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]

The wave energy converter (WEC) system, which extracts electricity through the relative heave motion of two concentric cylinders, comprises an inner cylinder and a torus-type outer cylinder sliding along the inner cylinder. To maximize the relative heave motion between two cylinders, the natural frequencies of the two cylinders must be precisely tuned to resonate and be situated on each side of the peak frequency of the wave spectrum. However, the demerit of this strategy is that it demands a deep draft of each cylinder for tuning, and a large-scale PTO damping device is necessary for mechanical power amplified by resonance. As an alternative to efficient and stable WECs, we adopt a new strategy in which the outer cylinder follows the incoming waves and the motion of the inner one is restricted to be minimal using a heave disk. The viscous damping due to formation of vortices at the disk edge is realized by the drag force in the Morison equation. The developed hydrodynamic model of two... [more]

With the rapid increase in wind power, its strong randomness has brought great challenges to power system operation. Accurate and timely ultra-short-term wind power prediction is essential for the stable operation of power systems. In this paper, an LsAdam−LSTM model is proposed for ultra-short-term wind power prediction, which is obtained by accelerating the long short-term memory (LSTM) network using an improved Adam optimizer with loss shrinkage (LsAdam). For a specific network topology, training progress heavily depends on the learning rate. To make the training loss of LSTM shrink faster with standard Adam, we use the past training loss-changing information to finely tune the next learning rate. Therefore, we design a gain coefficient according to the loss change to adjust the global learning rate in every epoch. In this way, the loss change in the training process can be incorporated into the learning progress and a closed-loop adaptive learning rate tuning mechanism can be const... [more]

Among the energy targets of the Vietnamese government, solar energy is expected to become the main source of renewable energy in the future. Solar energy is moving forward, with Vietnam outstripping Thailand and becoming the country that installed the largest capacity of solar power generation in Southeast Asia, reaching 16,362 MW in new installations in December 2021. In this study, we have experimentally analyzed and designed a capacity of 47.5 MW grid-connected photovoltaic plant mounted on the floatation system at Da Mi hydropower reservoir in Binh Thuan province. This was selected to be utilized as the first effort to develop the first large-capacity floating solar power plant on a hydroelectric reservoir in Vietnam. A detailed examination of the electrical analysis, including DC to DC converters, AC inverters to the transmission network, and PV module connectivity configurations, are in scope. The present research has the potential to make a contribution to the design of the DC e... [more]

Under rapid urbanization-induced global warming and resource depletion, growing interest in zero-energy building (ZEB) and zero-emission building (ZEB) technologies have emerged globally to improve energy performance in homes and shape sustainable cities. Although several countries have released ZEB-enhanced strategies and set national standards and policies to promote ZEBs, construction projects are still limited to demonstration projects. This paper reviews global ZEB activities and state-of-the-art technologies for energy-efficient residential building technologies [based on an evaluation of 40 residential buildings]. Over 40 residential buildings on different continents were reviewed, and their technical details and performance were evaluated. Our results show that 62.5% of the buildings achieved the +ZEB standard, 25% of the buildings were net-zero energy buildings, and only 12.5% of the buildings were near-zero energy buildings. Solar PV is the most widely used renewable energy s... [more]

With the aim of arriving at more efficient and sustainable transport, the search for improvements in power electronics converters is the key to systems with a high efficiency and reliability [...]

This study presents a simulation of potential changes in groundwater in three wells within a Quaternary gravel aquifer in the city of Ljubljana when groundwater cooled by about 4 °C is reinjected into it. The research focuses on the mass transport of calcite in the vicinity of boreholes. According to our results, the impact of the changes in the geochemical composition of the water is relatively small (around 1%). Although the waters are approximately in equilibrium, calcite may be dissolved and sometimes precipitated within the aquifer when cooled water is reinjected into it. The amounts of precipitated calcite always decrease with decreasing temperatures of the reinjected water, which can lead to calcite dissolution if the temperature difference is large enough and the water is only slightly oversaturated. This novel finding is significant since previously published studies have mostly focused on understanding the scaling (precipitation) of calcite and not its dissolution. The mass t... [more]

Permanent magnet synchronous generator (PMSG) wind power system with full power rating converter configuration is especially suitable for wind energy applications. Direct model predictive control (DMPC) has led to more possibilities in terms of choice because of its straightforward concept for PMSG wind turbine systems in high-power off-shore wind farms. However, due to complete dependence on the model knowledge, parameter mismatches will seriously deteriorate the system control performances. This work presents a model/parameter-independent predictive control method with a novel mechanism to update current/power variations online. The proposed method makes use of only two measurements from the former intervals and the selected control vectors to estimate all variations of the candidate vectors in the present interval. Benefiting from this updating mechanism, the proposed method is completely independent of the model parameters in the state prediction. However, it still has a very low c... [more]

In recent years, gasification gained attention again, both as an industrial application and as a research topic. This trend has led to the necessity to understand the process and optimize reactors for various materials and configurations. In this article, the thermal structure of a counter-current reactor is investigated to demonstrate that constraints on the temperature mainly determine the oxidation and the pyrolysis region. A non-dimensional set of equations is written and numerically solved using the method of lines (MOL) with spatial discretization based on a spectral algorithm. The results show that four thermal structures can be identified, two of which are the most common ones found in reactors of practical applications. Two stationary operation positions have been determined, one in the upper and one in the lower part of the reactor. Existence and stability conditions have been discussed based on non-dimensional parameters. The knowledge derived from this analysis was applied... [more]

The depletion of fossil fuel sources has encouraged the authorities to use renewable resources such as wind energy to generate electricity. A backup/storage system can improve the performance of wind turbines, due to fluctuations in power demand. The novelty of this study is to utilize a hybrid system for a wind farm, using the excess electricity generated by the wind turbines to produce hydrogen in an alkaline electrolyzer (AEL). The hydrogen storage tank stores the produced hydrogen and provides hydrogen to the proton-exchange membrane fuel cell (PEMFC) to generate electricity once the power demand is higher than the electricity generated by the wind turbines. The goal of this study is to use the wind profile of a region in Iran, namely the Cohen region, to analyze the performance of the suggested integrated system on a micro scale. The output results of this study can be used as a case study for construction in the future, based on the exact specification of NTK300 wind turbines. Th... [more]

This paper presents a numerical study on thermal energy mining from hot dry rock (HDR) using an enhanced geothermal system (EGS). In these simulations, the thermal−hydraulic−mechanical (THM) coupling model is employed on the basis of the embedded discrete fracture model. The evolution of physical fields of the fractured reservoir, including temperature field, pressure field, and stress field is studied over time, and the effects of different controllable factors, such as fracture morphology, fluid injection rate, and the distances between the injection well and producing well on the heat recovery capacity are investigated. The results show that the fracture morphology significantly influences heat extraction performance. The working fluid mainly flows along with the fracture networks, which causes locally low temperatures and low mean effective stress near fractures. The porosity and permeability increase due to the decrease in mean effective stress. For reservoir models with inclined... [more]

The European building sector is responsible for approximately 40% of total energy consumption and for 36% of greenhouse gas emissions. Identifying technological solutions capable of reducing energy consumption and greenhouse gas emissions is one of the main objectives of the European Commission. Ground source heat pumps (GSHPs) are of particular interest for this purpose, promising a considerable reduction in greenhouse gas emissions of HVAC systems. This paper reports the results of the energetic analysis carried out within the EU research project GEO4CIVHIC about the performance of geothermal heat pumps working with low-GWP refrigerants as alternatives for R134a and R410A. The work has been carried out through computer simulations based on base and regenerative reverse cycles. Several heat sink and heat source temperature conditions have been considered in order to evaluate the GSHPs’ performance in the whole range of real conditions that can be found in Europe. Particular attention... [more]

The Middle East, Gulf Cooperation Council Countries (GCC), and Kuwait, in particular, are currently experiencing a similar transition as the USA in the 1970s regarding the empowerment and independence of women, fueled by a declining birth rate from four per women to less than two. In addition, the percentage of women with university degrees has been increasing at a logarithmic rate every decade since the 1960s in the USA and since 1990 in Kuwait, resulting in women comprising well over half of all university graduates. This has led to women obtaining better jobs and enjoying greater independence to make their own decisions. In the 1960s, Toyota and other Japanese car manufactures used this phenomenon to penetrate the US market, with significant success. Their selling points were lower maintenance requirements, higher reliability, safety, better environment friendliness and slicker interior designs, the last being especially adapted to women’s tastes. We believe that Chinese and Korean... [more]