The popularity of electric vehicles (EVs) is increasing day by day due to their environmentally friendly operation and high milage as compared to conventional fossil fuel vehicles. Almost all leading manufacturers are working on the development of EVs. The main problem associated with EVs is that charging many of these vehicles from the grid supply system imposes an extra burden on them, especially during peak hours, which results in high per-unit costs. As a solution, EV charging stations integrated with hybrid renewable energy resources (HREs) are being preferred, which utilize multi-energy systems to produce electricity. These charging stations can either be grid-tied or isolated. Isolated EV charging stations are operated without any interconnection to the main grid. These stations are also termed standalone or remote EV charging stations, and due to the absence of a grid supply, storage becomes compulsory for these systems. To attain maximum benefits from a storage system, it must... [more]

Electric Technology Vehicles (ETVs: hybrid, electric, and plug-in hybrid) may reach price parity with incumbent internal combustion vehicles (ICEVs) in the near future. Climate policy for transportation will depend on the degree to which consumers prefer ETVs, and price parity is a key factor. In this study, we explore the interaction between future cost reductions and the economically motivated adoption of ETVs. We construct a model of the U.S. personal vehicle market accounting for heterogenous use and vehicle preferences, in which adoption induces cost reductions that increase future market share. Model results indicate that price parity is reached for most consumers in a number of cost scenarios, but not with constant ICEV costs and modest ETV cost declines. A price parity future suggests that government support could be temporary and phased out after a successful market transition. However, if ETVs continue to be more expensive than ICEVs, then lasting government support is needed... [more]

This work describes an experimental installation for the investigation of the combustion and injection processes. This installation is based on a two-stroke direct injection diesel engine with a total displacement of 3 L and a cylinder head equipped with three quartz windows. The windows are optical accesses that allow studying the process of injection, the atomization and evaporation of the fuel jet in an inert atmosphere (nitrogen), and the combustion process in a reactive atmosphere (ambient air). Additionally, the application of a two-color pyrometry technique to measure soot formation in this facility is presented. A methodological study is carried out regarding the influence of the dynamic range of the detectors and the wavelengths used. Maps of KL2C, flame temperature, and error probability are presented. The use of cameras with high dynamic range provides better results since the system seems to be less sensitive to measurement noise, and fewer points are obtained with a non-ph... [more]

Under the conditions of climate change and energy crisis stemming from the COVID-19 pandemic and the embargo on the supply of raw materials from Russia, high hopes are attached to the development of renewable energy in terms of meeting energy needs. Still, renewable energy has some drawbacks too. In the most dynamically growing solar and wind energy industries, the main problems that are indicated include this energy storage and ensuring the security of supplies. These are supposed to be solved by the digital transformation of renewable power generation plus the entry of market players that implement digital business models in renewable energy. The purpose of the article is to identify a framework “digital compass” of business models in renewable energy within a group of solar and wind energy start-ups, operating in energy storage and supply industries. At the base of this study there were: digital technologies, customer orientation, delivery of value and revenue stream. The research a... [more]

The recent study was concerned with employing the finite element method for heat and mass transfer of MHD Maxwell nanofluid flow over the stretching sheet under the effects of radiations and chemical reactions. Moreover, the effects of viscous dissipation and porous plate were considered. The mathematical model of the flow was described in the form of a set of partial differential equations (PDEs). Further, these PDEs were transformed into a set of nonlinear ordinary differential equations (ODEs) using similarity transformations. Rather than analytical integrations, numerical integration was used to compute integrals obtained by applying the finite element method. The mesh-free analysis and comparison of the finite element method with the finite difference method are also provided to justify the calculated results. The effect of different parameters on velocity, temperature and concentration profile is shown in graphs, and numerical values for physical quantities of interest are also g... [more]

Currently in Europe, road freight transport is characterized by the most dynamic advancement. Year after year, we may observe an increase in the amount of transported goods. The paper presents the emissions of gaseous exhaust components such as CO, THC, and NOx as well as fuel consumption in freight transport. The emission analysis was performed for the entire transport cycle covering the handling of the goods with forklifts and carriage with a heavy-duty truck. The investigations were performed under actual conditions of operation using a Portable Emission Measurement System (PEMS). The fuel mileage was determined using the carbon balance method. The test routes were designed so as to reproduce the transport-logistic system typical of small towns. The setting for the tests was a town located in central Poland near the A2 motorway constituting part of the trans-European logistic network with multiple locations of logistic centers. In order to present the real emissions during handling,... [more]

As one of the most appealing options for large-scale energy storage systems, the commercialization of aqueous zinc-ion batteries (AZIBs) has received considerable attention due to their cost effectiveness and inherent safety. A potential cathode material for the commercialization of AZIBs is the manganese-based cathode, but it suffers from poor cycle stability, owing to the Jahn−Teller effect, which leads to the dissolution of Mn in the electrolyte, as well as low electron/ion conductivity. In order to solve these problems, various strategies have been adopted to improve the stability of manganese-based cathode materials. Among those, the doping strategy has become popular, where the dopant is inserted into the intrinsic crystal structures of electrode materials, which would stabilize them and tune the electronic state of the redox center to realize high ion/electron transport. Herein, we summarize the ion doping strategy from the following aspects: (1) synthesis strategy of doped mang... [more]

Recently, the use of novel renewable energy has attracted attention for suppressing the generation of carbon dioxide to prevent global warming. There is growing interest in energy reduction in buildings using solar energy because of its ease of use and repair and excellent maintenance. Therefore, in this study, air-based Photovoltaic thermal (PVT) systems, which can increase the utilization of solar energy, are compared with the existing PV system through measurement. PVT systems can increase the amount of power generation by lowering the temperature of the panel using air passing through the lower part of the panel. It is also possible to use the heated air obtained from the panel as indoor heating or for supplying hot water in a building. As a result of measuring the performance of existing PV panels and PVT panels under the same weather conditions, the power generation efficiency of PVT panels through which air passes increases compared to PV panels. Overall, an air-based PVT system... [more]

The collapse deformation of shale has a significant influence on the exploitation process. Experimental analysis has indicated a correlation coefficient range from 0.9814 to 0.9981 and the established sample regression formula could be used to express the relationship between the dynamic elastic modulus and static elastic modulus of shale specimens. Based on the twin shear unified-strength theory, where coefficient b was considered to express the effect of intermediate principal stress, with the deduced regression formula, the unified solution of major principal strains describing a critical collapse of the shale shaft wall was derived. The results showed that the intermediate principal stress had a significant influence on the major principal strain, describing the critical collapse of the shale shaft wall. At the same depth, the critical collapse major principal strain increased with the increase in the b values. With the change in b value from 0 to 1, the calculated difference in cr... [more]

This study investigated the suitability of stone fruit seed as a source of biodiesel for transport. Stone fruit oil (SFO) was extracted from the seed and converted into biodiesel. The biodiesel yield of 95.75% was produced using the alkaline catalysed transesterification process with a methanol-to-oil molar ratio of 6:1, KOH catalyst concentration of 0.5 wt% (weight %), and a reaction temperature of 55 °C for 60 min. The physicochemical properties of the produced biodiesel were determined and found to be the closest match of standard diesel. The engine performance, emissions and combustion behaviour of a four-cylinder diesel engine fuelled with SFO biodiesel blends of 5%, 10% and 20% with diesel, v/v basis, were tested. The testing was performed at 100% engine load with speed ranging from 200 to 2400 rpm. The average brake specific fuel consumption and brake thermal efficiency of SFO blends were found to be 4.7% to 15.4% higher and 3.9% to 11.4% lower than those of diesel, respectively... [more]

Soot blowing optimization is a key, but challenging question in the health management of coal-fired power plant boiler. The monitoring and prediction of ash fouling for heat transfer surfaces is an important way to solve this problem. This study provides a hybrid data-driven model based on advanced machine-learning techniques for ash fouling prediction. First, the cleanliness factor is utilized to represent the level of ash fouling, which is the original data from the distributed control system. The wavelet threshold denoising algorithm is employed as the data preprocessing approach. Based on the empirical mode decomposition (EMD), the denoised cleanliness factor data is decoupled into a series of intrinsic mode functions (IMFs) and a residual component. Second, the support vector regression (SVR) model is used to fit the residual, and the Gaussian process regression (GPR) model is applied to estimate the IMFs. The cleanliness factor data of ash accumulation on the heat transfer surfac... [more]

In order to quantitatively evaluate the degree of protection in protective layer mining and provide guidance for the design of a secondary outburst elimination scheme, a variable weight-projection gray target dynamic evaluation model for the effectiveness of protective layer mining is established. The improved order relation analysis method was used to determine the subjective weight of each index toward the decision-making goal based on numerical diversity characteristics, and the initial fixed-weight calculation for mixed multi-attribute metrics was processed through the degree of index action. The variable weight function was used to dynamically adjust the fixed weight through the penalty and incentive index methods. Four indexes (gas content, gas pressure, coal seam permeability coefficient, and expansion deformation) were selected, the outburst elimination and anti-reflection were taken as the guide, and the critical value of each index for eliminating burst and the critical value... [more]

Dimethyl ether (DME)/C1-C4 alkane mixtures are ideal fuel for homogeneous charge compression ignition (HCCI) engines. The comparison of ignition delay and multi-stage ignition for DME/C1-C4 alkane mixtures can provide theoretical guidance for expanding the load range and controlling the ignition time of DME HCCI engines. However, the interaction mechanism between DME and C1-C4 alkane under engine relevant high-pressure and low-temperature conditions remains to be revealed, especially the comprehensive comparison of the negative temperature coefficient (NTC) and multi-stage ignition characteristic. Therefore, the CHEMKIN-PRO software is used to calculate the ignition delay process of DME/C1-C4 alkane mixtures (50%/50%) at different compressed temperatures (600−2000 K), pressures (20−50 bar), and equivalence ratios (0.5−2.0) and the multi-stage ignition process of DME/C1-C4 alkane mixtures (50%/50%) over the temperature of 650 K, pressure of 20 bar, and equivalence ratio range of 0.3−0.5... [more]

This work investigates the cost-efficient integration of renewable hydrogen into steelworks for the production of methane and methanol as an efficient way to decarbonize the steel industry. Three case studies that utilize a mixture of steelworks off-gases (blast furnace gas, coke oven gas, and basic oxygen furnace gas), which differ on the amount of used off-gases as well as on the end product (methane and/or methanol), are analyzed and evaluated in terms of their economic performance. The most influential cost factors are identified and sensitivity analyses are conducted for different operating and economic parameters. Renewable hydrogen produced by PEM electrolysis is the most expensive component in this scheme and responsible for over 80% of the total costs. Progress in the hydrogen economy (lower electrolyzer capital costs, improved electrolyzer efficiency, and lower electricity prices) is necessary to establish this technology in the future.

There is a need for new numerical tools to capture the physics of floating offshore wind turbines (FOWTs) more accurately to refine engineering designs and reduce costs. The conventional measurement apparatuses in tank tests, including wave probes, velocity and current profilers, and Doppler sensors, are unable to provide a full 3D picture of velocity, pressure, turbulence, and vorticity profile. In tank tests, use of the underwater stereoscopic particle image velocimetry (SPIV) method to fully characterise the 3D flow field around floating wind platforms can overcome some of the limitations associated with classical measurement techniques and provide a rich source of validation data to advance high-fidelity numerical tools. The underwater SPIV method has been widely used for marine and offshore applications, including ship and propeller wakes, wave dynamics, and tidal stream turbines; however, to date, this technology has not seen widespread use for the hydrodynamic study of FOWTs. Th... [more]

Despite South Africa’s international recognition in solar energy investments, the country is struggling to meet its growing energy needs. In recent years, national blackouts and load shedding have been a recurring experience in the country. The high cost of electrification and the overstrained national grid have left several rural communities without access to electricity. This study aims to explore the solar energy resources and performance of a 3.8 kWp stand-alone residential photovoltaic (PV) power system in one of the underutilised regions in South Africa. The study mainly uses ground measured solar radiation data to evaluate the solar resources of Alice and compare them with those in other parts of the world with mega solar PV projects. The components of solar radiation considered are global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance (DHI). The average total daily GHI, DNI, and DHI of Alice were 4.98, 5.74, and 1.44 kWh/m2. Clear... [more]

The transport sector generates a considerable amount of greenhouse gas (GHG) emissions worldwide, especially road transport, which accounts for 95% of the total GHGs. It is commonly known that Electric vehicles (EVs) can significantly reduce GHG emissions. However, with a fossil-fuel-based power generation system, EVs can produce more GHGs and therefore cannot be regarded as purely environmentally friendly. As a result, renewable energy sources (RES) such as photovoltaic (PV) can be integrated into the EV charging infrastructure to improve the sustainability of the transportation system. This paper reviews the state-of-the-art literature on power electronics converter systems, which interface with the utility grid, PV systems, and EVs. Comparisons are made in terms of their topologies, isolation, power and voltage ranges, efficiency, and bi-directional power capability for V2G operation. Specific attention is devoted to bidirectional isolated and non-isolated EV-interfaced converters i... [more]

The development of an efficient and durable oxygen evolution reaction (OER) electrode is needed to solve the bottleneck in the application of an anion exchange membrane water electrolyzer (AEMWE). In this work, the self-supporting NiFe layered double hydroxides (NiFe LDHs) “nanoflower” cluster OER electrode directly grown on the surface of nickel fiber felt (Ni fiber) was synthesized by a one-step impregnation at ambient pressure and temperature. The self-supporting NiFe LDHs/Ni fiber electrode showed excellent activity and stability in a three-electrode system and as the anode of AEMWE. In a three-electrode system, the NiFe LDHs/Ni fiber electrode showed excellent OER performance with an overpotential of 208 mV at a current density of 10 mA cm−2 in 1 M KOH. The NiFe LDHs/Ni fiber electrode was used as the anode of the AEMWE, showing high cell performance with a current density of 0.5 A cm−2 at 1.68 V and a stability test for 200 h in 1 M KOH at 70 °C. The electrocatalytic performance... [more]

The random nature of wind energy is an important reason for the low energy utilization rate of wind farms. The use of a compressed air energy storage system (CAES) can help reduce the random characteristics of wind power generation while also increasing the utilization rate of wind energy. However, the unreasonable capacity allocation of the CAES system results in high capital investment and a long payback period. In order to improve the economic benefits of energy storage, this paper studies the capacity configuration of compressed air energy storage systems under the condition of wind energy uncertainty. First, the typical hourly power distribution of wind power generation was obtained using historical data. Factors such as user load demand, time-of-use price of the power grid, system investment cost, power shortage cost, and power sales revenue were considered. Then, a model was built with the charging and discharging power and gas storage capacity of the CAES system as constraints,... [more]

The solute transport process in porous media is central to understanding many geophysical processes and determines the success of engineered applications. However, fundamental understanding of solute transport in heterogeneous porous media remains challenging especially when inertial effects are significant. To address this challenge, we employed direct numerical simulations in a variety of intrapore geometries at a high Reynolds number (Re = 10) flow regime, where recirculation zones (RZs) are present with significant inertial effects. We find that the volume of RZs depends on pore geometries. Moreover, RZs serve as an immobile domain that can trap and release solutes that lead to non-Fickian transport, characterized by the early arrival and heavy tailing of breakthrough curves and bimodal residence time distributions (RTDs). Lastly, the late time portion of RTDs is fitted to the power law function with determined exponent n, where n depends on the pore geometries and consequently the... [more]

This paper presents the concept of an expert system supporting the decision-making process of rational energy consumption by an electric car. The driving style and the average speed achieved are very important in terms of the driving range. In addition, the influence of ambient temperature on the efficiency of the electric vehicle and ultimately on energy consumption is very important. The proposed system, based on the method of multi-valued logic trees, allows minimizing the objective function, which is aimed at minimizing the energy consumption of an electric car at different ambient temperatures. The generated decisions, directed to the energy management system, can be processed in a variety of temporal and situational dimensions. The application of the system can also provide prompts to the driver on how to adjust the driving style by operating the accelerator and brake pedal. The expert system is an open system, allowing for further generalizations and modifications.

Accurate prediction of air-conditioning energy consumption in buildings is of great help in reducing building energy consumption. Nowadays, most research efforts on predictive models are based on large samples, while short-term prediction with one-month or less-than-one-month training sets receives less attention due to data uncertainty and unavailability for application in practice. This paper takes a government office building in Ningbo as a case study. The hourly HVAC system energy consumption is obtained through the Ningbo Building Energy Consumption Monitoring Platform, and the meteorological data are obtained from the meteorological station of Ningbo city. This study utilizes a Gaussian process regression with the help of a 12 × 12 grid search and prediction processing to predict short-term hourly building HVAC system energy consumption by using meteorological variables and short-term building HVAC energy consumption data. The accuracy R2 of the optimal Gaussian process regressio... [more]

When the thickness of the solar cell wafer and the amount of Ag to be used decreases, it is the best method to recover the power of the module after use at a minimum cost and reuse the module itself. Economic recovery technology can be applied to the power degradation, caused by the resistive solder bond (RSB) hotspot by poor soldering, because the recovery process can be simplified compared to the power loss that is often greater than 30%. This study demonstrated a quick recovery of the RSB hotspot with on-site recovery technology applied with resin and verified the performance and long-term reliability of on-site recovery technology, compared to the factory recovery method, where the back sheet is removed and laminated to recover the module. Both the factory and field recovery methods confirmed recovery results closer to the initial rated power output of the samples. Each sample was degraded by the RSB hotspot to ~62−65% of the initial power output, and the recovery process successfu... [more]

The fundamental aerodynamic interactions between a pair of wind lenses is experimentally investigated. In prior work, wind tunnel testing of lensed turbines in a side-by-side configuration revealed that one lensed turbine outperformed its counterpart in terms of power production. In the current study, particle image velocimetry (PIV) was performed in the wake of three different pairs of wind lens profiles and revealed an inherent bias in the wake properties at close proximities which led to one turbine outperforming the other. The merged wake location is skewed to a single lens in the lens pair depending on the extent of cancellation of inboard vorticity magnitude. At 0.1 to 0.2 x/D,the individual wakes merge as one, at which point the vortex shedding frequency and the modal strength behind the lens pairs is reduced. Coincidentally, it is at this spacing that the net power output of lensed turbines placed in a side-by-side configuration reaches the maximum.

Multi-well hydrofracturing is an important technology for forming complex fracture networks and increasing reservoir permeability. The distribution and design of horizontal wells affect fracture propagation; however, it is still unclear how the spacing between adjacent wells leads to fracture propagation, deflection and connection. In this study, the thermal-hydro-mechanical coupling effect in the hydrofracturing process is comprehensively considered and a multi-well hydrofracturing model based on the finite element−discrete element method is established. Using typical cases, the unstable propagation of hydraulic fractures in multiple horizontal wells under varying adjacent well spacings is studied. Combined with the shear stress shadow caused by in situ stress disturbed by fracture tip propagation, quantitative indexes (such as length, volume, deflection and unstable propagation behaviors of hydrofracturing fracture networks) are analyzed. The results show that the shear stress distur... [more]