The aim of the research is to analyse the energy transition in the Visegrad Group countries, because they depend on the production of energy from the burning of fossil fuels, and transition is a huge challenge for them. The diversity of the energy transformation in the V4 countries was examined by using two qualitative methods, including literature analysis and comparative analysis. The timeframe of the study was set for the period from 2020 to 2030, as these years are crucial for the implementation of the European Green Deal Programme. Four diagnostic features were taken into account in the analysis: the share of RES in final energy consumption, reduction of CO2 emissions in the non-Emissions Trading System (ETS) sector, date of withdrawal of coal from the economy, and energy efficiency. The analysis shows that the V4 countries have different approaches and levels of energy transformation in their economies. Poland is in the most difficult situation, being the most dependent on the pr... [more]

This study conducted core sampling of an offshore borehole for geological reservoir characterization of a potential CO2 storage site in southeast Korea. From this, two promising geological formations at ~739 and ~779 m were identified as prospective CO2 storage reservoirs. Injection efficiency and CO2 migration were evaluated based on directional measurements of permeabilities from core plugs. The directional transport properties were determined using both a portable probe permeameter and a pressure cell capable of applying different in situ confining pressures. Both steady state and unsteady state measurements were used to determine permeability—the method selected according to the expected permeability range of the specific sample. This expected range was based on rapid screening measurements acquired using a portable probe permeameter (PPP). Anticipated performance of the prototypical CO2 injection site was evaluated based on flow modeling of the CO2 plume migration pathway includin... [more]

Fault-tolerance is critical in power electronics, especially in Uninterruptible Power Supplies, given their role in protecting critical loads. Hence, it is crucial to develop fault-tolerant techniques to improve the resilience of these systems. This paper proposes a non-redundant fault-tolerant double conversion uninterruptible power supply based on 3-level converters. The proposed solution can correct open-circuit faults in all semiconductors (IGBTs and diodes) of all converters of the system (including the DC-DC converter), ensuring full-rated post-fault operation. This technique leverages the versatility of Finite-Control-Set Model Predictive Control to implement highly specific fault correction. This type of control enables a conditional exclusion of the switching states affected by each fault, allowing the converter to avoid these states when the fault compromises their output but still use them in all other conditions. Three main types of corrective actions are used: predictive c... [more]

Fractures and micropores have varying contributions to the gas permeability of fractured reservoirs. The quantification of the contribution of fractures and micropores that form a dual-porosity system for gas permeability is critical when attempting to accurately evaluate gas production. However, due to insufficient knowledge of fracture−matrix flow partitioning in such dual-porosity systems, it is challenging for previous models to quantitatively characterize the fracture heterogeneity and accurately evaluate the gas flow and permeability in fractured rocks. In this study, we propose a dual-porosity percolation model to quantitatively investigate the contributions of fractures and matrix micropores towards the gas permeability of fractured rocks. Using percolation theory, we establish fracture networks with complex heterogeneity, which are characterized by various fracture densities and percolation probabilities within a porous matrix with various fracture/matrix permeability ratios.... [more]

This paper presents a shunt active power filter connected to the grid via an LCL coupling circuit with implemented closed-loop control. The proposed control system allows selective harmonic currents compensation up to the 50th harmonic with the utilization of a model-based predictive current controller. As the system is fully predictive, it provides high effectiveness of the harmonic reduction, which is proved by waveforms achieved in performed tests. On the other hand, the control system is prone to loss of stability. Therefore, the paper is focused on the stability analysis of the discussed control system with the additional outer control loop of the supply current with predictive control of this current. The conducted stability analysis encompasses the assessment of system stability as a function of the coupling circuit parameter identification accuracy, whose values are implemented in the current controller, as well as parameters such as the sampling frequency and proportional-inte... [more]

Power system inertia is being reduced because of the increasing penetration of renewable energies, most of which use power electronic interfaces with the grid. This paper analyses the contribution of inertia emulation and droop control to the power system stability. Although inertia emulation may appear the best option to mitigate frequency disturbances, a thorough analysis of the shortcomings that face real-time implementations shows the opposite. Measurement noise and response delay for inertia emulation hinder controller performance, while the inherently fast droop response of electronic converters provides better frequency support. System stability, expressed in terms of rate of change of frequency (ROCOF) and frequency nadir, is therefore improved with droop control, compared to inertia emulation.

This paper presents a nonlinear cascaded control design that has been developed to (1) improve the self-sensing speed control performance of an interior permanent magnet synchronous motor (IPMSM) drive by reducing its speed and torque ripples and its phase current harmonic distortion and (2) attain the maximum torque while utilizing the minimum drive current. The nonlinear cascaded control system consists of two nonlinear controls for the speed and current control loop. A fuzzy logic controller (FLC) is employed for the outer speed control loop to regulate the rotor shaft speed. Model predictive current control (MPCC) is utilized for the inner current control loop to regulate the drive phase currents. The nonlinear equation for the dq reference current is derived to implement the maximum torque per armature (MTPA) control to achieve the maximum torque while using the minimum current values. The model reference adaptive system (MRAS) was employed for the speed self-sensing mechanism. Th... [more]

In this paper, a real-time capable reference governor superordinate model predictive controller (RG-MPC) is developed for fuel cell (FC) control suitable for automotive application. The RG-MPC provides reference trajectories for the subordinate proportional-integral (PI) controllers, which act directly on the FC system. Antiwindup and decoupling schemes, which are common problems in multivariable PI control, are unnecessary, given that the RG-MPC can inherently consider constraints and multivariable systems. The PI dynamics are incorporated into the prediction model used for control, ensuring the feasibility of the provided references for the PI controllers. The successive linearization technique is used in the RG-MPC to cope with the model’s nonlinear nature in real-time. The concept has been illustrated in a simulation scenario featuring efficient and safe power control of an FC stack in automotive application using real driving data obtained from an in-house-built FC vehicle. This w... [more]

The growth of solar energy is projected to slow down during 2023−25 despite the fall in costs due to economic deceleration, reduced incentives, and market barriers including the lack of relevant and flexible energy project planning and decision-making tools. This study proposes a flexible and computationally simple multi-criteria decision analysis (MCDA)-based model that takes technical, financial, environmental, social and legal aspects of all project options as input and outputs a feasibility score for each option, which enables ranking the options and identifying the best alternative. The proposed model is applied to a real-world photovoltaic solar farm planned at a site in England and comprising nine different configurations formed by varying system capacity, energy storage option, mode of stakeholder, and network connections. The results of our study show that in this case the options without battery storage and a greater number of off-taker connections are more favorable than the... [more]

In the framework of the empir projects myrails and windefcy, metas developed a primary standard for electrical power using commercial off-the-shelf components. The only custom part is the software that controls the sampling system and determines the amplitude and phase of the different frequency components of voltage and current. The system operates from dc up to 9 kHz, even with distorted signals. The basic system is limited to 700 V and 21 A. Its power uncertainty is 15 μW/VA at power frequencies and increases to 1.8 mW/VA at 9 kHz. With the extension up to 1000 V and 360 A, the system reaches power uncertainties of 20 μW/VA at power frequencies, increasing to 510 μW/VA at 9 kHz. For higher voltages or higher currents, the same principle is used. However, the uncertainties are dominated by the stability of the sources. The voltage and current channels can also be used independently to calibrate and test power quality instruments. Thanks to a time-stamping system, the system can also... [more]

This paper proposes a double layered multi parameters braking energy recovery control strategy for Hybrid Electric Vehicle, which can combine the mechanical brake system with the motor brake system in the braking process to achieve higher energy utilization efficiency and at the same time ensure that the vehicle has sufficient braking performance and safety performance. The first layer of the control strategy proposed in this paper aims to improve the braking force distribution coefficient of the front axle. On the basis of following the principle of braking force distribution, the braking force of the front axle and the rear axle is reasonably distributed according to the braking strength. The second layer is to obtain the proportional coefficient of regenerative braking, considering the influence of vehicle speed, braking strength, and power battery state of charge (SOC) on the front axle mechanical braking force and motor braking force distribution, and a three-input single-output f... [more]

Due to rapid population growth, technology, and economic development, electricity demand is rising, causing a gap between energy production and demand. With the emergence of the smart grid, residents can schedule their energy usage in response to the Demand Response (DR) program offered by a utility company to cope with the gap between demand and supply. This work first proposes a novel optimization-based energy management framework that adapts consumer power usage patterns using real-time pricing signals and generation from utility and photovoltaic-battery systems to minimize electricity cost, to reduce carbon emission, and to mitigate peak power consumption subjected to alleviating rebound peak generation. Secondly, a Hybrid Genetic Ant Colony Optimization (HGACO) algorithm is proposed to solve the complete scheduling model for three scenarios: without photovoltaic-battery systems, with photovoltaic systems, and with photovoltaic-battery systems. Thirdly, rebound peak generation is r... [more]

Environmental issues in energy policy, especially global warming, have received more attention lately than ever before. Excessive dependence on fossil fuels, deforestation, and land degradation are the three main factors that lead to increased carbon dioxide (CO2) emissions. Consequently, the global average temperature has doubled compared to anticipation. Various international protocols and agendas have been established, pledged to restore the global average temperature to the 1990 level. As a result, energy policies worldwide have also undergone various transformations to align with these protocols since then. As a developing nation, Malaysian’s electricity demand has continuously grown in the past two decades. To date, the electricity sector is still dominated by fossil fuels. Government incentives have been the most influential factor in the nation’s energy mix trend. Several energy policies implemented throughout the past 22 years have seen the shift from natural gas to coal power... [more]

Chemical hydrogen storage stands as a promising option to conventional storage methods. There are numerous hydrogen carrier molecules that afford satisfactory hydrogen capacity. Among them, ammonia borane has attracted great interest due to its high hydrogen capacity. Great efforts have been devoted to design and develop suitable catalysts to boost the production of hydrogen from ammonia borane, which is preferably attained by Ru catalysts. The present review summarizes some of the recent Ru-based heterogeneous catalysts applied in the hydrolytic dehydrogenation of ammonia borane, paying particular attention to those supported on carbon materials and oxides.

At present, electrical network stability is of the utmost importance because of the increase in electric demand and the integration of distributed generation deriving from renewable energy. In this paper, we proposed a static reactive power compensator model with common direct current voltage sources. Converter parameters were calculated and designed to fulfill specifications. In order to ascertain the device response for different operating modes as reactive power consumer and generator, we developed the model’s power and control circuits in Matlab Simulink. Simulations were performed for different conditions, and as a result, the current and voltage waveforms and the circular power chart were obtained. This paper has theoretically proven it is possible to achieve the consumption or generation of purely active or reactive power by implementing a static reactive power compensator with common DC voltage sources.

Predicting building air change rates is a challenge for designers seeking to deal with natural ventilation, a more and more popular passive strategy. Among the methods available for this task, computational fluid dynamics (CFD) appears the most compelling, in ascending use. However, CFD simulations require a range of settings and skills that inhibit its wide application. With the primary goal of providing a pragmatic CFD application to promote wind-driven ventilation assessments at the design phase, this paper presents a study that investigates natural ventilation integrating 3D parametric modeling and CFD. From pre- to post-processing, the workflow addresses all simulation steps: geometry and weather definition, including incident wind directions, a model set up, control, results’ edition, and visualization. Both indoor air velocities and air change rates (ACH) were calculated within the procedure, which used a test house and air measurements as a reference. The study explores alterna... [more]

Nonequilibrium statistical mechanics or molecular theory has put the transport equations of mass, momentum and energy on a firm or rigorous theoretical foundation that has played a critical role in their use and applications. Here, it is shown that those methods can be extended to nonequilibrium entropy conservation. As already known, the “closure” of the transport equations leads to the theory underlying the phenomenological laws, including Fick’s Law of Diffusion, Newton’s Law of Viscosity, and Fourier’s Law of Heat. In the case of entropy, closure leads to the relationship of entropy flux to heat as well as the Second Law or the necessity of positive entropy generation. It is further demonstrated how the complete set of transport equations, including entropy, can be simplified under physically restrictive assumptions, such as reversible flows and local equilibrium flows. This analysis, in general, yields a complete, rigorous set of transport equations for use in applications. Finall... [more]

High initial costs hinder innovative technologies for building envelopes. Life Cycle Assessment (LCA) should consider energy savings to show relevant economic benefits and potential to reduce energy consumption and CO2 emissions. Life Cycle Cost (LCC) and Life Cycle Energy (LCE) should focus on investment, operation, maintenance, dismantling, disposal, and/or recycling for the building. This study compares the LCC and LCE analysis of Water Flow Glazing (WFG) envelopes with traditional double and triple glazing facades. The assessment considers initial, operational, and disposal costs and energy consumption as well as different energy systems for heating and cooling. Real prototypes have been built in two different locations to record real-world data of yearly operational energy. WFG systems consistently showed a higher initial investment than traditional glazing. The final Life Cycle Cost analysis demonstrates that WFG systems are better over the operation phase only when it is compare... [more]

In this paper a general-purpose procedure for optimizing a resonant inductive wireless power transfer link adopting a multiple-input-multiple-output (MIMO) configuration is presented. The wireless link is described in a general−purpose way as a multi-port electrical network that can be the result of either analytical calculations, full−wave simulations, or measurements. An eigenvalue problem is then derived to determine the link optimal impedance terminations for efficiency maximization. A step-by-step procedure is proposed to solve the eigenvalue problem using a computer algebra system, it provides the configuration of the link, optimal sources, and loads for maximizing the efficiency. The main advantage of the proposed approach is that it is general: it is valid for any strictly−passive multi−port network and is therefore applicable to any wireless power transfer (WPT) link. To validate the presented theory, an example of application is illustrated for a link using three transmitters... [more]

This publication discusses the risks of further use of classical overcurrent protections in modern power systems. The increasing penetration of renewable energy sources has caused a lot of challenges, among other things, the development of energy communities that balance local generation and consumption. Usually the interconnection line between the energy community and power systems are only used to balance the shortage or overflow of energy. As a result, most of the time these connections can be low loaded. Such a state can cause incorrect operation of power system protection approached, because the current level values are smaller than the required activation level for the protections. This article presents the potential incorrect operation of digital power system protection with overcurrent function. The obtained simulation results clearly show that the correctness of protection operation is strongly dependent on the level load of lines and the parameters and structure of the protec... [more]

Many Caribbean island nations have historically been heavily dependent on imported fossil fuels for both power and transportation, while at the same time being at an enhanced risk from the impacts of climate change, although their emissions represent a very tiny fraction of the global total responsible for climate change. Small island developing states (SIDSs) are among the leaders in advocating for the ambitious 1.5 °C Paris Agreement target and the transition to 100% sustainable, renewable energy systems. In this work, three central results are presented. First, through GIS mapping of all Caribbean islands, the potential for near-coastal deep-water as a resource for ocean thermal energy conversion (OTEC) is shown, and these results are coupled with an estimate of the countries for which OTEC would be most advantageous due to a lack of other dispatchable renewable power options. Secondly, hourly data have been utilized to explicitly show the trade-offs between battery storage needs an... [more]

The experimental investigation of building-integrated photovoltaic thermal (BIPVT) solar systems is essential to characterise the operation of these elements under real conditions of use according to the climate and building type they pertain. BIPVT systems can increase and ensure energy performance and readiness without jeopardising the occupant comfort if correctly operated. The present work presents a case study’s experimental analysis composed of a BIPVT system for heat recovery located in a controlled test room. This work contribution focuses on the presentation of the obtained measured value results that correspond to the BIPVT main boundary conditions (weather and room characteristics) and the thermal behaviour and performance of the BIPVT system, located in the Solar XXI Building, a nZEB exposed to the mild Mediterranean climate conditions of Portugal.

In the process industry, a large amount of low-grade waste heat is discharged into the environment. Furthermore, district heating and cooling systems require considerable low-grade energy. The integration of the two systems has great significance for energy saving. Because the energy demand of consumers varies in periods, the design and operation of an industrial waste heat recovery system need to match with the fluctuations of district energy demand. However, the impact of the periodic changes on the integration schemes are not considered enough in existing research. In this study, a framework method for solving above problem is proposed. Industrial waste heat was integrated with a district heating and cooling system through a heat recovery loop. A three-step mathematical programming method was used in design and operation optimization for multiperiod integration. A case study was conducted, and the results show that the multiperiod optimization method can bring significant benefits t... [more]

Energy access and waste management are two of the most pressing developmental and environmental issues on a global level to help mitigate the accelerating impacts of climate change. They are particularly relevant in Sub−Saharan Africa where electrification rates are significantly below global averages and rural areas are lacking a formal waste management sector. This paper explores the potential of integrating solar energy into a biomass pyrolysis unit as a potentially synergetic solution to both issues. The full design of a slow pyrolysis batch reactor targeted at biochar production, following a strict cost minimization approach, is presented in light of the relevant considerations. SPEAR is powered using a Cassegrain optics parabolic dish system, integrated into the reactor via a manual tracking system and optically optimized with a Monte-Carlo ray tracing methodology. The design approach employed has led to the development an overall cost efficient system, with the potential to achi... [more]

With the tight coupling of multi-energy systems, accurate multiple-load forecasting will be the primary premise for the optimal operation of integrated energy systems. Therefore, this paper proposes a Copula correlation analysis combined with deep bidirectional long and short-term memory neural network forecasting model. First, Copula correlation analysis is used to conduct correlation analysis on multiple loads and various influencing factors. The influencing factors that have a great correlation with multiple loads were screened out as the input feature set of the model to eliminate the influence of interfering factors. Then, a deep bidirectional long and short-term memory neural network was constructed. Combined with the input feature set screened by the Copula correlation analysis method, the useful information contained in the historical data was more comprehensively learned from the forward and backward directions for training and forecasting. Through the actual calculation examp... [more]