In recent years, with the continuous development of new energy, how to efficiently use wind energy has received more and more market attention. Due to cost advantages, the development of small wind turbines is accelerating. Among them, the design and research of the airfoil design and research of the lift vertical axis wind turbine has matured, but because of the aerodynamic characteristics of the lift airfoil structure, it is impossible to start itself at low wind speed, resulting in the waste of low wind speed energy. Although the drag wind turbine has good self-starting performance, the wind energy utilization efficiency in the high-speed state is inefficient. Each has its own unique shortcomings, which directly affects the marketization of small wind turbines. In order to solve these problems, this paper presents a drag-lift hybrid type wind turbine structure based on an NACA0018 symmetrical airfoil, which can adaptively change the blade shape. This design can keep the blade in the... [more]

Life cycle analysis allows for the assessment of the qualitative and quantitative relationship between selected areas of human activity and the consequences for the environment. One of the important areas is the production of electricity and heat, for which the main raw material in Poland is hard coal. An alternative may be to use biogas as a fuel for energy purposes. This article presents the assessment of environmental hazards caused by the production of energy from biogas. The analysis took into account the change of the substrate from maize silage, commonly used in Polish biogas plants, to waste from the domestic agri-food industry. The evaluation covered the acquisition of substrates, their transport to a biogas plant, generation of electricity from biogas, and management of the generated by-products. The analysis was done in terms of both the impact and sensitivity categories. It was found that the emission of pollutants related to the acquisition of the substrate plays a key rol... [more]

Proppant is an essential material in hydraulic fracturing, and it can support artificial fractures for a long time. However, few people have applied proppant and conductive materials in the in-situ modification of shale oil. Here, we developed a graphene and resin coated (GRC) proppant with electrically conductive properties. The electrical conductivity of the GRC proppant improved by four orders of magnitude. The GRC proppant has a 54.58% improvement in suspension and 22.75% increase in settlement time at 0.25 wt% concentration compared with uncoated proppant. The GRC proppant’s adhesion reached 68.34 nN under 1 μN load force, increasing by 63.13% compared to uncoated proppant. This new electrically conductive proppant can be used as a conductive carrier to improve the efficiency of electric heating in in-situ modification technology of shale oil.

This paper presents a numerical study of waste heat recovery from a fluid stream using thermoelectric devices. The system consisted of a square section duct with spherical porous media placed in its central region. Hot air circulates continuously through the duct and exchanges energy with the solid matrix and subsequently with the thermoelectric modules. The mathematical model of the system was solved using ANSYS/FLUENT software, requiring the implementation of user-defined functions (UDFs) and user-defined scalars (UDS) regarding porous media and thermoelectric generation modelling. From the simulations carried out, global efficiency and electrical power values were obtained in the range of [0.11−4.51] [%] and [0.01−12.77] [W], respectively. Furthermore, for the set of variables analysed, it was observed that the performance of the system is favoured by an increase in the fluid inlet temperature and speed, as well as by a higher external heat transfer coefficient.

Catalytic upgrading of vapors from pyrolysis of triglycerides materials is a promising approach to achieve better conversions of hydrocarbons and production of liquid biofuels. Catalytic cracking often shows incomplete conversion due to distillation of initial reaction products and the addition of a second catalytic reactor, whereas pyrolytic vapors are made in contact to a solid catalyst was applied to improve the physical-chemical properties and quality of bio-oil. This work investigated the effect of catalyst content and reaction time by catalytic upgrading from pyrolysis vapors of residual fat at 450 °C and 1.0 atmosphere, on the yields of reaction products, physicochemical properties (density, kinematic viscosity, refractive index, and acid value), and chemical composition of organic liquid products (OLP), over a catalyst fixed bed reactor, in semi pilot scale. Pellets of red mud chemically activated with 1.0 M HCl were used as catalysts. The thermal catalytic cracking of residual... [more]

The cooling of E-machines was investigated using phase change material (PCM). The PCM is widely used in the cooling of electronic components because of its heat-absorbing and cooling properties. In this study, PCM OM35 (50:50) and OM35 (60:40) were used for the cooling of E-Machines, which are commonly known as electric vehicle motors. Three different configurations, viz. no rib, two ribs, and four ribs, were studied to understand the impact of thermal behaviour on bracket cooling. The ribs were added in between the brackets to enhance the heat transfer. Numerical simulations were performed using the volume of fluid multiphase analysis approach to model the behaviour of phase change inside the brackets for 18 KW E-Machines. Based on the study, a four rib configuration showed good performance compared to no rib and two rib configurations, and heat transfer improved by 6%. Heat transfer is thus improved by increasing the number of ribs placed between the brackets. The cyclic heat load wa... [more]

Rain erosion on wind turbine blades raises considerable interest in wind energy industry and research, and the definition of accurate erosion prediction systems can facilitate a rapid development of solutions for blade protection. We propose here the application of a novel methodology able to integrate a multibody aeroelastic simulation of the whole wind turbine, based on engineering models, with high-fidelity simulations of aerodynamics and particle transport and with semi-empirical models for the prediction of the damage incubation time. This methodology is applied to generate a parametric map of the blade regions potentially affected by erosion in terms of the fatigue life of the coating surface. This map can represent an important reference for the evaluation of the sustainability of maintenance, control and mitigation interventions.

The placement of the photovoltaic generation system (PVGS) and operation of the on-load tap changer (OLTC) should have great impacts on the system loss and voltage quality, which are the main concerns of the distribution operator. Considering these multiple evaluation indices and other constraints, this paper proposed a substation-based optimal PVGS placement and OLTC operation model. The objective function that was used to evaluate the optimal PVGS placement and OLTC operation consists of a minimization of system loss and voltage quality. The model’s constraints contain the voltage and line flow limits, voltage deviations, voltage unbalance, etc. Uncertainties of the load and irradiance are also included in the model. A nondominated sorting genetic algorithm II (NSGA II) is used to solve this multi-objective optimization problem. Comparisons of the substation-based and feeder-based planning are also studied in this paper. The test results demonstrate the substation-based planning coul... [more]

This work aims to characterize how home energy upgrade projects and programs in the US have evolved over the past decade. It also identifies what changes are needed to drive expansion of the US energy retrofit market in such a way that addresses carbon emissions from buildings, improves resilience and upgrades the housing stock. This review focuses on whole-home energy upgrades, targeting deep energy retrofit savings of >30%. The topics we cover include trends in home electrification, US and European home energy upgrade programs, energy upgrade measure costs, business economics, and health effects. Key changes in project design noted in this review include: (1) the electrification of dwellings with rapidly improving heat pump systems and low-cost solar photovoltaic technology; and (2) a shift away from high-cost building envelope strategies and towards more traditional home performance/weatherization envelope upgrades. Promising program design strategies covered include: (1) end-use el... [more]

Groundwater flow and transport are crucial for performance and safety assessment in the radioactive waste geological disposal. This study presents the groundwater flow and advective transport simulations for assessing the performance of a reference repository placed in fractured rocks. The study involves the concept of radionuclides migrating into the mobile water in fractures surrounding the deposition hole and calculates two specific quantitative indicators in the field of radioactive waste geological disposal. The indicators equivalent flow rate (Qeq) and flow-related transport resistance (F) are used to express the groundwater flow and transport resistance in the host rock. Based on the hydrogeological conceptual model, the study employs DarcyTools to model the groundwater flow and advective transport of a base case. This study then conducts sensitivity analyses by varying the hydraulic conductivity of the key hydrogeological unit and the excavation damage zone. The uncertainty ana... [more]

Flexible interconnection transformation of a distribution network using all-control power electronics technology will help to overcome the technical bottleneck of distributed generation (DG) penetration and high-quality power supply in the traditional distribution network. However, the flexible interconnection form that uses back-to-back power electronic converters to replace tie switches has disadvantages such as high cost and large footprint, so its mass promotion and application are bound to be limited. Therefore, a new topology of flexible interconnected distribution network with embedded DC system (FDN+EDC) with a better economy is proposed. Firstly, the topology of FDN+EDC is introduced to improve the controllability level of the distribution network under high percentage DG penetration, and is compared with the conventional flexible interconnection method. Secondly, in order to realize the coordinated optimal economic operation of source, network and load in the FDN+EDC, a dynam... [more]

Linear Friction Welding (LFW) is a unique welding process which enables dissimilar materials to be welded without filler material. In this study, bi-metallic Ti-64-CCM joints were manufactured utilizing LFW and subsequently analyzed. A coupled thermal-deformation model was created to accurately model both thermal and deformation profiles along the weld interface. Ti-64 and CCM stock were machined in accordance with ASTM standards for tensile testing. Temperature distribution of the two material surfaces were measured using an IR camera. Tensile testing was then performed to analyze weldability and bonding strength. A transient decoupled thermomechanical simulation model was generated to simulate the LFW process. The simulation model produced results within 5% error of both experimental results. The tensile testing results indicate that successful bonding of Ti-64 to CCM is possible for an oscillation amplitude of 2 mm under large forging pressure. The results also show that parameter o... [more]

A proton exchange membrane fuel cell (PEMFC) is a more environmentally friendly alternative to deliver electric power in various applications, including in the transportation industry. As PEMFC performance characteristics are inherently nonlinear and involved, the prediction of the performance in a given application for different operating conditions is important in order to optimize the efficiency of the system. Thus, modelling using artificial neural networks (ANNs) to predict its performance can significantly improve the capabilities of handling the multi-variable nonlinear performance of the PEMFC. However, further investigation is needed to develop a dynamic model using ANNs to predict the transient behavior of a PEMFC. This paper predicts the dynamic electrical and thermal performance of a PEMFC stack under various operating conditions. The input variables of the PEMFC stack for the analysis consist of the cathode inlet temperature, anode inlet pressure, anode and cathode inlet f... [more]

In this paper, a neural network model called Long Short-Term Temporal Convolutional Network (LST-TCN) model is proposed for short-term load forecasting. This model refers to the 1-D fully convolution network, causal convolution, and void convolution structure. In the convolution layer, a residual connection layer is added. Additionally, the model makes use of two networks to extract features from long-term data and periodic short-term data, respectively, and fuses the two features to calculate the final predicted value. Long Short-Term Memory (LSTM) and Temporal Convolutional Network (TCN) are used as comparison algorithms to train and forecast 3 h, 6 h, 12 h, 24 h, and 48 h ahead of daily electricity load together with LST-TCN. Three different performance metrics, including pinball loss, root mean squared error (RMSE), and mean absolute error (RASE), were used to evaluate the performance of the proposed algorithms. The results of the test set proved that LST-TCN has better generalizat... [more]

This paper presents the mathematical model and control of the voltage source inverter (VSI) connected to an alternating current (AC) microgrid. The VSI used in this work was a six-switch three-phase PWM inverter, whose output voltages were controlled in a synchronous (dq) reference frame via a sliding mode control strategy. The control strategy required only output voltages; other states of the system were estimated by using a high-gain observer. The power-sharing among multiple inverters was achieved by solving power flow equations of the electrical network. The stability analysis showed that the error was ultimately bound in the case of the real PWM inverter and/or with a nonlinear load in the electrical network. The microgrid was simulated using the SimPowerSystems Toolbox from MATLAB/Simulink. The simulation results show the effectiveness of the proposed control scheme. The output voltage regulation of the inverter and power-sharing was achieved with the ultimately bounded error fo... [more]

The main goal of hydraulic fracturing stimulation in unconventional and tight reservoirs is to maximize hydrocarbon production by creating an efficient stimulated reservoir volume (SRV) around the horizontal wells. To zreach this goal, a physics-based model is typically used to design and optimize the hydraulic fracturing process before executing the job. However, two critical issues make this approach insufficient for achieving the mentioned goal. First, the physics-based models are based on several simplified assumptions and do not correctly represent the physics of unconventional reservoirs; hence, they often fail to match the observed SRVs in the field. Second, the success of the executed stimulation job is evaluated after it is completed in the field, leaving no room to modify some parameters such as proppant concentration in the middle of the job. To this end, this paper proposes data-driven and global sensitivity approaches to address these two issues. It introduces a novel work... [more]

This article presents rheological models of fluids used in the drilling practice. It discusses the principles of determining drilling fluid rheological parameters based on data acquired from measurements by means of viscometers used in the drilling practice. The authors propose the application of the three-parameter Vom Berg and Hahn−Eyring models not used in the drilling industry so far. Necessary relationships have been developed for these models, which enable the determination of rheological parameters. In order to account for the influence of different flow conditions on the value of drilling fluid rheological parameters, the approach proposing the determination of rheological parameters of a given three-parameter model separately for low shear rates and high shear rates has been suggested. A practical application of the methodology proposed in this paper for determining the rheological parameters of the three-parameter Vom Berg and Hahn−Eyring models is presented using real drilli... [more]

Chloride diffusion through concrete is influenced by harsh environmental conditions such as high ambient temperature and relative humidity. This paper examined the influence of temperature gradient on chloride diffusion in concrete under high ambient temperature conditions. Chloride diffusion tests using cylindrical concrete samples were performed in constant temperature and temperature gradient conditions. In a temperature gradient condition, a much higher chloride concentration was measured than at constant temperatures, which could not be explained only by the mass diffusion driven by the concentration gradient. A new analytical model of chloride diffusion with the mass diffusion term including the temperature effect and the thermo-diffusion term including the temperature gradient effect was applied to the results, which showed that the thermo-diffusion contribution was significant. Using the analytical model with the mass diffusion (DCl) and thermo-diffusion (DT) coefficients, the... [more]

Electrified vehicles (EV) and marine vessels represent promising clean transportation solutions to reduce or eliminate petroleum fuel use, greenhouse gas emissions and air pollutants. The presently commonly used electric energy storage system (ESS) is based on lithium-ion batteries. These batteries are the electrified or hybridized powertrain’s most expensive component and show noticeable performance degradations under different use patterns. Therefore, battery life prediction models play a key role in realizing globally optimized EV design and energy control strategies. This research studies the data-driven modelling and prediction methods for Li-ion batteries’ performance degradation behaviour and the state of health (SOH) estimation. The research takes advantage of the increasingly available battery test and data to reduce prediction errors of the widely used semi-empirical modelling methods. Several data-driven modelling techniques have been applied, improved, and compared to ident... [more]

The main objective of this study was to conduct multi-stage and multi-variant prognostic research to assess the impact of e-mobility development on the Polish power system for the period 2022−2027. The research steps were as follows: forecast the number of electric vehicles (using seven methods), forecast annual power demand arising solely out of the operation of the forecast number of electric vehicles, forecast annual power demand with and without the impact of e-mobility growth (using six methods), forecast daily profiles of typical days with and without the impact of e-mobility growth (using three methods). For the purpose of this research, we developed a unique Growth Dynamics Model to forecast the number of electric vehicles in Poland. The application of Multi-Layer Perceptron (MLP) to the extrapolation of non-linear functions (to the forecast number of electric vehicles and forecast annual power demand without the impact of e-mobility growth) is our original, unique proposal to... [more]

Mahu oilfield is a typical tight gravel oil reservoir. At present, long-stage multi-cluster fracturing is widely used for reservoir stimulation, and multiple-clusters treatment is realized through cluster perforation. Field monitoring indicates that not all perforation clusters produce hydraulic fractures in the fracturing process, and each cluster of hydraulic fractures in the section will expand unevenly. The unbalanced expansion of multiple clusters of fractures in the section seriously affects the effect of reservoir reconstruction of horizontal wells. Aiming at the long-stage multi-cluster fracturing of horizontal wells, a multi-fracture propagation calculation model considering wellbore flow, performance friction, different fracture criteria at the tip, and the interaction stress among multiple fractures is established in this paper. In order to improve the calculation efficiency, an explicit Runge Kutta Legendre algorithm is proposed to solve the structural mesh, and the solutio... [more]

Photovoltaics (PV) and Solar Thermal (ST) collectors are sometimes competitors, as investment capacity, energy demand, and roof space are limited. Therefore, a ratio that quantifies the difference in annual energy output between ST and PV for different locations is useful. A market survey assessing the average price and performance both in 2013 and 2021 was conducted, showing a factor of 3 cell price decrease combined with a 20% efficiency increase, while ST showed negligible variation. Winsun simulations were conducted, and the results were plotted on the world map. Despite variations due to local climate, the ratio of energy production (ST/PV) increases at lower latitudes mainly due to (a) higher air temperature increasing ST output but decreasing the PV output; (b) solar radiation reducing ST efficiency to zero while having a minor impact on PV efficiency. The ratio was calculated for several ST operating temperatures. For latitudes lower than 66°, the ratio of a flat plate at 50 °C... [more]

Climate and energy policies are the key areas of the European Union’s development aspirations in the international arena. The European Green Deal sets ambitious new goals in this respect, emphasizing clean energy. The development of the energy sector, relying chiefly on renewable sources, is one of the conditions for the EU to transition to energies that do not produce waste that pollutes or is otherwise harmful to the Earth and human health. This paper assesses the development of renewable sources of energy in the EU and identifies challenges to the realization of the EU’s energy priorities. An analysis of renewable sources of energy in the EU in 2012 and 2020 is the prime method. The generation of primary energy from renewable sources, the share of energy from renewable sources in the final energy consumption, the structure of energy generation from renewable sources, and the share of energy from renewable sources in the energy used by the transport sector are discussed. Secondary da... [more]

Refrigeration systems based on cooling towers and chillers are widely used equipment in industrial buildings, such as shopping centers, gas and oil refineries and power plants, among many others. Cooling towers are used to recover the heat rejected by the refrigeration system. In this work, the refrigeration is composed of cooling towers dotted with ventilators and compression chillers. The growing environmental concerns and the current scenario of scarce water and energy resources have lead to the adoption of actions to obtain the maximum energy efficiency in such refrigeration equipment. This backs up the application of computational intelligence to optimize the operating conditions of the involved equipment and cooling processes. In this context, we utilize multi-objective optimization algorithms to determine the optimal operational setpoints of the cooling system regarding the cooling towers, its fans and the included chillers. We use evolutionary multi-objective optimization to pr... [more]

The textile industry is one of the largest environmental polluters in the world. Although waste management via anaerobic digestion (AD) is a sustainable strategy to transform waste into clean energy and water recovery, the efficiency of the AD process is reduced by the presence of recalcitrant materials, chemicals, and toxic contents. This study aims to investigate the performance of several chemical, physical, and biological pretreatments applied to improve the biodegradability of textile waste. We performed a meta-analysis with 117 data extracted from 13 published articles that evaluated the efficiency of pretreatments applied to textile waste prior to AD to increase biogas production measured as methane (CH4) yield. Even though the majority of the studies have focused on the effect of chemical and physical pretreatments, our results showed that the application of biological pretreatments are more efficient and eco-friendlier. Biological pretreatments can increase CH4 yield by up to... [more]