Supercritical carbon dioxide (S-CO2) Brayton cycle system is a promising closed-loop energy conversion system frequently mentioned in the automotive and power generation field in recent years. To develop a suitable design methodology for S-CO2 turbines with better performance, an understanding of the vortex flow patterns and associated aerodynamic loss inside a S-CO2 turbine is essential. In this paper, a hundred-kilowatt level S-CO2 axial turbine is designed and investigated using a three-dimensional transient viscous flow simulation. The NIST Span and Wagner equation of state model that considers the real gas effects is utilized to estimate the thermodynamic properties of the supercritical fluid. The numerical methods are experimentally validated. The results indicates that the aspect ratio and tip-to-hub ratio are different in the S-CO2 turbine from that in the gas turbine, and the vortex flow patterns are influenced notably by these geometrical parameters. Both the vortex structure... [more]

Urban activities, including urban mobility, play a crucial role in climate change mitigation. Urban mobility is currently at a crossroads. In a business as usual scenario, CO2 emissions from urban transportation will grow by one fourth by 2050. Nevertheless, during this period, it may drop by about one third. To make the drop happen, we need to introduce comprehensive policies and measures. Electrifying urban transit is one feasible solution. This study investigates whether and how urban water transit systems have been electrified—a means of transport which has not been well researched in this respect. A multilevel perspective and the comparative case study method were employed to answer the research questions. The comprehensive study focussed on 24 cities representing the current experience in planning and operating water transport, based mainly on secondary, primarily qualitative, data, such as industry reports, feasibility studies, urban policies, and scientific papers. The primary... [more]

The accelerated development of information and communication technologies (ICT) over the last three decades has encouraged researchers to analyse the impact of this phenomenon on the labour market. The potential decline in employment resulting from the proliferation of ICT may reduce access to basic energy services and even lead to energy poverty in the form of inability to heat the apartment as needed, allocating a significant part of revenues to expenses related to heating or problems with the timely payment of energy bills. Because access to energy is of fundamental importance for improving the quality of life and is crucial from the point of view of economic development, it is justified to verify the hypothesis that the accelerated development of ICT in EU countries may contribute to an increase in unemployment and, consequently, translate into a higher level of energy poverty. The described research results were obtained thanks to a comparative factor analysis based on secondary d... [more]

The world is looking to reduce carbon emissions, prevent global warming, and become more energy sustainable. Despite the various strategies for mitigating climate change, the fact remains that 80% of greenhouse gas emissions are attributable to activities associated with the built environment, and this is where a concentrated focus is needed. Moreover, most buildings are residential, not commercial or industrial. In essence, ways must be found to reduce energy consumption and CO2 emissions from existing houses and apartments globally if sustainability is to be realised. The recognised way to achieve this is through the retrofitting of existing residential buildings. Studies in this area have increased in recent times, but the extent of the work remains unmapped and undescribed. If further progress is to be made in this field, researchers’ knowledge domain so far must be documented. This literature review delivers that goal. A scientometric evaluation of research on residential retrofit... [more]

Scarcity of resources and their waste, as well as deteriorating quality of life and the environment, are pressing problems of modern civilisations. Rational and efficient energy consumption is one of the possibilities for preventing harmful practices and the degradation of ecosystems. Understanding the consumer’s way of thinking and acting by identifying his needs and preferences are essential for effective efforts for smart, sustainable, and inclusive economic growth. Therefore, the aim of this article was a comprehensive socioeconomic analysis of particular behavioural types of energy consumers, as a continuation of the authors’ previous research. The paper uses statistical methods (chi-square test and correspondence analysis) dedicated to non-metric variables for an effective analysis of the data obtained from the questionnaires. The identification of socioeconomic factors was carried out on a representative sample of n = 4506 respondents from eight European countries (the Czech Rep... [more]

In this study, two different parameter estimation algorithms are studied and compared. Iterated EKF and a nonlinear optimization algorithm based on on-line search methods are implemented to estimate parameters of a given permanent magnet synchronous motor whose dynamics are assumed to be known and nonlinear. In addition to parameters, initial conditions of the dynamical system are also considered to be unknown, and that comprises one of the differences of those two algorithms. The implementation of those algorithms for the problem and adaptations of the methods are detailed for some other variations of the problem that are reported in the literature. As for the computational aspect of the study, a convexity study is conducted to obtain the spherical neighborhood of the unknown terms around their correct values in the space. To obtain such a range is important to determine convexity properties of the optimization problem given in the estimation problem. In this study, an EKF-based param... [more]

Stepper motors are widely used in many applications where discrete, precise movement is required. There is a variety of dedicated stepper motor controllers (sometimes referred to as “step sticks”) available on the market. Those controllers provide a number of different motor control schemes that vary by aspects like current control method, reference current shape or maximum resolution increase (microstepping). The two most widely acknowledged signal shapes are sine-cosine microstepping and quadrature microstepping. The choice of the control scheme impacts torque output, torque variation, positioning error and maximum power supply requirements. This paper presents a family of generalised microstepping signal shapes, ranging from sine-cosine microstepping to quadrature microstepping. Derivation of signal shapes as well as their mathematical analyses are provided. Those signals are then implemented on the control board. A series of experiments is performed on a test bench to analyse the i... [more]

Over the last few years, a strong penetration of Intermittent Renewable Energy Sources (IRES) has been in progress in the Italian power system. In this new framework, the dispatching activity must improve its efficiency to ensure adequacy and security of the national electricity system. European market integration initiatives are making this goal achievable, provided that the coherency of market price signals and reserve procurement at the European level are guaranteed. For this reason, the Italian Transmission System Operator (TSO), Terna, started to investigate the opportunity to align the Italian reserve-procurement approach to the one adopted in most European countries, procuring Replacement Reserve (RR) in dedicated auctions held in advance of the day-ahead market. The aim of this new methodology is to improve the coherency of price signals arising from the integrated European day-ahead market, anticipating potential scarcity conditions, thus helping to keep adequacy standards hig... [more]

The development of artificial intelligence (AI) based techniques for electricity price forecasting (EPF) provides essential information to electricity market participants and managers because of its greater handling capability of complex input and output relationships. Therefore, this research investigates and analyzes the performance of different optimization methods in the training phase of artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) for the accuracy enhancement of EPF. In this work, a multi-objective optimization-based feature selection technique with the capability of eliminating non-linear and interacting features is implemented to create an efficient day-ahead price forecasting. In the beginning, the multi-objective binary backtracking search algorithm (MOBBSA)-based feature selection technique is used to examine various combinations of input variables to choose the suitable feature subsets, which minimizes, simultaneously, both the number of... [more]

As many countries have tried to construct a hydrogen (H2) society to escape the conventional energy paradigm by using fossil fuels, methane pyrolysis (MP) has received a lot of attention owing to its ability to produce H2 with no CO2 emission. In this study, a techno-economic analysis including a process simulation, itemized cost estimation, and sensitivity and scenario analysis was conducted for the system of thermal-based and catalyst-based MP (TMP-S1 and CMP-S2), and the system with the additional H2 production processes of carbon (C) gasification and water−gas shift (WGS) reaction (TMPG-S3 and CMPG-S4). Based on the technical performance expressed by H2 and C production rate, the ratio of H2 combusted to supply the heat required and the ratio of reactants for the gasifier (C, Air, and water (H2O)), unit H2 production costs of USD 2.14, 3.66, 3.53, and 3.82 kgH2−1 from TMP-S1, CMP-S2, TMPG-S3, and CMPG-S4, respectively, were obtained at 40% H2 combusted and a reactants ratio for C-A... [more]

Heat flow patterns variability related to the age of the consolidated, and differences in, sedimentary thickness of the sedimentary succession are important constraints upon the thermal state of the sedimentary fill and its geothermal energy potential. Heat flow in the Permian basin of central Europe varies from a low of 40 mWm−2 in the Precambrian Platform to 80 mWm−2 in the Paleozoic basement platform influencing temperature for geothermal potential drilling depth. Continuity of thermal patterns and compatibility of heat flow Q across the Permian basin across the Polish−German basin was known from heat flow data ever since the first heat flow map of Europe in 1979. Both Polish and German heat flow determinations used lab-measured thermal conductivity on cores. This is not the case for the recent heat flow map of Poland published in 2009 widely referenced in Polish geological literature. Significant differences in heat flow magnitude exist between many historical heat flow maps of Pol... [more]

High voltage electric power equipment requires rigorous regulation testing to specific standards which ensure proper and safe operation in the grid. Manufacturers conduct these tests in order to prove standard compliance and product liability. Variable linear or nonlinear loads are necessary for testing medium voltage (MV) high power AC power converters. Generally, those AC power converters or power supplies require performance validation, burn-in and/or lifetime testing under different load conditions, defined by the end-user or standards for the given applications. For flexible and efficient MV verification testing, this paper presents a five-level multilevel converter-based MV regenerative AC electronic load with one-cycle control (OCC), which is based on five-level diode-clamped multilevel converters with back-to-back structure and can emulate any impedance load. In this paper, especially the dc-link capacitor voltage balance of the proposed multilevel MV regenerative AC load is de... [more]

Uncertainty quantification in LIB manufacturing has received interest in order to improve the reliability of LIB. The uncertainty generated during the manufacturing causes variations in the performance of LIBs, thereby increasing capacity degradation and leading to failure. In this study, a reliability-based design optimization (RBDO) of LIBs is conducted to reduce performance failure while maximizing the specific energy. The design variables with uncertainty are the thickness, porosity, and particle size of the anode and cathode. The specific energy is defined as the objective function in the optimization design problem. To maintain the specific power in the initial design of the LIB, it is defined as the constraint function. Reliability is evaluated as the probability that the battery satisfies the performance of the required design. The results indicate that the design optimized through RBDO increases the specific energy by 42.4% in comparison with that of the initial design while r... [more]

The identification of critical periods and business cycles contributes significantly to the analysis of financial markets and the macroeconomy. Financialization and cointegration place a premium on the accurate recognition of time-varying volatility in commodity markets, especially those for crude oil and refined fuels. This article seeks to identify critical periods in the trading of energy-related commodities as a step toward understanding the temporal dynamics of those markets. This article proposes a novel application of unsupervised machine learning. A suite of clustering methods, applied to conditional volatility forecasts by trading days and individual assets or asset classes, can identify critical periods in energy-related commodity markets. Unsupervised machine learning achieves this task without rules-based or subjective definitions of crises. Five clustering methods—affinity propagation, mean-shift, spectral, k-means, and hierarchical agglomerative clustering—can identify an... [more]

Over the past few decades, energy demand around the globe has exponentially increased [...]

In recent years, geothermal energy use from low-temperature sandstone reservoirs has sharply increased. Nonetheless, the injection of heat-depleted geothermal fluids has not been an easy task because of well/formation damage and operational/economic issues. Sønderborg geothermal plant is a case example of heat-mining from a low-temperature reservoir. It is in the northeast of Sønderborg towards Augustenborg Fjord. The present work takes into consideration the regional and local geology of the Sønderborg area, construction of the wells, field experience and water chemistry. The main issues of the geothermal plant appear to be related to the construction of the wells and reinjection of the heat-depleted brine. Our water chemistry analysis and PHREEQC simulations indicate that geothermal brine was saturated with respect to carbonate and barite minerals. The excess of Ca2+ and SO42− ions could have led to the formation and precipitation of carbonate and sulfate scales. Moreover, the increm... [more]

Under the background of high wind power permeability, the frequency regulation capability of high voltage direct current (HVDC) sending-end system tends to deteriorate. For this reason, this paper regards the wind farm (WF) and HVDC as a combined frequency regulation system, and a fuzzy-based coordinated control strategy is proposed for the cooperation of HVDC and WF to participate in frequency regulation. First of all, at a system level, in order to realize the dynamic cooperation of the WF and the HVDC to participate in frequency regulation, two fuzzy logic controllers (FLCs) are designed to determine the total power support of the combined system and the participation coefficient of the WF in the frequency regulation according to the frequency characteristics of the sending-end system and the operation state of the WF, respectively. Secondly, at the WF level, considering the rotating kinetic energy and capacity of the wind turbines (WTs), a power allocation strategy is proposed to m... [more]

Community microgrids are set to change the landscape of future energy markets. The technology is being deployed in many cities around the globe. However, a wide-scale deployment faces three major issues: initial synchronization of microgrids with the utility grids, slip management during its operation, and mitigation of distortions produced by the inverter. This paper proposes a Phasor Measurement Unit (PMU) Assisted Inverter (PAI) that addresses these three issues in a single solution. The proposed PAI continually receives real-time data from a Phasor Measurement Unit installed in the distribution system of a utility company and keeps constructing a real-time reference signal for the inverter. To validate the concept, a unique intelligent DC microgrid architecture that employs the proposed Phasor Measurement Unit (PMU) Assisted Inverter (PAI) is also presented, alongside the cloud-based Artificial Intelligence (AI), which harnesses energy from community shared resources, such as batte... [more]

Power forecasting models offer valuable insights on the electricity consumption patterns of clients, enabling the development of advanced strategies and applications aimed at energy saving, increased energy efficiency, and smart energy pricing. The data collection process for client consumption models is not always ideal and the resulting datasets often lead to compromises in the implementation of forecasting models, as well as suboptimal performance, due to several challenges. Therefore, combinations of elements that highlight relationships between clients need to be investigated in order to achieve more accurate consumption predictions. In this study, we exploited the combined effects of client similarity and causality, and developed a power consumption forecasting model that utilizes ensembles of long short-term memory (LSTM) networks. Our novel approach enables the derivation of different representations of the predicted consumption based on feature sets influenced by similarity an... [more]

This study aims to develop a device for harvesting electrical energy from low-speed natural wind. Four linear Halbach arrays are adopted to design a high-performance galloping harvester with the advantage of high durability and efficiency at low-frequency vibrations. The results of magnetic field analysis reveal that there are optimal sizes of the main and transit magnets of the Halbach arrays and coil to obtain the maximum magnetic flux density normal to the coil. The experimental and simulation results show that the electrical external load resistance significantly affects the vibration amplitude and the galloping onset velocity of the harvester. The results also reveal that the performance of the original design using the quadruple Halbach array was lower than that of the existing harvester because of the heavy magnet mass embedded in the tip prism. The modified design, reducing mass, improved the performance by four times compared to the original design.

The Anthropocene thesis poses new challenges to human activity on the planet. These challenges also apply to the built environment. Climate change will increase existing threats, and create new ones, for both human and natural systems. Above all, the built environment is expected to provide structural stability, access to water necessary for life, and safe production of clean energy. This research-by-design was focused on designing an adaptive built environment for Anthropocene societies and the maintenance of their well-being, and on envisioning and conceptualizing new architectural solutions based on multidisciplinary knowledge and CAD parametric design methods and tools. The conceptual designs are the result of these studies. These visions show how wind loads can be reduced, water can be stored, diverse energy sources can be integrated into one work of architecture, and thermal comfort can be provided to support local communities and the life of the environment in the belief that th... [more]

The campus of the Karlsruhe Institute of Technology (KIT) contains several waste heat streams. In an effort to reduce greenhouse gas emissions by optimizing thermal power consumption on the campus, researchers at the KIT are proposing a ‘DeepStor’ project, which will sequester waste heat from these streams in an underground reservoir during the summer months, when the heat is not required. The stored heat will then be reproduced in the winter, when the campus’s thermal power demand is much higher. This paper contains a preliminary geochemical risk assessment for the operation of this subsurface, seasonal geothermal energy storage system. We used equilibrium thermodynamics to determine the potential phases and extent of mineral scale formation in the plant’s surface infrastructure, and to identify possible precipitation, dissolution, and ion exchange reactions that may lead to formation damage in the reservoir. The reservoir in question is the Meletta Beds of the Upper Rhein Graben’s Fr... [more]

Even the simplest version of the distribution networks face challenges such as maintaining load voltage and system frequency stability and at the same time minimizing the circulating reactive power in grid-forming nodes. As the consumers at the far end of the radial distribution network face serious voltage fluctuations and deviations once the load varies. Therefore, this paper presents an enhanced distributed control strategy to restore the load voltage magnitude and to realize power-sharing proportionally in islanded microgrids. This proposed study considers the voltage regulation at the load node as opposed to the inverter terminal. At the same time, a supervisory control layer is put on to observe and correct the load voltage and system frequency deviations. This presented method is aimed at replacing paralleled inverter control methods hitherto used. Stability analysis using system-wide methodical small-signal models, the MATLAB/Simulink, and experimental results obtained with con... [more]

Magnetotellurics (MT) is an important geophysical method for exploring geothermal systems, with the Earth resistivity obtained from the MT method proving to be useful for the hydrothermal imaging changes of the system. In this research, we applied the MT method to map the geothermal system of the Seulawah Agam volcano in northern Sumatra, a site intended for the construction of a geothermal power plant with an estimated energy of 230 Mwe. Herein, 3D MT measurements were carried out, covering the entire area of the volcano and the various intersecting local faults from the Seulimeum segment in the NW−SE direction. Based on Occam 2D inversion, a conductive anomaly (<10 ohm·m) near the surface was identified in response to specific manifestation areas, including the Heutsz crater on the northern side and the Cempaga crater on the southern side. A further conductive anomaly was also found at a depth of 1 km, which was presumably due to a clay cap layer covering the fluid in the reservoi... [more]

Hydrogen used as an energy carrier can provide an important route to the decarbonization of energy supplies, but realizing this opportunity will require both significantly increased production and transportation capacity. One route to increased transportation capacity is the shipping of liquid hydrogen, but this requires an energy-intensive liquefaction step. Recent study work has shown that the energy required in this process can be reduced through the implementation of new and improved process designs, but since all low-temperature processes are affected by the available heat-sink temperature, local ambient conditions will also have an impact. The objective of this work is to identify how the energy consumption associated with hydrogen liquefaction varies with heat-sink temperature through the optimization of design parameters for a next-generation mixed refrigerant based hydrogen liquefaction process. The results show that energy consumption increases by around 20% across the coolin... [more]