is provided, covering their rheological, dispersion, transport, magnetic, optical, and radiative properties. These fluids are increasingly utilized in heat exchangers, automotive radiators, engines, solar collectors, and electronic coolants, demonstrating their broad spectrum of practical applications. This review shows that the ongoing challenges are primarily centered on the preparation, stability, and commercialization of non-Newtonian nanofluids. Conclusively, the paper underscores the potential of non-Newtonian nanofluids to revolutionize various technological areas and advocates for continued research to develop more stable and efficient formulations, paving the way for innovative industrial and scientific applications.

Abstract There are numerous reports and publications in reputable scientific and engineering journals that attribute substantial enhancement in heat transfer capabilities for heat exchangers once they employ nanofluids as working fluids. By definition, a nanofluid is a working fluid that has a small volume fraction (5% or less) of a solid particle with dimensions in the nanoscale. The addition of this solid material has a reported significant impact on convective heat transfer in heat exchangers. This work investigates the significance of the reported enhancements in many recent related publications. Observations on these publications’ geographical origins, fundamental heat transfer calculations, experimental setups and lack of potential applications are critically made. Heat transfer calculations based on methodologies outlined in random selection of available papers were conducted along with a statistical analysis show paradoxically inconsistent conclusion as well as an apparent lack of complete comprehension of convective heat transfer mechanism. In some of the surveyed literature for example, heat transfer coefficient enhancements were reported to be up to 27% and 48%, whereas the recalculations presented in this work restrain proclaimed enactments to ~ 3.5% and − 4% (no enhancement), respectively. This work aims at allowing a healthy scientific debate on whether nanofluids are the sole answer to enhancing convective heat transfer in heat exchangers. The quantity of literature that confirms the latter statement have an undeniable critical mass, but this volition could be stemming from and heading to the wrong direction. Finally, the challenges imposed by the physical nature of nanoparticles, as well as economic limitations caused by the high price of conventional nanoparticles such as gold (80$/g), diamond (35$/g), and silver (6$/g) that hinder their commercialization, are presented.

Proton exchange membrane fuel cells (PEMFCs) are among the promising alternatives for clean energy generation, especially when hydrogen is the fuel used. Their operation is still faced with several challenges, and one of them is water accumulation in the cathode compartment. If PEMFCs are operated at temperatures above the boiling point of water, a significant obstacle would be eliminated due to the formation of water in the vapor phase. This prevents water from accumulating in the liquid phase which causes flooding. Therefore, this work aims to develop a novel composite membrane based on zirconium silicate (ZrSiO4) and Polyvinylidene fluoride (PVDF) for such high-temperature operation. The composite membrane was synthesized using solution casting, and its structural and chemical properties were characterized using thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The ZrSiO4/PVDF membrane demonstrated a maximum proton conductivity of 2.14 × 10−3 S/cm at room temperature with 8 wt% ZrSiO4, along with a water uptake value of 43.85 %. Consequently, when tested above the boiling point of water, the membrane exhibited a high conductivity of 2.13 × 10−3 S/cm at 105 °C. The results suggest the suitability of such zirconium silicate-based composite membranes for fuel cell applications operating above the boiling point of water.

Remarkably toxic, phenol requires efficient elimination from water. This study investigates the utilization of solid waste generated by stone-cutting factories for extracting phenol from wastewater. The solid waste underwent thermal treatment at 105 °C for 3 h for characterization. Batch adsorption experiments systematically assessed parameters like phenol concentration, adsorbent mass, contact time, temperature, and pH. Optimal removal transpired at pH 7.5, reaching equilibrium within 4 h. Phenol uptake equilibrium values were 8.1, 13.3, 16.2, 20.2, and 28.1 mg/g for initial concentrations of 50, 100, 150, 200, and 300 mg/L, respectively using 1 g of adsorbent at ambient temperature. The Langmuir model fit acceptably, yet the Freundlich model surpassed it. The most suitable kinetics model for phenol adsorption was the pseudo-second-order. The nature of the adsorption process was endothermic. Importantly, this study pioneers the promising application of solid waste generated from stone-cutting factories as an adsorbent material for effective phenol removal, offering a sustainable approach. Notably, no previous study has been conducted on phenol removal from wastewater using this specific adsorbent, rendering this work pivotal in exploring its potential. This solid waste presents an economical, readily available, and environmentally benign material for the adsorption process, expected to exhibit substantial adsorption capacity.

This mini review discusses the sustainability aspects of various fuels for proton exchange membrane fuel cells (PEMFCs). PEMFCs operate by converting the chemical energy in a fuel into electrical energy. The most crucial parameters in the operation process are the temperature, pressure, relative humidity, and air stoichiometry ratio, as presented in this work. The classical structure of a PEMFC consists of a proton exchange membrane, anode electrode, cathode electrode, catalyst layers (CLs), microporous layer (MPLs), gas diffusion layers (GDLs), two bipolar plates (BPs), and gas flow channels (GFCs). The mechanical behavior and the conductivity of the protons are highly dependent on the structure of the MEAs. This review discusses the various fuels and their production paths from sustainable sources. For the fuel production process to be renewable and sustainable, a hydrogen electrolyzer could be powered from solar energy, wind energy, geothermal energy, or hydroelectric energy, to produce hydrogen, which in turn could be fed into the fuel cell. This paper also reviews biomass-based routes for sustainable fuel production.

Thermal energy storage systems are extensively investigated because of their fundamental role in the storage of renewable energy and in the recovery of useful heat generated from various systems. The three mechanisms of thermal energy storage are discussed herein: sensible heat storage (QS,stor), latent heat storage (QL,stor), and sorption heat storage (QSP,stor). Various materials were evaluated in the literature for their potential as heat storage mediums in thermal storage systems. The evaluation criteria include their heat storage capacity, thermal conductivity, and cyclic stability for long-term usage. This work offers a comprehensive review of the recent advances in materials employed for thermal energy storage. It presents the various materials that have been synthesized in recent years to optimize the thermal performance of QS,stor, QL,stor, and QSP,stor systems, along with the challenges associated with thermal energy storage materials. The paper concludes that latent heat storage systems via the use of inorganic phase change materials (PCMs) would be ideal for high-temperature applications.

This work investigates the performance of a single-effect absorption chiller utilizing an aqueous lithium bromide solution as the working fluid and driven by hot fluid rejected from either a geothermal power plant or the outlet of a thermal solar collector. This relatively low enthalpy return fluid, which will otherwise be reinjected back into the earth, will be utilized as the thermal energy source of the chiller. Although such chillers are considered low-grade energy refrigeration cycles, the one proposed here has an advantage in terms of economy and efficiency. A parametric analysis is performed using Engineering Equation Solver software and is used to highlight the effect of the heat exchanger size on the coefficient of performance of the chiller. The analysis proved that the proposed device can operate with excellent cooling capacity, reaching 16 kW, and a relatively high coefficient of performance (~ 0.7) while being driven by the low-grade energy. The heat source temperature, solution heat exchanger effectiveness and the size of the absorber were shown to be key parameters for the design and operation of absorption chillers. Moreover, increasing the heat source mass flow rate has a significant impact on both cooling capacity and coefficient of performance at low values (< 10 kg/s) and unnoticeable impact at higher values (> 10 kg/s).

Microplastics pollution is a modern-day prevalent challenge that poses serious threats to the general wellbeing and sustainability of the planet. Due to their innately persistent nature, extreme durability, and high stability, they exhibit long residence time and could be transferred through the ecological chains. Current days have witnessed an increase in the accumulation of microplastics waste and debris. This is due to the protective measures imposed by governments and the World Health Organization (WHO) as part of the containment and mitigation efforts of the COVID-19 pandemic. Therefore, the development of versatile, robust, flexible, and efficient removal systems has become a necessity in order to control microplastics pollution. Herein, we review the repercussions of the pandemic on the state of microplastics contamination, sources and identification methods of microplastics in water, their toxicity and risks on the environment, as well as their degradation and conventional removal methods. This review focuses on adsorption and the use of biochar as one of the emerging adsorbents for the removal of microplastics. The efficiency of adsorption using biochar, mechanisms, and applications are discussed. The review addresses the increased rates of microplastics occurrence especially during the era of COVID-19, which requires more efficient and lower cost removal methods. The major conclusions drawn from this review include emphasizing the significant potential of adsorption processes in the removal of microplastics. Biochar is present among the available and most efficient biomass adsorbents especially when combined with other materials. Composite biochar materials play an important role in enhancing the removal and immobility of microplastics. However, more research is required to investigate this at a larger scale, improve efficiency and immobilization techniques.

In this work intrinsically magnetic quasi-crystalline Fe–Cu nanoparticles are used in an aqueous solution for heat transfer enhancement application. The experimental work commenced by synthesizing the Fe–Cu material via high energy ball milling in 1:1 ratio using 10 mm diameter stainless steel balls and crucibles, followed by cryogenic crushing to further reduce the particle size to the nanoscale. The results of grain size reduction are verified by transmission electron microscopy measurements that showed sizes down to 50 nm. Other measurements pertinent to the expected performance of these particles in solution are the determination of the zeta potential of the particles. To assess the enhancement of heat transfer characteristics within a closed vessel by the rotating magnetic agitation of the magnetic particles, the nano-powder is added to deionized water at different concentrations. The time required (Δt) to a reach a certain temperature difference (ΔT) is measured to construct the Wilson plot parameters for each of the fluids used. It is found that the addition of the Fe–Cu nanofluid has enhanced the transient heat transfer by up to 34.6%.

This work provides a comprehensive review on the incorporation of ionic liquid (ILs) into polymer blends and their utilization as proton exchanges membranes (PEM). Various conventional polymers that incorporate ILs are discussed, such as Nafion, poly (vinylidene fluoride), polybenzimidazole, sulfonated poly (ether ether ketone), and sulfonated polyimide. The methods of synthesis of IL/polymer composite membranes are summarized and the role of ionic liquids as electrolytes and structure directing agents in PEM fuel cells (PEMFCs) is presented. In addition, the obstacles that are reported to impede the development of commercial polymerized IL membranes are highlighted in this work. The paper concludes that the presence of certain ILs can increase the conductivity of the PEM, and consequently, enhance the performance of PEMFCs. Nevertheless, the leakage of ILs from composite membranes as well as the limited long-term thermal and mechanical stability are considered as the main challenges that limit the employment of IL/polymer composite membranes in PEMFCs, especially for high-temperature applications.

The present work involves a new and novel upgrading design to the classical solar chimney power plant (SCPP) structure. The SCPP design was modified by adding a co-centric secondary external chimney to the SCPP structure to enhance energy production. In the new improved design, named the solar double-chimney power plant (SDCPP), the internal chimney, operates like a traditional SCPP to produce electricity during the daytime whereas the secondary external chimney operates as 10 cooling towers (CT) in a series. Each CT is equipped with a turbine and water sprinklers for further energy production. The new design offers the operation of the SCPP during the day and the continuous operation of the CT (day-and-night). A mathematical model that includes the energy and mass balance equations of the system was built using MATLAB. The SDCPP system produced up to 993 MWh of electrical energy, which is 2.6 times higher than the traditional SCPP (377 MWh). The new design configuration achieved a percentage of thermal efficiency (%ηth) of 1.6%, which is 200 times greater than the SCPP. The economic assessment of the new system revealed a 50% reduction in the localized cost of energy (LCOE) compared with traditional SCPP. The key advantage of the new design is related to the use of low-cost material in constructing the secondary chimney to reduce the fixed capital cost and prompt the economic feasibility of the system. Overall, the proposed SDCPP offers a feasible and economic solution to produce electricity and to potentially reduce greenhouse gas emissions.

This work evaluates date palm waste as a cheap and available biomass feedstock in UAE for the production of biofuels. The thermochemical and biochemical routes including pyrolysis, gasification, and fermentation were investigated. Simulations were done to produce biofuels from biomass via Aspen Plus v.10. The simulation results showed that for a tonne of biomass feed, gasification produced 56 kg of hydrogen and fermentation yielded 233 kg of ethanol. Process energy requirements, however, proved to offset the bioethanol product value. For 1 tonne of biomass feed, the net duty for pyrolysis was 37 kJ, for gasification was 725 kJ, and for fermentation was 7481.5 kJ. Furthermore, for 1 tonne of date palm waste feed, pyrolysis generated a returned USD $768, gasification generated USD 166, but fermentation required an expenditure of USD 763, rendering it unfeasible. The fermentation economic analysis showed that reducing the system’s net duty to 6500 kJ/tonne biomass and converting 30% hemicellulose along with the cellulose content will result in a breakeven bioethanol fuel price of 1.85 USD/L. This fuel price falls within the acceptable 0.8–2.4 USD/L commercial feasibility range and is competitive with bioethanol produced in other processes. The economic analysis indicated that pyrolysis and gasification are economically more feasible than fermentation. To maximize profits, the wasted hemicellulose and lignin from fermentation are proposed to be used in thermochemical processes for further fuel production.

This work presents the synthesis and deposition of CuI and FeCu materials on copper substrates for dye-sensitized solar cell applications. FeCu is a metastable alloy of iron and copper powders and possesses good optical and intrinsic magnetic properties. Coupled with copper iodide as tandem layers, the deposition of these two materials was permutated over a pure copper substrate, characterized and then tested within a solar cell. The cell was sensitized with a natural dye extracted from a local desert plant (Calotropis gigantea) and operated with an iodine/triiodide electrolyte. The results show that the best layer arrangement was Cu/FeCu/CuI, which gave an efficiency of around 0.763% (compared to 0.196% from reported cells in the literature using a natural sensitizer).