Editor’s Choice Articles

The paper presents a design of repetitive control (RC) in the current control system of a three-phase grid-tied converter. The goal of the control system is to provide sinusoidal input filter currents under the conditions of distorted and asymmetrical grid voltage. A novel design of the RC is presented, in which the repetitive part is not excited by sharp and non-periodic changes of the reference signal, but it enables high-quality performance under periodic disturbance conditions. In the proposed system. RC cooperates with a discrete state feedback controller. An innovative approach to tuning is proposed in which parameters of the repetitive, as well as the state feedback controller, are selected as a result of the optimization process with the use of a particle swarm algorithm. The proposed control system is verified experimentally on a laboratory test bench. The achieved results confirm the high-quality system performance. Full article

Nitrate (NO₃⁻-N) and nitrites (NO₂⁻-N) are common pollutants in various water bodies causing serious threats not only to aquatic, but also to animals and human beings. In this study, we developed a strategy for efficiently reducing nitrates in microbial fuel cells (MFCs) powered by a granular activated carbon (GAC)-biocathode. GAC was developed by acclimatizing and enriching denitrifying bacteria under a redox potential (0.3 V) generated from MFCs. Thus, using the formed GAC-biocathode we continued to study their effect on denitrification with different cathode materials and circulation speeds in MFCs. The GAC-biocathode with its excellent capacitive property can actively reduce nitrate for over thirty days irrespective of the cathode material used. The stirring speed of GAC in the cathode showed a steady growth in potential generation from 0.25 V to 0.33 V. A rapid lag phase was observed when a new carbon cathode was used with enriched GAC. While a slow lag phase was seen when a stainless-steel cathode was replaced. These observations showed that effective storage and supply of electrons to the GAC plays a crucial role in the reduction process in MFCs. Electrochemical analysis of the GAC properties studied using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and zeta potential showed distinct properties with different abiotic and biocathode conditions. We found that the enrichment of electrotrophic bacteria on GAC facilitates the direct electron transfer in the cathode chamber for reducing NO₃⁻-N in MFCs as observed by scanning electron microscopy. Full article

Contact selectivity is a key parameter for enhancing and improving the power conversion efficiency (PCE) of crystalline silicon (c-Si)-based solar cells. Carrier selective contacts (CSC) are the key technology which has the potential to achieve a higher PCE for c-Si-based solar cells closer to their theoretical efficiency limit. A recent and state-of-the-art approach in this domain is the tunnel oxide passivated contact (TOPCon) approach, which is completely different from the existing classical heterojunction solar cells. The main and core element of this contact is the tunnel oxide, and its main role is to cut back the minority carrier recombination at the interface. A state-of-the-art n-type c-Si-based TOPCon solar cell featuring a passivated rear contact was experimentally analyzed, and the highest PCE record of ~25.7% was achieved. It has a high fill factor (FF) of ~83.3%. These reported results prove that the highest efficiency potential is that of the passivated full area rear contact structures and it is more efficient than that of the partial rear contact (PRC) structures. In this paper, a review is presented which considers the key characteristics of TOPCon solar cells, i.e., minority carrier recombination, contact resistance, and surface passivation. Additionally, practical challenges and key issues related to TOPCon solar cells are also highlighted. Finally, the focus turns to the characteristics of TOPCon solar cells, which offer an improved and better understanding of doping layers and tunnel oxide along with their mutual and combined effect on the overall performance of TOPCon solar cells. Full article

Renewable energy solutions are appropriate for on-grid and off-grid applications, acting as a supporter for the utility network or rural locations without the need to develop or extend costly and difficult grid infrastructure. As a result, hybrid renewable energy sources have become a popular option for grid-connected or standalone systems. This paper examines hybrid renewable energy power production systems with a focus on energy sustainability, reliability due to irregularities, techno-economic feasibility, and being environmentally friendly. In attaining a reliable, clean, and cost-effective system, sizing optimal hybrid renewable energy sources (HRES) is a crucial challenge. The presenters went further to outline the best sizing approach that can be used in HRES, taking into consideration the key components, parameters, methods, and data. Moreover, the goal functions, constraints from design, system components, optimization software tools, and meta-heuristic algorithm methodologies were highlighted for the available studies in this timely synopsis of the state of the art. Additionally, current issues resulting from scaling HRES were also identified and discussed. The latest trends and advances in planning problems were thoroughly addressed. Finally, this paper provides suggestions for further research into the appropriate component sizing in HRES. Full article

Rooftop solar photovoltaic (PV) systems could significantly contribute to renewable energy production and reduce domestic energy costs. In Italy, as in other countries, the current incentives generate a modest annual increase after the generous fiscal incentives that kick-started the PV market in the 2008–2013 period. Several factors are, however, at play that can speed up the installation process, such as the improvements in PV technology at declining prices, the increased availability of battery-storage (BS) systems, the growing use of electric appliances, the uptake of electric cars, and the increased environmental awareness. We integrate two research methodologies, discrete choice modeling and agent-based modeling, to understand how these factors will influence households’ decisions regarding PV and BS installations and how agents interact in their socioeconomic environment. We predict that in Italy, given the preference structure of homeowners, the continuing decline in costs, and the social interaction, 40–45% of homeowners will have PV or PV and BS installed by 2030, thanks to the existing investment tax credit policy. Full article

Energy policy investments are usually evaluated using a cost-benefit analysis (CBA), which requires an estimation of the social discount rate (SDR). The choice of SDR can be crucial for the outcome of the appraisal, as energy-related investments generate long-term impacts affecting climate change. Once discounted, these impacts are highly sensitive to slight changes in the value of the SDR. Some countries (the UK and France) switched from a constant SDR to the declining rate scheme—a solution that limits the impact sensitivity. To our knowledge, none of the CEE countries apply DDR in CBA. While a constant SDR is a relatively well-established approach, declining SDRs are estimated to be used much less frequently, particularly for CEE EU member countries and energy policies. The rationale for the decline can rest on uncertainty over future discount rates, as shown by the approach developed by Weitzman and Gollier, which extends the classical Ramsey model. We applied this approach in our paper, as the Ramsey formula is the prevailing formula for EU countries’ SDR estimates. We estimated a flat SDR via the Ramsey formula with Gollier’s “precautionary term”, and next, we calculated Weitzman’s certainty equivalent rates for the 500-year horizon. Ramsey’s SDRs, obtained using consumption growth rates dating back to 1996, varied between 6.77% for Lithuania and 2.95% for Czechia and declined by 0.15% on average (Gollier’s term). Declining SDRs for the longest horizon dropped to approx. 0.5% (from 0.35% for Bulgaria to 0.67% for Poland), and the descent is deeper and faster when forward SDRs (following the UK Green Book approach) were considered (0.01% to 0.04%). The results are important for long-term policies regarding energy and climate change in CEE EU member countries, but they are still dependent on fossil fuels and experience an investment gap to fulfil EU climate goals. Full article

Ceramic tile manufacturing is a highly energy-intensive process. Concerns about carbon emissions and energy costs make energy management crucial for this sector, which holds a leading role in Italian industry. The paper discusses the energetic and environmental performance of cogeneration (CHP) in the ceramic industry, where prime mover exhaust heat is supplied to a spray-dryer system, contributing to the satisfaction of the thermal demand and decreasing natural gas consumption. A thermodynamic model of a dryer unit, validated against real data, has been set-up to provide a detailed representation of the thermal fluxes involved in the process. Then, the thermal integration with two types of CHP prime movers of similar electric size (4 MW) is investigated. Energetic results show that the gas turbine can contribute up to 81% of dryer thermal consumption, whilst internal combustion engine contribution is limited to 26%. A methodology was ad-hoc defined for the environmental assessment of CHP, accounting for global (CO₂) and local (CO and NO_X) emissions. Results confirm that CHP units guarantee reduction of CO₂ and NO_X compared to separate generation, with maximum values equal to 81 g/kWh_th and 173 mg/kWh_th, respectively; CO emission is decreased only in the case of gas turbine operation, with savings equal to 185 mg/kWh_th. Full article

In the current study, a high temperature thermal storage system with a hybrid of phase change material and graphite as the storage materials is designed and evaluated as to its applicability for use as a utility-scale Carnot battery. The design includes an externally heated liquid sodium tank, which is used as the heat transfer fluid. This is used to charge and discharge the storage system consisting of a graphite storage medium sandwiched by two phase change materials. Finally, electrical generation is by way of a supercritical carbon dioxide Brayton cycle operated at 700 °C. Detailed modelling of these designs was conducted by way of a previously validated numerical model to predict performance metrics. Using the aforementioned designs, a preliminary cost estimate was undertaken to better determine applicability. From these results, it was found that while the graphite system was the most effective at storing energy, it was also the highest cost due to the high cost of graphite. In total, 18 storage tanks containing nearly 17,400 tons of storage material were required to store the 1200 MWh_t required to run the sCO₂ power block for 10 h. Under the study conditions, the cost of a PCM-based Carnot battery was estimated to be $476/kWh_e, comparable to other storage technologies. Furthermore, it was found that if the cost of the graphite and/or steel could be reduced, the cost of the system could be reduced to $321/kWh_e. Full article

The heterogeneous network (HetNet) is a specified cellular platform to tackle the rapidly growing anticipated data traffic. From a communications perspective, data loads can be mapped to energy loads that are generally placed on the operator networks. Meanwhile, renewable energy-aided networks offer to curtailed fossil fuel consumption, so to reduce the environmental pollution. This paper proposes a renewable energy based power supply architecture for the off-grid HetNet using a novel energy sharing model. Solar photovoltaics (PV) along with sufficient energy storage devices are used for each macro, micro, pico, or femto base station (BS). Additionally, a biomass generator (BG) is used for macro and micro BSs. The collocated macro and micro BSs are connected through end-to-end resistive lines. A novel-weighted proportional-fair resource-scheduling algorithm with sleep mechanisms is proposed for non-real time (NRT) applications by trading-off the power consumption and communication delays. Furthermore, the proposed algorithm with an extended discontinuous reception (eDRX) and power saving mode (PSM) for narrowband internet of things (IoT) applications extends the battery lifetime for IoT devices. HOMER optimization software is used to perform optimal system architecture, economic, and carbon footprint analyses while the Monte-Carlo simulation tool is used for evaluating the throughput and energy efficiency performances. The proposed algorithms are validated through the practical data of the rural areas of Bangladesh from which it is evident that the proposed power supply architecture is energy-efficient, cost-effective, reliable, and eco-friendly. Full article

Sustainable energy strategies have been a critical subject for sustainable development, especially in cities. Citizens, as an integral part of the urban environment, play a significant role in urban spaces, as does their health. An accurate understanding of citizens’ mental, social, and physical health in urban settings is required to design and plan better cities. This study aims to assess the level of alignment with health factors in Mahabad, a major medium-sized city in Iran. Previous studies indicate that the built environment can influence health dimensions. Health factors depend to a great extent on how well the environment is formed and how it is put together. This research is a descriptive, analytical, cross-sectional study that analyzes the environment’s psychological elements and physical and mental health factors of Mahabad’s citizens. According to the Cochran model, 384 questionnaires were distributed among households. For data analysis, SPSS 12 and Arc GIS software were used. The main results of this research show that five factors, “Environmental quality”, “Identity and social relationships”, and “Readability”, have the most impact on the physical and mental health of citizens (respondents). These issues are much more pronounced in the downtown neighborhoods. This study showed that urban experts can understand different levels of public health by knowing the historical, social, cultural, and economic factors and characteristics. The result will help decision makers, city authorities, designers, and urban planners to be more informed about citizens’ health and the ways to improve it. Full article

Electric Vehicles are becoming increasingly popular due to their environment friendly operation. As the demand for electric vehicles increases, it has become quite important to explore their charging strategies. Since charging and traction do not normally occur simultaneously and the power electronics converters for both operations have some similarities, the practice of integrating both charging and traction systems is becoming popular. These types of chargers are termed ‘Integrated Chargers’. The aim of this paper is to review the available literature on the integrated chargers and present a critical analysis of the pros and cons of different integrated charging architectures. Integrated chargers for electric vehicles with three-phase permanent magnet synchronous machines, multi-phase machines and switched reluctance machines were compared. The challenges with the published integrated chargers and the future aspect of the work were been discussed. Full article

This article reviews the main methodologies employed for the optimal location, sizing, and operation of Distributed Generators (DGs) and Energy Storage Systems (ESSs) in electrical networks. For such purpose, we first analyzed the devices that comprise a microgrid (MG) in an environment with Distributed Energy Resources (DERs) and their modes of operation. Following that, we examined the planning and operation of each DER considered in this study (DGs and ESSs). Finally, we addressed the joint integration of DGs and ESSs into MGs. From this literature review, we were able to identify both the objective functions and constraints that are most commonly used to formulate the problem of the optimal integration and operation of DGs and ESSs in MGs. Moreover, this review allowed us to identify the methodologies that have been employed for such integration, as well as the current needs in the field. With this information, the purpose is to develop new mathematical formulations and approaches for the optimal integration and operation of DERs into MGs that provide financial and operational benefits. Full article

Real-time battery SOX estimation including the state of charge (SOC), state of energy (SOE), and state of health (SOH) is the crucial evaluation indicator to assess the performance of automotive battery management systems (BMSs). Recently, intelligent models in terms of deep learning (DL) have received massive attention in electric vehicle (EV) BMS applications due to their improved generalization performance and strong computation capability to work under different conditions. However, estimation of accurate and robust SOC, SOH, and SOE in real-time is challenging since they are internal battery parameters and depend on the battery’s materials, chemical reactions, and aging as well as environmental temperature settings. Therefore, the goal of this review is to present a comprehensive explanation of various DL approaches for battery SOX estimation, highlighting features, configurations, datasets, battery chemistries, targets, results, and contributions. Various DL methods are critically discussed, outlining advantages, disadvantages, and research gaps. In addition, various open challenges, issues, and concerns are investigated to identify existing concerns, limitations, and challenges. Finally, future suggestions and guidelines are delivered toward accurate and robust SOX estimation for sustainable operation and management in EV operation. Full article

The objective of this review paper is to provide an overview of the current state-of-the-art in solar road deployment, including the availability of anti-reflection and anti-soiling coating materials for photovoltaic (PV) technology. Solar roads are built using embedded PV panels that convert sunlight into electricity, which can be stored for later use. Prototypes of solar roads have been tested on various continents, but the lack of suitable PV materials has limited their effectiveness compared to conventional PV systems. By analyzing the existing literature on solar roads and PV materials, including anti-reflection and anti-soiling coatings, we aim to identify gaps in knowledge and propose an action plan to improve the resiliency, durability, and reliability of PV panels in solar road applications. This will enable the deployment of solar roads as a clean, renewable energy source. Full article

Battery degradation is a main concern for electric vehicle (EV) users, and a reliable capacity estimation is of major importance. Every EV battery management system (BMS) provides a variety of information, including measured current and voltage, and estimated capacity of the battery. However, these estimations are not transparent and are manufacturer-specific, although measurement accuracy is unknown. This article uses extensive measurements from six diverse EVs to compare and assess capacity estimation with three different methods: (1) reading capacity estimation from the BMS through the central area network (CAN)-bus, (2) using an empirical capacity estimation (ECE) method with external current measurements, and (3) using the same method with measurements coming from the BMS. We show that the use of BMS current measurements provides consistent capacity estimation (a difference of approximately 1%) and can circumvent the need for costly experimental equipment and DC chargers. This data can simplify the ECE method only by using an on-board diagnostics port (OBDII) reader and an AC charger, as the car measures the current directly at the battery terminals. Full article

A smart and decentralized electrical system, powered by grid-connected renewable energy (RE) with a reliable storage system, has the potential to change the future socio-economic dynamics. Climate change may, however, affect the potential of RE and its related technologies. This study investigated the impact of climate change on photovoltaic cells’ temperature response and energy potential under two CO₂ emission scenarios, RCP2.6 and 8.5, for the near future (2024–2040) and mid-century (2041–2065) in Togo. An integrated Regional Climate Model version 4 (RegCM4) from the CORDEX-CORE initiative datasets has been used as input. The latter platform recorded various weather variables, such as solar irradiance, air temperature, wind speed and direction, and relative humidity. Results showed that PV cells’ temperature would likely rise over all five regions in the country and may trigger a decline in the PV potential under RCP2.6 and 8.5. However, the magnitude of the induced change, caused by the changing climate, depended on two major factors: (1) the PV technology and (2) geographical position. Results also revealed that these dissimilarities were more pronounced under RCP8.5 with the amorphous technology. It was further found that, nationally, the average cell temperature would have risen by 1 °C and 1.82 °C under RCP2.6 and 8.5, in that order, during the 2024–2065 period for a-Si technology. Finally, the PV potential would likely decrease, on average, by 0.23% for RCP2.6 and 0.4% for RCP8.5 for a-Si technology. Full article

Sodium-ion batteries (SIBs) are among the most cost-effective and environmentally benign electrical energy storage devices required to match the needs of commercialized stationary and automotive applications. Because of its excellent chemical characteristics, infinite abundance, and low cost, the SIB is an excellent technology for grid energy storage compared with others. When used as anodes, titanium compounds based on the Ti⁴⁺/Ti³⁺ redox couple have a potential of typically 0.5–1.0 V, which is far from the potential of dangerous sodium plating (0.0–0.1 V). This ensures the operational safety of large-scale SIBs. Low lattice strain, usually associated with Ti-based materials, is also helpful for the longevity of the cycling of SIBs. Numerous Ti-based anode materials are being developed for use in SIBs. In particular, due to adequate electrode–electrolyte interaction and rapid charge transportation, hierarchical porous (HP) Ti-based anode materials were reported as having high specific capacity, current density, and cycling stability. HPTi-based anode materials for SIBs have the potential to be used in automobiles and portable, flexible, and wearable electronic devices. This review addresses recent developments in HPTiO₂-based SIBs and their preparation, properties, performance, and challenges. Full article

Improving air quality, reducing greenhouse gas emissions, and achieving independence from fossil fuels have led most countries towards deploying solar photovoltaics (PV) in the power distribution grid and electrifying the transportation fleet. Internal combustion engine (ICE) vehicles are, in particular, one of the main culprits of injecting greenhouse gas emissions into the atmosphere, making electric vehicles (EVs) an important tool in combating climate change. Despite their considerable environmental and economic benefits, the integration of PVs and EVs can introduce unique operational challenges for the power distribution grid. If not coordinated, high penetration of PVs and EVs can result in variety of power quality issues, such as instances of overvoltage and undervoltage, frequency fluctuations, and/or increased losses. This paper proposes a mixed-integer multi-objective nonlinear optimization model for optimal energy dispatch in a power distribution grid with high penetration of PV and EV resources. The model proposed here is an extension of the traditional voltage and var optimization (VVO) into a comprehensive and coordinated control of voltage, active power, and reactive power. A modified version of the IEEE 123-bus test distribution system is used to demonstrate the effectiveness of the proposed solution. Full article

Lithium batteries employed in lightweight fixed-wing UAVs are required to operate with large temperature variations and, especially for the emerging applications in hybrid propulsion systems, with relevant transient loads. The detailed dynamic modelling of battery packs is thus of paramount importance to verify the feasibility of innovative hybrid systems, as well as to support the design of battery management systems for safety/reliability enhancement. This paper deals with the development of a generalised approach for the dynamic modelling of battery packs via Thevenin circuits with modular hysteretic elements (open circuit voltage, internal resistance, RC grids). The model takes into account the parameters’ dependency on the state of charge, temperature, and both the amplitude and sign of the current load. As a relevant case study, the modelling approach is here applied to the Li-Po battery pack (1850 mAh, 6 cells, 22.2 V) employed in the lightweight fixed-wing UAV Rapier X-25 developed by Sky Eye Systems (Cascina, Italy). The procedure for parameter identification with experimental measurements, obtained at different temperatures and current loads, is firstly presented, and then the battery model is verified by simulating an entire Hybrid Pulse Power Characterisation test campaign. Finally, the model is used to evaluate the battery performance within the altitude (i.e., temperature) envelope of the reference UAV. The experiments demonstrate the relevant hysteretic behaviour of the characteristic relaxation times, and this phenomenon is here modelled by inserting Bouc–Wen hysteresis models on RC grid capacitances. The maximum relative error in the terminal output voltage of the battery is smaller than 1% for any value of state of charge greater than 10%. Full article

The conventional volt-VAR control (VVC) in distribution systems has limitations in solving the overvoltage problem caused by massive solar photovoltaic (PV) deployment. As an alternative method, VVC using solar PV smart inverters (PVSIs) has come into the limelight, which can respond quickly and effectively to solve the overvoltage problem by absorbing reactive power. However, the network power loss, that is, the sum of line losses in the distribution network, increases with reactive power. Dynamic distribution network reconfiguration (DNR), which hourly controls the network topology by controlling sectionalizing and tie switches, can also solve the overvoltage problem and reduce network loss by changing the power flow in the network. In this study, to improve the voltage profile and minimize the network power loss, we propose a control scheme that integrates the dynamic DNR with volt-VAR control of PVSIs. The proposed control scheme is practically usable for three reasons: Primarily, the proposed scheme is based on a deep reinforcement learning (DRL) algorithm, which does not require accurate distribution system parameters. Furthermore, we propose the use of a heterogeneous multiagent DRL algorithm to control the switches centrally and PVSIs locally. Finally, a practical communication network in the distribution system is assumed. PVSIs only send their status to the central control center, and there is no communication between the PVSIs. A modified 33-bus distribution test feeder reflecting the system conditions of South Korea is used for the case study. The results of this case study demonstrates that the proposed control scheme effectively improves the voltage profile of the distribution system. In addition, the proposed scheme reduces the total power loss in the distribution system, which is the sum of the network power loss and curtailed energy, owing to the voltage violation of the solar PV output. Full article

One of the relevant factors in smart energy management is the ability to predict the consumption of energy in smart households and use the resulting data for planning and operating energy generation. For the utility to save money on energy generation, it must be able to forecast electrical demands and schedule generation resources to meet the demand. In this paper, we propose an optimized deep network model for predicting future consumption of energy in smart households based on the Dipper Throated Optimization (DTO) algorithm and Long Short-Term Memory (LSTM). The proposed deep network consists of three parts, the first part contains a single layer of bidirectional LSTM, the second part contains a set of stacked unidirectional LSTM, and the third part contains a single layer of fully connected neurons. The design of the proposed deep network targets represents the temporal dependencies of energy consumption for boosting prediction accuracy. The parameters of the proposed deep network are optimized using the DTO algorithm. The proposed model is validated using the publicly available UCI household energy dataset. In comparison to the other competing machine learning models, such as Random Forest (RF), Support Vector Machine (SVM), K-Nearest Neighbor (KNN), Multi-Layer Perceptron (MLP), Sequence-to-Sequence (Seq2Seq), and standard LSTM, the performance of the proposed model shows promising effectiveness and superiority when evaluated using eight evaluation criteria including Root Mean Square Error (RMSE) and $R^2$. Experimental results show that the proposed optimized deep model achieved an RMSE of (0.0047) and $R^2$ of (0.998), which outperform those values achieved by the other models. In addition, a sensitivity analysis is performed to study the stability and significance of the proposed approach. The recorded results confirm the effectiveness, superiority, and stability of the proposed approach in predicting the future consumption of energy in smart households. Full article

This paper describes the present and the future of the energy sector in relation to the dominant and constantly evolving form of the global economic system. These considerations have their starting point in transformations of the energy sector in prosumer capitalism, which has dramatically changed the picture of the global economy in recent years. Subsequently, a futuristic approach is applied to determine the role and importance of energy from renewable sources for further human development. The main objective of the paper is to explain the current situation of the energy sector in prosumer capitalism and to extrapolate these relationships for the future, considering the need to enter the path of sustainable development to eliminate the global warming processes and climate changes. A review of the existing scientific literature was applied as the research method. The historical wave concept, proposed by Toffler, was found to be highly useful because of its high potential in futurology, where it enables one to study megatrends. The Fourth Wave was linked to prosumer capitalism, and it provided the base for defining the next ones: the Fifth Wave of Computing (ecosocialism) and the Sixth Wave in the form of technological and energy communism (solar communism). It also turned out that the key to solving mankind’s energy problems lies in the global mean entropy budget. The literature review shows that founding the global energy system on solar radiation is the only known method for eliminating the anthropogenic greenhouse effect, which is the source of global warming and, consequently, of climate change. Therefore, the second law of thermodynamics provides a physical, economic, and logical justification for introducing a new and ultimate management form—solar communism—by 2050. Full article

Drying is an extremely energy-intensive process. Superheated steam as a drying medium can improve the energy efficiency of the drying processes. In superheated steam drying, waste heat can be recovered by condensing the exhaust steam or raising its specific enthalpy. Spray drying is widely used in industry, even though its energy efficiency is often low. Substitution of air by superheated steam as a drying medium in a spray dryer may reduce the energy consumption of the drying process by 20–30%; moreover, if excess steam generated by moisture evaporation is upgraded to a higher temperature level and reused for drying, the energy demand could be decreased by even 80%. A literature review showed that superheated steam spray drying was successfully applied for both thermally resistant and a wide range of thermally sensitive materials. Superheated steam drying gives a number of advantages in terms of product properties, i.e., higher particle porosity due to rapid moisture evaporation results in improved powder rehydration properties. Additionally, steam drying may be applied for in situ particle crystallization. Taking into account the advantages of superheated steam drying and the potential application of this technology in spray drying systems, there is a great need for further research in this field. This literature review aimed to present an energy-saving solution, i.e., superheated steam spray drying process, showing its advantages and potential applications, followed by drying kinetics, providing analysis of the research papers on experimental studies as well as mathematical modeling of this drying technique. Full article

The powertrain performance in an electric vehicle is fully dependent on the electrical and thermal constraints of the static converters ensuring the power transfer taking place between the energy storage systems and the electromechanical machines. These constraints depend on the architectures of the power converters, and their control strategies. Particularly, the maximal limits are reached in maneuvers such as hard regenerative braking circumstances. Indeed, braking recovery is a critical phase in the vehicle’s operation, and its duration and intensity may strongly impact the vehicle’s battery behavior or integrated hybrid storage system. The innovative objective of the paper is to propose an electrothermal multicriteria comparative study based on electrical and thermal criteria for two competitive powertrains. These semi-active power configurations (a 3-level DC/DC converter-based, and a Z-source converter-based) are implemented in a two-front wheel driven electric vehicle during extreme regenerative braking conditions. Open-loop and closed-loop controls were implemented in the Z-source using the maximal constant boost control with 3rd harmonic injection modulation technique. We considered two paralleled IGBT modules instead of the single shoot-through structure. Our approach is based on simulation during an extreme braking maneuver leading to heavy repercussions on the overall powertrain system. The aim is to investigate the challenging structure of the Z-source. Results showed that the proposed 3-level DC/DC-based topology has better performances in terms of power losses, efficiency, thermal behavior, and electromagnetic interference. Full article

Consistent accumulation of petroleum hydrocarbon (PH) in soil and sediments is a big concern and, thus, warrants a static technology to continuously remediate PH-contaminated soil. Bioelectrochemical systems (BESs) can offer the desired solution using the inimitable metabolic response of electroactive microbes without involving a physiochemical process. To date, a wide range of BES-based applications for PH bioremediations under different environmental conditions is readily available in the literature. Here, the latest development trend in BESs for PH bioremediation is critically analyzed and discussed. The reactor design and operational factors that affect the performance of BESs and their strategic manipulations such as designing novel reactors to improve anodic reactions, enhancing soil physiology (electrical conductivity, mass diffusion, hydraulic conductivity), electrode modifications, operational conditions, microbial communities, etc., are elaborated to fortify the understanding of this technology for future research. Most of the literature noticed that a low mass diffusion condition in soil restricts the microbes from interacting with the contaminant farther to the electrodes. Therefore, more research efforts are warranted, mainly to optimize soil parameters by specific amendments, electrode modifications, optimizing experimental parameters, integrating different technologies, and conducting life cycle and life cycle cost analysis to make this technology viable for field-scale applications. Full article

Aiming at integrating different energy sectors and exploiting the synergies coming from the interaction of different energy carriers, sector coupling allows for a greater flexibility of the energy system, by increasing renewables’ penetration and reducing carbon emissions. At the local level, sector coupling fits well in the concept of an integrated local energy community (ILEC), where active consumers make common choices for satisfying their energy needs through the optimal management of a set of multi-carrier energy technologies, by achieving better economic and environmental benefits compared to the business-as-usual scenario. This paper discusses the stochastic operation optimization of the smart Savona Campus of the University of Genoa, according to economic and environmental criteria. The campus is treated as an ILEC with two electrically interconnected multi-energy hubs involving technologies such as PV, solar thermal, combined heat and power systems, electric and geothermal heat pumps, absorption chillers, electric and thermal storage. Under this prism, the ILEC can participate in the day-ahead market (DAM) with proper bidding strategies. To assess the renewables’ uncertainties, the roulette wheel method is used to generate an initial set of scenarios for solar irradiance, and the fast forward selection algorithm is then applied to preserve the most representative scenarios, while reducing the computational load of the next optimization phase. A stochastic optimization model is thus formulated through mixed-integer linear programming (MILP), with the aim to optimize the operation strategies of the various technologies in the ILEC, as well as the bidding strategies of the ILECs in the DAM, considering both energy costs and carbon emissions through a multi-objective approach. Case study results show how the optimal bidding strategies of the ILEC on the DAM allow minimizing of the users’ net daily cost, and, as in the case of environmental optimization, the ILEC operates in self-consumption mode. Moreover, in comparison to the current operation strategies, the optimized case allows reduction of the daily net energy cost in a range from 5 to 14%, and the net daily carbon emissions in a range from 6 to 18%. Full article

To date, hundreds of millions tons of plastics has been produced worldwide. Their production and disposal are associated with high pollution and carbon release into the atmosphere. A more environmentally friendly alternative is bioplastics, and the most popular is polyhydroxybutyrate (PHB) polymer. Large amounts of PHB can be obtained from activated sludge where used cooking oil or other industrial waste can be used as potential substrates. In this work, efficient bioplastic production strategies are studied, and the considered substrate is a mixture of oil and peptone. Pseudomonas fluorescens bacteria are used to accumulate PHB, and the cultivation of microorganisms is carried out in batch and continuous-flow bioreactors. Microscopic observations and laboratory essays are performed to confirm presence of PHB and other key parameters. The obtained results allow us to determine the optimal feeding strategy. Full article

A potential method of storing and transporting hydrogen safely in a cost-effective and practical way involves the utilization of molecules that contain hydrogen in their structure such as ammonia. Because of its high hydrogen content and carbon-free molecular structure, as well as the maturity of related technology (easy liquefaction), ammonia has gained attention as a “hydrogen carrier” for the generation of energy. Unfortunately, hydrogen production from ammonia requires an efficient catalyst to achieve high conversion at low reaction temperatures. Recently, very attractive results have been obtained with low-surface-area materials. This review paper is focused on summarizing and comparing recent advances in novel, economic and active catalysts for this reaction, paying particular attention to materials with low surface area such as silicon carbide (SiC) and perovskites (ABO₃ structure). The effects of the supports, the active phase and the addition of promoters in such low-porosity materials have been analyzed in detail. Advances in adequate catalytic systems (including support and active metal) benefit the perspective of ammonia as a hydrogen carrier for the decarbonization of the energy sector and accelerate the “hydrogen economy”. Full article

CO₂ emissions associated with hydrogen production can be reduced replacing steam methane reforming with electrolysis using renewable electricity with a trade-off of increasing energy consumption, water consumption and cost. In this research, a linear programming optimization model of a hydrogen production system that considers simultaneously energy consumption, water consumption, CO₂ emissions and cost on a cradle-to-gate basis was developed. The model was used to evaluate the impact of CO₂ intensity on the optimum design of a hydrogen production system for Japan considering different stakeholders’ priorities. Hydrogen is produced using steam methane reforming and electrolysis. Electricity sources include grid, wind, solar photovoltaic, geothermal and hydro. Independent of the stakeholders’ priorities, steam methane reforming dominates hydrogen production for cradle-to-gate CO₂ intensities larger than 9 kg CO₂/kg H₂, while electrolysis using renewable electricity dominates for lower cradle-to-gate CO₂ intensities. Reducing the cradle-to-gate CO₂ intensity increases energy consumption, water consumption and specific cost of hydrogen production. For a cradle-to-gate CO₂ intensity of 0 kg CO₂/kg H₂, the specific cost of hydrogen production varies between 8.81 and 13.6 USD/kg H₂; higher than the specific cost of hydrogen production targeted by the Japanese government in 2030 of 30 JPY/Nm³, 3.19 USD/kg H₂. Full article

Low salinity water injection (LSWI) is considered to be more cost-effective and has less environmental impacts over conventional chemical Enhanced Oil Recovery (EOR) methods. CO₂ Water-Alternating-Gas (WAG) injection is also a leading EOR flooding process. The hybrid EOR method, CO₂ low salinity (LS) WAG injection, which incorporates low salinity water into CO₂ WAG injection, is potentially beneficial in terms of optimizing oil recovery and decreasing operational costs. Experimental and simulation studies reveal that CO₂ LSWAG injection is influenced by CO₂ solubility in brine, brine salinity and composition, rock composition, WAG parameters, and wettability. However, the mechanism for increased recovery using this hybrid method is still debatable and the conditions under which CO₂ LSWAG injection is effective are still uncertain. Hence, a comprehensive review of the existing literature investigating LSWI and CO₂ WAG injection, and laboratory and simulation studies of CO₂ LSWAG injection is essential to understand current research progress, highlight knowledge gaps and identify future research directions. With the identified research gap, a core-scale simulation study on hysteresis effect in CO₂ LSWAG injection is carried out. The results indicate different changing trend in oil recovery due to the impact of salinity on hysteresis and excluding of hysteresis effect in CO₂ LSWAG injection simulation and optimization might lead to significant errors. Full article

The European Union’s relative disregard for the economic, geopolitical and climatic concerns of its peripheral Eastern countries has contributed to making the war in Ukraine possible. Its consequences are now returning in the form of energy dependence and economic instability on the Union as a whole and the risk of economic crisis and deindustrialisation. This should prompt a re-assessment of the EU’s strategy towards its eastern neighbours, particularly in the energy and climate policy field. This evaluation starts from the issue of control over cheap energy as a key material foundation of state and interstate power. On this basis, we analyse the struggle between Russia and the European core states over Ukraine in terms of the ability to extract an economic surplus through the unequal exchange of energy. The current escalation should be understood as an attempt by the Russian petrostate to preserve the economic basis of its regime, which is threatened by the prospect of a low-carbon transition in Europe. We conclude that a massive acceleration of the transition away from fossil fuels is the key to economic, geopolitical and climate stabilisation, highlighting possible policy instruments the EU could use to secure its production system and protect citizens’ security. Full article

The design and optimization of photobioreactor(s) (PBR) benefit from the development of robust and quantitatively accurate computational fluid dynamics (CFD) models, which incorporate the complex interplay of fundamental phenomena. In the present work, we propose a comprehensive computational model for tubular photobioreactors equipped with glass sponges. The simulation model requires a minimum of at least three submodels for hydrodynamics, light supply, and biomass kinetics, respectively. First, by modeling the hydrodynamics, the light–dark cycles can be detected and the mixing characteristics of the flow (besides the mass transport) can be analyzed. Second, the radiative transport model is deployed to predict the local light intensities according to the wavelength of the light and scattering characteristics of the culture. The third submodel implements the biomass growth kinetic by coupling the local light intensities to hydrodynamic information of the CO₂ concentration, which allows to predict the algal growth. In combination, the novel mesoscopic simulation model is applied to a tubular PBR with transparent walls and an internal sponge structure. We showcase the coupled simulation results and validate specific submodel outcomes by comparing the experiments. The overall flow velocity, light distribution, and light intensities for individual algae trajectories are extracted and discussed. Conclusively, such insights into complex hydrodynamics and homogeneous illumination are very promising for CFD-based optimization of PBR. Full article

Energy determines the social, economic, and environmental aspects that enable the advancement of communities. For this reason, this paper aims to analyze the quality of the energy service in the Non-Interconnected Zones (NIZ) of Colombia. For this purpose, clustering techniques (K-means, K-medoids, divisive analysis clustering, and heatmaps) are applied for data analysis in the context of the NIZ to identify patterns or hidden information in the Colombian government data related to the state of the electricity service in these localities during the years 2019–2020. A descriptive statistical analysis and validation of the results of the clustering techniques is also carried out using R software. Through the implementation of clustering algorithms such as K-means, K-medoids, and divisive analysis clustering, potential areas for the development of renewable and alternative energy projects are identified, considering places with deficiencies in their current electricity service, higher consumption, or places with very low daily hours of electricity service. Additionally, relationships were identified in the dataset that can be considered as tools that would support decision-making for academia and industry, as well as the definition of guidelines or strategies from the government to improve energy efficiency and quality for these places, and consequently, the living conditions of the residents of Colombia’s NIZs. Full article

To enable the fast growth of the floating offshore wind industry, simulation models must be validated with experimental data. Floating wind model-scale experiments in wind–wave facilities have been performed over the last two decades with varying levels of fidelity and limitations. However, the turbine controls in these experiments have considered only limited control strategies and implementations. To allow for control co-design, this research focuses on implementing and experimentally validating more advanced turbine control actions and strategies in a wind–wave basin for a 1:70-scale model of the International Energy Agency’s wind 15 MW reference wind turbine. The control strategies analyzed include torque control, collective pitch control, and transition region control (setpoint smoothing). Our experimental and numerical results include the effects of varying rotor speeds, blade pitches, and wind environments on the turbine thrust and torque. Numerical models from three different software tools are presented and compared to the experimental results. Their ability to effectively represent the aero-dynamic response of the wind turbine to the control actions is successfully validated. Finally, turbine controller tuning parameters based on the derivatives of thrust and torque are derived to allow for improved offshore wind turbine dynamics and to validate the ability of modeling tools to model the dynamics of floating offshore wind turbines with control co-design. Full article

Introducing a cathode modification layer is an effective method to obtaining highly efficient organic solar cells (OSCs) and improving their stability. Herein, we innovatively introduced a double cathode modification layer (SnO₂/ZnO) into a non-fullerene OSCs based on PM7:IT-4F and explored the mechanisms. The effects of SnO₂/ZnO film on charge carriers transfer in OSCs are studied via a variety of electrical testing methods including Photo-CELIV measurements. As a result, a cathode buffer layer with low recombination rate and high carrier mobility could be introduced, which is beneficial to electron transport and collection. The champion device based on the double cathode modification layer acquires an efficiency of 12.91%, obviously higher than that of the single cathode modification layer (SnO₂ or ZnO) device. Moreover, The SnO₂/ZnO double layer is demonstrated to be of great help in the improvement of device stability, and our work could provide a new inspiration for the preparation of OSCs cathode modification layer. Full article

Finland has approximately 150,000 oil-heated private homes. In 2020, the Finnish government launched subsidies for private homeowner energy renovations. In this study, we examine the impact of two new energy renovation subsidies, the ELY grant and the ARA grant, from an energy efficiency point of view. Data from these subsidies reveal that a typical energy renovation case is a building from the 1970s where the oil boiler is replaced with an air-to-water heat pump. With additional data from the Finnish Energy certificate registry, a reference 1970s house is constructed and modelled in the building simulation programme, IDA ICE 4.8. Combinations of several renovation measures are simulated: air-to-water heat pump, ground-source heat pump, ventilation heat recovery and improved insulation. We found that resorting mainly to air-to-water heat pumps is not the most energy-effective solution. Ground-source heat pumps deliver a more significant reduction in delivered energy, especially with additional measures on insulation and heat recovery. Ground-source heat pumps also demand slightly less power than air-to-water heat pumps. Onsite solar PV generation helps supplement part of the power needed for heat pump solutions. Subsidy policies should emphasize deep renovation, ventilation heat recovery and onsite electricity generation. Full article

Grid stability and supply security need to be maintained when generation and consumption mismatches occur. A potential solution to this problem could be using Energy Storage Technologies (EST). Since many alternatives exist, appropriate technology selection becomes a key challenge. Current research focuses on ranking and selecting the most suitable technology, regardless of the grid services to be provided. In this study, a multi-criteria decision making (MCDM) problem is formulated considering fifteen selection criteria and the opinions of five energy storage experts groups. Literature and expert consultation data have been converted to triangular fuzzy (TF) numbers to cope with ambiguity and heterogeneity and eighteen technologies have been ranked applying the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method. The proposed method has been implemented on a software tool and assessed in four representative microgrid services of interest for the ENERISLA Project. The results show that pump hydro storage is the most suitable EST for frequency regulation, time shifting and seasonal storage applications, while flywheels best suit inertial response. It is concluded that the proposed methodology provides an intuitive framework for EST selection under multi-agent uncertainty and different grid application scenarios. Full article

One of the challenges that urgently needs to be addressed, both in current times and in the future, is to improve the heading speed of coal roadways. The roof instability of the heading face is the main factor restricting the rapid heading of coal roadways. Based on the theory of thin plate, a mechanical model of the roof in the heading face is established, the distribution law of deflection, stress, and internal force is discussed, and the supporting principle of the roof is clarified. Through a Flac3D numerical simulation, the main influencing factors of roof stability in the heading face are analyzed, including ground stress, surrounding rock strength, roadway section, unsupported distance, etc., and the regression analysis of each factor is carried out by evaluating the amount of roof subsidence. The results show that the maximum tensile stress and the corresponding bending moment of the roof appear at the fixed supported edge, and the maximum compressive stress and the maximum value of the corresponding bending moment appear at the center of the roof slightly close to the simply supported edge. In the on-site construction process, the position close to the fixed supported edge needs to be supported first. The roof subsidence has a positive exponential relationship with the stress level, a negative exponential relationship with the surrounding rock strength, a quadratic functional relationship with the roadway section, and a logarithmic relationship with the unsupported distance. In fractional support, the initial partial support can timely reduce the roof span and partially recover the confining pressure. Under certain geological and production conditions, the use of fractional support can not only effectively maintain the stability of the roadway but also speed up the heading speed. According to the research results, it is determined that in the auxiliary transportation roadway of the Caojiatan Coal Mine, the 122,110 working face adopts the fractional support model, the maximum roof subsidence is 18 mm, the roof is stable, and the monthly progress is more than 1000 m, which significantly improves the roadway heading speed. Full article

In most manufacturing industries, squirrel cage induction motors (SCIMs) are essential due to their robust nature, high torque generation, and low maintenance costs, so their failure often times affects productivity, profitability, reliability, etc. While various research studies presented techniques for addressing most of these machines’ prevailing issues, fault detection in cases of low slip or, low load, and no loading conditions for motor current signature analysis still remains a great concern. When compared to the impact on the machine at full load conditions, fault detection at low load conditions helps mitigate the impact of the damage on SCIM and reduces maintenance costs. Using stator current data from the SCIM’s direct online starter method, this study presents a feature engineering-aided fault classification method for SCIM at minor-load conditions based on a filter approach using the support vector classification (SVC) algorithm as the classifier. This method leverages the loop-hole of the Fourier Transform at minor-load conditions by harnessing the uniqueness of the Hilbert Transform (HT) to present a methodology that combines different feature engineering technologies to excite, extract, and select 10 discriminant information using a filter-based approach as the selection tool for fault classification. With the selected features, the SVC performed exceptionally well, with a significant diagnostic performance accuracy of 97.32%. Further testing with other well-known robust classifiers such as decision tree (DT), random forest (RF), k-nearest neighbor (KNN), gradient boost classifier (GBC), stochastic gradient descent (SGD), and global assessment metrics revealed that the SVC is reliable in terms of accuracy and computation speeds. Full article

The production of electricity from photovoltaic panels has experienced significant developments. To manage the energy flows introduced into the electricity grid, it is necessary to estimate the productivity of PV panels under the climatic conditions. In this study, a photovoltaic panel is modelled from thermal and electrical points of view to evaluate electrical performance and identify the temperature distribution in the layers. The analysis performed is time dependent and the problem is solved using the finite difference technique. A methodology is introduced to estimate the cloudiness of the sky, which affects radiative heat exchange. The calculation method is validated using experimental data recorded in a laboratory of the University of Calabria. Temperature and electrical power are predicted with RMSE of 1.5–2.0 °C and NRMSE of 1.2–2.1%, respectively. The evaluation of the temperature profile inside the panel is essential to understand how heat is dissipated. The results show that the top surface (glass) is almost always colder than the back of the panel, despite being exposed to radiation. In addition, the upper surface dissipates more heat power than the lower one. Cooling systems, such as spray cooling, work better if they are installed on the back of the panel. Full article

Electricity price forecasts have become a fundamental factor affecting the decision-making of all market participants. Extreme price volatility has forced market participants to hedge against volume risks and price movements. Hence, getting an accurate price forecast from a few hours to a few days ahead is very important and very challenging due to various factors. This paper proposes an integrated long-term recurrent convolutional network (ILRCN) model to predict electricity prices considering the majority of contributing attributes to the market price as input. The proposed ILRCN model combines the functionalities of a convolutional neural network and long short-term memory (LSTM) algorithm along with the proposed novel conditional error correction term. The combined ILRCN model can identify the linear and nonlinear behavior within the input data. ERCOT wholesale market price data along with load profile, temperature, and other factors for the Houston region have been used to illustrate the proposed model. The performance of the proposed ILRCN electricity price forecasting model is verified using performance/evaluation metrics like mean absolute error and accuracy. Case studies reveal that the proposed ILRCN model shows the highest accuracy and efficiency in electricity price forecasting as compared to the support vector machine (SVM) model, fully connected neural network model, LSTM model, and the traditional LRCN model without the conditional error correction stage. Full article

This paper proposes a novel and robust method of sensorless speed control using a deadbeat observer for an interior permanent magnet synchronous motor (IPMSM). The proposed sensorless speed control method uses a deadbeat observer to estimate the extended electromotive force (EEMF) in a rotational coordinate system. The estimated EEMF is used in the IPMSM velocity estimation algorithm. The deadbeat EEMF observer (DEEMFO) shows greater robustness compared to the reconstructor, which estimates the EEMF by simply recalculating the voltage equation. Unlike a reconstructor, DEEMFO has a feedback component, so it can compensate for errors due to uncertainty in motor parameters and errors due to parameter fluctuations that may occur during use. By simulating and experimenting with speed, load torque, and parameter fluctuations, it is proved to be more robust and precise than the reconstructor. The simulation is performed with MATLAB/Simulink, and the experiments were carried out using a DSP TMS320F28335 and a motor-generator set (M-G Set). The simulation and experiment results show the reliability and precision of the proposed sensorless control method. Full article

Safety issues arising from a hydrogen explosion accident in Korea are discussed herein. In order to increase the safety of hydrogen refueling stations (HRSs), the Korea Gas Safety Corporation (KGS) decided to install a damage-mitigation wall, also referred to as a barrier, around the storage tanks at the HRSs after evaluating the consequences of hypothetical hydrogen explosion accidents based on the characteristics of each HRS. To propose a new regulation related to the barrier installation at the HRSs, which can ensure a proper separation distance between the HRS and its surrounding protected facilities in a complex city, KGS planned to test various barrier models under hypothetical hydrogen explosion accidents to develop a standard model of the barrier. A numerical simulation to investigate the effect of the recommended barrier during hypothetical hydrogen explosion accidents in the HRS will be performed before installing the barrier at the HRSs. A computational fluid dynamic (CFD) code based on the open-source software OpenFOAM will be developed for the numerical simulation of various accident scenarios. As the first step in the development of the CFD code, we conducted a hydrogen vapor cloud explosion test with a barrier in an open space, which was conducted by the Stanford Research Institute (SRI), using the modified XiFoam solver in OpenFOAM-v1912. A vapor cloud explosion (VCE) accident may occur due to the leakage of gaseous hydrogen or liquefied hydrogen owing to a failure of piping connected to the storage tank in an HRS. The analysis results using the modified XiFoam predicted the peak overpressure variation from the near field to the far field of the explosion site through the barrier with an error range of approximately ±30% if a proper analysis methodology including the proper mesh distribution in the grid model is chosen. In addition, we applied the proposed analysis methodology using the modified XiFoam to barrier shapes that varied from that used in the test to investigate its applicability to predict peak overpressure variations with various barrier shapes. Through the application analysis, we concluded that the proposed analysis methodology is sufficient for evaluating the safety effect of the barrier, which will be recommended through experimental research, during VCE accidents at the HRSs. Full article

Over the past few decades, there have been rapid advances in solid-state technology as well as a reduction in cost. This, coupled with the functionality and efficiency improvements they afford, has resulted in a massive increase in the use of electronic devices. Where traditionally, there were a few well-known nonlinear loads that needed to be considered, now there are numerous low-power devices. Although individually insignificant, collectively, they are very significant. This paper presents a tensor-based harmonic analysis approach that is capable of capturing important interactions while being computationally efficient enough to model a large distribution system. Numerical experiments are used to highlight the advantages of the tensor framework. Numerous papers have investigated the tensor parametrisation or its mathematical equivalent—harmonically coupled admittance matrices (also known as frequency coupling matrices). However, this paper, for the first time, demonstrates how these models can be applied to perform harmonic modelling of a complete low voltage (LV) distribution system. Full article

The article presents a model for finding the most suitable locations for setting up micro-biogas plants (<50 kW), which represent an efficient way of processing organic waste in small local communities. The input parameters of the model, which was made with GIS tools, were the number of farms and heads of large livestock with their locations, the number of food establishments and their collected food waste and waste fat. We tested the case study model in the Gorenjska region in Slovenia. The result of processing the input data in the model are four locations in three municipalities Naklo 1, Naklo 2, Kranj and Cerklje. We evaluated the locations with economic indicators net present value (NPV), internal rate of return (IRR) and discounted payback period (DPP). With sensitivity analysis, we investigated the impact of increasing investment costs, decreasing energy prices and different scenarios with adding corn silage to the anaerobic process. Location Naklo 1 has NPV 31,410.26 €, IRR 10.53% and DPP 22 years, Naklo 2 has NPV −58,808.91 € and DPP of more than 25 years, location Kranj has NPV 140,313.00 €, IRR 13.07% and DPP 16 years, location Cerklje has NPV −43,026.82 € and DPP of more than 25 years. Full article

The present study is aimed at investigating the ability of a CFD modeling of liquid–liquid jet breakup to resolve the principal mechanisms relevant to jet breakup as well as submillimeter-scale drop size. It is generally known that jet leading edge breaks up by boundary layer stripping (BLS), and jet lateral surface breaks up by Kelvin–Helmholtz instability (KHI). The jet breakup rate as well as the resulting particle size are important parameters that would largely govern the intensity of a steam explosion in severe reactor accidents. First, a two-dimensional simulation of KHI along the melt-liquid coolant interface was performed using the VOF model in ANSYS Fluent with fine meshes as small as 0.02 mm. The dominant wavelength obtained by FFT analysis of calculated melt volume fractions showed that the fastest growing wavelength from the linear analysis of KHI is seen only at the very early development of the instability, and it increases gradually. Second, a three-dimensional simulation of BLS was performed, and the shapes and sizes of the melt particles were obtained. The particle size distributions from KHI and BLS simulations were compared with COLDJET experimental data of Woods metal and water, and it showed that the finer drops of one millimeter or smaller are produced by Kelvin–Helmholtz instability, and the drops of a few millimeters in diameter are mainly produced by boundary layer stripping. Full article

This paper reviews the progress in applying the plasma-driven solution electrolysis (PDSE), which is also referred to as the contact glow-discharge electrolysis (CGDE) or plasma electrolysis, for hydrogen production. The physicochemical processes responsible for the formation of PDSE and effects occurring at the discharge electrode in the cathodic and anodic regimes of the PDSE operation are described. The influence of the PDSE process parameters, especially the discharge polarity, magnitude of the applied voltage, type and concentration of the typical electrolytic solutions (K₂CO₃, Na₂CO₃, KOH, NaOH, H₂SO₄), presence of organic additives (CH₃OH, C₂H₅OH, CH₃COOH), temperature of the electrolytic solution, the active length and immersion depth of the discharge electrode into the electrolytic solution, on the energy efficiency (%), energy yield (g(H₂)/kWh), and hydrogen production rate (g(H₂)/h) is presented and discussed. This analysis showed that in the cathodic regime of PDSE, the hydrogen production rate is 33.3 times higher than that in the anodic regime of PDSE, whereas the Faradaic and energy efficiencies are 11 and 12.5 times greater, respectively, than that in the anodic one. It also revealed the energy yield of hydrogen production in the cathodic regime of PDSE in the methanol–water mixture, as the electrolytic solution is 3.9 times greater compared to that of the alkaline electrolysis, 4.1 times greater compared to the polymer electrolyte membrane electrolysis, 2.8 times greater compared to the solid oxide electrolysis, 1.75 times greater than that obtained in the microwave (2.45 GHz) plasma, and 5.8% greater compared to natural gas steam reforming. Full article

This study presents an extensive evaluation of heat transfer characteristics, flow patterns, and pressure drop for saturation pressures ranging from 460–660 kPa in a horizontal smooth tube of 5 mm internal diameter using R134a as the working fluid. The effect of saturation pressures for mass fluxes of 150–300 kg/m²s and heat fluxes of 8.26–23.3 kW/m² which are typical of refrigeration and air conditioning applications are also investigated. Flow patterns observed during the study are predicted with a well-known flow pattern map of Wojtan et al. The experimental results are compared with seven (7) correlations developed based on different theories to find which correlation best predicts the experimental data. The results show that, at low mass flux, increasing saturation pressure results in an increased heat transfer coefficient. This effect is more pronounced in the low vapor quality region and the dominant mechanism is nucleate boiling. At high mass flux, increasing saturation pressure leads to an insignificant increase in the heat transfer coefficient. At this high mass flux but low heat flux, the heat transfer coefficient increases with vapor quality, indicating convective boiling dominance. However, for high heat flux, the heat transfer coefficient is linear over vapor quality, indicating nucleate boiling dominance. Pressure drop is observed to decrease with increasing saturation pressure. Increasing saturation pressure increases the vapor quality at which the flow pattern transitions from intermittent flow to annular flow. The flow patterns predicted are a mixture of slug and stratified wavy and purely stratified wavy for low mass fluxes. For increased mass fluxes, the flow patterns predicted are slug, intermittent, annular, and dryout. Cooper’s model was the best predictor of the experimental data and the trend of heat transfer coefficient. Full article

Existing secondary control methods using fault-tolerant and/or $H_{\infty }$ control techniques for multi-inverter microgrids generally assume bounded faults and/or disturbances. Herein, we study unknown unbounded attacks on the input channels of both frequency and voltage control loops of inverters that could deteriorate the cooperative performance and affect the microgrid stability. We propose a fully distributed attack-resilient control framework using adaptive control techniques that, using stability analysis with Lyapunov techniques, are shown to preserve the uniformly ultimately bounded consensus for frequency regulation and voltage containment. Moreover, the ultimate bound can be set by adjusting the tuning parameters. The proposed result is validated for a modified IEEE 34-bus test feeder benchmark system augmented with four inverters. Full article

Photovoltaic (PV) - concentrated solar power (CSP) hybrid power plants are an attractive option for supplying cheap and dispatchable solar electricity. Hybridization options for both technologies were investigated, combining their benefits by a deeper integration. Simulations of the different systems were performed for seven different sites by varying their design parameters to obtain the optimal configurations under certain boundary conditions. A techno-economic analysis was performed using the levelized cost of electricity (LCOE) and nighttime electricity fraction as variables for the representation. Hybrid power plants were compared to pure CSP plants, PV-battery plants, and PV plants with an electric resistance heater (ERH), thermal energy storage (TES), and power block (PB). Future cost projections were also considered. Full article