Carnot batteries store surplus power as heat. They consist of a heat pump, which upgrades a low-temperature thermal energy storage, a high-temperature storage system for the upgraded thermal energy, and a heat engine that converts the stored high-temperature thermal energy into power. A Carnot battery is proposed based on supercritical CO2 Brayton thermodynamic cycles. The low-temperature storage is a two-tank molten salt system at 380 °C/290 °C fed by a field of parabolic trough collectors. The high-temperature storage consists of another two-tank molten salt system at 589 °C/405 °C. Printed circuit heat exchangers would be required to withstand the high pressure of the cycles, but shell and tube heat exchangers are proposed instead to avoid clogging issues with molten salts. The conventional allocation of high-temperature molten salt heat exchangers is then modified. Using solar energy to enhance the low-temperature thermal source allowed a round-trip efficiency of 1.15 (COP of 2.46... [more]

The heat loss caused by radiation and persistently laminar natural convection in a solar cooker cavity that has a rectangular cavity or a trapezoidal cavity are computationally explored in this paper. The hot bottom and the adiabatic side wall are both taken into account. Two possibilities are considered for the top wall: first, a cold wall, and, second, losses from wind-induced convection and radiation. The parameters of heat loss in various depth cavities have been investigated along with a variety of external heat transfer coefficient values above the glass surface were simulated. The emissivity of the bottom surface, the absolute temperature ratio, on heat loss from the considered geometries, are also calculated. Analysis of the cavity’s flow pattern and isotherms at different depths has been conducted, and it is discovered that the total rate of heat transfer from the top wall increases as the bottom wall’s emissivity, the absolute temperature ratio, the Rayleigh number, and the e... [more]

The ice-templated method (ITM) has drawn significant attention to the improvement of the electrochemical properties of various materials. The ITM approach is relatively straightforward and can produce hierarchically porous structures that exhibit superior performance in mass transfer, and the unique morphology has been shown to significantly enhance electrochemical performance, making it a promising method for energy storage and conversion applications. In this review, we aim to present an overview of the ITM and its applications in the electrochemical energy storage and conversion field. The fundamental principles underlying the ITM will be discussed, as well as the factors that influence the morphology and properties of the resulting structures. We will then proceed to comprehensively explore the applications of ITM in the fabrication of high-performance electrodes for supercapacitors, batteries, and fuel cells. We intend to find the key advances in the use of ITM and evaluate its po... [more]

Mathematical models for the simulation of the operation of various projectile-throwing systems are continuously modified, simultaneously with the development of propellants. For these models, properly determined values of energetic ballistic characteristics of propellants are very important. This paper presents an original test and the results of closed vessel comparative investigations. The study analyses specific combustion characteristics of single-base propellants using conventional black powder ignition, plasma ignition, and gas ignition. The results of the study indicate the need to take into account—in the calculation of the burning rate—not only the dynamics of gas pressure changes but also the real (experimental) form function, which differs from the theoretical one resulting from the assumed geometric burning model. The obtained results allow for a critical analysis of the existing methods used for the determination of values of ballistic characteristics of propellants. Furth... [more]

Remaining useful life prediction is of great significance for battery safety and maintenance. The remaining useful life prediction method, based on a physical model, has wide applicability and high prediction accuracy, which is the research hotspot of the next generation battery life prediction method. In this study, the prediction methods of battery life were compared and analyzed, and the prediction methods based on the physical model were summarized. The prediction methods were classified according to their different characteristics including the electrochemical model, equivalent circuit model, and empirical model. By analyzing the emphasis of electrochemical process simplification, different electrochemical models were classified including the P2D model, SP model, and electrochemical fusion model. The equivalent circuit model was divided into the Rint model, Thevenin model, PNGV model, and RC model for the change of electronic components in the model. According to the different mat... [more]

The need to reduce pollution and the shortage of fossil fuels has led to the increased development of hybrid and full electric vehicles. There is also increased development and an increased use of renewable energy resources such as photovoltaic, wind, tidal, etc. These two trends pose serious challenges to the existing grids: a lack of supply power when the demand is high, deficient management of excess power, an increased number off grid faults, grid instabilities and others. One way to increase the penetration of electric vehicles (EV) into the market and to keep the existing grid infrastructure is to combine renewable energy resources with the grid and local battery packs to make EV charging stations. This paper focuses on developing such an EV charging station. The main advantages of the proposed EV charger include the fact that it uses only off-the-shelf inverters, and it is intended to be used in households where the maximum installed power is 3.6 kW to enable fast-charging opera... [more]

Bioenergy with Carbon Capture and Storage (BECCS) technologies are fundamental to reach negative CO2 emissions by removing it from the atmosphere and storing it underground. A promising solution to implement BECCS is pressurized Chemical Looping Combustion (CLC), which involves coupling a pressurized CLC reactor system to a turboexpander. The typical configuration chosen is to have an air reactor and a fuel reactor based on coupled circulating fluidized beds. The fluidization regime in both reactors is preferred to be fast fluidization to enhance gas particle contact and solids circulation among reactors. To design the two reactors, Aspen Plus software was used, given that the new version has a module for fluidized bed modeling. At first, the oxygen carrier was designed ex novo, but given that it is a composite compound mainly made by nickel oxide freeze-granulated on alumina (Ni40Al-FG), the molecular structure has been inserted in Aspen Plus. Then, based on the power of the gas turbi... [more]

Ocean wave height is one of the critical factors to decide the efficiency of the ocean wave energy conversion system. Usually, only when the resonate occurs between the ocean wave height (ocean wave speed in the vertical direction) and ocean wave energy conversion system, can the conversion efficiency from ocean wave energy into electric energy be maximized. Therefore, this paper proposes two predication methods to predict the future ocean wave height in 1.5−2.5 s. Firstly, the data fitting of real ocean wave height is achieved by the polynomial method, which is beneficial to the predication of ocean wave height. Secondly, the models of the moving average (MA) predication method and auto regressive (AR) predication method are presented by the time series analysis process. Lastly, after the predication of ocean wave height by the MA method and AR method, and compared with the data fitting result of real ocean wave height, it can be found that the AR method is more accurate for the predi... [more]

The use of fuels with tendencies to reduce carbon dioxide emissions, particularly gaseous fuels, and improve combustion systems is one of the directions for increasing an internal combustion engine’s attractiveness as a power source. This article presents the effects of combining natural gas combustion with a multi-stage combustion system. A two- and three-stage lean charge combustion system was proposed in order to increase the energy system efficiency. In order to achieve this, a single-cylinder test engine was used, with two interchangeably implemented combustion systems. The tests were carried out with two values of the excess air coefficient (λ = 1.3 and λ = 1.5), as well as two different fuel dose values (qo = 0.35 and 0.55 mg/inj), injected into the prechamber at the same indicated mean effective pressure value (IMEP = 6.5 bar) and the same engine speed (n = 1500 rpm). Based on the obtained research results, it was found that the use of a three-stage system limited the maximum c... [more]

In hot climates, such as sub-Sahara Africa, window sizing and orientation pose challenges as they add, through solar insolation, to the building cooling energy demand and thus the cause of indoor overheating risk. This risk can be reduced through passive building-design-integrated measures, e.g., optimizing the window size, orientation and solar shading strategies. Through an IDA-ICE building performance simulation tool, the current study explores the impact of window size, optimization and building-integrated PV panels as shading strategies on cooling energy demands in three cities (Niamey, Nairobi and Harare) in sub-Sahara Africa. Results show that thermal comfort and cooling energy demand are sensitive to a window-to-wall ratio (WWR) > 70%, while the need for artificial lighting is negligible for a WWR > 50%, particularly in the north for cities in the Southern hemisphere and the south in the Northern hemisphere. A WWR > 70% in the east and west should be avoided unless shading devi... [more]

The degradation of the insulation system in liquid-filled power transformers is a serious concern for electric power utilities. The insulation system’s ageing is accelerated by moisture, acids, oxidation products, and other decay particles (soluble and colloidal). The presence of these ageing by-products is detrimental to the insulation system and may further lead to premature ageing and serious consequences. The ageing mechanisms of oil-paper insulation are complex, highly interrelated, and strongly temperature-dependent. The operating temperature of the transformer insulating system has a direct relationship with the loading profile. The major aspect that is witnessed with the fluctuating temperatures is moisture migration and subsequent bubble evolution. In other words, gas bubbles evolve from the release of water vapor from the cellulosic insulation wrapped around the transformer windings. The models presented in the existing standards, such as the IEC Std. 60076-7:2018 and the IEE... [more]

The demand for energy storage systems is rising together with the proportion of renewable energy sources (RES) in power systems. The highest capacity among the various energy storage systems in power systems is provided by pumped-storage hydropower (PSH). In this paper, the ability of the real-time digital simulator (RTDS), e.g., dSpace−SCALEXIO, to emulate a complex pumped-storage hydropower plant with four units, two common penstocks, a surge tank, and a long headrace tunnel is investigated. The RTDS is the smart brain of an advanced lab setup called power hardware in the loop (PHIL), which is an extremely safe and useful lab system for electrical power system research and testing hardware and methods under various conditions. In this research, the capability of an RTDS to emulate the behavior of a pumped-storage hydropower plant including four Francis pump-turbines, four short penstocks, two common penstocks, a surge tank, and a long headrace tunnel is evaluated. Francis pump-turbin... [more]

Straight-channel heat sinks are widely used as a cooling method for electronic devices and lithium battery thermal management. This study aims to enhance the thermal performance of a straight-channel heat sink while decreasing the pressure drop. In this design, the height of inside channels is reduced to provide open space above the channel while the size of the heat sink remains constant. Both experimental investigation and numerical analysis were conducted to study the thermal efficiency of heat sinks with varying heights, at flow rates ranging from 6.94 to 19.56 m3/s and heat fluxes between 3.8 and 7.43 W/cm2. The comparison is carried out between channels with four different heights in terms of temperature distribution, local Nusselt number, velocity, and flow characteristic. The results indicate that lowering the height of the channel from 12.7 to 7 and 4 mm raises the highest temperature of the heat sink, whereas the change in height to 10 mm reduces the temperature. Furthermore,... [more]

The stability of electricity service mainly depends on two main factors. One of them is the country’s power plant capacity and electricity imports. Another factor is the network that delivers electricity to consumers. Recently, consumer electricity production has appeared as a third factor due to the spread of renewable energies. The article focuses on the transformation of the structure of Hungary’s electricity sources between 2010 and 2020. We used the concentration indicator to examine the structure of export−import deliveries with neighboring countries. We also analyzed the centralization of Hungary’s electricity-generating units and the composition of their fuels. In this article, we examined the increasingly widespread renewable energies, which are replacing the traditional—mainly fossil fuel—energy carriers. The relationship between coal, natural gas, nuclear, solar, wind, water, and bioenergy, as well as net imports, were analyzed using a Pearson correlation matrix. This articl... [more]

Concentrating photovoltaic thermal (CPVT) technology has the potential to support the industrial sector with renewable electricity and heat simultaneously. The implementation of spectral splitting emerges as a possible approach to significantly increase the conversion efficiency, and furthermore, to hurdle the fundamental discrepancy of CPVT systems, that the electrical and the thermal receiver part have opposing temperature requirements. This paper provides an introductive description of beam splitting methodology and presents an updated review of the latest developments in the specific sector of spectral splitting by selective absorption. Furthermore, a novel CPVT receiver design utilizing bendable PV cells and an innovative heat transfer fluid are explained in detail. Simulation results illustrate the possibilities of spectral splitting to raise the electrical conversion efficiency in CPVT receivers by up to 42.9%. Potential improvements in receiver designs are discussed for further... [more]

The initial design phase for offshore wind farms does not require complete geotechnical mapping and individual cone penetration testing (CPT) for each expected turbine location. Instead, background information from open source studies and previous historic records for geology and seismic data are typically used at this early stage to develop a preliminary ground model. This study focuses specifically on the interpolation and extrapolation of cone penetration test (CPT) data. A detailed methodology is presented for the process of using a limited number of CPTs to characterise the geotechnical behavior of an offshore site using artificial neural networks. In the presented study, the optimised neural network achieved a predictive error of 0.067. Accuracy is greatest at depths of less than 10 m. The pitfalls of using machine learning for geospatial interpolation are explained and discussed.

An accurate state-of-health (SOH) prediction of lithium-ion batteries (LIBs) is crucial to their safe and reliable. Although recently the data-driven methods have drawn great attention, owe to its efficient deep learning, it is worthwhile to continue devoting many efforts to prediction performance. In practice, fast charging mode has been widely applied in battery replenishing, which poses challenges for SOH prediction due to the diversity of charging conditions and electrochemical properties of LIBs; although, the process is stable and detectable. Furthermore, most previous data-driven prediction methods based discriminative model cannot describe the whole picture of the problem though sample data, affecting robustness of model in real-life applications. In this study, it is presented a SOH prediction model based on diffusion model, as an efficient new family of deep generative model, with time series information tackled through Bi-LSTM and the features derived from the voltage profil... [more]

The paper presents a physics-based method to calculate in real time the distribution of temperature in the active part of liquid immersed power transformers (LIPT) in a transient thermal processes during grid operation. The method is based on the detailed dynamic thermal-hydraulic network model (THNM). Commonly, up to now, lumped models have been used, whereby the temperatures are calculated at a few points (top-oil and hot-spot), and the parameters are determined from basic or extended temperature-rise tests and/or field operation. Numerous simplifications are made in such models and the accuracy of calculation decreases when the transformer operates outside the range of tested values (cooling stage, loading). The dynamic THNM reaches the optimum of accuracy and simplicity, being feasible for on-line application. The paper presents fundamental equations of dynamic THNM, which are structurally different from static THNM equations. The paper offers the numerical solver for the case of a... [more]

Cell wall disturbance is an important step in the downstream process of improving the efficiency of lipid extraction from microalgae. Surfactants have been proven to be efficient alternatives to organic solvents in the extraction process. In this study, an effective approach involving deep eutectic solvent (DES) (choline chloride and carboxylic acids) treatment supplemented with surfactants has been developed to disrupt the cell walls of microalgae and increase the extraction of lipids suitable for biodiesel production. A combination of polar and non-polar solvents (ethyl acetate and n-butanol) was used for the lipid extraction process. Microalgae biomass pretreated with choline chloride malonic acid supplemented with the surfactant hexadecyl trimethylammonium chloride (HTAC) showed the best results, improving lipid extraction by 12.365%. Further elucidation of the detailed mechanism behind the cell disruption of the microalga wall by DES was achieved using density functional theory (D... [more]

Road transport is one of the most important factors for the national economy due to its universality and comprehensive possibilities of transporting people and goods. Unfortunately, from the energy point of view, it is also the most cost-intensive and has a negative influence on the natural environment. For these reasons, issues related to limiting the use of conventional fuels are very important, which results in reducing emissions from this sector, as well as reducing transport costs. This article presents currently used energy sources for propulsion of road vehicles, including fossil and alternative fuels, gaseous fuels and other energy sources such as fuel cells. The following section presents technologies that allow to recover some of the energy lost in motor vehicles and internal combustion engines used for their propulsion. The principle of operation of these solutions, their structure and their main features are presented. The last part focuses on discussing and identifying the... [more]

In daily life, energy plays a critical role. Hydrogen energy is widely recognized as one of the cleanest energy carriers available today. However, hydrogen must be produced as it does not exist freely in nature. Various methods are available for hydrogen production, including electrolysis, thermochemical technology, and biological methods. This study explores the production of biological hydrogen through the degradation of organic substrates by anaerobic microorganisms. Bacillus paramycoides and Cereibacter azotoformans strains were selected as they have not yet been studied for biological hydrogen fermentation. This study investigates the ability of these microorganisms to produce biological hydrogen. Initially, the cells were identified using cell morphology study, gram staining procedure, and 16S ribosomal RNA (rRNA) gene polymerase chain reaction. The cells were revealed as Bacillus paramycoides (MCCC 1A04098) and Cereibacter azotoformans (JCM 9340). Moreover, the growth behaviour... [more]

Small dust grains cause a higher intensity of increase in the flow resistance of the fibrous filter bed, which, due to the established value of the permissible resistance, results in a shorter period of operation of the air filter and the vehicle. At the same time, the mass of dust per unit of filtration area takes on smaller values. Such a phenomenon occurs in the two-stage “multicyclone-baffle filter” engine inlet air filtration system. The main objective of this study was to experimentally determine the mass of dust retained per unit of filtration area (dust absorption coefficient km) of the PowerCore filter bed operating under two-stage filtration conditions, which cannot be found in the available literature. The original methodology and conditions for determining the dust absorption coefficient km of a PowerCore filter bed operating under two-stage filtration conditions are presented. Tests were carried out on the characteristics of filtration efficiency and accuracy, as well as o... [more]

The shift to renewable sources of energy has become a critical economic priority in African countries due to energy challenges. However, investors in the development of renewable energy face problems with decision making due to the existence of multiple criteria, such as oil prices and the associated macroeconomic performance. This study aims to analyze the differential effects of international oil prices and other macroeconomic factors on the development of renewable energy in both oil-importing and oil-exporting countries in Africa. The study uses a panel vector error correction model (P-VECM) to analyze data from five net oil exporters (Algeria, Angola, Egypt, Libya and Nigeria) and five net oil importers (Kenya, Ethiopia, Congo, Mozambique and South Africa). The study finds that higher oil prices positively affect the development of renewable energy in oil-importing countries by making renewable energy more economically competitive. Economic growth is also identified as a major dri... [more]

The application of fuzzy hybrid methods has significantly increased in recent years across various sectors. However, the application of fuzzy hybrid methods for modeling systems or processes, such as fuzzy machine learning, fuzzy simulation, and fuzzy decision-making, has been relatively limited in the energy sector. Moreover, compared to standard methods, the benefits of fuzzy-hybrid methods for capturing complex problems are not adequately explored for the solar energy sector, which is one of the most important renewable energy sources in electric grids. This paper investigates the application of fuzzy hybrid systems in the solar energy sector compared to other sectors through a systematic review of journal articles published from 2012 to 2022. Selection criteria for choosing an appropriate method in each investigated fuzzy hybrid method are also presented and discussed. This study contributes to the existing literature in the solar energy domain by providing a state-of-the-art revie... [more]

Effective implementation of renewable energy sources (RES) is one of the main challenges in regard to the organization of local energy microgrids with buildings. One of the solutions is the use of dynamic building façades with photovoltaic (PV) panels, in particular the innovative perovskite solar cells (PSCs). This paper describes a case study performed on a pilot installation of perovskite PV panels located in Poland, Central-Eastern Europe. Results of preliminary measurements on this installation are provided in terms of verifying its energy efficiency and the possibility of selecting settings for the façade dynamics control system. Our experiments have considered the sun-tracking mechanism and its energy consumption as well as the impact of weather conditions at different times of the year. The energy efficiency results for the PV system, with average levels below 10%, are rather low. Therefore, even small energy savings in the operation of the PV system itself are significant. Cha... [more]