In this paper, a strategy for reducing the electromagnetic interferences induced by power lines on metallic pipelines is proposed and numerically investigated. The study considers a set of steel conductors interposed between the power line and the pipeline. Different shapes of conductor cross sections and different magnetic permeabilities are considered, to identify the solution exhibiting the greatest mitigation efficiency for the same amount of material. The investigation is carried out by means of a quasi-3D finite element analysis. Results show that the main mechanism responsible for the mitigation is constituted by the currents induced in the screening conductors by the power line. Hence, a high magnetic permeability can have a detrimental effect since it reduces the skin depth to values below the size of the screening conductor. In this case, a reduction of the screening current and in the mitigation efficiency is observed. Nevertheless, the study shows that the use of strip-shap... [more]

In this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC−DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC−DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the ma... [more]

Solar energy has been one of the accessible and affordable renewable energy technologies for the last few decades. Photovoltaics and solar thermal collectors are mature technologies to harness solar energy. However, the efficiency of photovoltaics decays at increased operating temperatures, and solar thermal collectors suffer from low exergy. Furthermore, along with several financial, structural, technical and socio-cultural barriers, the limited shadow-free space on building rooftops has significantly affected the adoption of solar energy. Thus, Photovoltaic Thermal (PVT) collectors that combine the advantages of photovoltaic cells and solar thermal collector into a single system have been developed. This study gives an extensive review of different PVT systems for residential applications, their performance indicators, progress, limitations and research opportunities. The literature review indicated that PVT systems used air, water, bi-fluids, nanofluids, refrigerants and phase-chang... [more]

A significant proportion of the total energy consumption in office buildings is attributable to lighting. Enhancements in energy efficiency are currently achieved through strategies to reduce artificial lighting by intelligent daylight utilization. Control strategies in the field of daylighting and artificial lighting are mostly rule-based and focus either on comfort aspects or energy objectives. This paper aims to provide an overview of published scientific literature on enhanced control strategies, in which new control approaches are critically analysed regarding the fulfilment of energy efficiency targets and comfort criteria simultaneously. For this purpose, subject-specific review articles from the period between 2015 and 2020 and their research sources from as far back as 1978 are analysed. Results show clearly that building controls increasingly need to address multiple trades to achieve a maximum improvement in user comfort and energy efficiency. User acceptance can be highligh... [more]

Peer-to-Peer (P2P), Transactive Energy (TE) and Community Self-Consumption (CSC) are exciting energy generation and use models, offering several opportunities for prosumers, micro-grids and services to the grid; however, they require numerous components to function efficiently. Various hardware devices are required to transmit data and control the generation and consumption equipment, whereas software is needed to use the gathered information to monitor and manage the hardware and energy trading. Data can be gathered from a variety of origins from within the grid and external sources; however, these data must be well-structured and consistent to be useful. This paper sets out to gather information regarding the hardware, software and data from the several archetypes available, focusing on existing projects and trials in these areas to see what the most-common hardware, software and data components are. The result presents a concise overview of the hardware, software and data-related to... [more]

The aquatic plant Pistia stratiotes L. is environmentally hazardous and requires effective methods for its utilization. The harmfulness of these plants is determined by their excessive growth in water bodies and degradation of local aquatic ecosystems. Mechanical removal of these plants is widespread but requires fairly resource-intensive technology. However, these aquatic plants are polymer-containing substrates and have a great potential for conversion into bioenergy. The aim of the work was to determine the main patterns of Pistia stratiotes L. degradation via granular microbial preparation (GMP) to obtain biomethane gas while simultaneously detoxifying toxic copper compounds. The composition of the gas phase was determined via gas chromatography. The pH and redox potential parameters were determined potentiometrically, and Cu(II) concentration photocolorimetrically. Applying the preparation, high efficiency of biomethane fermentation of aquatic plants and Cu(II) detoxification were... [more]

An inverter, whose inductor current is periodic, is the key equipment for photovoltaic power generation, fuel cell power generation, etc. A nonlinear inductor, whose inductance will be changed by its current, can be used to improve the grid current quality of the inverter, although making the mathematical model of the inverter system more complex. In this paper, the voltage-controlled full-bridge inverter with a nonlinear inductor is investigated and its mathematical model is established. The influence of parameters on the dynamical behaviors of this system is analyzed by using the harmonic balance method and the Floquet theory. Consequently, the mechanism for the occurrence of medium-frequency oscillation is revealed. The hardware circuit for the voltage-controlled full-bridge inverter with a nonlinear inductor is designed and some experimental results are presented for confirmation. The research results show that the mechanism for the occurrence of medium-frequency oscillation is Hop... [more]

Twenty percent of global electricity supplied to the buildings is used for preventing air temperature increase; its consumption for this prevention will triple by 2050 up to China’s present needs. Heat removed from the thermal power plants may drive cold generation in the absorption devices where mass and heat transfer are two-phase phenomena; hence liquid film break-up into the rivulets is extensively investigated, which needs knowledge of the velocity profiles. Laminar flow in a pipe is used in the preliminary study, velocity profile of developed flow is used as a benchmark. The study account writes the applied apparatus with their calibration procedure, and the uncertainty estimation algorithm. The calibration regression line with the slope close to one and a high Pearson’s coefficient value is the final outcome. Therefore, the apparatus may be applied in the principal research.

Home energy monitoring has recently become a very important issue and a means to reduce energy consumption in the residential sector. Sensors and control systems are deployed at various locations in a house and an intelligent system is used to efficiently manage the consumed energy. Low power communication systems are used to provide low power consumption from a smart meter. Several of these systems are battery operated. Other systems use AC/DC adapters to supply power to sensors and communication systems. However, even using low-power technology, such as ZigBee, the power consumption of a router can be high because it must always be powered on. In this work, to evaluate power consumption, a system for monitoring energy usage and indoor air quality was developed. A technique is proposed to efficiently supply power to the components of the system. All sensor nodes are battery operated, and relays are used to control the battery charging process. In addition, an energy harvesting system... [more]

Power production from coal combustion is one of two major anthropogenic sources of mercury emission to the atmosphere. The aim of this study is the analysis of the carbon footprint of mercury removal technologies through sorbents injection related to the removal of 1 kg of mercury from flue gases. Two sorbents, i.e., powdered activated carbon and the coke dust, were analysed. The assessment included both direct and indirect emissions related to various energy and material needs life cycle including coal mining and transport, sorbents production, transport of sorbents to the power plants, and injection into flue gases. The results show that at the average mercury concentration in processed flue gasses accounting to 28.0 µg Hg/Nm3, removal of 1 kg of mercury from flue gases required 14.925 Mg of powdered activated carbon and 33.594 Mg of coke dust, respectively. However, the whole life cycle carbon footprint for powdered activated carbon amounted to 89.548 Mg CO2-e·kg−1 Hg, whereas for c... [more]

This article presents an estimation method of the BLDC rotor position with asymmetrically arranged Hall sensors. Position estimation is necessary to control the motor by methods other than block commutation. A sinusoidal control method was selected for the research, which significantly reduces torque ripples and acoustic noise and is quite simple to implement. Inaccurate performance of the elements determining the position of the BLDC motor rotor causes a large error in the position estimation and has a negative impact on the operation of the drive controlled in this way. Using the developed control algorithms, it is possible to correctly determine the mechanical position of the rotor even for multi-pole motors. The proposed method is relatively easy to implement and does not require modification of control systems, being limited to changes only in the software of such devices. The tests of the actual system clearly show the usefulness of such a control method and its effectiveness.

Power flow analysis is an inevitable methodology in the planning and operation of the power grid. It has been performed for the transmission system, however, along with the penetration of the distributed energy resources, the target has been expanded to the distribution system as well. However, it is not easy to apply the conventional method to the distribution system since the essential information for the power flow analysis, say the impedance and the topology, are not available for the distribution system. To this end, this paper proposes an alternative method based on practically available parameters at the terminal nodes without the precedent information. Since the available information is different between high-voltage and low-voltage systems, we develop two various machine learning schemes. Specifically, the high-voltage model incorporates the slack node voltage, which can be practically obtained at the substation, and yields a time-invariant model. On the other hand, the low vo... [more]

This paper investigates the maximum photovoltaic (PV) penetration limits on both overhead lines and underground cables medium voltage radial distribution system. The maximum PV penetration limit is estimated considering both bus voltage limit (1.05 p.u.) and feeder current ampacity (1 p.u.). All factors affect the max PV penetration limit are investigated in detail. Substation voltage, load percentage, load power factor, and power system frequency (50 Hz or 60 Hz) are analyzed. The maximum PV penetration limit associated with overhead lines is usually higher than the value associated with the underground cables for high substation voltage (substation voltage = 1.05 and 1.04 p.u.). The maximum PV penetration limit decreases dramatically with low load percentage for both feeder types but still the overhead lines accept PV plant higher than the underground cables. Conversely, the maximum PV penetration increases with load power factor decreasing and the overhead lines capability for hosti... [more]

Security of supply of water, which meets the quality parameters specified in applicable standards, is now the basis for the functioning of most societies. In addition to climatic, biological, chemical, and physical hazards, it is worth paying attention to consumers’ subjective perception of the quality of tap water supplied in the area of Poland. The article discusses various activities related to water resources management and analyses the results of an evaluation of selected quality parameters of tap water in Poland. A novelty on a European scale here is an examination of the evaluation of these parameters based on potential seasonal differences (spring, summer, autumn, winter). For the first time in the world literature, PROFIT analysis was used to evaluate selected parameters of tap water quality. The aim of the article was to present a model for the evaluation of the parameters of tap water supplied in different seasons of the year in Poland. Due to the complexity of the research... [more]

The thermal diffusivity of building materials is an extremely important parameter influencing the subsequent thermal comfort of building users. By definition, thermal diffusivity describes how quickly heat from a hot source can flow through a material. Therefore, this parameter includes both the thermal conductivity and the heat capacity of the material. This parameter is often neglected in heat-related calculations which, in the case of dynamic problems, leads to unreliable results. It should be taken into account that heat flows through all materials at a finite speed. On the other hand, knowing the correct thermal diffusivity value of building materials, it is possible to accurately determine the internal parameters in rooms over time. There are several methods for determining thermal diffusivity, most of which are destined to determine this property in laboratories. The aim of the present research is to show how the thermal diffusivity of materials can be determined in existing bui... [more]

This paper presents both the results of a study of the existing heat exchanger network (HEN) of an industrial unit for ethylbenzene (EB) production by the alkylation of benzene with ethylene, and an analysis of four different HEN retrofit projects carried out using process integration methods. The project of modernization of HEN was carried out using classical methods of Pinch analysis. For this case, the value of ΔTmin is determined, which is limited by the technological conditions of the process. Additionally, two different heat pump (HP) integration options and the joint retrofit Pinch project with HP integration are under consideration. The economic analysis of each of the projects was carried out. It is shown that the best results will be obtained when implementing the joint project. As a result, steam consumption will be reduced by 34% and carbon dioxide emissions will be decreased by the same amount.

Extracting oil from spent coffee grounds (SCG) for biodiesel production has recently attracted much research interest. Large amounts of organic solvents are involved for oil extraction and biodiesel synthesis. Hydrothermal liquefaction (HTL) is an emerging thermochemical technology with great potential for biocrude production from a broad range of feedstocks. This study attempted to compare two SCG valorization options: route 1, oil extraction for biodiesel production followed by HTL of defatted SCG; and route 2, direct HTL of raw SCG. The microwave-assisted extraction conditions were optimized to effectively remove oil from SCG using response surface methodology. Under optimal conditions, an SCG oil yield of 8.4 wt.% could be achieved. HTL of defatted SCG generated less biocrude (18.9 wt.%) than that of raw SCG (28.1 wt.%). The biochemical compositions of resultant biocrudes were largely different from each other. The life cycle assessment was conducted on each of the SCG valorization... [more]

The main purpose of this article was to determine the impact on the equilibrium of the local transport system from privileging EVs by permitting them to use bus lanes. The study used two sets of data: information on infrastructure and traffic management; and information on the recorded road network loads and traffic volumes generated by a given shopping centre—the E. Leclerc shopping centre (an important traffic generator within the city of Łódź, Poland). These sets were then used to develop a microsimulation traffic model for the shopping centre and the associated effects on the localised transport system. The model was constructed by means of the PTV Vissim software tool. An initial simulation was conducted that formed a basis for subsequent scenarios (in total, 17 simulations were performed). On the basis of the conducted analyses, it was established that—for the researched part of the transport system—privileging the still rather uncommon battery electric vehicles (BEVs) engendered... [more]

Groundwater velocity has significant effects on the formation of a frozen curtain during freezing. In order to study the influence of the velocity on a frozen curtain, a large physical model test platform was established for double-pipe freezing. Based on this platform, freezing tests for different velocities were carried out. Quartz sand was selected as a similar material. The freezing temperature of the saturated sand layer was found by analyzing the results of the nuclear magnetic resonance (NMR). Based on the study of the thermal physical properties of the sand layer, the freezing test results were analyzed, and the results showed that the flow led to the differential development of the temperature between the upstream and downstream sections of the freezing pipes. Moreover, the larger the velocity, the greater the difference. The flow prolonged the overlapping time of the frozen curtains. Additionally, the flow slowed down the development of the frozen curtain area and the frozen... [more]

Utilising pyrolysis as a waste tyre processing technology has various economic and social advantages, along with the fact that it is an effective conversion method. Despite extensive research and a notable likelihood of success, this technology has not yet seen implementation in industrial and commercial settings. In this review, over 100 recent publications are reviewed and summarised to give attention to the current state of global tyre waste management, pyrolysis technology, and plastic waste conversion into liquid fuel. The study also investigated the suitability of pyrolysis oil for use in diesel engines and provided the results on diesel engine performance and emission characteristics. Most studies show that discarded tyres can yield 40−60% liquid oil with a calorific value of more than 40 MJ/kg, indicating that they are appropriate for direct use as boiler and furnace fuel. It has a low cetane index, as well as high viscosity, density, and aromatic content. According to diesel e... [more]

The energy efficiency of the construction sector should be determined by the cleanliness of the environment and, thus, the health of society. The scientific aim of this article was to develop a methodology for determining the optimum thickness of thermal insulation, taking into account both economic and ecological aspects and considering both heating and cooling costs. The method takes into account the number of degree days of the heating period, as well as the number of degree days of the cooling period. Variants in terms of different types of thermal insulation, various types of construction materials for building walls, climatic zones and heat sources, were taken into consideration. In order to find the optimum thicknesses of thermal insulation, both in economic and ecological terms, a metacriterion was used. The optimum thicknesses of thermal insulation with the use of the metacriterion were obtained in the range of 0.11−0.55 m. It was observed that the values of the optimum heat t... [more]

Public attention to climate change challenges our locked-in fossil fuel-dependent energy sector. Natural gas is replacing other fossil fuels in our energy mix. One way to reduce the greenhouse gas (GHG) impact of fossil natural gas is to replace it with renewable natural gas (RNG). The benefits of utilizing RNG are that it has no climate change impact when combusted and utilized in the same applications as fossil natural gas. RNG can be injected into the gas grid, used as a transportation fuel, or used for heating and electricity generation. Less common applications include utilizing RNG to produce chemicals, such as methanol, dimethyl ether, and ammonia. The GHG impact should be quantified before committing to RNG. This study quantifies the potential production of biogas (i.e., the precursor to RNG) and RNG from agricultural and waste sources in New York State (NYS). It is unique because it is the first study to provide this analysis. The results showed that only about 10% of the stat... [more]

This paper presents the results of a multi-disciplinary effort to clarify the state of the art and the state of practice, and necessary future research for creating the seamless integration and application of light in buildings, regardless of source, which is purposely modulated to illuminate surfaces and designed in a way that is comfortable, healthy, pleasing, cost-effective, and energy efficient. The authors unwrap the research, tools, and technical gaps preventing the full integration of electric lighting and daylighting with advanced façades through the coordination of lighting and windows research activities. The study and a stakeholder workshop captured current technology readiness levels (TRL), as well as research thrusts and implementation guidelines, and identified research priorities, presenting an analysis of the current landscape of lighting metrics—and which metrics are in the critical path for developing integrated daylighting and electric lighting systems, and their des... [more]

This paper describes benchmark calculations for the APR1400 nuclear reactor performed using the high-fidelity deterministic whole-core simulator MPACT compared to reference solutions generated by the Monte Carlo code McCARD. The methodology presented in this paper is a common approach in the field of nuclear reactor analysis, when measured data are not available for comparison, and may be more broadly applied in other simulation applications of energy systems. The benchmark consists of several problems that span the complexity of single pins to a hot full power cycle depletion. Overall, MPACT shows excellent agreement compared to the reference solutions. MPACT effectively predicts the reactivity for different geometries and several temperature and boron conditions. The largest deviation from McCARD occurs for cold zero conditions in which the fuel, moderator, and cladding are all 300 K. Possible reasons for this are discussed. Excluding these cases, the ρ reactivity difference from McC... [more]

Advancements in the nuclear industry have led to the development of fully digitized main control rooms (MCRs)—often termed advanced MCRs—for newly built nuclear power plants (NPPs). Diagnosis is a major part of the cognitive activity in NPP MCRs. Advanced MCRs are expected to improve the working environment and reduce human error, especially during the diagnosis of unexpected scenarios. However, with the introduction of new types of tasks and errors by digital MCRs, a new method to analyze the diagnosis errors in these new types of MCRs is required. Task analysis for operator diagnosis in an advanced MCR based on emergency operation was performed to determine the error modes. The cause-based decision tree (CBDT) method—originally developed for analog control rooms—was then revised to a modified CBDT (MCBDT) based on the error mode categorizations. This work examines the possible adoption of the MCBDT method for the evaluation of diagnosis errors in advanced MCRs. We have also provided... [more]