Evacuated tube solar water heaters are gaining more attention in the present market scenario as compared to conventional collectors. Such collectors are versatile because no solar tracking is required and the operating temperature range is also broad. Comparatively, it is cost-effective and may attain higher thermal efficiency. However, like other collectors, continuous energy supply is sometimes hampered by the intermittent nature of solar radiation. This problem can be partially resolved by using phase change materials (PCM) in the evacuated tube solar collector (ETC). PCMs can store the energy during the sunshine hours, which can be released when solar energy is not available. In the literature, several studies are available pertaining to the use of PCMs in ETC-based solar water heaters. The literature indicates that the integration of PCMs with ETCs has several merits. Nevertheless, systematic, and comprehensive review papers dedicated to such integrated energy storage systems with... [more]

The present review mainly discusses advanced pretreatment techniques for converting lignocellulosic biomass into hydrogen. The focus of this review is also to acquire knowledge concerning lignocellulosic biomass pretreatment processes and their impact on the efficiency of biohydrogen fermentation. The deconstruction of lignocellulosic biomass is presented using various pretreatment techniques albeit with several advantages and disadvantages, particularly about the interference due to the generated inhibitory compounds is toxic to microbes used for fermentation. The use of an appropriate pretreatment process can make the recalcitrant lignocellulosic biomass substrates amenable for further microbial fermentation to produce hydrogen. Although till date there is no ideal pretreatment step available to develop a cost-effective process for conversion of lignocellulosic materials into fermentable sugars, nanotechnology seem to be a more sustainable approach as compared to the traditional proc... [more]

This article presents a simple and low-cost green synthesized single-layer NiO selective solar absorber nanocoating prepared by spin coating on a Cu substrate at different rotational speeds (RS). The effects of substrate RS on the structural, morphological, chemical, and optical properties of the NiO nanocoatings were thoroughly investigated. The XRD results reveal the formation of pure diffraction peaks indexed to face-centered cubic NiO nanocoatings. SEM confirmed the uniform distribution of the NiO thin films with a nanosphere-like structure and the influence of RS variation on the formation of NiO nanostructures. EDS and XPS confirmed the presence of Ni and O in the green synthesized NiO coatings. AFM showed homogeneous nanopillar-like NiO thin films with the average surface roughness decreasing from 13.6 to 9.06 nm as the RS increased from 700 to 1300 RPM. Raman spectroscopy of the nanocoatings showed normal modes related to longitudinal optical and transverse optical phonons, and... [more]

For wellbore stability issues induced by drilling operations in natural gas hydrate-containing reservoirs, wellbore stability research will focus on the mechanical properties of hydrate reservoirs. According to the content of the research, the response relationship between the hydrate core and the base physical property changes under different engineering parameters is established, and the law of hydrate mechanical property changes with temperature and pressure is studied for various physical properties. According to theoretical research and experimental data, it has been determined that: hydrate core-resolved gas and transverse and longitudinal wave velocity have a positive correlation with saturation and pressure and a negative correlation with temperature; a negative correlation exists between resistivity and saturation. The hydrate core stiffness strength correlates positively with saturation and adversely with temperature. Under the identical strain conditions, when saturation, po... [more]

The existing recycling methods of PHA-based material are ineffective in terms of increasing resource efficiency and the production of high value end-of-life products. Therefore, in this study, a novel approach of acidogenic fermentation was proposed to recycle PHB-based composites reinforced with natural fibers such as cellulose, chitin, chitosan, orange waste, sawdust, soy protein, and starch. The inclusion of cellulose, chitosan, and sawdust improved the impact properties of the composites while other fillers had various effects on the mechanical properties. These three composites and neat PHB were subsequently subjected to biological degradation via acidogenic digestion to determine the possibility of converting PHB-based composites into volatile fatty acids (VFAs). Two different pH levels of 6 and 10 were applied to assess the effect of pH on the bioconversion and inhibition of the methanogenesis. The results showed promising PHB degradation, contributing to considerable VFA produc... [more]

With the rapid development of power electronic techniques and the increasing cost of permanent magnets (PMs) materials, switched reluctance motors (SRMs) have recently gained more attention. However, traditional SRMs have a relatively low torque density. For the sake of increasing the motor torque density, this paper proposes a novel segmental rotor type SRM. The proposed motor adopts hybrid stator poles and concentrated windings in the stator side and a segmental rotor structure in the rotor side, which is completely different from the structures of the traditional SRM. The special structure of the motor shortens the magnetic flux paths of the motor, separates the parts of the magnetic flux paths from one another, and eradicates the magnetic flux reversal in the motor stator in order to improve the electric utilization and output torque density of the motor. Meanwhile, the requirement of the magneto-motive force and the core loss of the motor is also decreased, thereby improving the e... [more]

In this paper, the use of Metal-Organic Framework (MOF) materials as an option for the energy efficiency enhancement of HVAC systems is investigated. In particular, the possibility of using MOFs as dehumidifying materials to reduce the latent load associated with the moisture content of the airflows is studied. A literature review is proposed, highlighting the benefits of using MOFs instead of other adsorbents (e.g., silica-gel) and discussing the unique features (high water uptake capacity and low regeneration temperatures) that make MOFs a preferential desiccant. The possibility to finely tune these properties is also underlined, reporting some explicative examples. A theoretical proposal of a psychrometric transformation, to be performed in a HVAC system equipped with a MOF-Assisted Dehumidifier (MAD), is presented. This transformation is compared with a traditional one (cooling and dehumidification operated by a cooling coil with low temperatures of the coolant). The preliminary nu... [more]

AGV systems are considered a necessary element of the recently created cyber-physical systems whose task is to support material flows in intelligent factories. The implementation of AGV systems in cyber-physical systems generates new types of threats, and the level of risk of adverse events related to the operation of these systems is changing. This article aims to present the results of an open-access literature review, the purpose of which was to identify issues addressed in studies of the analysis and risk management of AGV systems, to group publications according to the proposed topical framework, and to identify gaps in the current research. We used the PRISMA concept to review the literature. After completing all stages of the procedure, 153 publications on risk in AGV systems were selected for analysis. To ensure the high quality of the analysis, access to the full texts of the selected documents was necessary. For this reason, we have limited the collection to open-access publi... [more]

The most common methods of reducing mercury emissions are the use of fixed bed granular sorbents and sorbent injection. However, both of these methods have disadvantages, such as increasing the flow resistance or the need to remove the sorbent from flue gas, respectively. These disadvantages can be eliminated by using sorbents permanently bound to construction materials (fixed sorbent materials—FSMs) or mixed with construction materials (sorbent polymer composites—SPCs). The approach is unique in the world literature as well as the development of three stands and procedures enabling the testing of FSMs or SPC materials based on Tarflen as a construction material. In order to further tests of FSMs and SPCs, the system for laboratory tests and two systems for industrial tests are developed. These stands and procedures enable determination of the influence of: FSM or SPC module shapes, flue gas properties (e.g., composition, temperature, flow rate), and mercury concentration on the effect... [more]

Building construction in rural Kyrgyzstan is heavily dominated by earthen buildings. Old and inappropriate residential building structures contribute significantly to high domestic space heating energy consumption. Therefore, it is necessary to understand the relevant building construction techniques. However, the scant information on Kyrgyz building techniques, especially for high-altitude rural settlements, was the prime motivation to perform the presented study. The key objective of the study is to investigate residential building construction techniques in high-altitude rural Kyrgyzstan, and this was to be achieved by house visits during field trips, literature review, and pilot interviews with local people. The analysis enabled the detailed identification of individual building envelopes as well as predominant building materials to be recorded. Based on the assessment, a housing profile was created that represents the typical characteristics of traditional rural Kyrgyz houses. Fur... [more]

The main goal of the publication was to show the differences in profit when using manure directly as fertilizer (after the storage period) or as a substrate for biogas plants with a cogeneration unit, and then using the digestate for fertilization purposes. The comparison covers the streams of costs, revenues and profits over the year between 14 October 2021 and 14 October 2022. This period was chosen due to the energy and fertilization crisis caused by the war in Ukraine. Profitability forecasts for biogas investments (including the payback period) are presented, with the reduction of greenhouse gas emissions, i.e., methane and nitrous oxide, taken into account. The performed economic, energy and ecological calculations of manure management can be used as guidelines when considering investing in biogas plants, as well as what is recently becoming a new trend: the carbon footprint of dairy production. Input substrate parameters, gaseous emissions and biogas yields were obtained from ow... [more]

Molten salt reactors (MSRs), as one of the six main technologies of Gen IV, can meet the broad area of sustainability, economics, safety and reliability, proliferation resistance and physical protection goals. One of the main and first challenges in designing molten salt fast reactors (MSFRs) is the selection of an appropriate molten salt fuel system based on the envisaged applications and objectives. In this study’s series, a full-scope evaluation has been conducted about employing either chloride or fluoride salt fuels as the main competitors’ candidates for fuel salt in MSFR designs. Two distinguished projects, EVOL (CNRS, Grenoble-France), based on fluoride salt, and iMAGINE (The University of Liverpool, UK), based on chloride salts, were considered in order to achieve this goal as case studies. The first part of this series (part 1—this article) deals with the investigation of the thermophysical properties of the salt fuel system, criticality search and neutron-flux energy spectru... [more]

The crude glycerol produced as a byproduct of transesterification synthesis has very few applications because it comprises of significant amounts of methanol, catalyst, and soap. On the other hand, transesterifications of highly acidic oil in the presence of an alkaline catalyst are problematic due to the presence of high amounts of free fatty acids. In this study, the free fatty acid level of high acid oil, which was initially determined to be 19.25%, was decreased to permit the direct production of biodiesel via glycerolysis with pure glycerol, making direct transesterification feasible. Through a process of purification, crude glycerol was refined to 92.5% purity. It was revealed that the physiochemical parameters of density, moisture content, ash content, matter organic non-glycerol content, pH, and Na/K concentrations of generated purified glycerol are equal to those of commercially available glycerol. In contrast, glycerolysis treatment successfully decreased the free fatty acid... [more]

This paper uses ANSYS Fluent to simulate the heat dissipation of a phase change material (PCM)-based cooling system combined with novel spiral fins for a single battery cell. Compared with a circular fin, a spiral fin with the same contact length can reduce the battery temperature by 0.72 °C, and has a superior temperature uniformity. For the PCM-based system with spiral fins, increasing the spiral width from 2 mm to 8 mm can reduce the battery temperature from 41.27 °C to 39.9 °C. As the number of spiral turns increases from two to eight, the maximum temperature rise of the battery shows a downward trend, and six turns can effectively satisfy the heat dissipation requirements of the battery. With respect to the effect of ambient temperature on the cooling performance, the system with a PCM-spiral fin still exhibits optimal cooling effectiveness compared with the pure PCM and PCM-circular systems.

Wooden construction constitutes a specific branch of the building industry that focuses on high-quality materials, a developed sense of aesthetics connected with comfort and functionality, and concern for ecology and durability. This type of construction has a positive effect on human quality of life. This article focuses on modular frame construction and technological aspects of wooden houses built according to Canadian or Scandinavian technologies. Taking weather conditions of Scandinavian countries into consideration, timber is a popular building material, which, when preserving certain parameters such as density of rings, may provide durability of a modular wooden building even up to 200−300 years. This article is a review and presents the possibility of producing frame buildings in Europe (Poland) in accordance with the applicable standards, including a heat transfer coefficient U = 2 [W/(m²·K]. In Poland, wooden frame buildings can be traced back to the 14th century. Wooden frame... [more]

Proper management and treatment of end-of-life fluorescent lamps with a toxic metal of mercury has attracted critical concern in the solid waste community. In this study, material flow analysis (MFA) and substance flow of mercury were performed on the lamps by life cycle in South Korea. It was found that, in 2020, approximately 2957 tons (or 27.9 million units) of end-of-life fluorescent lamps from households were collected and recycled by the recycling facilities in South Korea. Approximately 278 kg of mercury was recovered from the lamps and treated at the hazardous incineration facilities. Based on the results of dynamic flow analysis, the amount of fluorescent lamps to be retried is expected to continually decrease to be about 14.2 million units, which is estimated to be 23 kg of mercury. However, continued collection efforts on end-of-life fluorescent lamps owing to increasing demands for light-emitting diode lamps should be made from the perspectives of proper treatment of mercur... [more]

Fast pyrolysis of five post-consumer plastic waste materials was studied using pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) technique. Prescription medicine bottles, landfill liners, and one type of industrial plastic waste represented polyolefin-based polymers, whereas packaging material represented polystyrene, and other industrial plastic waste represented polyurethane. The noncatalytic and catalytic degradation mechanisms of all five post-consumer plastic wastes were elucidated. The noncatalytic pyrolysis experiments were conducted at a temperature of 600 °C for a residence time of 5 min. For catalytic pyrolysis, a spent FCC catalyst was utilized for polystyrene, a sulfated zirconia-based catalyst was utilized for polyurethane, and a Y-zeolite catalyst was used for polyolefinic plastic waste. The results suggested that the thermal reaction has higher monomeric and oligomeric selectivity than the catalytic reaction. Results from the catalytic runs showed th... [more]

In nanoscience, nanotechnology is applied to various technologies, and research is actively being conducted. As the application of multi-walled carbon nanotubes (MWCNTs) in various fields increases, efforts have been made to develop dispersion and functionalization technologies. In order to effectively use MWCNT nanofluids, it is most important to solve the problem of dispersion. In this study, MWCNTs were improved in dispersibility and functionalized through various chemical and mechanical treatments. In addition, MWCNTs aggregation was alleviated by using cellulose nanocrystal (CNC) as a dispersant. The processing results of MWCNTs and CNC were analyzed through transmission electron microscopy (TEM) and the dispersion was characterized by UV−Vis spectroscopy. The addition of CNC to MWCNTs has been confirmed to have high dispersibility and improved stability compared to untreated MWCNTs, and this effect affects the quality of the machine.

Ordinary Portland cement (OPC) is currently the preferred material for the creation of barriers in wells during their construction and abandonment globally. OPC, however, is a very carbon-intensive material with some inherent technical weaknesses. These include a low casing-to-cement bond strength which may allow for the formation of micro-annuli, which in turn can become a conduit for greenhouse gas transport (primarily of methane, a powerful greenhouse gas) to surface. Alkali-activated materials (AAMs), also known as geopolymers, have a much lower manufacturing carbon footprint than OPC and can be a good alternative to OPC for primary and remedial well cementing applications. This paper reports on a comprehensive study into the use of Class F fly ash-based geopolymers for a large variety of downhole well conditions, ranging from lower-temperature surface and intermediate casing cementing conditions to much higher temperature conditions (up to 204 °C (400 °F)) that can be encountered... [more]

Due to the ever-growing importance of rechargeable lithium-ion batteries, the development of electrode materials and their processing techniques remains a hot topic in academia and industry. Even the well-developed and widely utilized active materials present issues, such as surface reactivity, irreversible capacity in the first cycle, and ageing. Thus, there have been many efforts to modify the surface of active materials to enhance the electrochemical performance of the resulting electrodes and cells. Herein, we review the attempts to use polymer coatings on the anode active materials. This type of coating stands out because of the possibility of acting as an artificial solid electrolyte interphase (SEI), serving as an anode protective layer. We discuss the prominent examples of anodes with different mechanisms: intercalation (graphite and titanium oxides), alloy (silicon, tin, and germanium), and conversion (transition metal oxides) anodes. Finally, we give our perspective on the fu... [more]

Biomass is one of the most important sources of renewable energy in the energy industry. It is assumed that by 2050 the global energy deposit could be covered in 33−50% of biomass combustion. As with conventional fuels, the combustion of biomass produces combustion by-products, such as fly ash. Therefore, along with the growing interest in the use of biomass as a source of energy, the production of ash as a combustion by-product increases every year. It is estimated that approximately 476 million tons of ashes per year can be produced from biomass combustion. For example, the calorific value of dry wood mass tends to be between 18.5 MJ × kg−1 and 19.5 MJ × kg−1, while the ash content resulting from thermal treatment of wood is from 0.4 to 3.9% of dry fuel mass. However, biomass ash is a waste that is particularly difficult to characterize due to the large variability of the chemical composition depending on the biomass and combustion technology. In addition, this waste is, on the one h... [more]

An important feature of this research is the investigation of the de-alloyed catalysts based on the nanoparticles with a simple structure (alloy) and a complex structure (gradient). The resulting samples exhibit the 2−4 times higher mass activity in the ORR compared with the commercial Pt/C. The novelty of this study is due to the application of the express-electrochemical experiment to register the trend of changes in the ORR activity caused by rearranging the structure of bimetallic nanoparticles. The state-of-the-art protocol makes it possible to establish the dependence of properties of the de-alloyed catalysts on the nanoparticles’ structure obtained at the stage of the material’s synthesis. The study shows the possibility of determining the rate of the ongoing reorganization of bimetallic nanoparticles with different architectures. The PtCu/C electrocatalysts for proton-exchange membrane fuel cells presented in this work are commercially promising in terms of both the high functi... [more]

Determining the geomechanical properties of hydrate-bearing sands (HBS), such as strength and stiffness, are critical for evaluating the potential for the economic and safe recovery of methane gas from HBS reservoirs. To date, results from numerous independent laboratory studies on synthesized HBS have shown that strength and stiffness are largely influenced by hydrate saturation, the method adopted for hydrate formation, and to a lesser extent, the confining stresses applied during testing. However, a significant scatter is observed in the data even when these conditions are similar. These include recent studies on natural HBS where sands with larger particle size distribution (PSD) exhibited higher strengths despite lower hydrate saturation. To investigate the impact of PSD, and the role that specific hydrate formation conditions might impose, on the strength and stiffness of HBS, a series of laboratory tests were carried out on sand specimens formed with different particle size dist... [more]

Magnetorheological (MR) dampers are controlled energy-dissipating devices utilizing smart fluids. They operate in a fast and valveless manner by taking advantage of the rheological properties of MR fluids. The magnitude of the response of MR fluids, when subjected to magnetic fields, is of sufficient magnitude to employ them in various applications, namely, vibration damping, energy absorption, exoskeletons, etc. At the same time, predicting their response to arbitrary mechanical and electrical inputs is still a research challenge. Due to the non-linearities involved in material properties or the design of the solenoid used for activating the fluid modeling the relationships between the control circuit and the material’s response is complex. Modeling studies can be classified into two categories. The parametric approach requires the knowledge of the internal material’s properties and takes advantage of physics formulas to infer the I/O relationships present in the damper. For compariso... [more]

Due to the depletion of fossil fuels and the destruction wrought by global warming caused by the combustion of fossil fuels, the search for renewable energy sources has become a major global concern. This study aimed to assess the bio-oil production from teff husk via slow pyrolysis process. The pyrolysis of teff husk took place in a batch reactor at a temperature between 400 °C and 500 °C with a 120 min retention time. At 450 °C, the pyrolysis process produced 32.96 wt.% of optimum bio-oil yield and had a HHV of 25.32 MJ/kg. TGA, FTIR, and SEM-EDX were used to analyze the produced bio-oil to investigate its thermal decomposition, functional groups, and surface morphology with its elemental composition, respectively. Alcohols, aromatic, phenols, alkanes, esters, and ethers were the primary compounds of the bio-oil produced by the slow pyrolysis of teff husk. The HHV of the biochar ranged from 21.22 to 22.85 MJ/kg. As a result, teff husk can be used to make biofuel; however, further bio... [more]