Methane hydrates were studied in systems containing aqueous dissolved surfactants in oil emulsions with a volume ratio of 40/60. Two commercial surfactants, named synperonic PE/F127 and cetyltrimethylammonium bromide, were evaluated at 0, 350, 700 and 1500 ppm. Experiments were made by applying the cooling−heating path in an isochoric high-pressure cell at different initial pressures of 5.5, 8.0, 10.0 and 12.0 MPa. The obtained parameters were induction time, temperature onset, pressure drop, and dissociation conditions. The results revealed that the dissociation curve for methane in water-in-oil emulsions was not modified by the surfactants. The crystallization (onset) temperature was higher using synperonic PE/F127 in comparison with zero composition, while the opposite occurred with cetyltrimethylammonium bromide. Both surfactants induced a delaying effect on the induction time and a lesser pressure drop.

Thermal energy storage using phase change materials (PCMs) is a promising technology for improving the thermal performance of buildings and reducing their energy consumption. However, the effectiveness of passive PCMs in buildings depends on their optimal design regarding the building typology and typical climate conditions. Within this context, the present contribution introduces a novel multiobjective computational method to optimize the thermophysical properties of cementitious building panels enhanced with a microencapsulated PCM (MPCM). To achieve this, a parametric model for PCM-based cementitious composites is developed in EnergyPlus, considering as design variables the melting temperature of PCMs and the thickness and thermal conductivity of the panel. A multiobjective genetic algorithm is dynamically coupled with the building energy model to find the best trade-off between annual heating and cooling loads. The optimization results obtained for a case study building in Sofia (B... [more]

This paper investigates the characterization of an electric double-layer capacitor (EDLC). In this study, the 300 F and 400 F EDLC supercapacitors are connected in a circuit in a laboratory experiment to produce their charge/discharge profiles at a constant current. The acquired charge/discharge profiles were used to determine the mathematical parameters of the EDLCs using the “Faranda model”, or “two-branch model”, of the EDLC. The parameters extracted from the equivalent circuit model were then used as inputs to a designed Python/MATLAB/Simulink (PMS)-hybrid model of an EDLC. This was simulated to obtain charge/discharge profiles. The resulting experimental- and simulated-charge/discharge profiles of the EDLCs were compared with each other, by superimposing their profiles to determine the accuracy of the PMS model. The PMS model was found to be very accurate. The innovation of this work lies in modeling a supercapacitor, mostly in the Python programming language in combination with a... [more]

A mixture of lanthanum strontium cobalt ferrite (LSCF) and nickel oxide (NiO) makes for a desirable cathode material for an IT-SOFC due to its excellent oxygen reduction capability. This study investigates the effect of NiO addition into LSCF cathode on its physical and electrochemical properties. To optimise the amount of NiO addition, both electrochemical impedance spectra and bode phase were used to examine various weight ratios of nickel oxide and LSCF cathode. Brunauer-Emmett-Teller (BET) and thermal analyses validated the electrochemical observation that the LSCF:NiO ratio yields sensible oxygen reduction reaction and stoichiometric findings. Initial characterisation, comprising of phase and bonding analyses, indicated that LSCF-NiO was successfully synthesised at 800 °C using an improved modified sol gel technique. The addition of 5% nickel oxide to LSCF results in the lowest area specific resistance (ASR) value overall. The Bode phase implies that the addition of 5% nickel oxid... [more]

Electric motors are utilitarian devices of great potential as they can limit the amount of pollution by drastically reducing the release of harmful gases. The implementation of the right type of advanced materials plays a vital role in the amelioration of modern automobiles while maintaining and/or improving the performance and efficiency of the electric motor. The use of lightweight materials could result in a better-performing vehicle that can be much less heavy. The replacement of regular cast iron, steel, and aluminum with lightweight materials such as fiber-reinforced polymer, carbon fiber, and polymer composites can reduce the weight of the motor without impacting its performance and improve its energy-saving capacity. This paper explores a way to reduce motor weight by employing a PA6GF30 30% glass fiber-reinforced polymer casing to reduce the weight of the motor while making cooling system modifications. This material was applied to the motor casing, which resulted in a signifi... [more]

This research activity aims to evaluate electrical insulation system (EIS) intended for electrical machine winding wires. The evaluation is based on mechanical, thermal, and electrical properties tests following international standards for enameled wires. Dielectric parameters such as dissipation factor, partial discharge inception voltage (PDIV), parallel capacitance, and parallel resistance behavior of different insulator configurations on twisted-pair samples are observed during thermal aging tests. Those configurations are formed of different combinations of dielectric layers based on conventional polymers (polyester-imide (PEI), polyamide-imide (PAI), polyimide (PI)) used as coating wires. A study using two mineral varnishes (silica-based) obtained by the sol-gel process integrated on these classical enamels an outer layer of extrusion of thermoplastic polymer with and without mineral fillers. Given the high consummation of energy and the use of unsustainable materials involving t... [more]

Hydrogen fuel cell technology is securing a place in the future of advanced mobility and the energy revolution, as engineers explore multiple paths in the quest for decarbonization. The feasibility of hydrogen-based fuel cell vehicles particularly relies on the development of safe, lightweight and cost-competitive solutions for hydrogen storage. After the demonstration of hundreds of prototype vehicles, today, commercial hydrogen tanks are in the first stages of market introduction, adopting configurations that use composite materials. However, production rates remain low and costs high. This paper intends to provide an insight into the evolving scenario of solutions for hydrogen storage in the transportation sector. Current applications in different sectors of transport are covered, focusing on their individual requirements. Furthermore, this work addresses the efforts to produce economically attractive composite tanks, discussing the challenges surrounding material choices and manufa... [more]

This paper describes the results of experimental studies on heat transfer in a shell and tube heat exchanger during the phase changes of the HFE 7000 refrigerant. The studies were performed using a mixture of water and a microencapsulated phase change material as a coolant. HFE 7000 refrigerant condenses on the external surface of the copper tube, while a mixture of water and phase change materials flows through the channels as coolant. Currently, there is a lack of research describing cooling using phase change materials in heat exchangers. There are a number of publications describing the heat exchange in heat exchangers during phase changes under air or water cooling. Therefore, the research hypothesis was adopted that the use of mixed water and microencapsulated material as a heat transfer fluid would increase the heat capacity and contribute to the enhancement of the heat exchange in the heat exchanger. This will enable an increase in the total heat transfer coefficient and the he... [more]

This review summarizes the performance of potential catalysts for the synthesis of dimethyl carbonate (DMC) using CO2 as a feedstock by two major processes—the direct route of carbonylation of alcohols and the indirect route of alcoholysis of urea. The reaction mechanisms and corresponding catalysts that were previously investigated are discussed. The major challenges associated with the conversion of CO2 to DMC are the low yields, low DMC selectivity, and thermodynamic limitations (alcohol carbonylation) of reversible reactions with low equilibrium constants. This occurs mainly due to the highly stable carbon dioxide molecules. The development of novel catalysts with high yields and high selectivity needs to be studied to overcome these technical challenges. In addition, to enhance the DMC yield, the use of dehydrating agents for water removal from the reaction mixture is recommended and discussed in detail in this article. This review critically examines the different catalysts used... [more]

Phase change material (PCM)-based thermal energy storage (TES) systems are widely used for repeated intermittent heating and cooling applications. However, such systems typically face some challenges due to the low thermal conductivity and expensive encapsulation process of PCMs. The present study overcomes these challenges by proposing a lightweight, low-cost, and low thermal resistance TES system that realizes a fluid-to-PCM additively manufactured metal-polymer composite heat exchanger (HX), based on our previously developed cross-media approach. A robust and simplified, analytical-based, 1D reduced-order model (ROM) was developed to compute the TES system performance, saving computational time compared to modeling the entire TES system using PCM-related transient CFD modeling. The TES model was reduced to a segment-level model comprising a single PCM-wire cylindrical domain based on the tube-bank geometry formed by the metal fin-wires. A detailed study on the geometric behavior of... [more]

In the present work, the optimization of a new coating formulation was investigated, taking attention to an industrially focused research approach used for the engineering design of the adsorber. The adsorbent was a composite zeolite or silica-gel based coating applied by using new flexible polymer matrices. The FC-80 formulation represents a good compromise between mechanical stability and absorption capacity. Using the developed coating process, a new compact HEX design was developed to reach the AHP target performance with easy and fast manufacturing. The specific cooling power of the coated heat exchanger was estimated to be about 500 W/kg of adsorbent. The new coated HEX was integrated in a new adsorption chiller and has been tested by a laboratory test-rig under realistic operating conditions. Results of preliminary testing demonstrated that the prototype provides a cooling capacity of around 10 kW with a COP of 0.54.

In this study, pyrolysis of municipal sewage sludge samples from different sources including cattle and chicken manure as well as brook mud, was investigated using a thermogravimetric analysis coupled with a Fourier transform infrared spectrometer (TG-FTIR) at different heating rates (25, 50 and 100 °C/min). In order to determine the kinetic parameters, Arrhenius, model-free Kissinger−Akira−Sunose (KAS), as well as Friedman and Flynn−Wall−Ozawa (FWO) methods were compared. The thermogravimetric results revealed that pyrolysis involved different stages, and that the main decomposition reactions took place in the range of 200−600 °C. In this range, decomposition of biodegradable components (e.g., lipids and polysaccharides), proteins and carbohydrates occurred; meanwhile, there were samples (e.g., cattle manure, brook mud) in which the decomposition step could be observed even at temperatures above 700 °C. According to the Arrhenius method, the activation energies of the first decomposit... [more]

This article presents a new approach for the efficient calculation of sensitivities in radiation dose estimates, subject to imprecisely known nuclear material cross-section data. The method is a combined application of adjoint-based models to perform, simultaneously, both the sensitivity calculation together with optimal adaptive mesh refinement. Adjoint-based sensitivity methods are known for their efficiency since they enable sensitivities of all parameters to be formed through only two solutions to the problem. However, the efficient solutions can also be obtained by their computation on optimal meshes, here guided by goal-based adjoint approaches. It is shown that both mesh adaptivity and sensitivity can be computed by the same adjoint solution, meaning both can be performed without additional costs. A simple demonstration is presented based on the Maynard fixed-source problem where uncertainties, with respect to material cross-sections, of doses received in local regions are exami... [more]

Energy consumption in the building sector is a major concern, particularly in this time of worldwide population and energy demand increases. To reduce energy consumption due to HVAC systems in the building sector, different models based on measured data have been developed to estimate the cooling load. The purpose of this work is to develop a linear regression model for cooling load of a research room based on the radiant time series (RTS) components of the cooling load that consider the building material and the environment. Using the forward step method, linear regression models were developed for both all-seasons and seasonal data from three years of cooling load data obtained from the RTS method for a research room at Mangosuthu University of Technology (MUT), South Africa. The male and female occupants, window cooling load, and roof cooling load were found to be the most influential predictors for the cooling load model. The obtained relative errors between the best all-seasons mo... [more]

Water content and water−coal interface wettability are always the difficult issues of coalbed methane adsorption/desorption. In order to study the effects of the pore structure and wettability of different macro coal components on methane adsorption and desorption, we compared and analyzed the wettability difference between vitrain and durain, and revealed the influence of wettability on methane adsorption and desorption through a pore structure analysis, wettability measurements, an adsorption−desorption experiment and adsorption heat calculations under different conditions, taking the No. 4 coal in Dafosi Coal Mine of the Huanglong coalfield as the research object. The results show that both vitrain and durain are relatively hydrophilic substances. However, vitrain has a low ash content, high volatility, and less oxygen, and the pores are mainly semi-closed pores compared with dark coal. Vitrain also has poor connectivity, poor sorting, a small pore diameter, and a coarser surface, r... [more]

In recent years, the number of articles reporting the addition of nanomaterials to enhance the process of anaerobic digestion has exponentially increased. The benefits of this addition can be observed from different aspects: an increase in biogas production, enrichment of methane in biogas, elimination of foaming problems, a more stable and robust operation, absence of inhibition problems, etc. In the literature, one of the current focuses of research on this topic is the mechanism responsible for this enhancement. In this sense, several hypotheses have been formulated, with the effect on the redox potential caused by nanoparticles probably being the most accepted, although supplementation with trace materials coming from nanomaterials and the changes in microbial populations have been also highlighted. The types of nanomaterials tested for the improvement of anaerobic digestion is today very diverse, although metallic and, especially, iron-based nanoparticles, are the most frequently... [more]

Chromated copper arsenate-treated (cca) wood disposal faces environmental restrictions due to its toxicity, heavy metal leaching in storage sites, and greenhouse gas emissions during incineration. Thus, finding new management methods for this contaminated wood at the end of life is crucial. This study evaluated the effect of pyrolysis temperature (300, 400, and 500 °C), particle size, biochar yield, and the behavior of arsenic (As), chromium (Cr), and copper (Cu) during treated-wood pyrolysis. The highest biochar yield was obtained at 300 °C for fine particles. The biochar retention of heavy metals decreased with increasing pyrolysis temperature. At 300 °C, the highest biochar As, Cr, and Cu retentions were 76, 91, and 83%. At 500 °C, biochar only retained 43% of the As. Additionally, heavy metal leaching from the biochar exceeded the Environmental Protection Agency’s (EPA) maximum concentration limit of 5 mg/L. High-density polyethylene encapsulation of contaminated biochar reduced th... [more]

The efficient development of carbonate oil deposits with excessive fissuring is a current challenge. Uneven and rapid well stream watering is considered as one of the factors that make the process of the development of carbon deposits more complicated. The purpose of the research is to diagnose and evaluate the mechanisms of well stream watering for carbon deposits and find applicable technology to prevent it. An overview of in situ water shut-off technologies was carried out. A description of the main materials used for water shut-off is presented, and selective methods are studied in more detail. A carbonate basin of an oil field is selected as the object of investigation. The geological and physical characteristics of this deposit are given. Analysis of possible causes and sources of water cut of the fluid is made according to the technique of K.S. Chan, under which the main reason for the watering of the well production is the breakthrough of formation and injection water through a... [more]

This research presents a finite element multi-physics design methodology that can be used to develop and optimise the inherent functions and geometry of an innovative regenerative eddy current (REC) damper for the suspension of B class vehicles. This methodology was inspired by a previous work which has been applied successfully for the development of an eddy current (EC) damper used for the same type of applications. It is based on a multifield finite element coupled model that can be used to fulfil the electromagnetic, thermal, and fluid dynamic field properties and boundary conditions of a REC damper, as well as its non-linear material properties and boundary conditions, while also analysing its damping performance. The proposed REC damper features a variable fail-safe damping force, while electric power is advantageously regenerated at high suspension frequencies. Its damping performance has been benchmarked against that of a regular hydraulic shock absorber (selected as a referenc... [more]

Hydrogen-based technologies are among the most promising solutions to fulfill the zero-emission scenario and ensure the energy independence of many countries. Hydrogen is considered a green energy carrier, which can be utilized in the energy, transport, and chemical sectors. However, efficient and safe large-scale hydrogen storage is still challenging. The most frequently used hydrogen storage solutions in industry, i.e., compression and liquefaction, are highly energy-consuming. Underground hydrogen storage is considered the most economical and safe option for large-scale utilization at various time scales. Among underground geological formations, salt caverns are the most promising for hydrogen storage, due to their suitable physicochemical and mechanical properties that ensure safe and efficient storage even at high pressures. In this paper, recent advances in underground storage with a particular emphasis on salt cavern utilization in Europe are presented. The initial experience in... [more]

Scientific and technical issues related to the extraction and processing of raw materials are inextricably linked with environmental concerns. The extraction, transportation and processing of raw materials and the creation of new products place a heavy burden on the environment. Therefore, the development of new technologies for the extraction and processing of raw materials which meet the demand for specific products while respecting environmental resources and saving energy can be considered one of the key challenges of modern science. The development of methods to optimize the course of certain processes related to the raw materials industry, limiting its impact on the environment, and the use of modern measurement techniques or modeling are key areas of research and development for the economy. The aim of this Special Issue was to identify certain important issues, including those related to the raw materials industry and the optimization of its processes, obtaining energy from alt... [more]

Solar photovoltaic-thermal (PV/T) technology is the main strategy for harvesting solar energy due to its non-polluting, stability, good visibility and security features. The aim of the project is to develop a mathematical model of a PV/T module integrated with optical filtration and MXene-enhanced PCM. In this system, a single MXene-enhanced PCM layer is attached between the PV panel and absorber pipe with solid MXene-PCM for storage and cooling purposes. Additionally, the thermal fluid is utilized in the copper absorber pipe and connected to the heat pump system for enhancing system thermal and electrical efficiency. Furthermore, the influences of the optical filtration channel height, concentration of the nanoparticles on PV surface temperature and overall system efficiency are also discussed. This study demonstrates that the annual thermal and electrical energy output can reach 5370 kWh per annum with 74.92% of thermal efficiency and 5620 kWh with 14.65% of electrical efficiency, re... [more]

Porous adsorbent material is promising to be used to regeneratively remove CO2 from space shuttles. In this work, the amount and isosteric heat of CO2 adsorption in solid amine are experimentally studied at pressures ranging from 0 to 6 bar and temperatures ranging from 20 °C to 60 °C. The amount and isosteric heat of water adsorption in the solid amine is tested at different humidities (relative humidity 30−80%). The effective thermal conductivity of the solid amine at different atmospheres (air, N2, CO2 and water), pressures and temperatures is also investigated. The results show that the best temperature for CO2 adsorption in the solid amine is 45 °C under dry conditions. The amount of water adsorption increases with enhanced humidity, while the isosteric heat of water adsorption remains a constant value. The effective thermal conductivity of the solid amine increases with an increase in pressure. The adsorbed phase (CO2 and water) in the solid amine makes a contribution to improvin... [more]

Fuel cells (FCs) have received huge attention for development from lab and pilot scales to full commercial scale. This is mainly due to their inherent advantage of direct conversion of chemical energy to electrical energy as a high-quality energy supply and, hence, higher conversion efficiency. Additionally, FCs have been produced at a wide range of capacities with high flexibility due to modularity characteristics. Using the right materials and efficient manufacturing processes is directly proportional to the total production cost. This work explored the different components of proton exchange membrane fuel cells (PEMFCs) and their manufacturing processes. The challenges associated with these manufacturing processes were critically analyzed, and possible mitigation strategies were proposed. The PEMFC is a relatively new and developing technology so there is a need for a thorough analysis to comprehend the current state of fuel cell operational characteristics and discover new areas fo... [more]

The US highway system features a huge flux of energy transportation in terms of weight, speed, volume, flow density, and noise levels, with accompanying environmental effects. The adverse effects of high-volume traffic cause health concerns for nearby residential areas. Both chronic and acute exposure to PM 2.5 have detrimental effects on respiratory and cardiovascular health, and motor vehicles contribute 25−35% of direct PM 2.5 emissions. In addition to traffic-related pollutants, residing near major roadways is also associated with exposure to increased noise, and both affect the health and quality of life of residents. While regulatory and policy actions may reduce some exposures, engineering means may offer novel and significant methods to address these critical health and environmental issues. The goal of this study was to harvest highway-noise energy to induce surface charge via a piezoelectric material to entrap airborne particles, including PM 2.5. In this study, we experiment... [more]