The present study is devoted to the modeling, design, and experimental study of a heat pipe heat exchanger utilized as a recuperator in small air conditioning systems (airflow ≈ 300−500 m3/h), comprised of individually finned heat pipes. A thermal heat pipe heat exchanger model was developed, based on available correlations. Based on the previous experimental works of authors, refrigerant R404A was recognized as the best working fluid with a 20% heat pipe filling ratio. An engineering analysis of parametric calculations performed with the aid of the computational model concluded 20 rows of finned heat pipes in the staggered arrangement as a guarantee of stable heat exchanger effectiveness ≈ 60%. The optimization of the overall cost function by the “brute-force” method has backed up the choice of the best heat exchanger parameters. The 0.05 m traversal (finned pipes in contact with each other) and 0.062 m longitudinal distance were optimized to maximize effectiveness (up to 66%) and min... [more]

The article describes a compression-ignition engine working with a dual-fuel system installed in diesel locomotive TEP70 BS. The model of the locomotive engine has been created applying AVL BOOST and Diesel RK software and engine performance simulations. Combustion characteristics have been identified employing the mixtures of different fuels. The paper compares ecological (CO2, NOx, PM) and energy (in-cylinder pressure, temperature and the rate of heat release (ROHR)) indicators of a diesel and fuel mixtures-driven locomotive. The performed simulation has shown that different fuel proportions increased methane content and decreased diesel content in the fuel mixture, as well as causing higher in-cylinder pressure and ROHR; however, in-cylinder temperature dropped. CO2, NOx and PM emissions decrease in all cases thus raising methane and reducing diesel content in the fuel mixture.

In microgrid projects, social ownership involves aspects beyond their operation that may compromise the sustainability of the system. For this reason, the development of analysis methods to assess the feasibility and impact during the design stages of these solutions is of growing interest. Recent studies have proposed methods that allow an individual analysis of technological components and social behaviors. However, a complete evaluation of the performance and the impact of these projects should allow the simultaneous evaluation of the behavior of these subsystems, allowing the analysis of their interactions and effects in a dynamic way. Accordingly, this paper presents simulation and emulation models to evaluate the impact of a microgrid in isolated communities. These models contemplate sublevels that consider the energetic, automation and computational aspects in the microgrids and a multi-agent system (MAS) that is used to study the environmental and economic impact of the microgr... [more]

When looking for energy-saving solutions, one should bear in mind the savings that can be obtained through behavioral changes. The article shows that a simple incentive can have a statistically significant impact on employees’ pro-ecological behavior. First, the introduction refers to the general perspective of striving for a global implementation of the Sustainable Developments Goals (SDGs). Additionally, the stakeholders’ point of view is presented, based on reports submitted to the Responsible Business Forum competition (Poland). The two motivating trends are referenced, which include increasing the contribution of powering office buildings to the overall energy demand and increasing the appreciation of behavioral changes as alternatives or complements to technological solutions in pursuit of the SDGs. The following sections of the article present an experiment carried out at one faculty of the University of Warsaw, which consisted of checking the effect of the incentive to lower th... [more]

Geological sequestration of acid gases, including CO2, is now a growing solution to prevent progressive Earth climate change. Disposal of environmentally harmful greenhouse gases must be performed safely and securely to minimise leakage risk and possible uncontrolled emissions of injected gases outside the sequestration structure. The paper describes a series of research activities at the Borzęcin sequestration site located in western Poland, which were designed to study the migration paths of injected acid gases (mainly mixture of CO2 and H2S) into the water-bearing layers underlying natural gas reservoir. Along with understanding the nature and dynamics of acid gases migration within the sequestration structure, the research was also addressed to assess its leak-tightness and the long-term safety of the entire reinjection facility. As a part of the research works, two downhole sampling campaigns were completed in 2018−2019, where samples of water underlying the Borzęcin reservoir wer... [more]

New grid-connected systems have imposed additional requirements regarding reliability, power quality, high levels of power processing capacity, and fault support, where power converters have a crucial role in fulfilling these requirements. Overcoming one of these challenges, this paper proposes a new alternative application to improve the low-voltage ride-through (LVRT) support based on the arm impedance employment of the modular multilevel converter (MMC) by attenuating the fault impacts, avoiding overcurrents and overvoltages. This proposal does not require additional hardware or control loops for LVRT support, only using PI controllers. This paper evaluates symmetrical and asymmetrical grid fault impacts on the converter DC side of four converter topologies: two-level voltage source converter topology (2L-VSC), neutral point clamped (NPC), MMC, and 2L-VSC equipped with a DC-chopper, employing the same control structure for the four topologies, highlighting that the MMC contributed b... [more]

Increasing the efficiency of the solar energy harvesting system is an urgent need in light of the climate changes we live in nowadays. The most significant data to be processed in the photovoltaic harvesters are the curve of solar radiation intensity to achieve the maximum benefits of the solar incident light. This processing contains complicated procedures, and the used algorithms are also high computational power-consuming which makes using special software and high potential hardware essential requirements. An explanation of the Minimum Energy Effect method is presented in this article. Our proposed algorithm uses this method to provide a simple and high-accuracy mathematical tool for generating a simple alternative curve instead of the complicated original nonlinear curve of solar radiation intensity. The produced curve is suitable for further operations, such as derivatives, integrals, or even simple addition/subtraction. Our algorithm provides a gradual procedure to find an optim... [more]

The cooling structure of a battery pack and coupled liquid cooling and phase change material (PCM) were designed in a thermal management system to enhance the cooling performance and extend the service life of lithium-ion battery packs. Numerical simulations were conducted based on the finite volume method. This study focuses on factors such as the layout of the terminal, flow rate of the coolant, different sections of the cooling pipe, position of the cooling pipe, and coupled liquid cooling, and investigates their influences on the operating temperature. The results show that a reasonable terminal layout can reduce heat generation inside the batteries. The appropriate flow rate and position of the cooling pipe effectively reduced the maximum temperature and minimized energy consumption. Then, the PCM was placed between the adjacent batteries near the outlet to enhance the uniformity of the battery pack. The temperature difference was reduced to near 5 K. This study provides a clear d... [more]

A voltage-parameter map (VP-Map) is proposed for predicting the performance of electric vehicles (EVs) and hybrid EVs (HEVs), which varies with respect to the parameters in a variable load and flux-weakening range, and determining the design parameters. Through this, the maximum torque that can be generated at the maximum speed, the input current for generation of the rated torque, and whether the vehicle is operable with a light load are predicted, and the design parameters suitable for the 120-kW class interior permanent-magnet (PM) synchronous motor for HEVs, which is the target electric motor of this study, are determined. A flux-concentrating PM synchronous motor (FCPMSM) is proposed that can be designed using the desired design parameters depending on the degree of the flux concentration. The validity of the VP-Map was verified by analyzing the characteristics of three types of FCPMSMs with different parameter combinations, and a PM synchronous motor for an EV having a high outpu... [more]

The power density of traction drives can be increased with advanced cooling systems or reduced losses. In induction machines with housing and shaft cooling, the produced heat in the stator and rotor winding system needs to be extracted over the rotor and stator lamination. The influence of soft magnetic material parameters, such as texture, thickness or alloy components on the magnetization and loss behavior, are well studied. Studies about influencing factors on the thermal conductivity are hard to find. Within this study, eight different soft magnetic materials are analyzed. An analytical approach is introduced to calculate the thermal conductivity. Temperature-dependent measurements of the electric resistivity are performed to obtain sufficient data for the analytical approach. An experimental approach is performed. The thermal diffusivity, density, and specific heat capacity are determined. An accuracy study of all measurements is performed. The analytical and the experimental appr... [more]

At present, magnetically coupled resonance wireless power transfer (MCRWPT) is the main technology used in electric vehicle wireless power transfer (WPT) due to its advantages of high transmission power and high efficiency. The resonant compensation circuit of the system generally adopts the double LCC (DLCC) structure, which has many capacitor and inductor components. Therefore, it is necessary to optimize the circuit parameters to improve the transmission performance of the system. In this study, the DLCC compensation circuit was modeled and analyzed to lay the foundation for parameter optimization. Secondly, the size parameters of the energy transmitting and receiving coil were determined, and the influence of the change of the primary and secondary compensation inductance on the circuit element stress and output performance was analyzed to determine the optimal compensation inductance value. Thirdly, the realization condition of zero voltage switching (ZVS) was analyzed, the relati... [more]

Distribution networks are currently subject to a huge revolution in terms of assets being installed. In particular, the massive spread of renewable energy sources has drastically changed the way of approaching the grid. For example, renewables affected (i) the production of the legacy power plants, (ii) the quality of the supplied energy, decreasing it, (iii) the fault detection and location, etc. To mitigate the significant drawbacks of the renewables’ presence, several intelligent electronic devices have been (and are being) developed and installed among the grid. The aim is to increase grid monitoring and knowledge of its status. However, considering the significant number of nodes of the distribution network, compared to the transmission one, the process of installing new equipment is not effortless and is also quite expensive. This work aims at emphasizing a new concept of distributed monitoring systems, based on the phasor measurement unit’s current measurements, and a controllin... [more]

To increase the efficiency of a natural gas engine, the use of a Miller camshaft was analysed. To avoid a decline in the low-end torque and also in the transient response, a pressure wave supercharger (Comprex™) was compared to the conventional single-stage turbocharger. The analyses for this conceptual comparison were performed experimentally, and the data were then used to run simulations of driving cycles for light commercial vehicles. A torque increase of 49% resulted at 1250 rpm when the Comprex™ was used in combination with a Miller camshaft. Despite the Miller camshaft, the Comprex™ transient response was still faster than the turbocharged engine. Using the same camshaft, the turbocharged engine took 2.5-times as long to reach the same torque. Water injection was used to increase the peak power output while respecting the temperature limitations. As the Comprex™ enables engine braking by design, we show that the use of friction brakes was reduced by two-thirds. Finally, a six-ti... [more]

Microgrids are defined as an interconnection of several renewable energy sources in order to provide the load power demand at any time. Due to the intermittence of renewable energy sources, storage systems are necessary, and they are generally used as a backup system. Indeed, to manage the power flows along the entire microgrid, an energy management strategy (EMS) is necessary. This paper describes a microgrid energy management system, which is composed of solar panels and wind turbines as renewable sources, Li-ion batteries, electrical grids as backup sources, and AC/DC loads. The proposed EMS is based on the maximum extraction of energy from the renewable sources, by making them operate under Maximum Power Point Tracking (MPPT) mode; both of those MPPT algorithms are implemented with a multi-agent system (MAS). In addition, management of the stored energy is performed through the optimal control of battery charging and discharging using artificial neural network controllers (ANNCs).... [more]

Solar energy is going to be a major component of global energy generation. Loss due to dust deposition has raised a great concern to the investors in this field. Pre-estimation of this reduced generation and hence the economic loss will help the operators’ readiness for efficient and enhanced economic energy management of the system. In an earlier article, a physics−based model is proposed for assessment of dust accumulation under various climatic conditions which is validated by data of a single location. In this paper, the universality of this model is established and is used to demonstrate the effect of generation loss due to dust deposition and of cleaning. Variation in the soiling pattern due to climatic covariates has also been studied. Generation loss is calculated for Solar Photovoltaic power plants of different capacities at various locations in India. Finally this model has also been extended to predict the generation accounting for the soiling loss in Photovoltaic system. Al... [more]

It is well known that in a turbulent world (full of processed information), information has a particularly high value. Wide access to technology makes the data transformation and transmission processes faster and more vulnerable to leaks and unauthorized access. This publication discusses the concept of information security management based on a development of a machine called documentomat. It is the machine built to automatically release documents with regard to high security standards. The entire flow of the documents in the company has been presented and the formalized process of decision-making to develop and finally build above-mentioned machine was described. The problems and doubts raised during the machine building process were presented along with the solutions adopted. The device has been designed, constructed, and programmed within the resources of one micro-sized limited liability company in Europe. Thus, it is the solution working in a real world that may find application... [more]

With the advent of a new Precision Time Protocol specification, new opportunities abound for clock synchronization possibilities within power grid control systems. The third iteration of the Institute of Electrical and Electronics Engineers Standard 1588 specification provides several new features specifically aimed at complex, wide-area deployments in which situational awareness and control require precise time agreement. This paper describes the challenges faced by existing technology, introduces the new time distribution specification, and provides examples to explain how it represents a game-changing innovation.

Considering the problems of the low energy recovery efficiency and the short driving range of pure electric vehicles, a new electromechanical−hydraulic coupled power electric vehicle is proposed. First, we develop an electromechanical−hydraulic coupled power electric vehicle model and design an energy management strategy to match it. On this basis, an optimization strategy is proposed with the goal of improving the braking energy recovery efficiency and avoiding the impact of high-speed braking energy recovery on the hydraulic system. The energy recovery mode conversion is optimized for different vehicle speeds when braking. Finally, the proposed optimization strategy is verified by joint simulation. The results show that when the vehicle speed is higher than 10 m/s for energy recovery mode switching, the total recovery efficiency of the whole vehicle increases to 97.273% and the SOC of the power battery increases by 0.14%. This provides strong support for improving the driving range o... [more]

Buried and operating district heating (DH) pipes are exposed to thermal degradation of their polyurethane (PUR) insulation over time, and their status is hard to assess without excavation. By using DH pipe valves in manholes as measurement points during a shutdown with an ensuing cooling period, non-destructive assessments can be performed. This study compares new improved field measurements with numerical simulations of the temperature decline in drainage valves and shutdown valves. The drainage valve measurements were used to thermally assess part of a buried DH network. Results indicate that by using the drainage valves as measurement points in a cooling method, the thermal conductivity of the buried DH network could be predicted with an accuracy of >95%. In addition, a general diagnostic protocol has been established for assessing the thermal status of a DH network, ready for network owners to use.

Due to the tendency for excessive moisture adsorption by raw, unprocessed biomass, various methods of biomass valorization are in use, allowing for the improvement of physical−chemical biomass properties, including hydrophobicity. One of the methods is torrefaction, which changes the hydrophilic properties of the biomass to hydrophobic. Therefore, in this study, the influence of the torrefaction temperature and the exposure time to moisture adsorption conditions on the hydrophobic properties of waste biomass from the agri-food industry (lemon peel, mandarin peel, grapefruit peel, and butternut-squash peel) were analyzed. The torrefaction was carried out at the following temperatures: 200, 220, 240, 260, 280, 300, and 320 °C. The hydrophobic properties were determined by using the EMC (Equilibrium Moisture Content) method, conducting an experiment in the climatic chamber at atmospheric pressure, a temperature of 25 °C, and relative humidity of 80%. The total residence time of the materi... [more]

The oxyfuel combustion of a model MSW (municipal solid waste) under various conditions was carried out in a lab-scale reactor. The aim was to study the behavior of MSW and identify challenges and opportunities associated with the development of this technology in the context of integration with CCS (carbon capture and storage). The experimental results show the effects of the oxidizer composition on the combustion process. Complete combustion can be attained under a variety of oxyfuel conditions, and the differences highlighted with O2/CO2 as an oxidizer compared with O2/N2 do not constitute showstoppers. MSW oxyfuel combustion hence offers a great potential for the combined (1) treatment of waste (contaminants’ destruction, volume, and weight reduction), (2) production of heat/power, and (3) CCS with negative CO2 emissions.

National economic development largely depends on the development of the energy sector. Its condition is most commonly assessed based on the situation over the last year. An alternative approach, however, is to evaluate fluctuations in development that have occurred over a longer period. In this paper, both methodologies have been applied, in order to assess, based on the results, which of them is more accurate. The article hypothesizes that the second method is more accurate. To prove this empirically, values representing the energy development in various sectors (industrial, agricultural, transport, service and the other (miscellaneous) sectors) in various European countries over the 2009−2018 period were estimated. The development fluctuations that occurred during the period under consideration were evaluated according to two parameters—intensity and stability. The first parameter was taken to be the difference between the values representing energy development in a given sectors at... [more]

Photovoltaic energy generation potential can be tapped with maximum efficacy by characterizing the source behaviour. Characterization refers to the systematic terminal measurement-based PV modeling which can further facilitate output prediction and fault detection. Most of the existing PV characterization methods fail for high-power PV array due to increased thermal losses in electronic components. Here, we propose a switched-mode power converter-based PV characterization setup which is designed with input filter to limit switching ripple entering into PV array under test, thereby enhancing system life and efficiency. The high resonant frequency input filter ensures its compactness with high-speed characterization capability. To further enhance the system performance, a closed-loop current control of the system is designed for high bandwidth and stable phase margins. Variation of the controller parameters under varying ambient conditions of 200−1000 W/m2 irradiation and 25−70 °C temper... [more]

Large scale testing of newly developed Li-ion cells is associated with high costs for the interested parties, and ideally, testing time should be kept to a minimum. In this work, an ageing model was developed and trained with real data from a large-scale testing experiment in order to answer how much testing time and data would have been really needed to achieve similar model generalisation performance on previously unseen data. A linear regression model was used, and the feature engineering, extraction and selection steps are shown herein, alongside accurate prediction results for the majority of the accelerated ageing experiments. Information analysis was performed to achieve the desired data reduction, obtaining similar model properties with a fifth of the number of cells and half of the testing time. The proposed ageing model uses features commonly found in the literature, and the structure is simple enough for the training to be performed online in an EV. It has good generalisatio... [more]

This work aims to improve the stability of a system that consists of one generator using a dual-input stabilizer of a power system. For this purpose, a new design method based on a chaotic JAYA algorithm is proposed. This algorithm hybridizes the original JAYA algorithm with chaos to improve its exploration and exploitation capabilities. Indeed, the disordered numbers generated by the chaotic map are exploited to control the standard JAYA algorithm’s search equations. The issue of design is stated as an optimization problem. The proposed technique is involved in the selection of optimal values of the dual-input power system stabilizer (PSS) parameters. The efficiency of the proposed controller is assessed under various loading conditions and compared with the original JAYA, cuckoo search and particle swarm optimization (PSO) algorithms. The target function consists of the integration of absolute error multiplied by the time, including the speed deviation is considered for the controlle... [more]