This paper presents a mathematical model of the heat and mass transfer processes for a rotary-spray honey dehydrator with a heat pump and a closed air circuit. An analytical calculation model, based on the energy balance equations of the dehydrator and heat pump, was used to model the transient dehydration process of honey in a dehydrator. The presented article includes a different approach to modelling both the dryer and the heat pump assisting the drying process. The novel quality of this study lies in the use of original equations to determine the heat and mass transfer coefficients between honey and air and using an actual model of a cooling unit to model the honey dehydration process. The experimentally verified calculation algorithm enables an analysis of the effects of air flow rate, mixer rotation speed, and cooling unit power on the efficiency of the drying process. The dehydrator calculation model was used to minimize the drying time by selecting the optimal evaporative tempe... [more]

This paper presents comprehensive analytical, numerical and experimental research of the compact and integrated high-power pulse generation and forming system based on the flux compression generator and the electro-explosive forming fuse. The paper includes the analysis of the presented solution, starting from the individual components studies, i.e., the separate flux compression generator tests in field conditions and the forming fuse laboratory test, through the formulation of the extended quasi-empirical components models aimed at enabling their optimal parameters determination at the early design stage and ending with the description of the integrated system studies in field conditions. Based on detailed research, it was possible to achieve very high parameters of the generated pulses, i.e., overvoltages of up to 340 kV with the available source power reaching 25 GW. A very high convergence of the simulation and the results of experimental research has been obtained. The parameters... [more]

Buildings are responsible for approximately 30−40% of energy consumption in Europe, and this is a fact. Along with this fact is also evident the existence of a defined and strict legislation framework regarding energy efficiency, decarbonization, sustainability, and renewable energy systems in building applications. Moreover, information and communication technologies, along with smart metering for efficient monitoring, has come to cooperate with a building’s systems (smart buildings) to aim for more advanced and efficient energy management. Furthermore, the well-being in buildings still remains a crucial issue, especially nowadays that health and air quality are top priority goals for occupants. Taking all the above into consideration, this paper aims to analyze ventilation technologies in relation to energy consumption and environmental impact assessment using the life cycle approach. Based on the review analysis of the existing ventilation technologies, the emphasis is given to para... [more]

Aviation has been one of the key engines of the globalization process and, at the same, time one of the industries most affected by the COVID-19 pandemic and the parallel economic crisis. As safety seems to be the key issue at aerodromes, the aim of this article is to analyze what kind of safety hazards have the coronavirus slowdown created and which of them pose the greatest risk for aerodrome safety in the long run. What is more, the goal of the paper is to direct managers’ attention to proper crisis management in line with sustainability. The main findings are that all classified hazards cause, according to an expert’s assessment, similar safety risk at aerodromes, though limited workforce training and development are perceived as posing the greatest risk. The recommended solution to minimize the occurrence of the hazard is proactive risk management, which means that managers try to anticipate possible hazards in advance and act accordingly, which requires continual controlling comb... [more]

Photovoltaic-thermal (PVT) collectors are hybrid solar collectors that convert solar and ambient energy into thermal and electrical energy. Integrated PVT-HP, in which PVT collectors are combined with a heat pump, offers an efficient and renewable option to replace conventional fossil fuel-based energy systems in residential buildings. Currently, system concepts in which the selection, design and control of the components are aligned towards the system performance are lacking. The development of a system model enables the comparison of a variety of system parameters and system designs, informed decision making based on the energetic performance and the market diffusion of PVT-HP systems. This contribution presents a simulation model of a PVT-HP system. By means of numerical simulations, with simulation program TRNSYS, the energetic performance of a PVT-HP system and the system components are investigated. It is shown that the PVT-HP can cover the annual energy demand of a residential b... [more]

Roof bolting is the most popular type of support for underground mines’ workings. However, in Polish coal mines it is used only as a supplementary support. To raise the effectiveness and economic score of horizontal development works, JSW (Jastrzębska Spółka Węglowa) started a project to introduce the independent rock bolting support in its mines. The key element of the project is the monitoring of mine workings supported with roof bolting, as appropriate control allows one to ensure a proper level of safety. The following work presents a monitoring system for mine working supported with roof bolting applied in the project, as well as results of the measurements obtained using this system. The aim of the monitoring was to prove that independent roof bolting provides a proper level of safety and thus is applicable in conditions of Polish underground coal mines, particularly Budryk mine. It was to be proved by the evaluation of data obtained from instrumented bolts, extensometers of diff... [more]

The paper presents a set of prototype smart grid technologies and services and validates the economic viability of the proposed solution using cost−benefit analysis (CBA). The study considered the EU-funded project called RESOLVD and implemented the technologies and services in a real-life pilot. The paper focuses on the analysis of technological solutions which enhance the operational efficiency and the hosting capacity of low-voltage electricity distribution grids. The solutions provided better integration of a hybrid battery storage system, with the grid interfacing power electronics, smart gateways for the interconnection of assets at the grid edge, and sensors enhancing infrastructure observability and control. The result from the CBA indicates the economic viability of the project, high scalability, and replicability. The economic benefits were realized with the breakeven value of eight secondary substations (SS) and 16 feeders. The scenario test on the DSO’s willingness to pay f... [more]

The effects of the diameter and location of an inserted wire on methane−air flame characteristics in a micro-burner, with a backward-facing step, were investigated numerically. Our goal was to shed light on the parameters that the authors had not already considered in the previous study. To do so, the effects of the studied parameters on the flame location and distribution of temperature, H, and OH species, were scrutinized. It was shown that increasing the inserted wire’s diameter and relocating the inserted wire towards the outlet had polynomial and linear effects on the flame location in the burner, respectively. Although changing these two parameters did not have any obvious effects on the maximum temperature of the auxiliary axis in the burner or the external wall, effects on the peak values of the hot-flame critical chemical species of OH and H were recognized. Furthermore, it was shown that the temperature distribution on the outer surface of the burner was more influenced by th... [more]

Biomethane liquefaction may help decarbonization in heavy transportation and other hard-to-abate sectors. Small-scale liquefaction plants (<10 ton/day) are suitable for small biogas plants located near farms and other agricultural activities. “Internal refrigerant” refrigeration cycles (e.g., Kapitza cycle) are often proposed for small-scale natural gas liquefaction due to their simplicity. An optimized Kapitza-based cycle is modeled and simulated, and then several modifications were studied to evaluate their influence on the energetic and economic performances. Results showed a specific consumption ranging between 0.65 kWh/kg and 0.54 kWh/kg of bio-LNG with no significant improvements by increasing cycle complexity. Instead, a reduction of 17% was achieved with the implementation of absorption chillers, that effectively turn waste heat into useful cooling energy. An economic assessment was finally carried showing that the Levelized Cost of Liquefation is more affected by electricit... [more]

This work aims to optimize the recovery of methyl methacrylate (MMA) by depolymerization of polymethyl methacrylate (PMMA) dental resins fragments/residues. In order to pilot the experiments at technical scale, the PMMA dental resins scraps were submitted by thermogravimetric analysis (TG/DTG/DTA). The experiments were conducted at 345, 405, and 420 °C, atmospheric pressure, using a pilot scale reactor of 143 L. The liquid phase products obtained at 420 °C, atmospheric pressure, were subjected to fractional distillation using a pilot scale column at 105 °C. The physicochemical properties (density, kinematic viscosity, and refractive index) of reaction liquid products, obtained at 345 °C, atmospheric pressure, were determined experimentally. The compositional analysis of reaction liquid products at 345 °C, 30, 40, 50, 60, 70, 80, and 110 min, at 405 °C, 50, 70, and 130 min, and at 420 °C, 40, 50, 80, 100, 110, and 130 min were determined by GC-MS. The morphology of PMMA dental resins fr... [more]

Multilevel inverters are increasingly being employed for industrial applications, such as speed control of motors and grid integration of distributed generation systems. The focus is on developing topologies that utilize fewer lower-rating switches and power sources while working efficiently and reliably. This work pertains to developing a three-phase multilevel inverter that employs switching capacitors and a single DC power supply that produces a nine-stage, three-phase voltage output. A recently proposed powerful meta-heuristic technique called symbiotic organism search (SOS) has been applied to identify the optimum switching angles for Selective Harmonic Elimination (SHE) from the output voltage waveform. A thorough converter analysis has also been done in the MATLAB/SIMULINK environment and is validated with the real-time hardware-in-the-loop (HIL) experiment results.

The literature is replete with concerns on the environmental impact of steam-assisted gravity drainage (SAGD), but rigorous analysis of its improved environmental performance over the past 20 years remains unresolved, as well as the underlying technological reasons for this improvement. Here, we present an analysis of historical and future greenhouse gas (GHG) performance of SAGD operations in Alberta, Canada, considering for the first-time factors that affected technology deployment. Depending on the case, the results show a reduction of 1.4−24% of SAGD GHG intensity over the past 12 years. Improvements mainly arise from incremental changes adopted based on technical, environmental, socio-economic, and policy drivers. Considering these factors, we propose policy interventions to accelerate further reductions of GHG emissions. However, if similar behaviour from industry continues, anticipated GHG intensity reduction will range between 6.5−40% by 2030, leading to an intensity between 58... [more]

Renewable energy generation in Ukraine is developing slower than state strategies and expectations, with the installations for energy generation based on biogas currently being among the lowest in terms of installed capacity. Most of those involved in energy generation from agricultural biogas are large enterprises, while the small and medium-sized farms are far less involved. Thus the article aims to assess the economic feasibility of biogas production from agricultural waste by specific farm types and sizes, with a special focus on small and medium-sized farms. The research results present findings in two dimensions, first defining the economic feasibility of biogas installations in Ukraine based on investment costs and the rate of return at both the current and potential feed-in tariff, and second, analyzing the influence of state regulation and support on the economic feasibility of agricultural biogas production in Ukraine. The results emphasize that the construction of small gene... [more]

The energy transition from inefficient fossil-based to sustainable energy systems can face various lock-ins. There are no pathways that are free of stress. However, many routes are possible. A good understanding of the dynamic behavior of systems is crucial, and proper support tools are needed to assess the outcomes of every selected pathway. This study aims to develop an Internet-based interface tool for the national energy simulation model as a tool for a “hybrid forum”; study energy transition lock-ins in one of the Eastern European countries; and apply the interface tool to study different pathways to Latvia’s climate and energy goals. System dynamics are used to reach the goals of the study. A causal loop diagram is applied to study feedback loops and lock-ins, a stock-and-flow structure is used to build a simulation model, and a user interface tool is built on top of it. The results show that the developed interface tool is user-friendly and can be used as a discussion platform.... [more]

With the increased necessity of a high power density and efficient system in aerospace and marine industries, integrated motor drives provide an excellent solution in the modern era. Therefore, a close structural and functional integration of passive components has become a prerequisite task to make a compact overall system. This article reviews the existing motor drives system with integrated passive technologies. To start, the design aspect of the traditional and integrated filter inductors, using the area product approach, is discussed. Subsequently, layouts of traditional and integrated inductors are presented. The available capacitor technologies, suitable for integration, are also discussed with pros and cons of each capacitor type.

Inlet temperature is vital to the thermal efficiency of gas turbines, which is becoming increasingly important in the context of structural changes in power supplies with more intermittent renewable power sources. Blade cooling is a key method for gas turbines to maintain high inlet temperatures whilst also meeting material temperature limits. However, the implementation of blade cooling within a gas turbine—for instance, thermal barrier coatings (TBCs)—might also change its heat transfer characteristics and lead to challenges in calculating its internal temperature and thermal efficiency. Existing studies have mainly focused on the materials and mechanisms of TBCs and the impact of TBCs on turbine blades. However, these analyses are insufficient for measuring the overall impact of TBCs on turbines. In this study, the impact of TBC thickness on the performance of gas turbines is analyzed. An improved mathematical model for turbine flow passage is proposed, considering the impact of coo... [more]

To achieve the climate goals of the Paris Agreement, greenhouse gas emissions from the electricity sector must be substantially reduced. We develop an agent-based model of the electricity system with heterogeneous agents who invest in power generating capacity under uncertainty. The heterogeneity is characterised by the hurdle rates the agents employ (to manage risk) and by their expectations of the future carbon prices. We analyse the impact of the heterogeneity on the transition to a low carbon electricity system. Results show that under an increasing CO2 tax scenario, the agents start investing heavily in wind, followed by nuclear and to some extent in natural gas fired power plants both with and without carbon capture and storage as well as biogas fired power plants. However, the degree to which different technologies are used depend strongly on the carbon tax expectations and the hurdle rate employed by the agents. Comparing to the case with homogeneous agents, the introduction of... [more]

During oil fields operation, gas is extracted along with oil. In this article it is suggested to use jet pumps for utilization of the associated oil gas, burning of which causes environmental degradation and poses a potential threat to the human body. In order to determine the possibility of simultaneous application of a sucker-rod pump, which is driven by a rocking machine, and a jet pump (ejector) in the oil well, it is necessary to estimate the distribution of pressure along the borehole from the bottomhole to the mouth for two cases: when the well is operated only be the sucker-rod pump and while additional installation of the oil-gas jet pump above its dynamic level. For this purpose, commonly known methods of Poettman-Carpenter and Baksendel were used. In addition, the equations of high-pressure and low-pressure oil-gas jet pumps were obtained for the case, when the working stream of the jet pump is a gas-oil production mixture and the injected stream is a gas from the annulus of... [more]

This paper focuses on the estimation of energy consumption of Electric Vehicles (EVs) by means of models derived from traffic flow theory and vehicle locomotion laws. In particular, it proposes a bi-level procedure with the aim to calibrate (or update) the whole parameters of traffic flow models and energy consumption laws by means of Floating Car Data (FCD) and probe vehicle data. The reported models may be part of a procedure for designing and planning transport and energy systems. This aim is to verify if, and in what amount, the existing parameters of the resistances/energy consumptions model calibrated in the literature for Internal Combustion Engines Vehicles (ICEVs) change for EVs, considering the above circular dependency between supply, demand, and supply−demand interaction. The final results concern updated parameters to be used for eco-driving and eco-routing applications for design and a planning transport system adopting a multidisciplinary approach. The focus of this manu... [more]

The Baode block on the eastern margin of the Ordos Basin is a key area for the development of low-rank coalbed methane (CBM) in China. In order to find out the genesis of CBM and its storage and seepage space in Baode block, the isotopic testing of gas samples was carried out to reveal the origin of CH4 and CO2, as well, mercury intrusion porosimetry, low temperature nitrogen adsorption, and X-ray CT tests were performed to characterize the pores and fractures in No. 4 + 5 and No. 8 + 9 coal seams. The results showed that the average volume fraction of CH4, N2, and CO2 is 88.31%, 4.73%, and 6.36%, respectively. No. 4 + 5 and No. 8 + 9 coal seams both have biogenic gas and thermogenic methane. Meanwhile, No. 4 + 5 and No. 8 + 9 coal seams both contain CO2 generated by coal pyrolysis, which belongs to organic genetic gas, while shallow CO2 is greatly affected by the action of microorganisms and belongs to biogenic gas. The average proportion of micropores, transition pores, mesopores, an... [more]

From the breakdown of the Kaplan rotor of a hydrogenerator unit and the monitored data collected during its operation before such a failure, this work presents a post-occurrence data analysis in which a previously developed hybrid method based on unsupervised machine learning techniques is applied to detect and diagnose failure before a unit shutdown. In addition to demonstrating the efficiency and capacity of the developed method in an application with real data, the conducted analysis seeks to shed light on the events that occurred at the considered hydroelectric power plant, helping to understand the failure mode evolution and outcome. The results of the fault detection and diagnosis process clearly demonstrated how the evolution of failure modes took place in the analyzed equipment. The detection of potential failures far in advance would support adequate maintenance planning and mitigating actions that could prevent unit breakdown and the consequent damage and financial losses.

This paper presents results from a practical assessment of the endurance of an inverted flag energy harvester, tested over multiple days in a wind tunnel to provide first insights into flapping fatigue and failure. The inverted flag is a composite bimorph, composed of PVDF (polyvinylidene difluoride) strips combined with a passive metallic core to provide sufficient stiffness. The flag, derived from an earlier, more extensive study, flaps with a typical amplitude of ~120 degrees and a frequency of ~2 Hz, generating a constant power of ~0.09 mW in a wind velocity of 6 m/s. The flag was observed to complete ~5×105 cycles before failure, corresponding to ~70 h of operation. The energy generated over this lifespan is estimated to be sufficient to power a standard low-power temperature sensor for several months at a sampling rate of one sample/minute, which would be adequate for applications such as wildfire detection, environmental monitoring, and agriculture management. This study indicat... [more]

The demand for liquefied natural gas (LNG) as an energy commodity is increasing, although its respective supply chain is subjected to risks, uncertainties, and disturbances. An analysis of experiences from the global LNG supply chain highlights many of these risks. As such, there is an incumbent need to develop resilient LNG supply chains. In this study, the risks associated with the LNG supply chain are categorized into four dimensions: Political and regulatory, safety and security, environmental effects, and reliability of new technologies. A SWOT method is then implemented to identify strengths, weaknesses, opportunities, and threats within the LNG supply chain, where the LNG supply chain of Qatar is considered as a case study. Relevant strategies are then recommended using a SWOT matrix to maximize strengths and opportunities, while avoiding or minimizing weaknesses and threats within the LNG supply chain. Finally, major parameters to be considered to develop a resilient LNG manage... [more]

International policies for sustainable development have led to an increase in distributed power production based on renewable resources [...]

Energy poverty in Aotearoa New Zealand is well-documented, and tertiary students have been identified as an at-risk group. However, there has been very little research on tertiary students’ experiences of energy poverty in New Zealand. This paper used a nationwide online survey to investigate the extent and impact of energy poverty among tertiary students. Furthermore, it aimed to identify disparities between different demographic groups, understand the effects of COVID-19 and evaluate the effectiveness of the support policies available to students. Responses from 522 students were analysed; 85% were under 30 years old, 72% were female, 14% identified as Māori, and 14% reported having long-term disabilities or health concerns. The findings of this study are concerning. Tertiary students in New Zealand are largely living in dwelling conditions that do not meet recommended health standards and exacerbate energy poverty. Energy poverty has adverse effects on their physical and mental heal... [more]