For conventional power plants, the integration of thermal energy storage opens up a promising opportunity to meet future technical requirements in terms of flexibility while at the same time improving cost-effectiveness. In the FLEXI- TES joint project, the flexibilization of coal-fired steam power plants by integrating thermal energy storage (TES) into the power plant process is being investigated. In the concept phase at the beginning of the research project, various storage integration concepts were developed and evaluated. Finally, three lead concepts with different storage technologies and integration points in the power plant were identified. By means of stationary system simulations, the changes of net power output during charging and discharging as well as different storage efficiencies were calculated. Depending on the concept and the operating strategy, a reduction of the minimum load by up to 4% of the net capacity during charging and a load increase by up to 5% of the net c... [more]

Latent heat storage has higher energy density, but most phase change materials (PCMs) have low thermal conductivity. Current research focuses on conduction dominated heat transfer mechanism to increase the heat transfer performance. However, convection also has important effects on promoting PCM melting and solidification processes. Therefore, an active stirring method with conduction dominated heat transfer mechanism was studied. A shell storage with stirrer inside was constructed and tested. Paraffin was selected as the PCM; the heat transfer fluid (HTF) was water. The results show that average charging rate increased by 32.23 J/s than that without stirring, and the average discharging rate increased by 47.39 J/s. Completion time for charging/discharging with stirring was shortened by 9.61% and 48.61% than that without stirring. In the charging process, the average power of motor was 16.08 W, and the average discharging rate was greater than 500 J/s, accounting for less than 3.2%. In... [more]

Pinecones, a common biomass waste, has an interesting composition in terms of cellulose and lignine content that makes them excellent precursors in various activated carbon production processes. The synthesized, nanostructured, activated carbon materials show textural properties, a high specific surface area, and a large volume of micropores, which are all features that make them suitable for various applications ranging from the purification of water to energy storage. Amongst them, a very interesting application is hydrogen storage. For this purpose, activated carbon from pinecones were prepared using chemical activation with different KOH/precursor ratios, and their hydrogen adsorption capacity was evaluated at liquid nitrogen temperatures (77 K) at pressures of up to 80 bar using a Sievert’s type volumetric apparatus. Regarding the comprehensive characterization of the samples’ textural properties, the measurement of the surface area was carried out using the Brunauer−Emmett−Teller... [more]

Elliptical diesel nozzles affect the fuel−air mixing process, and thus combustion and exhaust emissions. Experiments were conducted to study biodiesel spray liquid-phase behaviors for elliptical and circular nozzles through the Mie-scattering method under evaporative conditions. Based on the measurements, the results show that the elliptical nozzle spray liquid-phase penetration is smaller than the circular one under steady-state conditions. The deformation and the axis-switching behaviors of the elliptical jet are helpful in accelerating the breakup of the liquid core. Moreover, the injection pressure has little impact on the penetration of the liquid-phase spray for either geometrical orifice. Additionally, increasing the ambient temperature can reduce the penetration of liquid-phase spray, because an increase in temperature increases the rate of evaporation. The differences in steady liquid-phase penetration between circular and elliptical sprays decrease as the ambient temperature... [more]

Using renewable H2 for CO2 hydrogenation to methane not only achieves CO2 utilization, but also mitigates the greenhouse effect. In this work, several Ni-based catalysts with V species using 3D-mesoporous KIT-6 (Korea Advanced Institute of Science and Technology, KIT) as support were prepared at different contents of NiO and V2O5. Small Ni nanoparticles with high dispersibility on 20Ni-0.5V/KIT-6 were identified by X-ray diffraction (XRD), TEM and hydrogen temperature-programmed desorption (H2-TPD) analysis, which promoted the production of more Ni active sites for enhancing catalytic activity for CO2 methanation. Moreover, TEM and hydrogen temperature-programmed reduction (H2-TPR) characterizations confirmed that a proper amount of Ni and V species was favorable to preserve the 3D-mesoporous structure and strengthen the interaction between active Ni and KIT-6. The synergistic effect between Ni and V could strengthen surface basicity to elevate the ability of CO2 activity on the 20Ni-0... [more]

The paper presents technical solutions for a power grid that undergoes the elimination of a significant number of coal-based power generating units. The purpose of the solutions is to adapt the existing machines with sufficient lifespans to the new operating conditions. In particular these include steam turbines. The steam turbines’ cycles may be extended with energy storage systems based on a molten salt. This allows to increase the flexibility of the power generating units while maintaining the largest possible efficiency of the power generation. The solutions presented here allow to connect the steam turbines cycles to renewable energy sources and reduce the overall number of the units that create the fundamental layer of the power grid. The analysis of the solutions involves numerical modeling. The paper describes the assumptions and the results of the modeling for chosen cases of the modernization. The researched considered a number of options that differed in the investment costs... [more]

Variable speed generators can improve overall genset performance by allowing the diesel engine to reduce its speed at lower loads. In this project, a variable speed diesel generator (VSDG) uses a rotating stator driven by a compensator motor. At lower loads, the stator turns in the opposite direction of the rotor, a process that can be used for purposes like maintaining a fixed relative speed between the two components of a generator. This allows the diesel engine to turn at a lower speed (same as the rotor) and to increase its efficiency. The present research addresses the control of the compensator motor driving the generator’s stator using a variable-frequency drive that adapts the speed to its optimal value according to the load. The performance of the proposed control strategy was tested using a Freescale microcontroller card programmed in C-code to determine the appropriate voltage for the variable-frequency drive. The control algorithm uses a real-time application implemented on... [more]

Lithium ion (Li-Ion) and lithium polymer (Li-Po) batteries need to be used within certain voltage/current limits. Failure to observe these limits may result in damage to the battery. In this work, we propose a low voltage battery management system (LV-BMS) that balances the processes of the battery cells in the battery pack and the activating-deactivating of cells by guaranteeing that the operation is within these limits. The system operates autonomously and provides energy from the internal battery. It has a modular structure and the software is designed to control the charging and discharging of eight battery cells at most. A STM32F103 microcontroller is used for system control. The fuzzy logic controller (FLC) is used to set the discharge voltage limit to prevent damage to the battery cells, shorten the settlement time and create a specialized design for charge control. The proposed structure enables solar panel or power supplies with different voltage values between 5 V and 8 V to... [more]

The high energy consumption of cooling systems justifies the need for strategies to increase the efficiency of the facilities, in order to reduce the related CO2 emissions. This study aims to improve the performance and reduce the energy consumption of an 8.6 MW air cooled chiller. This installed capacity is biased due to the screw compressors, of 2.98 Energy Efficiency Ratio (EER) at full load (characteristics provided by the manufacturer). The chiller unit has been modified by placing evaporating cooling pads before the condensing coils. The chiller has been monitored for three months, recording over 544,322 measurements (5 min-step data), with and without the evaporative cooling pads, to assess the performance. Data comparison has been done by selecting two days (with and without evaporative panels) with the same health care load and temperatures. Implementing the proposed strategy yields an improvement in the European Seasonal Energy Efficiency Ratio (ESEER) from 3.69 to 4.83, whil... [more]

In recent years, most of the growth in electricity demand is covered by renewable and nuclear energy sources. However, electricity generation in fossil-fired power plants is also increasing resulting in the increase of CO2 emissions. Nuclear energy has to be considered as one of the available tools to accomplish CO2 emission reduction in electricity sector. Light water reactors (LWR) are currently the dominant nuclear technology but their intensive application in long-term period is constrained by available uranium fuel resources. Fast breeder reactors’ (FBR) technology is not used on a larger scale. Plutonium resources are limited, but do have the potential of stronger buildup if light water reactors, as the source of plutonium, are used on a larger scale. The appropriate dynamics for LWR/FBR buildup till the end of the 21st century is developed under assumptions of different LWR life times, and different uranium fuel resources available. The possible CO2 emission reduction is calcula... [more]

This paper reports the effect of high-pressure torsion (HPT) on the first hydrogenation of LaNi5. We found that, for loose powder, reduction of particle size has an effect of increasing the incubation time and decreasing the hydrogen capacity. A higher amount of HPT turns only marginally reduce the incubation time but has no effect on hydrogen capacity. In all cases, the first dehydrogenation and subsequent hydrogenation have the same kinetics, irrespective of the particle size or number of HPT turns. Therefore, for LaNi5, HPT has a beneficial effect only for the first hydrogenation.

Steam methane (CH4−H2O) reforming in the presence of a catalyst, usually nickel, is the most common technology for generating synthesis gas as a feedstock in chemical synthesis and a source of pure H2 and CO. What is essential from the perspective of further gas use is the parameter describing a ratio of equilibrium concentration of hydrogen to carbon monoxide (H/C=xH2/xCO). The parameter is determined by operating temperature and the initial ratio of steam concentration to methane SC=xH2O0/xCH40. In this paper, the author presents a thermodynamic analysis of the effect of green hydrogen addition to a fuel mixture on the steam methane reforming process of gaseous phase (CH4/H2)−H2O. The thermodynamic analysis of conversion of hydrogen-enriched methane (CH4/H2)−H2O has been performed using parametric equation formalism, allowing for determining the equilibrium composition of the process in progress. A thermodynamic condition of carbon precipitation in methane reforming (CH4/H2) with the... [more]

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of three types of propellants: a single-base propellant, a double-base propellant and a low vulnerability (LOVA) propellant, as determined via closed vessel tests (CVT). Conventional gunpowder ignition and plasma jet ignition methods were used. The influence of the ignition method on the values of the propellant characteristics obtained in CVT was analysed. It was found that the method of ignition has an influence on the values of propellant characteristics, determined in CVT. An analysis of the experimental form functions showed that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants in which the burning process deviates from the geometric burning law.

Heat cost allocators (HCAs) have a high market share in existing buildings, which may cause problems, especially with variable heat cost allocation due to wrong readings from HCAs and/or the method used in the heat cost allocation process. That is why we proposed two easily applicable and clear methods, which may be used with two types of HCAs commonly used in the billing practice. The proposed methods were presented on the example of the actual allocation of variable heating costs for a multi-family building located in Poland, and the results of billing were compared with three other methods of variable heating costs allocation. Owing to the proposed methods, higher (K = 0.5260 for schema A, K = 0.4468 for schema B) values of the correlation coefficient between heating costs and the average indoor temperature were obtained than for the methods commonly used in accounting practice. Additionally, the use of the proposed method allows for the elimination of defective indications of heat... [more]

The fracturing technique is widely used in many fields. Fracture has a greater impact on the movement of fluids in formations. Knowing information about a fracture is key to judging its effect, but detailed information about complex fracture networks is difficult to obtain. In this paper, we propose a new method to describe the shape of a complex fracture network. This method is based on microseismic results and uses the L-system to establish a method for characterizing a complex fracture network. The method also combines with decomposition to construct a new method called the multiobjective fracture network inversion algorithm based on decomposition (MOFNIAD). The coverage of microseismic monitoring results and the degree of fitting of production data are the two objective functions of the inversion fracture network. The multiobjective fracture network inversion algorithm can be optimized to obtain multiple optimal solutions that meet different target weights. Therefore, this paper es... [more]

The quantitative evaluation of cluster wind power output volatility and source-load timing matching is vital to the planning and operation of the future power system dominated by new energy. However, the existing volatility evaluation methods of cluster wind power output do not fully consider timing volatility, or are not suitable for small sample data scenarios. Meanwhile, the existing source-load timing matching evaluation indicator ignores the impact of wind power permeability on the timing matching degree between wind power output and load. Therefore, the authors propose quantitative evaluation methods of cluster wind power output volatility and source-load timing matching in regional power grid. Firstly, the volatility-based smoothing coefficient is defined to quantitatively evaluate the smoothing effect of wind-farm cluster power output. Then, the source-load timing matching coefficient considering wind power permeability is proposed to quantitatively evaluate the timing matching... [more]

Railway transit forms the backbone of sustainable transportation systems, which are necessary to limit the effects of global warming. In this paper, the authors seek to determine whether there is a statistically significant difference in energy consumption between distinct railway vehicle types. Firstly, the energy consumption measurement methods in the railway transportation sector are described and compared to each other in respect to precision and cost. Secondly, the use of energy consumption as a criterion in rolling stock tenders with the associated norm is analysed, particularly with regard to the life-cycle cost of railway vehicles. In the next part real life data on energy consumption of six distinct passenger electrical railway vehicle types is presented and analysed in order to compare the efficiency of different types of rolling stock. The differences in energy efficiency between rolling stock types may be used to improve the procurement process ensuring train operating comp... [more]

The use of biofuels for spark ignition engines is proposed to diversify fuel sources and reduce fossil fuel consumption, optimize engine performance, and reduce pollutant emissions. Additionally, when these biofuels are produced from low-grade wastes, they constitute valorisation pathways for these otherwise unprofitable wastes. In this study, ethanol and pyrolysis biogasoline made from low-grade wastes were evaluated as additives for commercial gasoline (RON95, RON98) in tests performed in a spark ignition engine. Binary fuel mixtures of ethanol + gasoline or biogasoline + gasoline with biofuel incorporation of 2% (w/w) to 10% (w/w) were evaluated and compared with ternary fuel mixtures of ethanol + biogasoline + gasoline with biofuel incorporation rates from 1% (w/w) to 5% (w/w). The fuel mix performance was assessed by determination of torque and power, fuel consumption and efficiency, and emissions (HC, CO, and NOx). An electronic control unit (ECU) was used to regulate the air−fue... [more]

In the last decades, rigorous research has been carried out with the end of understanding the gas dynamic phenomenon and although different preventive techniques have been employed, even today there are numerous accidents even with the loss of life. This work analyses an alternative and innovative method of fracturing and degassing coal, by generating CO2 with a pyrotechnic device called PYROC (Pyrotechnic Break Cartridges). Medium-scale tests of generation of CO2 into coal samples are carried out and their effect is analysed comparing the initial and final permeabilities of the coal samples once the generation of CO2 has finished. These permeabilities are calculated by injecting methane. Besides, the influence of different parameters as the length of the boreholes, the pressure of the gas or the initial permeability of the coal have been analysed with a numerical simulation of one face of one of the sublevels of a mine. The results show that the method increases the safety in mining o... [more]

Nonlinear control problems in turbofan engines are challenging. No single nonlinear controller can achieve desired control effects in a full flight envelope, but in the case of multiple controllers, there exist problems in the bumpless transfer between different controllers. To this end, this paper presents a bumpless transfer mechanism for an uncertain switched system based on integral sliding mode control (ISMC), and the mechanism can be used for the speed control of turbofan engines. The uncertain switched system is used to describe the turbofan engine dynamics. Then, the ISMC controller is derived for subsystems of the uncertain switched system. A resetting scheme is introduced for the ISMC controller to ensure the continuity of control inputs during the controller transition, as well as the bumpless transfer. In view of the transient behavior caused by controller switching, the global stability of the switched system is analyzed using the multiple Lyapunov function approach and av... [more]

The fuel qualities of several biodiesels containing highly saturated, mono, and poly unsaturated fatty acids, as well as their combustion and exhaust emission characteristics, were studied. Six biodiesel samples were divided into two groups based on their fatty acid composition, including group 1 (coconut, castor, and jatropha) and group II (palm, karanja, and waste cooking oil biodiesel). All fuels (in both groups) were tested in a single-cylinder off-road diesel engine. Castor and karanja biodiesel, both rich in mono-unsaturation level, have a high viscosity of about 14.5 and 5.04 mm2/s, respectively. The coconut and palm biodiesels are rich in saturation level with cetane numbers of 62 and 60, respectively. In both groups, highly saturated and poly-unsaturated methyl esters presented better combustion efficiency and less formation of polluted emissions than mono-unsaturation. At full load, coconut and palm biodiesel displayed 38% and 10% advanced start of combustion, respectively, w... [more]

Vertical axis turbines, which extract kinetic energy from currents, can produce electricity independently from a current’s direction. Hence, this type of turbines raises interest for harvesting energy from tidal currents, where flow changes direction during flood and ebb tides, and where currents present large variation of direction during tide. Methods for representing vertical axis turbines in tidal farms should be implemented in order to predict correctly power production with an acceptable time cost. The Actuator Cylinder (AC) is one of them. Numerical results in terms of wakes, with the study of velocity profiles, and efforts are compared to experiences, as well as showed that the method is sufficiently accurate and for a reasonable computing time, which is of prime importance for tidal turbines farms studies. The Actuator Cylinder method is implemented in ANSYS Fluent in a 2D stationary resolution. The method is then applied to a double levels of two counter-rotating rotors marin... [more]

Decarbonization is an activity aimed at reducing greenhouse gas emissions to limit climate change and global warming. Ensuring macroeconomic stabilization is the basis for ecological action. The question is whether macroeconomic stabilization helps companies, institutions and countries act for decarbonization. This article presents research on the impact of components of macroeconomic stabilization on decarbonization and energy efficiency in the largest greenhouse gas emitters in the European Union from 1990 to 2020. We focus on the following countries, France, Germany, Italy, Poland and Spain. The contribution to knowledge is using the pentagon of macroeconomic stabilization to assess macroeconomic stabilization’s impact on decarbonization and energy efficiency. According to the correlation coefficients, the Ordinary Least Squares and the Seemingly Unrelated Regression method, there is a statistically significant impact of components of macroeconomics stabilization on decarbonization... [more]

In many electrical grids, the share of renewable energy generation increases. As these generators are typically connected to the grid via inverters, the level of grid inertia decreases. Such grids may therefore suffer from high rates of change of frequency during power imbalances. Modern wind turbines can help in controlling the frequency in such grids by providing synthetic inertia. A controller to provide synthetic inertia with wind turbines was developed at the Wind Energy Technology Institute in collaboration with Suzlon Energy. For this controller the influence of providing synthetic inertia on the mechanical loads of the wind turbine is assessed for different grid frequency scenarios. Such a scenario-based load analysis has not been published before, especially as the scenarios are derived from real measurements. The effect of the loads strongly depends on the analyzed grid frequency behavior. Ten months of high quality grid frequency measurements of the Indian grid are analyzed... [more]

In the present study, we provide useful data related to one of the most promising materials in thin-film solar cell technologies: Cu2ZnSnS4 (CZTS) kesterite structures. Sol-gel spin coating and chemical bath deposition methods were used to fabricate and further investigate Mo/CZTS/CdS/ZnO/AZO heterostructures. In order to examine the crystal structure of the samples, Raman scattering measurements using two excitation wavelengths (514.5 nm and 785 nm) were performed. Three Raman bands related to CZTS were found, as well as one that had its origin in CdS. By using laser ablation and performing Raman spectroscopy on these modified samples, it was shown that during the manufacturing process a MoS2 interlayer was formed between the CZTS and Mo layers. Our method proved that the CZTS layer in a multilayer device structure fabricated by solution-based methods can be decomposed, and thus a detailed analysis of the layer can be performed. Subsequently, current-voltage curves were investigated i... [more]