The paper presents several theories related to definitions of powers and power factors in non-sinusoidal and non-symmetrical regimes. The theories must meet some requirements: (a) to facilitate the measuring of power quantities by using acquired electrical waveforms; (b) to support the correct quantification of powers and power factors for a fair charge; (c) to support solutions for efficient compensation of non-sinusoidal and non-symmetrical regimes, simultaneous with the power factor compensation along the fundamental harmonic. Only theories meeting the above-mentioned requirements are approached. Aspects specific to power definitions are discussed and commented. Three theories rely on the Fourier decomposition of non-sinusoidal waveforms, valid only for steady signals, whilst the fourth relies on the Discrete Wavelet Transform (DWT) and can also be applied to unsteady signals. Dedicated original data acquisition systems were used to acquire experimental data for three case studies.... [more]

In this article, we analyze the energy consumption data of business customers registered by trading companies in Poland. We focus on estimating missing data in hourly series, as forecasts of this frequency are needed to determine the volume of electricity orders on the power exchange or the contract market. Our goal is to identify an appropriate method of imputation missing data for this type of data. Trading companies expect a specific solution, so we use a procedure that allows to choose the imputation method, which will consequently improve the accuracy of forecasting energy consumption. Using this procedure, a statistical analysis of the occurrence of missing values is performed. Then, three techniques for generating missing data are selected (missing data are generated in randomly selected series without missing values). The selected imputation methods are tested and the best method is chosen based on MAE and MAPE errors.

The development of primary frequency regulation (FR) technology has prompted wind power to provide support for active power control systems, and it is critical to accurately assess and predict the wind power FR potential. Therefore, a prediction model for wind power virtual inertia and primary FR potential is proposed. Firstly, the primary FR control mode is divided and the mapping relationship of operating wind speed and FR potential is constructed. Secondly, a hybrid prediction method of singular spectrum analysis (SSA) and Gaussian process regression (GPR) is proposed for predicting the speed of wind. Finally, the wind speed sequence is adopted to calculate the FR potential with various regulation modes in future time. The results show the advantages of the proposed method in the prediction accuracy of wind power FR potential and the ability to characterize the uncertainty information of the prediction results. Accurate modeling and prediction of wind power FR potential can signific... [more]

The European transition to green economy is based on long-term strategies. The Europe 2020 Strategy was launched in 2010 in order to promote smart, sustainable, and inclusive growth in the region. Later, the ambitions regarding this strategy were followed by the Green Deal and Sustainable Development Goals. Now, the effort of countries towards the green economy is even more relevant than ever because of the context of today’s global energy crisis and economic uncertainty due to many challenges such as the COVID-19 pandemic or Russia invasion of Ukraine. This paper seeks to assess the countries’ achievements in seeking climate change and energy targets of the Europe 2020 Strategy by applying the innovative multi-criteria decision-making (MCDM) technique. The kernel-based comprehensive assessment (KerCA) method was applied for the calculations of the progress achieved and countries’ rankings. It allows to evaluate countries’ achievements and compare them using the mathematical models. Th... [more]

Although European energy policy supports the reduction of energy consumption, the current economic and political situation in Poland and uncertainty related to the origin of energy sources do not support it. Therefore, the aim of this paper is to identify and assess the factors that affect the energy-saving behaviour of Polish consumers in the process of energy consumption. The research problem concerns the specificity of behaviours that are part of new trends in consumption, such as greening and the ethical dimension of consumption. The research question arises as to what the social responsibility of consumers is in the process of energy consumption. The research problem comes down to the question of factors that determine the behaviour of an individual consumer in the energy market. In order to realise the indicated purpose of the article, a conceptual research model was built and direct research was conducted using the research method, which was an online survey (CAWI). The research... [more]

Among the renewable energy resources, solar thermal is one of the technologies that significantly contribute to energy supply and reduce global greenhouse gas (GHG) emissions. Solar water heating (SWH) contributes a large proportion of the global solar thermal capacity, with 63% installation for domestic hot water (DHW) systems, 28% for large DHW systems, and the remaining 9% for other applications such as swimming pools heating, solar district heating, and space heating. Still, now, there are many challenges and limitations of those SWH technologies. The present work reviews the current challenges faced in the domestic SWH industry globally. The integration of thermal energy storage (TES) systems for better collector’s radiation absorption and overall performance are also highlighted. Many countries worldwide seem to face similar challenges within the SWH technologies and industry. It is proven that these challenges and limitations can hinder the global capacity of solar thermal utili... [more]

Carbon emissions trading (CET) is now one of China’s key policy tools for achieving the goals of carbon peak and carbon neutrality. To comprehensively explore the consequences of China’s CET policy, the study first evaluated the content validity of CET policies across China’s 31 provinces, autonomous regions, and municipalities falling directly under the central government using policy strengths, tools, and measures from 2011 to 2020. The spatiotemporal drivers of regional carbon efficiency improvements from aspects of actual policy effect, average policy content validity effect, and policy quantity effect were also evaluated via the logarithmic mean Divisia index. This analysis revealed that the policy content validity was increasing in general and was higher in pilot regions. On average, the policy quantity effect was the primary driver of carbon efficiency improvements in both pilot and non-pilot regions, but the actual policy effect failed to promote carbon efficiency in both regio... [more]

Phase change material (PCM)-based thermal energy storage (TES) systems are widely used for repeated intermittent heating and cooling applications. However, such systems typically face some challenges due to the low thermal conductivity and expensive encapsulation process of PCMs. The present study overcomes these challenges by proposing a lightweight, low-cost, and low thermal resistance TES system that realizes a fluid-to-PCM additively manufactured metal-polymer composite heat exchanger (HX), based on our previously developed cross-media approach. A robust and simplified, analytical-based, 1D reduced-order model (ROM) was developed to compute the TES system performance, saving computational time compared to modeling the entire TES system using PCM-related transient CFD modeling. The TES model was reduced to a segment-level model comprising a single PCM-wire cylindrical domain based on the tube-bank geometry formed by the metal fin-wires. A detailed study on the geometric behavior of... [more]

Lignocellulosic biomass is included in the group of renewable energy sources. Its calorific value is high, owing to which it can be successfully used in the production of second-generation fuels, e.g., biogas. However, its complex structure makes it necessary to apply a pretreatment in order to increase the biogas output. This study presents the usability of a pulsed electric field in grass silage pretreatment in methane fermentation and compares it with microwave-induced disintegration. The experiment shows that substrate disintegration with a pulsed electric field (PEF) results in an increase in methane output. The productivity of methane from PEF pretreatment silage increased by 20.1% compared to the untreated control. The application of microwave disintegration, with the assumption that the same energy is used for the pretreatment, resulted in a methane output increase of 6% compared to the control. The highest biogas production output in PEF-pretreated samples was 535.57 NL/kg VS,... [more]

This paper is concerned with designing a dynamical synchronization (via a robust cooperative control) of an electromechanical system network (EMSN), consisting of nonidentical brushed DC motors, where only the motors’ angular velocity measurements are available. The challenge of the proposed approach is that the actuation provided by the motor needs to handle external disturbances to achieve the velocity tracking task and handle the interaction between both motors cooperatively to share the load and the disturbance rejection. The control’s basis involves differential flatness and an active disturbance rejection control (ADRC) framework augmented using ideas from the graph theory analysis and multi-agent networks. Experimental results verify the theoretical developments and show the effectiveness of the proposed control strategy despite unexpectedly changing load disturbance and parameters uncertainties. The proposed algorithm is suitable for embedded use due to its simplicity. It can b... [more]

In this study, a modified non-stationary geometry-based scattering model for tunnel vehicle-to-vehicle (V2V) multiple-input multiple-output Ricean fading channels is presented. The proposed channel introduces non-line-of-sight three-dimensional multi-bounced scattering propagation paths under an assumption of equivalent scattering points to depict the tunnel environments, in which the scatterers are randomly distributed on the semi-cylindrical tunnel wall (i.e., cable racks, jetfans, road signs, lighting facilities). Furthermore, the time-varying channel statistics (i.e., the space and frequency correlation functions) resulting from the relative movement between the mobile transmitter and mobile receiver are analyzed. Finally, numerical results show that the space correlations of the proposed model significantly decrease when the multi-bounced scattering rays are taken into account; moreover, when the velocity and the antenna angle γR increase, the correlations decrease therewith, whic... [more]

In the present work, the optimization of a new coating formulation was investigated, taking attention to an industrially focused research approach used for the engineering design of the adsorber. The adsorbent was a composite zeolite or silica-gel based coating applied by using new flexible polymer matrices. The FC-80 formulation represents a good compromise between mechanical stability and absorption capacity. Using the developed coating process, a new compact HEX design was developed to reach the AHP target performance with easy and fast manufacturing. The specific cooling power of the coated heat exchanger was estimated to be about 500 W/kg of adsorbent. The new coated HEX was integrated in a new adsorption chiller and has been tested by a laboratory test-rig under realistic operating conditions. Results of preliminary testing demonstrated that the prototype provides a cooling capacity of around 10 kW with a COP of 0.54.

This work aimed to improve how the equipment of a grid-tied solar-wind system used the installed power of the storage battery while reducing the cost of electricity consumed by a local object from the grid. A method for calculating the parameters for a given load schedule is proposed, along with the value of the reduction in electricity consumption. Values for the power generation of a wind generator and photovoltaic battery are based on archival data. The possible power ratio of the wind generator and the photovoltaic battery is 1:8.33. The formation of the state of charge of the battery involves: a calculation of its value for the morning peak according to the forecast for the next day; adjustable discharge in the evening with full or partial compensation for the load consumption according to the forecast for the next day; a night charge with a given current value. At a one-tariff plan, one battery discharge cycle per day is used. A night charge from the grid is not used. With a two-... [more]

This paper presents the development and implementation of a reinforcement learning agent as the mode selector for a multi-chamber actuator in a load-sensing architecture. The agent selects the mode of the actuator to minimise system energy losses. The agent was trained in a simulated environment and afterwards deployed to the real system. Simulation results indicated the capability of the agent to reduce energy consumption, while maintaining the actuation performance. Experimental results showed the capability of the agent to learn via simulation and to control the real system.

More than 78 million tons of photovoltaic modules (PVMs) will reach their end of life (EOL) by 2050. If they are not responsibly managed, they can (a) pollute our terrestrial ecosystem, (b) indirectly encourage continuous mining and extraction of Earth’s finite resources, and (c) diminish the net environmental benefit of harvesting solar energy. Conversely, successfully recovering them could reduce resource extraction and waste and generate sufficient economic return and value to finance the production of another 2 billion PVMs by 2050. Therefore, EOL PVMs must participate in the circular economy, and business and political leaders are actively devising strategies to enable their participation. This article aims to facilitate and expedite their efforts by comprehensively reviewing and presenting the latest progress and developments in EOL PVM recovery methods and processes. It also identifies and thoroughly discusses several interrelated observations that impede or accelerate their eff... [more]

In this study, pyrolysis of municipal sewage sludge samples from different sources including cattle and chicken manure as well as brook mud, was investigated using a thermogravimetric analysis coupled with a Fourier transform infrared spectrometer (TG-FTIR) at different heating rates (25, 50 and 100 °C/min). In order to determine the kinetic parameters, Arrhenius, model-free Kissinger−Akira−Sunose (KAS), as well as Friedman and Flynn−Wall−Ozawa (FWO) methods were compared. The thermogravimetric results revealed that pyrolysis involved different stages, and that the main decomposition reactions took place in the range of 200−600 °C. In this range, decomposition of biodegradable components (e.g., lipids and polysaccharides), proteins and carbohydrates occurred; meanwhile, there were samples (e.g., cattle manure, brook mud) in which the decomposition step could be observed even at temperatures above 700 °C. According to the Arrhenius method, the activation energies of the first decomposit... [more]

Because of its benefits in terms of high speed, non-destructiveness, and three-dimensionality, as well as ease of integration with computer simulation, computed tomography (CT) technology is widely applied in reservoir geology research. However, rock imaging is restricted by the device used as there is not a win−win for both the image receptive field and corresponding resolution. Convolutional neural network-based super-resolution reconstruction has become a hot topic in improving the performance of CT images. With the help of a convolution kernel, it can effectively extract characteristics and ignore disturbance information. The dismal truth is that convolutional neural networks still have numerous issues, particularly unclear texture details. To address these challenges, a generative adversarial network (RDCA-SRGAN) was designed to improve rock CT image resolution using the combination of residual learning and a dual-channel attention mechanism. Specifically, our generator employs re... [more]

A concern for ensuring energy security is particularly important in the 2020s, a decade significantly marked by economic and political uncertainty: the coronavirus pandemic, the Russian-Ukrainian war, and inflation turning into stagflation in many markets. Additionally, the national and international climate policy promoting the acquisition of energy from non-renewable sources is only a part of the problem that forces a revision of the direction and degree of diversification of energy sources. States, bearing in mind the inevitability of change, in order to maintain energy security, should not only accurately read these phenomena but also effectively prevent them. One of the available solutions is to build a multi-energy concern to ensure energy independence through diversified production and distribution of electricity and non-renewable fuels. To this end, a large international entity centred around the PKN Orlen group has existed in Poland for several years. The construction of this... [more]

Simulation models of transport systems are a key tool for solving many problems in the field of management of these systems. The methodologies for creating such models use datasets on both transport infrastructure and demand for the delivery of goods or passenger transport, however, many factors are considered based on assumptions due to the complexity. This article describes the approach to modeling the cargo transportation system for road transport in Poland based on data obtained by the Central Statistical Office from the TD-E survey. This approach avoids many assumptions about demand as the demand parameters are estimated based on a sample representing the general population—a set of all economic entities generating freight traffic. Basic procedures in the developed approach have been implemented as Python scripts. As a result of the use of the proposed methodology, a country-wide road transport model was obtained based on the TD-E survey from 2018. The adequacy of the developed mo... [more]

The Ordos Basin contains abundant coal resources in the Upper Paleozoic strata. They are shallowly buried or exposed in the periphery of the basin, forming recoverable coal mines and coalbed methane resources. For the deeply buried coal seams of the basin, however, due to complex changes and difficult mining, less attention was paid before. In recent years, with the exploitation of tight gas related to coal source rocks, a large amount of drilling and seismic data has been accumulated in the southeastern Ordos Basin, which makes it possible to study the distribution change and factors controlling Upper Paleozoic coal seams. Delineation of deep coal development and distribution is an important basis for coal, coalbed methane and related tight gas resources in the Upper Paleozoic. We use core, logging and seismic data to analyze the coal geophysics, thickness variation, paleotopography and sedimentary facies in the southeastern Ordos Basin. The lower part of the Shanxi Formation (Fm.) an... [more]

The horizontal drop film evaporator is a key component of the mechanical vapor recompression crystallization system, which can be used to evaporate effluent and recycle secondary vapor energy. However, the properties of heat transfer and flow of the salty effluent sprayed external of the horizontal drop film evaporation tube are obviously different from that of ordinary water. We established a 3D model for a horizontal drop film evaporator in the system, and water and sodium sulfate mixture were manufactured to reproduce the real salty effluent. By applying the VOF (volume of fluid) model, the liquid-gas interface of a salty effluent spray drop film formed on a horizontal tube in the evaporator was traced. The impacts of various heat flux, sodium sulfate content, spray density, and temperature on the local Nusselt number were studied, and a dimensionless correlation was established. The results showed that the effect of surface tension cannot be negligible; as the sodium sulfate conten... [more]

Aerosol pollutant particles indoors significantly affect public health. The conventional wisdom is that natural ventilation will alleviate the dispersion of airborne or aerosol particles. However, we show that the problem is far more complex and that natural ventilation should be applied under specific conditions to be effective. We performed several simulations of a simplified (and easily reproducible) room with a window opening and aerosol particles stratified layers. Opening a window can scatter particles present in stratified layers indoors and potentially contribute to the degradation of indoor air quality for a significant period of time. Moreover, we show that thermal instabilities arising from the temperature gradients due to temperature differences between the indoor and outdoor environment spread the particles randomly indoors, adversely affecting air quality and architectural design. Recommendations for more efficient natural ventilation minimizing aerosol pollutant particle... [more]

This paper introduces a new geometry for the study of dry band formation. Firstly, a thermoelectric simulation of a 69 kV uniformly polluted composite insulator was performed. The results obtained show that thermal stress is greater at the rod surface where current density is maximum. In order to experimentally reproduce the constriction of current density lines on the insulator rod surface, which is the cause of dry band formation, the development of a new simple geometric setup, which was then tested experimentally, was proposed. For this purpose, an ESDD value corresponding to a high level of pollution was used for each polluted sample, and the samples were placed in a climate chamber at constant 90% relative humidity and a constant ambient temperature of 20 °C. Low-voltage tests permitted the determination of the wetting duration, which corresponds to the maximum surface conductance of the polluted layer. The values obtained agree with the 10−40 min duration recommended in IEC 6050... [more]

Solar photovoltaic PV plants worldwide are continuously monitored and carefully protected to ensure safe and reliable operation through detecting and isolating faults. Faults are very common in modern solar PV systems which interrupt normal system operation adversely affecting the performance of the PV systems. When undetected, faults not only cause significant reduction in the efficiency and life span of the PV system, but also result in damage and fire hazards compromising their reliability. Therefore, early fault detection and diagnosis of photovoltaic plants is a necessity for safe and reliable operation required for growing solar PV systems. Unfortunately, several recent fire incidents have been reported recently caused by undetected faults in solar PV systems. Motivated by this challenge, this paper, utilizing a proposed fuzzy logic algorithm, presents a novel technique for detecting and classifying faults in solar PV systems. Furthermore, the proposed method introduces fault ind... [more]

By 2025, biogas is estimated to become a larger part of Indonesia’s energy mix. Biogas is a renewable energy source that also has economic and environmental advantages. Domestic biogas generation has been embraced in Indonesia as a response to the country’s energy security concerns in rural areas. Since the 1970s, 48,038 biogas plants have been built in the region. To fully develop this technology, Indonesia must discontinue relying on fossil fuels and substitute current fossil-fuel-based energy. This article provides an overview of renewable technology in Indonesia, as well as addressing domestic energy demands and referring to existing literature on the socio-technical and socio-economic barriers to biogas adoption in Indonesia. Based on a rigorous review of 71 publications published in Web of Science (WoS) between 2010 and 2021, this study explores existing barriers for biogas adoption by summarizing the current literature from technical, economic, social and environmental perspecti... [more]