Load forecasting is one of the most important step to maintain demand-supply balance and stability in a power system. With the advent of artificial intelligence and machine learning tools, load forecasting/energy consumption prediction is conducted with increased accuracy. The application of several machine learning techniques to predict energy consumption has been reported. However, a detailed analysis of different techniques is beneficial to choose the right approach to specific cases. This paper presents a study of different prediction models in energy forecasting. The prediction models are implemented in Matlab. The training and testing results for the data set is presented.
Microgrids are going to take a major part of the future electricity distribution system, where they will form a local, controllable entity, consisting of various consumers, local energy producers and network energy storages. To be able plan, forecast and calculate the consumption and regulation energy values in advance by an algorithm - it is very important to have an accurate forecast, which takes the PV production too, into consideration. However, because of the low number of consumers and prosumers - the ordinary forecasting methods - which are applied in the transmission system-level consumption prediction - are not easily applicable in this situation, therefore a new approach is recommended. This paper focuses on developing such a method, that is capable of predicting a microgrid's electricity consumption in a D-1 and D-2 basis either from only the historical consumption data, or the history data and externalities. To do this, several real-life consumption data packages are analyzed and used to train a neural network. This network's parameters are subject to change throughout the process, according to the characteristics of the actual data, which is being predicted by it. Furthermore, in order to validate and evaluate the neural network's predictions - a classical ARIMA prediction model is also implemented and evaluated.
The importance of energy consumption to allow societies to thrive is well established and prospects of energy needs is well derived through the scientific literature. Yet, lesser discussions persist on the future availability of energy for current industrial economies, a crucial indicator for development. It is defined as net-energy analysis, where one must appropriate more energy than required to get it. The most common indicators are the energy payback time and the EROI (Energy Return of Investment). These indicators are used throughout literature either for energy vectors, energy systems or for broader societal applications. Following growing concerns about climate change, and with the increasing difficulty of extraction of fossil fuels, EROIs became tools to study the global energy transition with a focus on a possible minimum EROI required to maintain a complex society. However, the indicator is used with a large variety of methods, definitions, and boundaries. This led to a lack of consensus on whether a transition to renewable-based energy systems could still provide sufficient net energy for societies to thrive. The concepts of EROI were studied by compiling its various definitions, boundaries, and limits, allowing a clear view of the indicator to understand where and how it could be used. This led to finding three main classes of indicators: the physical EROI, an indicator based on energy consumption, a price-based societal EROI, an indicator using monetary expenditures to look at energy-related expenditures, and finally a socioeconomic EROI which looks at energy expenditures within a nation's economy. A detailed review of those use cases led to understanding that the EROI is often badly calculated through wrong boundaries, goals, or with old data and that no norm exists for its calculation. These inconsistencies tend to negatively bias renewable technologies as a solution to the energy transition. Furthermore, most calculations of minimal EROIs are based on fossil fuel infrastructure, with current energy systems being highly inefficient. The previously calculated minimal EROIs through literature, penalizing renewable technologies, are challenged. The study discusses the possibility of transitioning away from fossil fuels' dependence based on updated data and literature to finally conclude that renewable can offer sufficient energy through the energy transition. This sufficiency however comes with short-term limits followed by a possible drop in net-energy due to the transitory nature of the global shift to mitigate climate change.
The H2020 INTERRFACE project designs, develops, and exploits an Interoperable pan-European Grid Services Architecture to act as the interface between the power system (TSO and DSO) and the customers and allow the seamless and coordinated operation of all stakeholders to use and procure common services. The project exploits state-of-the-art digital tools based on peer-to-peer (P2P) local market to provide new opportunities for electricity market participation and thus engage consumers into the INTERRFACE proposed market structures that are designed to exploit Distributed Energy Resources and empowers customers to become active market participants. In this paper, a network modeling method is introduced and validated through the metering data of a test area. The model considers voltage limits, asymmetry, and overloading violations. Simulation results show that the modeling considerations are adequate to analyze the effects on the local grid assets and provide reflective tariff signals for proper grid utilization. Therefore, the proposed design can serve as the network calculation principle of low voltage P2P markets in the future.
In the reconstruction of distribution heating networks of the direct heating systems, a new heating network is necessary to meet the current heat demand. Old original thermal networks do not meet operating requirements. The solved study we assessed the heat distribution of central heating was originally in steel, and hot water distribution was originally in galvanised steel. This distribution network has been assessed for the city in eastern Slovakia, where the new proposal aim to save operating costs, by reducing heat losses in pipe distribution. The reconstruction of heating networks had the nature of the need for pipeline replacement. Central heating, which was originally designed in steel pipes, we compared with new preinsulated steel pipes and with preinsulated flexible plastic pipes. Final design for central heating, which was with the lowest heat losses was designed in combination in steel and plastic. Part of the distribution above DN 100 has been designed in preinsulated steel pipe and smaller dimensions under DN 100 were designed in preinsulated flexible plastic pipes. This combination of steel and plastic is called a hybrid system. After calculation heat loses in distribution for hot water, we compare new polypropylene pipes to preinsulated flexible plastic pipes. Final design was rated for preinsulated flexible plastic pipes. By modernizing the heat distribution, there will be a significant increase in the efficiency of heat energy distribution into sampling sites. By reducing heat looses to the surroundings, it can be saved in the production and transmission of the heat transfer substance. Due to the correct design for a particular project, we can reduce heat losses in heating networks by 26-46% compared to originally proposed steel pipes. Reducing heat losses in hot water distribution optimization would reduce by 23 to 43% of the original proposal that was designed in polypropylene. The new pipe distribution is provided by the desired parameters of the heat transfer substance for end users and contributes to the overall improvement in the operation of the heating network.
An electrostatic precipitator (ESP) is an industrial equipment used for many years. Its main objective has been to mitigate the environmental impact due to the emission of gases that are produced in large industries. Mathematical models have been established for most of the physical phenomena that happen inside ESP. In this research work, the ESP geometrical dimensions are defined based on an ESP prototype, for instance, flat collecting plates and seven circular corona wires are used, and the corresponding models, parameters, operating conditions, and boundary conditions are described and simulated in a Multiphysics software. As relevant results found are the resolution of the transport equation and trajectory of particle motion. Besides, a comparison among the models for particle charging is shown in the results section, emphasizing when the particle radius is about 0.2 μm, where Lawless's model is used as a reference, which has been mentioned in most research works.
Thermal baths in Slovakia produce waste pool water, which is most often discharged to the water recipient. Cooling of waste pool water is ensured by means of cooling ponds or canals. However, cooling the water from the pool is not sufficient. Therefore, thermal bath operators face sanctions for environmental pollution. The possibility of ensuring the maximum temperature of waste pool water is by means of a heat recovery system, which will be presented in the article. If it is not possible to apply a heat recovery system, it is necessary to ensure sufficient cooling of the water in another way. Another possibility of increasing the cooling of wastewater is to ensure a sufficient evaporate area which has a great effect on water cooling. Another crucial parameter that affects the cooling of wastewater is the speed of air flow above the water surface. The article is focused on influence of air flow rate and evaporation surface on cooling of waste pool water produced by thermal baths and briefly introduces another wastewater cooling option, which is a heat recovery system. The results presented in the article indicate a significant impact of the evaporation area on the heat flow through the evaporation.
The objective of this paper is to determine the effect of accelerated start-stop cycling protocol on a high temperature polymer electrolyte membrane fuel cell performance under operating temperature of 160 $^{\circ}\mathbf{C}$ and current density of 0.4 A cm-2. The degradation rates during 200 start-stop cycles are analysed and discussed. The results are supported by polarization curves and electrochemical impedance spectroscopy. The overall degradation over 200 start-stop cycles is -49 mV and the average degradation rate per one cycle is -0.25 mV.
Industrial activities are closely related to environmental issues which are displayed as frequent extreme weather conditions, natural disasters, and other intensive changes. European Green Deal is the latest European action plan to mitigate climate change and introduce sustainable development by policymakers. The environmental impact of companies is very important to meet future sustainability. One of the basic steps in the analysis of the environmental profile of the company is the identification of hot spots by using the carbon footprint methodology. The workflow and the tool for the carbon footprint methodology implementation were developed for the case of strategic planning for a medium-sized company following the standardized methodology given by the GHG Protocol. Relevant emission sources within the hot spots are identified and analyzed. The sensitivity analysis for different pre-defined scenarios is made to meet the company's mid and long-term strategic goals. Results show that the main contributors to the overall carbon footprint are purchased electricity, purchased heat, and combustion of fuels in company-owned/controlled vehicles. GHG emissions from purchased electricity and heat heavily depend on emission factors of electricity and heat sources. Also, changes in electricity and heat supply sources have a significant impact on GHG emissions.
The goal is a model-experimental study of the vibration that occurs in the nodes of the motor-gear unit (hereinafter referred to as MGU) installed on the motor bogie of an electric train under operating conditions. Vibration measurement was carried out experimentally on a motor stand using vibration sensors of the SKF CMXA 80 type, installed on the casing of the traction gearbox and the frame of the traction motor. For measurements, a system was used that allows continuous recording of the vibration transducer signal over eight channels. Experimental data on the parameters of vibrations that occur on the bearing shield of the output shaft of the MGU were obtained by simulating the departure of a motor bogie by instantaneous load shedding. A pattern has been established that the vibration level under skid conditions in three coordinates X, Y, Z has sharp bursts of activity. During the MGU operation in the traction mode, it was found that a sharp increase in the amplitude of harmonics with frequencies that are multiples of the gear frequency is associated with the coincidence with the natural frequency of the MGU case. When switching to the coast down mode in the frequency range of about 1.5 kHz, a random vibration is recorded on the MGU body, the RMS acceleration value of which exceeds 50 $\boldsymbol{\mathrm{m}/\mathrm{s}^{2}}$ , which is comparable to the acceleration value when passing the skid.
In 2019, Covid-19 pandemic appeared and affected the health of humanity. The virus can spread between people in various ways, but mostly from infected liquid particles. A fundamental method of defense is the use of a face mask in public, however, the efficiency of wearing a mask can be influenced by a number of factors. Most of the masks have a classification based on its filtration efficiency. There are three categories, the FFP1, FFP2 and FFP3, where FFP means „filtering facepiece”. All the 3 types can filter particles down to the size of 0.6 micrometer, but the FFP1's efficiency is 80%, the FFP2's 94%, while the FFP3's reaches 99%. In the USA they use the same categories, but call it KN80, KN95 and KN100. The problem is that the commonly used textile masks do not have a classification, which means that these cannot protect the wearer from being infected. The aim of our research is to improve the filter efficiency of masks, and we have described in this paper the first phase, the construction and testing of the laboratory model. Two cases were considered, with one needle and five needle solutions. During the experiments, the electrode distance was varied. When using more needles, the nanofibers covered a larger area, but there was a greater roughness between the fibers generated. Considering that electrospinning starts after a critical electric field strength, some calculations were performed in COMSOL model.
Natural gas refers to a mixture of the hydrocarbons such as Methane, Ethane, Propane, Butane, and other substances. One of the advantages of this fuel is that it emits relatively low amounts of pollutants; therefore, it appears to be more environmentally friendly than coal or oil. Large amounts of natural gas can be transported via pipelines (as pressurized gas) or alternatively in the liquid phase by tankers (as liquefied natural gas or LNG). A liquefaction of natural gas, which produces LNG at around $-162\ ^{\circ}\mathrm{C}$ from ambient temperature, requires a lot of energy. The LNG needs to be regasified and warmed up to ambient temperature to utilize this fuel. During vaporization, some of the energy used for liquefaction can be restored. One of the ways to do that is the application of a direct expander, where part of this “cold energy” can be recovered (to produce the electricity) from this LNG during regasification. Since the composition of the LNG in selected countries (e.g., Algeria, Australia, Malaysia, Nigeria, Oman, Qatar, Trinidad and Tobago) is different, the gasification process and the energy recovery will differ as well. This work presents a comparative analysis of energy recovery from LNG by direct expander with different gas compositions. Comparing the recoverable energies from the typical LNGs used in the listed countries, the most energy can be recovered from the LNG produced in Trinidad and Tobago (which consists of 96.9% Methane, 2.7% Ethane, 0.3% Propane, and 0.1% Butane).
Active rectifiers are commonly used converters in interfacing AC and DC grids due to their bidirectional power flow capabilities. Nowadays the development workflow of power converters includes real-time simulation steps to validate control concepts with hardware implementation in a safe environment. The paper presents the development process of a real-time HIL simulation framework for rapid-prototyping of advanced control algorithms of an Active-Front-End (AFE) rectifier. The control concepts and the main circuit models are realized in Matlab/Simulink and fitted for code-generation.
Recently, several new challenges have emerged in the electricity system that needs to be addressed appropriately by system operators. The flexible, resilient operation of the grid requires knowledge of the real-time relationships of power line conductors. This paper aims to present the thermal behavior of high voltage conductors based on international project experience. Given that the results of special sensors with different thermal monitoring approaches are available, the conductor's radial and longitudinal temperature variation and magnitude can be presented. The thermal state of the conductor can be traced not only by measurement but also by calculations of physical models. In this paper, the measurement results of the two sensors are compared with the estimates of a physical model. In the light of the results, guidelines can be formulated that will result in more reliable and accurate thermal modeling and transfer capacity calculations.
Dynamic line rating (DLR) is a state-of-the-art technology for flexible transmission capacity allocation of overhead lines both in the main distribution and transmission systems. Based on a systematic implementation, DLR technology is not only used to uprate power lines, but also effectively can be applied against the risk posed by the extreme environmental conditions, such as thermal overload of the phase conductors or ice formation. Therefore, the practical usability of this methodology is widely researched, moreover several pilot projects had been implemented for that purpose, too. The international line rating calculation models are based on the thermal equilibrium of the phase conductors. Contrarily, a new calculation method is proposed in this article, which is based on the thermal monitoring of the phase conductors instead of the measurement of the environmental factors. The practical applicability, the advantages and limitations of the model are also discussed in this paper.
Transactive Energy Systems (TES) represent a new approach to achieve an optimal utilisation of distributed energy resources (DER) as well as realising a better integration of prosumers. As transactive participants, producers, consumers and prosumers take part in achieving a dynamic and efficient grid operation based on economic and control mechanisms. A key challenge of realising TES is to enable a decentralised structure. With the gaining popularity of Distributed Ledger Technologies (DLT) and especially Blockchain in the year 2017, this trend has also gained traction in the field of TES to build a decentralised system. However, even before the aforementioned DLT approaches from 2017 onwards, there have been functioning TES implementations that are not based on DLT. It is also important to note that with all the advantages that the use of DLT brings, there are also new challenges linked with. The objective of this paper is to analyse, whether the use of DLT for TES is scientifically plausible or can be identified as a temporal hype. At first, the foundations of TES as well as the basic principles of using DLT for TES are being presented. Furthermore, different implementations of TES with and without the use of DLT are being shown. On this basis a comparative analysis of regular TES as well as TES based on DLT is executed. Within this framework an assessment of the effectiveness of using DLT for TES is formed.
The establishment of a dynamic line rating (DLR) system by using smart grid technologies with advanced meteorological and line monitoring sensors makes the electric power system more flexible. By developing a DLR-based system, it can lead to many benefits, including transmission capacity growth and an increased security of supply at consumers side, while the reliability of the network also can be enhanced. Accordingly, there is an opportunity not only constantly monitoring the transmission lines' load but also the thermal state of the conductors, on which based different types of degradation can be detected, even prevented. To get a more comprehensive picture of a power line, the aging of such parts like fittings, jumpers and conductors can be considered through monitoring the weather parameters, line loading and thermal state of the line elements. In addition, the sag of the overhead line spans is one of the most important factors in connection with the available transmission capacity. Thus, a case study was conducted in which the permanent degradation of the conductors was examined based on sag monitoring. This study summarizes the aging models of power line elements, which practical application is shown via a case study.
This paper discusses control solutions for the heating needs of a multifunctional office and residential building. The building is heated by district heating and heat pumps, whose different bivalent plants are analysed. To determine these bivalent operating states, optimisation calculations were performed in terms of primary energy consumption, operating costs and CO2 emissions. In summary we can conclude the optimal operating mechanism.
The technology of additive manufacturing (AM) offers great opportunities, such as complex geometries and shapes of desired products. In contrast to other conventional methods, specifically subtractive and formative, where the material is subtracted or filled into a form, the principle of AM is material addition. The material is added in thin layers, one on top of the other, and then sintered, usually using a laser or an electron beam. The process is then continuously repeated until the product is finished. The presented paper discusses AM methods that use metal materials and it describes the application of these methods in the nuclear power industry. The most common technologies are powder bed fusion (PBF) and direct energy deposition (DED). This contribution also discusses the materials AISI 316L and 08CH18N10T, as they are widely used in the nuclear industry and are part of future experiments.
