Power utilities worldwide commonly use the radial distribution system because of its advantages of being simple in structure and having relatively inexpensive installation costs. It has a disadvantage in that its power supply reliability is low because the load side of the fault section will suffer from an outage in the event of a fault in the system. However, recently, with ICT (Information and Communication Technologies) development, system reliability is required to be high as the outage-susceptible loads increase. In addition, the increase in the connection of distributed resources such as renewable energy and electric vehicles is making it impossible to predict the power flow and reducing line utilization. Therefore, a loop power distribution system is proposed as a measure to solve this problem. Because all buses (nodes) in a loop distribution system have two or more power supply routes, they are more reliable than the radial system. It allows them to improve line utilization by... [more]

Hydrogen bromine redox flow batteries (RFB) are considered to be one of the most promising storage alternatives, as this technology offers both high energy and high-power density. In this work a printed circuit board type of segmented current collector for the measurement of locally resolved current density was developed. This analytical tool was inserted as hydrogen anode current collector in a hydrogen-bromine test cell. Charging and discharging operation was monitored under different stoichiometric flow conditions and the impact on current distribution is presented. This technique offers the possibility to prove cell limiting conditions with spatial resolution, improving our understanding and determining optimal operating conditions for a given design.

Partial shading conditions (PSCs) can significantly reduce the output energy produced by photovoltaic (PV) systems. Moreover, when such conditions occur, conventional and advanced maximum power point tracking (MPPT) systems fail to operate the PV system at its peak because the bypassing diodes may cause the PV system to become trapped at a low power point when they are in conduction mode. The PV system can be operated at the global maximum power point (MPP) with the help of global peak searching tools. However, the frequent use of these tools will reduce the output of PV systems since they force the PV system to operate outside its power region while scanning the I-V curve in order to determine the global MPP. Thus, the global peak searching tools should be deployed only when a PSC occurs. In this paper, a simple and accurate method is proposed for detecting PSCs by means of monitoring the sign of voltage changes (positive or negative). The method predicts a PSC if the sign of successi... [more]

Achieving high penetration of electric vehicles (EVs) is one of the objectives proposed by the scientific community to mitigate the negative environmental impact caused by conventional mobility. The limited autonomy and the excessive time to recharge the battery discourage the final consumer from opting for new environmentally friendly mobility alternatives. Consequently, it is essential to provide the urban road network with charging infrastructure (CI) to ensure that the demand generated by EV users is met. The types of terminals to be considered in charging stations (CS) are fast and ultra-fast. The high energy requirements in these types of terminals could stress the electrical systems, reducing the quality of service. To size and forecast the resources needed in CI, it is of great interest to model and predict the maximum number of EVs, in each hour, that each CS will have to serve according to the geographic area in which they are located. Our proposal is not based on an assumed... [more]

An important revenue stream for electric battery operators is often arbitraging the hourly price spreads in the day-ahead auction. The optimal approach to this is challenging if risk is a consideration as this requires the estimation of density functions. Since the hourly prices are not normal and not independent, creating spread densities from the difference of separately estimated price densities is generally intractable. Thus, forecasts of all intraday hourly spreads were directly specified as an upper triangular matrix containing densities. The model was a flexible four-parameter distribution used to produce dynamic parameter estimates conditional upon exogenous factors, most importantly wind, solar and the day-ahead demand forecasts. These forecasts supported the optimal daily scheduling of a storage facility, operating on single and multiple cycles per day. The optimization is innovative in its use of spread trades rather than hourly prices, which this paper argues, is more attra... [more]

The main aim of the present study was to improve the oxidation stability and cold flow properties of biodiesel produced from waste frying/cooking oil and palm oil. In this work, waste frying/cooking methyl ester (WFME) and palm methyl ester (PME) were prepared using an alkali-catalyzed transesterification process, and the physicochemical properties of the pure biodiesel as well as of binary blends among them were investigated. The results indicated that palm biodiesel and WFME18, produced from a mixture of frying, cooking, sunflower, and corn oils, can be used as antioxidant additives, enhancing biodiesel stability. Additionally, it was found that WFME1 and WFME12 derived from waste residential canola oil can be used as cold flow improvers for enhancing the cold flow properties of palm biodiesel. Moreover, ultra-low sulfur diesel fuel winter (ULSDFW), ultra-low sulfur diesel fuel summer (ULSDFS), kerosene (KF), and benzene (BF) were utilized to enhance the cold flow properties of the s... [more]

With the integration of Intermitted Renewables Energy (I-RE) electricity production, capacity is shifting from central to decentral. So, the question is if it is also necessary to adjust the current load balancing system from a central to more decentral system. Therefore, an assessment is made on the overall effectiveness and costs of decentralized load balancing, using Flexible Renewable Energy (F-RE) in the shape of biogas, Demand Side Management (DSM), Power Curtailment (PC), and electricity Storage (ST) compared to increased grid capacity (GC). As a case, an average municipality in The Netherlands is supplied by 100% I-RE (wind and solar energy), which is dynamically modeled in the PowerPlan model using multiple scenarios including several combinations of balancing technologies. Results are expressed in yearly production mix, self-consumption, grid strain, Net Load Demand Signal, and added cost. Results indicate that in an optimized scenario, self-consumption of the municipality re... [more]

Infrasound, i.e., low-frequency noise in the frequency range of 10−200 Hz, produced by rotating wind turbine blades has become a matter of concern because it is harmful to human health. Today, with the rapid increase of wind turbine size, this kind of noise is more worrying than ever. Although much effort has been made to design quiet wind turbine blades, today there is still a lack of effective techniques to reduce infrasound emissions from existing blades. To fill this gap in technology, a biomimetic technique that can be readily applied to reduce infrasound emissions of existing wind turbine blades is studied in this paper using both numerical simulation and experimental testing approaches. The numerical study of the technique is based on the analysis of the sound field distribution near the blade, which is derived by performing both aerodynamic and acoustic simulations of the blade. The experimental study of the technique is based on laboratory tests of two scale models of the blad... [more]

Fuel cell-powered Autonomous Underwater Vehicles (AUVs) represent a growing area of research as fuel cells can increase their endurance. Fuel cells consume hydrogen and oxygen to generate electricity. Typically, the fuel cell generates as much heat as electrical energy, and heat management becomes a crucial parameter when designing AUVs. For underwater applications, there is a need to store both gases and several types of storage units with different characteristics exist which have impacts on the energy density and heat behavior. This study aims at including the heat properties of the storage units in the design process of fuel cell-powered AUVs. A heat balance over the energy system of an AUV is calculated for each combination of hydrogen and oxygen storage units. In addition, a multi-criteria decision-making analysis is conducted, considering the calculated total heat, the specific energy, the energy density and the volumetric mass of each combination of storage units as criteria, e... [more]

Since the industrial revolution, the world’s economy has mainly relied on the consumption of fossil fuels. The burning of coal releases vast amounts of toxic COx greenhouse gasses into the atmosphere that bear an undesirable environmental impact. The ongoing offshore oil exploration activities; the infrastructure for oil extraction, production, and transportation; and the inevitable oil spills cause severe damage to the environment and huge loss of sea life, flora, and fauna. Recent awareness of the environmental issues and the worldwide climate change spurred public interest in clean and environmentally friendly “green” energy generation. Solar energy is an abundant and inexhaustible resource that can meet much of the worlds’ energy needs and, thus, has been in the focus of scientific attention for many years. Yet, converting solar energy into usable electric power is a formidable engineering and economical challenge. The recent environmental awareness triggered governments and privat... [more]

Hydrothermal liquefaction is one of the common thermochemical conversion methods adapted to convert high-water content biomass feedstocks to biofuels and many other valuable industrial chemicals. The hydrothermal process is broadly classified into carbonization, liquefaction, and gasification with hydrothermal liquefaction conducted in the intermediate temperature range of 250−374 °C and pressure of 4−25 MPa. Due to the ease of adaptability, there has been considerable research into the process on using various types of biomass feedstocks. Over the years, various solvents and co-solvents have been used as mediums of conversion, to promote easy decomposition of the lignocellulosic components in biomass. The product separation process, to obtain the final products, typically involves multiple extraction and evaporation steps, which greatly depend on the type of extractive solvents and process parameters. In general, the main aim of the hydrothermal process is to produce a primary product... [more]

In view of the deliberations on new Euro 7 emission standards to be introduced by 2025, original equipment manufacturers (OEMs) are already hard at work to further minimise the pollutant emissions of their vehicles. A particular challenge in this context will be compliance with new particulate number (PN) limits. It is expected that these will be tightened significantly, especially by including particulates down to 10 nm. This will lead to a substantially increased effort in the calibration of gasoline particulate filter (GPF) control systems. Therefore, it is of great interest to implement advanced methods that enable shortened and at the same time more accurate GPF calibration techniques. In this context, this study presents an innovative GPF calibration procedure that can enable a uniquely efficient development process. In doing so, some calibration work packages involving GPF soot loading and regeneration are transferred to a modern burner test bench. This approach can minimise the... [more]

Economic complexity makes it possible to assess the development of the countries, the relations of innovation, and the differentiation of products. The article considers the links between the hypotheses of the Kuznets environmental curve and economic complexity using panel data for the group of BRICS countries (Brazil, Russia, India, China, and South Africa) from 1990 to 2015. As an econometric strategy, this study considered the panel fully modified least squares (FMOLS), panel dynamic least squares (DOLS), fixed effects (FE), and Panel Quantile Regression. The empirical results showed that economic complexity, income per capita, renewable energy, and carbon dioxide emissions are integrated with the first difference when applying the unit root test. The arguments of Pedroni and Kao cointegration tests were also used. According to these results, the variables used in this research are cointegrated in the long run. The results validated the arguments of the EKC hypothesis, i.e., the inc... [more]

Classic forecasting methods of natural gas consumption extrapolate trends from the past to subsequent periods of time. The paper presents a different approach that uses analogues to create long-term forecasts of the annual natural gas consumption. The energy intensity (energy consumption per dollar of Gross Domestic Product—GDP) and gas share in energy mix in some countries, usually more developed, are the starting point for forecasts of other countries in the later period. The novelty of the approach arises in the use of cluster analysis to create similar groups of countries and periods based on two indicators: energy intensity of GDP and share of natural gas consumption in the energy mix, and then the use of fuzzy decision trees for classifying countries in different years into clusters based on several other economic indicators. The final long-term forecasts are obtained with the use of fuzzy decision trees by combining the forecasts for different fuzzy sets made by the method of re... [more]

The article discusses the findings related to the calorific value as well as the explosion and combustion parameters of dust from the raw biomass of fruit trees, i.e., apple, cherry, and pear branches, and from biochars produced using this type of biomass during pyrolysis processes conducted under various conditions. The plant biomass was thermally processed at 400, 450, or 500 °C for a duration of 5, 10, or 15 min. The study aimed to identify the calorific value of the biomass obtained from waste produced in orchards and to estimate the explosion hazard during the processing of such materials and during the storage of the resulting solid fuels. Tests were conducted to assess the total contents of carbon, ash, nitrogen, hydrogen, and volatile substances as well as the calorific value. The findings show a significant effect of the thermal transformation of fruit tree branches on the calorific value of the biochars that were produced. It was found that the mean calorific value of all of... [more]

Anaerobic Digestion (AD) is a well-established process that is becoming increasingly popular, especially as a technology for organic waste treatment; the process produces biogas, which can be upgraded to biomethane, which can be used in the transport sector or injected into the natural gas grid. Considering the sensitivity of Anaerobic Digestion to several process parameters, mathematical modeling and numerical simulations can be useful to improve both design and control of the process. Therefore, several different modeling approaches were presented in the literature, aiming at providing suitable tools for the design and simulation of these systems. The purpose of this study is to analyze the recent advancements in the biomethane production from different points of view. Special attention is paid to the integration of this technology with additional renewable energy sources, such as solar, geothermal and wind, aimed at achieving a fully renewable biomethane production. In this case, au... [more]

This paper reports the results of heat transfer during refrigerant flow in rectangular mini-channels at stationary conditions. The impacts of selected parameters on boiling are discussed, i.e., thermal and flow parameters, dimensions and orientation of the channels. Four refrigerants (FC-72, HFE-649, HFE-7000 and HFE-7100) were used as the working fluid. Research was carried out on the experimental set-up with the test section with a single rectangular mini-channel of 180 mm long and with a group of five parallel mini-channels, each 32 mm long. The temperature of the mini-channel’s heated wall was measured by infrared thermography. Local values of the heat transfer coefficient at the contact surface between the fluid and the plate were calculated using the 1D mathematical method. The results are presented as the relationship between the heat transfer coefficient and the distance along the mini-channel length and boiling curves. Two-phase flow patterns are shown. Moreover, the results c... [more]

In the current context of transition from the powertrains of cars equipped with internal combustion engines to powertrains based on electricity, there is a need to intensify studies and research related to the command-and-control systems of electric vehicles. One of the important systems in the construction of an electric vehicle is the thermal management system of the battery with the role of optimizing the operation of the battery in terms of performance and life. The article aims to critically analyze the studies and research conducted so far related to the type, design and operating principles of battery thermal management systems (BTMSs) used in the construction of various shaped Li-ion batteries, with focus on cooling technologies. The advantages and disadvantages of the individual components, as well as of the proposed BTM solutions, are extensively investigated, with regard also to the adaptability of these systems to the different Li-ion battery shapes. The information thus sy... [more]

Renewable energy sources, in particular those based on solar radiation, are growing rapidly and are planned to play an instrumental role in building power systems to reach the 2030 and 2050 energy and climate mitigation objectives. However, new actors have been introduced into the energy field, highlighting the importance of the role of citizens and communities in building such energy systems. To outline the significance of citizens in the development of solar energy communities and to describe the benefits of and barriers to their implementation so far, a comprehensive literature review has been carried out based on 64 thoroughly selected, reliable scientific publications (published within 2015−2021), revealing the latest trends, technologies and research in this field. The research focuses on four consumer interest areas: policy, economic, technical and social, covering the following subsections: policy, trading model, economic assessment, business model, energy management, demand re... [more]

The effect of cyclic carbonation−decarbonation operating parameters on Zr-doped CaO sorbent CO2 uptake capacity evolution is examined. It is revealed that the capacity steady state value increases with the decrease in the carbonation temperature, CO2 concentration in the gas flow upon carbonation and with the increase in the heating rate from the carbonation to the decarbonation stages. The rise in decarbonation temperature leads to a dramatic decrease in the sorbent performance. It is found that if carbonation occurs at 630 °C in the gas flow containing 15 vol.% CO2 and decarbonation is carried out at 742 °C, the sorbent shows the highest values of the initial and steady state CO2 uptake capacity, namely, 10.7 mmol/g and 9.4 mmol/g, respectively.

Electric motors and boilers lead the industrial components which consume the largest portion of energy in an industry. This study explores the energy audit data of the condiment industry in India. The study mainly focuses on the estimation of the load factor, energy use, energy savings and annual bill savings with payback period of the electric motors of the plant. During the audit, it was found that there were several motors running under loaded conditions despite non-availability of variable speed drives installed in the plant. Therefore, variable speed drives are recommended to be installed to save energy by reducing the motors speed by up to 60%. According to the estimation, about 276 MWh, 551 MWh and 827 MWh electrical energy can be saved for 20%, 40% and 60% speed reduction of the motors using variable speed drives, respectively, where in most of the cases the payback period remains below 1 year. Furthermore, some suggestions are made to improve the poor power factor of running m... [more]

We introduce the concept of the nuclear battery, a standardized, factory-fabricated, road transportable, plug-and-play micro-reactor. Nuclear batteries have the potential to provide on-demand, carbon-free, economic, resilient, and safe energy for distributed heat and electricity applications in every sector of the economy. The cost targets for nuclear batteries in these markets are 20−50 USD/MWht (6−15 USD/MMBTU) and 70−115 USD/MWhe for heat and electricity, respectively. We present a parametric study of the nuclear battery’s levelized cost of heat and electricity, suggesting that those cost targets are within reach. The cost of heat and electricity from nuclear batteries is expected to depend strongly on core power rating, fuel enrichment, fuel burnup, size of the onsite staff, fabrication costs and financing. Notional examples of cheap and expensive nuclear battery designs are provided.

This paper shows the results of an in-depth techno-economic analysis of the public transport sector in a small to midsize city and its surrounding area. Public battery-electric and hydrogen fuel cell buses are comparatively evaluated by means of a total cost of ownership (TCO) model building on historical data and a projection of market prices. Additionally, a structural analysis of the public transport system of a specific city is performed, assessing best fitting bus lines for the use of electric or hydrogen busses, which is supported by a brief acceptance evaluation of the local citizens. The TCO results for electric buses show a strong cost decrease until the year 2030, reaching 23.5% lower TCOs compared to the conventional diesel bus. The optimal electric bus charging system will be the opportunity (pantograph) charging infrastructure. However, the opportunity charging method is applicable under the assumption that several buses share the same station and there is a “hotspot” wher... [more]

Assessing the optimal placement and design of a large-scale high temperature energy storage system in crystalline bedrock is a challenging task. This study applies and evaluates various methods and strategies for pre-site investigation for a potential high temperature borehole thermal energy storage (HT-BTES) system at Linköping in Sweden. The storage is required to shift approximately 70 GWh of excess heat generated from a waste incineration plant during the summer to the winter season. Ideally, the site for the HT-BTES system should be able to accommodate up to 1400 wells to 300 m depth. The presence of major fracture zones, high groundwater flow, anisotropic thermal properties, and thick Quaternary overburden are all factors that play an important role in the performance of an HT-BTES system. Inadequate input data to the modeling and design increases the risk of unsatisfactory performance, unwanted thermal impact on the surroundings, and suboptimal placement of the HT-BTES system, e... [more]

The purpose of this study is to analyze the applicability of a sunken vessel as an artificial reef in a high wave energy area in a shallow water zone. Artificial reefs in general shapes are unlikely to be installed and maintained stably in high-energy wave zones. To solve this problem, a method for using a large 2000-ton class sunken vessel as an artificial reef was proposed in this study. Accordingly, we analyzed the applicability, including stability, of the sunken vessel as an artificial reef on the east coast of South Korea, where high-energy waves and swells are observed frequently. In the analysis process, various methods, such as numerical simulation and a hydraulic model experiment, were utilized. 2D and 3D numerical simulations were conducted to simulate the wave energy in the area where the sunken vessel was installed as an artificial reef to identify wave force applied to the vessel. Moreover, a hydraulic model experiment using a sunken vessel model as an artificial reef was... [more]