Natural gas is one of the main energy sources in Poland and accounts for about 15% of the primary energy consumed in the country. Poland covers only 1/5 of its demand from domestic deposits. The rest is imported from Russia, Germany, Norway, the Czech Republic, Ukraine, and Central Asia. An important issue concerning the market of energy resources is the question of the direct impact of the prices of energy resources on the income of exporting and importing countries. It should also be remembered that unexpected and large fluctuations are detrimental to both exporters and importers of primary fuels. The article analyzes natural gas deposits in Poland, raw material trade and proposes a model for forecasting the volume of its consumption, which takes into account historical consumption, prices of energy resources and assumptions of Poland’s energy policy until 2040. A hybrid model was built by combining ARIMA with LSTM artificial neural networks. The validity of the constructed model was... [more]

Polymer electrolyte membrane fuel cells were analyzed to investigate changes in the structure of the flow field and operating conditions. The cell performance, which was controlled by adjusting the width of the cathodic channel, improved as the backpressure increases. With the anodic and cathodic flow channels mismatched, the maximum power densities at 3.0 bar for a narrow cathodic channel were 1115 and 1024 mW/cm2, and those for a wide cathodic channel were 959 and 868 mW/cm2, respectively. The diffusion characteristics were investigated using the non-dimensional numbers Re (Reynolds), Sc (Schmidt), and Sh (Sherwood) to confirm the improvement of mass transport. The narrower the channel or the higher the operating pressure, the larger Re was and the smaller Sc and Sh became. In particular, the wider the anodic channel, the larger the value of Sh.

Recently, the use of new and renewable energy sources to reduce carbon dioxide emissions and minimize global warming has attracted attention. Among the different renewable energy sources, solar energy is utilized for energy reduction in buildings because of its ease of use and excellent maintenance and repair. In this study, an air-based photovoltaic/thermal (PVT) system that improves solar energy utilization was developed, and its performance was experimentally compared with that of the existing photovoltaic (PV) system. The PVT system could increase the amount of generated power by decreasing the panel temperature raised by the air passing through the lower part of the panel. Moreover, it was possible to use the high-temperature air collected from the panel for heating or hot-water supply in the building. Based on the experimental results obtained for the PV and PVT panels subjected to the same weather conditions, the power generation efficiency of the PVT panel through which air was... [more]

The main purpose of this special edition of “Advances in Fluid Power Systems” was to present new scientific work in the field of fluid power systems for the hydraulic and pneumatic control of machines and devices that are used in various industries [...]

Nowadays, new challenges arise relating to the compensation of power quality problems, where the introduction of innovative solutions based on power electronics is of paramount importance. The evolution from conventional electrical power grids to smart grids requires the use of a large number of power electronics converters, indispensable for the integration of key technologies, such as renewable energies, electric mobility and energy storage systems, which adds importance to power quality issues. Addressing these topics, this paper presents an extensive review on power electronics technologies applied to power quality improvement, highlighting, and explaining the main phenomena associated with the occurrence of power quality problems in smart grids, their cause and effects for different activity sectors, and the main power electronics topologies for each technological solution. More specifically, the paper presents a review and classification of the main power quality problems and the... [more]

The increasing popularity of automated systems and the increased market share of producers of robotic feeding equipment for cows causes the need for a deeper study of energy demand in such technologies. This article provides an analysis of the inputs of energy accumulated in conventional (CFS) and automated feeding systems (AFS) for cattle. The aim of this is to determine the impact of robotic technologies for the preparation and feeding of fodder on the cumulative energy inputs. The aim of this paper is to investigate the effect of machinery and the equipment applied to the cumulative energy intensity in cattle farming facilities. The cumulative energy consumption for four technologies of automated cattle feeding (AFS) was tested and compared to the energy consumption for six technologies with a conventional feeding system (CFS). The research involved nine cow barn facilities for dairy cows and one for beef cattle. An evaluation has been made for cattle farming structures (milk and me... [more]

Complete pump characteristics (CPCs) are the key for establishing pump boundary conditions and simulating hydraulic transients. However, they are not normally available from manufacturers, making pump station design difficult to carry out. To solve this issue, a novel method considering the inherent operating characteristics of the centrifugal pump is therefore proposed to predict the CPCs. First, depending on the Euler equations and the velocity triangles at the pump impeller, a mathematical model describing the complete characteristics of a centrifugal pump is deduced. Then, based on multiple measured CPCs, the nonlinear functional relationship between the characteristic parameters of the characteristic operating points (COPs) and the specific speed is established. Finally, by combining the mathematical model with the nonlinear relationship, the CPCs for a given specific speed are successfully predicted. A case study shows that the predicted CPCs are basically consistent with the mea... [more]

Tar remaining in the gasification cavity during underground coal gasification (UCG) is an important pollution source, while the reported studies only focus on the tar behavior at the outlet. The present work aims to compare the tar properties from the reaction zone and the outlet, analyze the tar evolution during gasification, and discuss possible measures to control tar pollution. Tar was sampled with a self-developed equipment from an ex-situ underground coal gasification experimental system and analyzed by GC-MS. The gas composition, temperature, and PM10 were also compared for the reaction zone and the outlet. Compared with the tar from reaction zone, the tar from outlet has a smaller percentage of high boiling point content, PAHs, C, O, N, S, Cl, Si, and a larger percentage of H. The PAHs percentage in tar at the outlet in this work is closer to the field data than the lab data from literature, indicating the experimental system gives a good simulation of tar behavior in undergrou... [more]

This paper presents the analysis, modeling, simulation and practical studies of resonant inverters with a voltage limitation on the resonant capacitor. The power circuits obtained in this way are characterized by the fact that the power consumption does not depend on the load changes, but is a function of the operating frequency, the value of the resonant capacitor and the supply voltage—these are the so-called inverters with energy dosing. Analytical dependences, simulations and experimental results were determined, which described the behavior of the studied power electronic devices. The obtained expressions for the inverter current in the different stages of the converter operation were the basis for the creation of the engineering methodology for their design and prototyping. Based on the derived basic ratios and characteristics, the capabilities of these devices for self-adaptation to the needs and changes of the load were demonstrated. A comparison of the characteristics of class... [more]

The aim of this study was to assess the impact of the area under rapeseed cultivation on the economic performance and organization of farms. The study was conducted in 164 rapeseed farms in different Polish voivodeships. A targeted sampling procedure was used to select farms for the study. The studied population was divided into four groups depending on area under rapeseed cultivation rates. The selected farms were located in voivodeships with the highest rapeseed acreage rates of the total cropped area. The economic performance of the examined farms improved with increases in rapeseed area. Farms with larger rapeseed areas were characterized by higher production values and better economic performance. On average, the total production value per farm was highest in the group of farms with rapeseed areas of 20.1−30 ha. Similar results were noted when total production values were expressed per ha of arable land, per full-time employee and per man-hour. Total production value was lowest in... [more]

The effective operation of photovoltaic systems depends on many factors and parameters that must be continuously monitored. The factors listed in the article are frequently variable, which makes it very difficult to predict the amount of radiation that will reach photovoltaic panels and can be converted into electricity. Therefore, to optimize the operating point of a photovoltaic power plant, it is necessary to track the changes in these quantities. IoT systems may help in controlling and managing a power plant, storage, and energy flow to the power grid. The results recorded at the hybrid power plant of the Faculty of Electrical Engineering of the Bialystok University of Technology are useful for a comprehensive analysis of the operation of the plant and ways of its optimization. It is shown that implementation of a comprehensive maintenance system may deliver extensive important information regarding the PV plant installation.

This paper presents an experimental study on a shell and tube mini heat exchanger (STMHE). The STMHE consisted of seven tubes in a triangular arrangement, with an 0.8 mm inner diameter and 1.0 mm outer diameter. The heat exchanger shell had an inner diameter of 11 mm, and the heat exchanger had no baffles. For the adopted operating conditions, the Reynolds number on the tube side varied in the range of 300−3000, and 2000−12,000 on the shell side. The aim of this study was to determine pressure drop values during fluid flow and Nusselt number correlations for the heat transfer. A new method based on optimisation was used to derive the equations for calculating the heat transfer coefficients. It allowed the determine of the correlation equations for the heat transfer coefficients simultaneously for both sides of the heat exchanger. The obtained correlations yielded overall heat transfer coefficient values that, in most cases, did not differ by more than ±10% from those determined experim... [more]

Battery Management Systems (BMSs) are used to manage the utilization of batteries and their operation in Electric and Hybrid Vehicles. It is imperative for efficient and safe operation of batteries to be able to accurately estimate the State of Charge (SoC), State of Health (SoH) and State of Power (SoP). The SoC and SoH estimation must remain robust and accurate despite aging and in presence of noise, uncertainties and sensor biases. This paper introduces a robust adaptive filter referred to as the Adaptive Smooth Variable Structure Filter with a time-varying Boundary Layer (ASVSF-VBL) for the estimation of the SoC and SoH in electrified vehicles. The internal model of the filter is a third-order equivalent circuit model (ECM) and its state vector is augmented to enable estimation of the internal resistance and current bias. It is shown that system and measurement noise covariance adaptation for the SVSF-VBL approach improves the performance in state estimation of a battery. The estim... [more]

In the present study, a nozzle was used to improve the flow performance of an intake manifold, and its effects on the automobile engine output and the exhaust gas were experimentally studied. It was found that the engine output of a vehicle with a mileage of 30,000 km increased by 4.7% and 6.5% when nozzles with diameters of 5 and 2.5 mm were used. In addition, the engine output of a vehicle with a mileage of 180,000 km increased by 3.3% and 13.3% when nozzles with diameters of 5 and 2.5 mm were used compared to those of the same vehicle when no nozzle was used. Thus, using a nozzle for the inflow of outside air created a uniform combustion environment to improve the engine output and reduce harmful exhaust gases, such as hydrocarbon, carbon monoxide, and nitrogen oxides, by generating vortexes inside the intake manifold and increasing the degree of mixing. Furthermore, the smaller nozzle with a diameter of 2.5 mm had greater effects.

Air pollution with particulate matter from transport sources is a serious problem in terms of air quality and its impact on human health. The article attempts to test the emitted particles from piston engines in terms of their physical properties and chemical composition. The research test objects were a diesel engine with Euro 5 emission class and a petrol engine, which was a part of the scooter drive system. The conducted research consisted in the analysis of the number, mass, and volume of particles, as well as chemical analysis, using the methods: Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM-EDS), and Evolved gas analysis (EGA). The diesel engine emitted particles in the range of 50−120 nm. With the increase in the engine load, the specific emission of particulate matter increased. In the case of a gasoline engine running without load, the emission of particles smaller than 30 nm was mainly observed. Increasin... [more]

At present, the penetration of wind-driven electric generators or wind power plants (WPPs) in electric power systems is getting more and more extensive. To evaluate the steady state performances of such power systems, developing a valid WPP model is therefore necessary. This paper proposes a new method in modeling the most popular type of WPP, i.e., DFIG (doubly fed induction generator)-based WPP, to be used in power system steady state load flow analysis. The proposed model is simple and derived based on the formulas that calculate turbine mechanical power and DFIG power. The main contribution of the paper is that, in contrast to the previous models where the DFIG power factor has been assumed to be constant at unity, the constant voltage model proposed in this paper allows the power factor to vary in order to keep the voltage at the desired value. Another important contribution is that the proposed model can be implemented in both sub-synchronous and super-synchronous conditions (it... [more]

Due to their weak nature, such as low inertia, offshore energy hubs are prone to unprecedented fast dynamic phenomena. This can lead to undesired instability problems. Recent literature, with main focus on onshore systems, suggests that electrolysers could be an attractive option to support wind generators in the mitigation of balancing problems. This paper presents an Electromagnetic Transient (EMT) model for real-time simulation based study of the dynamics of active power and voltage responses of offshore hubs due to wind speed fluctuations. The purpose of this study was to ascertain the ability of an electrolyser to support an offshore energy hub under different scenarios and with different locations of the electrolyser. Two locations of Proton Exchange Membrane (PEM) electrolysers were considered: centralised (at the AC common bus of the hub) or distributed (at the DC link of the wind turbines). Numerical simulations conducted in RSCAD® on a 2 GW offshore hub with 4 × 500 MW wind p... [more]

With the increase of combustion temperatures, the thermal radiation effect for hot components in the new generation of aero-engines has become a key factor in the combustion process, cooling structure design, and thermal protection. A radiation loading system can be used as an external heat source to simulate the real thermal environment of hot components in aero-engines. Total receiving power, as well as 3-D heat flux distribution, should better coincide with real conditions. With the aid of freeform optics and the feedback optimization method, the current study develops a concentrating-type radiation heating system fit for the leading-edge surface of a C3X turbine vane. A xenon lamp combined with a freeform reflector was optimized for controllable heat flux. A design method in the area of illumination engineering was innovatively extended for the current model. Considering the effect of polar angular radiative flux distribution of a xenon lamp, a Monte Carlo ray tracing (MCRT) method... [more]

Electrical faults can lead to transient and dynamic excitations of the electromagnetic generator torque in wind turbines. The fast changes in the generator torque lead to load oscillations and rapid changes in the speed of rotation. The combination of dynamic load reversals and changing rotational speeds can be detrimental to gearbox components. This paper shows, via simulation, that the smearing risk increases due to the electrical faults for cylindrical roller bearings on the high speed shaft of a wind turbine research nacelle. A grid fault was examined for the research nacelle with a doubly fed induction generator concept. Furthermore, a converter fault was analyzed for the full size converter concept. Both wind turbine grid connection concepts used the same mechanical drive train. Thus, the mechanical component loading was comparable. During the grid fault, the risk of smearing increased momentarily by a maximum of around 1.8 times. During the converter fault, the risk of smearing... [more]

The sulfur-iodine (SI) cycle holds great promise as an alternative large-scale process for converting water into hydrogen without CO2 emissions. A major issue regarding the long-term stability and activity of the catalysts is their poor sulfur deactivation resistance in the HI feeding process. In this work, the effect of Ru addition for enhancing the activity and sulfur resistance of SiO2-supported Ni catalysts in the HI decomposition reaction has been investigated. The presence of H2SO4 molecules in the HI results in severe sulfur deactivation of the Ru-free Ni/SiO2 catalysts by blocking the active sites. However, Ni−Ru/SiO2 catalysts show higher catalytic activity without sulfur-poisoning by 25% and exhibit more superior catalytic performance than the Ru-free catalyst. The addition of Ru to the Ni/SiO2 catalyst promotes the stability and activity of the catalysts. The experimental trends in activity and sulfur tolerance are consistent with the theoretical modeling, with the catalytic... [more]

Heat transfer systems for chemical processes must be designed to be as efficient as possible. As heat transfer is such an energy-intensive stage in many chemical processes, failing to focus on efficiency can push up costs unnecessarily. Many problems involving heat transfer in the presence of a chemically reactive species in the domain of the physical sciences are still unsolved because of their complex mathematical formulations. The same is the case for heat transfer in chemically reactive magnetized Tangent hyperbolic liquids equipped above the permeable domain. Therefore, in this work, a classical remedy for such types of problems is offered by performing Lie symmetry analysis. In particular, non-Newtonian Tangent hyperbolic fluid is considered in three different physical frames, namely, (i) chemically reactive and non-reactive fluids, (ii) magnetized and non-magnetized fluids, and (iii) porous and non-porous media. Heat generation, heat absorption, velocity, and temperature slips a... [more]

With diminishing fossil fuel resources and increasing environmental concerns, large-scale deployment of Renewable Energy Sources (RES) has accelerated the transition towards clean energy systems, leading to significant RES generation share in power systems worldwide. Among different RES, solar PV is receiving major focus as it is most abundant in nature compared to others, complimented by falling prices of PV technology. However, variable, intermittent and non-synchronous nature of PV power generation technology introduces several technical challenges, ranging from short-term issues, such as low inertia, frequency stability, voltage stability and small signal stability, to long-term issues, such as unit commitment and scheduling issues. Therefore, such technical issues often limit the amount of non-synchronous instantaneous power that can be securely accommodated by a grid. In this backdrop, this research work proposes a tool to estimate maximum PV penetration level that a given power... [more]

This study aims to design and optimize an organic Rankine cycle (ORC) and radial inflow turbine to recover waste heat from a polymer exchange membrane (PEM) fuel cell. ORCs can take advantage of low-quality waste heat sources. Developments in this area have seen previously unusable, small waste heat sources become available for exploitation. Hydrogen PEM fuel cells operate at low temperatures (70 °C) and are in used in a range of applications, for example, as a balancing or backup power source in renewable hydrogen plants. The efficiency of an ORC is significantly affected by the source temperature and the efficiency of the expander. In this case, a radial inflow turbine was selected due to the high efficiency in ORCs with high density fluids. Small scale radial inflow turbines are of particular interest for improving the efficiency of small-scale low temperature cycles. Turbines generally have higher efficiency than positive displacement expanders, which are typically used. In this st... [more]

Energy storage will be required over a wide range of discharge durations in future zero-emission grids, from milliseconds to months. No single technology is well suited for the complete range. Using 9 years of UK data, this paper explores how to combine different energy storage technologies to minimize the total cost of electricity (TCoE) in a 100% renewable-based grid. Hydrogen, compressed air energy storage (CAES) and Li-ion batteries are considered short-, medium-, and long-duration energy stores, respectively. This paper analyzes different system configurations to find the one leading to the lowest overall cost. Results suggest that the UK will need a storage capacity of ~66.6 TWh to decarbonize its grid. This figure considers a mix of 85% wind + 15% solar-photovoltaics, and 15% over-generation. The optimum distribution of the storage capacity is: 55.3 TWh in hydrogen, 11.1 TWh in CAES and 168 GWh in Li-ion batteries. More than 60% of all energy emerging from storage comes from med... [more]

Thermal power plants (TPPs) with back-pressure steam turbines (BPSTs) were widely used for electricity and steam production in the Union of Soviet Socialist Republics (USSR) due to their high efficiency. The collapse of the USSR in 1991 led to a decrease in industrial production, as a result of which, steam production in Russia was reduced and BPSTs were left without load. To resume the operation of TPPs with BPSTs, it is necessary to modernize the existing power units. This paper presents the results of the thermodynamic analysis of different methods of modernization of TPPs with BPSTs: the superstructure of the steam low-pressure turbine (LPT) and the superstructure of the power unit operating on low-boiling-point fluid. The influence of ambient temperature on the developed cycles’ efficiency was evaluated. It was found that the usage of low-boiling-point fluid is thermodynamically efficient for an ambient temperature lower than 7 °C. Moreover, recommendations for the choice of recon... [more]