Surfactants and nanoparticles play crucial roles in controlling the oil-water interfacial phenomenon. The natural oil-wet mineral nanoparticles that exist in crude oil could remarkably affect water-oil interfacial characteristics. Most of recent studies focus on the effect of hydrophilic nanoparticles dispersed in water on the oil-water interfacial phenomenon for the nanoparticle enhanced oil recovery. However, studies of the impact of the oil-wet nanoparticles existed in crude oil on interfacial behaviour are rare. In this study, the impacts of Span 80 surfactant and hydrophobic SiO2 nanoparticles on the crude oil-water interfacial characteristics were studied by measuring the dynamic and equilibrium crude oil-water interfacial tensions. The results show the existence of nanoparticles leading to higher crude oil-water interfacial tensions than those without nanoparticles at low surfactant concentrations below 2000 ppm. At a Span 80 surfactant concentration of 1000 ppm, the increase of... [more]

The present work involves a new and novel upgrading design to the classical solar chimney power plant (SCPP) structure. The SCPP design was modified by adding a co-centric secondary external chimney to the SCPP structure to enhance energy production. In the new improved design, named the solar double-chimney power plant (SDCPP), the internal chimney, operates like a traditional SCPP to produce electricity during the daytime whereas the secondary external chimney operates as 10 cooling towers (CT) in a series. Each CT is equipped with a turbine and water sprinklers for further energy production. The new design offers the operation of the SCPP during the day and the continuous operation of the CT (day-and-night). A mathematical model that includes the energy and mass balance equations of the system was built using MATLAB. The SDCPP system produced up to 993 MWh of electrical energy, which is 2.6 times higher than the traditional SCPP (377 MWh). The new design configuration achieved a per... [more]

Combustible aqueous foams and foamed emulsions represent prospective energy carriers. This paper is devoted to the overview of model assumptions required for numerical simulations of combustion and detonation processes in aqueous foams. The basic mathematical model is proposed and used for the analysis of the combustion development in the wet aqueous foam containing bubbles filled with reactive gas. The numerical results agree with the recent experimental data on combustion and detonation in aqueous foams containing premixed hydrogen−oxygen. The obtained results allowed for distinguishing the mechanisms of flame acceleration, transition to detonation, detonation propagation, and decay.

The microporous layer (MPL) constitutes a critical component of the gas diffusion layer within the membrane electrode assembly (MEA) of a proton exchange membrane fuel cell (PEM FC). The MPL plays a fundamental role in various processes during FC operation: control of membrane humidification, heat distribution throughout the MEA, excess water removal from the cathode, and transportation of fuel to the reaction sites. Previously, we investigated the performance of a fuel cell unit employing an MPL based on laser-induced graphene (LIG) produced by the laser pyrolysis of polymeric (polyimide) substrates. The prototype LIG-based unit was tested over the typical range of relative humidity and temperature conditions. The polarization curves observed in that study displayed broad ohmic loss regions and high stability along the concentration loss regions, an interesting electrical behavior that justified developing the present voltage-current density study for the same FC prototype compared to... [more]

Epidemiological research has shown that there is a positive correlation between the incidence of disease and mortality in humans and the mass concentration of particulate matter. An average 1 g of suspended dust emitted in a room results in the same exposure as 1 kg emitted to the outside air. In this study, the authors described the state of knowledge on dust pollution inside and outside buildings (I/O ratios), and methods of testing the PM infiltration process parameters. According to the law of indoor−outdoor particle mass balance and the physical basis of aerosol penetration theory, a relatively simple but new method for estimating the penetration factor P was tested. On the basis of the curve of dynamic changes of internal dust concentration in the process of particle concentration decay and next of the followed curve of dynamic rebound of particle concentration, authors measured penetration factor of ambient PM2.5 through building envelope. Authors modification of the method is t... [more]

Huge efforts have been made in recent decades to improve energy saving in the building sector, particularly focused on the role of façades. Among the explored viable solutions, climate-adaptive building shells [CABS] consider promising solutions to control solar radiation, both in terms of illuminance and heating levels, but are still piloting these solutions due to their complex designs and necessary costs. The present study aims to provide a speedy but reliable methodology to evaluate the potential impacts of adopting active/passive CABS systems during the preliminary design stage. The proposed methodology allows the evaluation and comparison, when multiple options are considered, of the effects of each solution in terms of the energy needs, thermal comfort and lighting, while reducing the required effort and time for an extensive analysis of the overall building level. This is based on the use of a “virtual test room” where different conditions and configurations can be explored. A... [more]

Statistical analysis methods have been widely used in all industries. In well logs analyses, they have been used from the very beginning to predict petrophysical parameters such as permeability and porosity or to generate synthetic curves such as density or sonic logs. Initially, logs were generated as simple functions of other measurements. Then, as a result of the popularisation of algorithms such as the k-nearest neighbours (k-NN) or artificial neural networks (ANN), logs were created based on other logs. In this study, various industry and general scientific programmes were used for statistical data analysis, treating the well logs data as individual data sets, obtaining very convergent results. The methods developed for processing well logs data, such as Multi-Resolution Graph-Based Clustering (MRGBC), as well as algorithms commonly used in statistical analysis such as Kohonen self-organising maps (SOM), k-NN, and ANN were applied. The use of the aforementioned statis-tical method... [more]

In this paper, the technological advances in concentrating solar power are reviewed. A comprehensive system approach within this scope is attempted to include advances of highly specialized developments in all aspects of the technology. Advances in geometric optics for enhancement in solar concentration and temperature are reviewed along with receiver configurations for efficient heat transfer. Advances in sensible and latent heat storage materials, as well as development in thermochemical processes, are also reviewed in conjunction with efficient system integration as well as alternative energy generation technologies. This comprehensive approach aims in highlighting promising concentrating solar power components for further development and wider solar energy utilization.

The role of a pre-cooler is critical to the sCO2-BC as it not only acts as a sink but also controls the conditions at the main compressor’s inlet that are vital to the cycle’s overall performance. Despite their prime importance, studies on the pre-cooler’s design are hard to find in the literature. This is partly due to the unavailability of data around the complex thermohydraulic characteristics linked with their operation close to the critical point. Henceforth, the current work deals with designing and optimizing pre-cooler by utilizing machine learning (ML), an in-house recuperator and pre-cooler design, an analysis code (RPDAC), and a cycle design point code (CDPC). Initially, data computed using 3D Reynolds averaged Navier-Stokes (RANS) equation is used to train the machine learning (ML) model based on the deep neural network (DNN) to predict Nusselt number (Nu) and friction factor (f). The trained ML model is then used in the pre-cooler design and optimization code (RPDAC) to ge... [more]

In the area of the the Krško alluvial field, the Brežice hydroelectric power plant (BHPP), with its surface water reservoir, was completed in 2017. The new BHPP reservoir dam is located approximately 7 km air distance downstream of the old Krško nuclear power plant (NEK) reservoir dam. The NEK dam was built in the 1970s. The primary purpose of the NEK reservoir is to provide fresh water for cooling the NEK nuclear reactor. To assess the impact of the newly built surface water reservoir on groundwater, we performed a series of data analyses prior to its construction. One part of the analysis relating to data from the monitoring facility of the NEK showed an interesting correspondence between the water level oscillation in the NEK reservoir and the groundwater oscillation in the nearby observation well. Based on measurements taken in 2000, we sought to estimate the clogging of the Sava riverbed sediments in the area of the old NEK surface water reservoir. To determine the permeability of... [more]

Various environmental policy instruments supporting the development of renewable energy are used on an increasing scale as part of the policy of mitigating climate change and more. In our paper, we examine the influence of environmental policy stringency on renewable energy production in the Czech Republic, Hungary, Poland and Slovakia for the period 1993−2012 after controlling for gross domestic product per capita growth, CO2 emissions per capita and income inequality. We use the Panel Pooled Mean Group Autoregressive Distributive Lag model to analyze the long-run and the short-run relationship between restrictiveness of environmental policy and renewable energy generation. The results reveal that, in the long run, a more stringent environmental policy has a positive impact both on the increase in the absolute volume of renewable energy production, as well as on the replacement of energy from fossil sources. Our main findings indicate that renewable energy production is positively inf... [more]

Frequent fluctuations of CNG engine operating conditions make the waste heat source have uncertain, nonlinear, and strong coupling characteristics. These characteristics are not conducive to the efficient recovery of the DORC system. The systematic evaluation of the CNG engine waste heat source and the comprehensive performance of the DORC system is conducive to the efficient use of waste heat. Based on the theory of internal combustion (IC) engine thermal balance, this paper analyzes the dynamic characteristics of compressed natural gas (CNG) engine waste heat energy under full operating conditions. Then, based on the operating characteristics of the dual loop organic Rankine cycle (DORC) system, thermodynamic models, heat transfer models, and economic models are constructed. The dynamic response characteristics analysis and energy, exergy, and economic (3E) evaluation of the DORC system under full operating conditions are carried out. The results show that the maximum values of net p... [more]

After the failure of the power system, a large amount of alarm information will flood into the dispatching terminal instantly. At the same time, there are inevitable problems, such as the abnormal operation of the protection and the circuit breaker, the lack of alarm information, and so on. This kind of uncertainty problem brings great trouble to the fault diagnosis algorithm. As a data processing algorithm for an uncertain information set, Top-k Skyline query algorithm can eliminate the data points that do not meet the requirements in the information set, and then output the final K results in order. Based on this background, this paper proposes a power grid fault diagnosis method based on the Top-k Skyline query algorithm considering alarm information loss. Firstly, the fault area is determined by using the information of the electrical quantity and switching value. Then, backward reasoning Petri nets are established for the nodes in the fault area to form the data set of fault hypot... [more]

Electric forklifts are extremely important for the world’s logistics and industry. Lead acid batteries are the most common energy storage system for electric forklifts; however, to ensure more energy efficiency and less environmental pollution, they are starting to use lithium batteries. All lithium batteries need a battery management system (BMS) for safety, long life cycle and better efficiency. This system is capable to estimate the battery state of charge, state of health and state of function, but those cannot be measured directly and must be estimated indirectly using battery models. Consequently, accurate battery models are essential for implementation of advance BMS and enhance its accuracy. This work presents a comparison between four different models, four different types of optimizers algorithms and seven different experiment designs. The purpose is defining the best model, with the best optimizer, and the best experiment design for battery parameter estimation. This best mo... [more]

The use of sea wind energy is restricted by the limited availability of suitable sites in shallow waters. To overcome this challenge, wind turbines located on offshore semi-submersible platforms appear as a valuable option, as they also allow the exploitation of other resources like wave energy or aquaculture. Nevertheless, the literature addressing this kind of design is scarce, and the interactions of the wind turbine and the platform movements increase the complexity of the control system with respect to the wind turbines with fixed foundations. Within this context, fuzzy control is a promising alternative to deal with these issues. However, while fuzzy controllers can be an alternative to substitute conventional PI control, the latter is a well-known, robust choice for operators. In this sense, fuzzy controllers can be designed to work in collaboration with PI controllers to ease their adoption. To this end, this paper addresses those gaps in the literature by presenting a methodol... [more]

In this paper, a novel SIBO (Single-Inductor Bipolar-Output) DC/DC Boost converter is proposed to power OLED (Organic Light-Emitting Diode) microdisplays. The proposed topology merges a conventional SISO (Single-Inductor Single-Output) DC/DC Boost converter and a switched capacitor inverter to produce a SIBO converter without both the cross-regulation effect and the unbalanced output voltages. Moreover, its control circuit and efficiency are almost the same as the conventional SISO Boost converter. Therefore, the novel converter maintains the power density, the small form factor, and the high efficiency of its conventional counterpart. The proposed converter was analyzed under continuous-conduction mode operation using the moving average operator and charge conservation principle. As a result, the authors proposed an equation set with the main averages and ripples of the circuit variables expressed as analytical functions of the circuit components, the input voltage, and the duty cycle... [more]

Islands are widely recognised as ideal pilot sites that can spearhead the transition to clean energy and development towards a sustainable and healthy society. One of the assumptions underpinning this notion is that island communities are more ready to engage with smart grids (SGs) than people on the mainland. This is believed to be due to the high costs of energy on islands and the idea that the sense of community and collective action is stronger on islands than on the mainland. This paper presents findings from a survey conducted to assess people’s perception of, and readiness to engage with, SG and demand response (DR) in the communities of three islands taking part in a H2020 project called REACT. The main objective of the survey, conducted in 2020, was to inform the recruitment of participants in the project, which is piloting different technologies required for SGs and DR with communities on the three islands. The results show that many island residents are motivated to take par... [more]

Wind turbines are typically organised as a fleet in a wind park, subject to similar, but varying, environmental conditions. This makes it possible to assess and benchmark a turbine’s output performance by comparing it to the other assets in the fleet. However, such a comparison cannot be performed straightforwardly on time series production data since the performance of a wind turbine is affected by a diverse set of factors (e.g., weather conditions). All these factors also produce a continuous stream of data, which, if discretised in an appropriate fashion, might allow us to uncover relevant insights into the turbine’s operations and behaviour. In this paper, we exploit the outcome of two inherently different discretisation approaches by statistical and visual analytics. As the first discretisation method, a complex layered integration approach is used. The DNA-like outcome allows us to apply advanced visual analytics, facilitating insightful operating mode monitoring. The second disc... [more]

The design and development of wind turbines in low-wind-speed areas involves several technical and financial challenges related to maximizing conversion efficiency and minimizing cost. Unfortunately, much of the African continent is dominated by low-wind-speed resources. In this study, a multi-parameter optimization method is used to explore the design of a novel Ferris wheel wind turbine (FWT) technology, which has an 800-kW generation capability. We used the tip speed ratio, lift-to-drag ratio and power coefficient to determine the optimal efficiency by varying the number of blades and rim diameters. The capital cost estimates, as affected by rim diameter and the number of blades, are presented. This paper studies FWTs at their rated wind speeds because wind turbines have their maximum performance at the rated wind speeds, and this allows one to observe the effects of changing the rim diameter and the number of blades without the need to consider the location of the turbine. The resu... [more]

Since the triboelectric nanogenerator (TENG) was invented, it has received extensive attention from researchers. Among the many pieces of research based on TENG, the research of hybridized generators is progressing rapidly. In recent years, the research and application of the electromagnetic−triboelectric hybridized nanogenerator (EMG-TENG) have made great progress. This review mainly focuses on the latest research development of EMG-TENG and elaborates on the principles, materials, structure, and applications of EMG-TENG. In this paper, the microscopic charge transfer mechanism of TENG is explained by the most primitive friction electrification phenomenon and electrostatic induction phenomenon. The commonly used materials for fabricating TENG and the selection and modification methods of the materials are introduced. According to the difference in structure, EMG-TENG is divided into two categories: vibratory EMG-TENG and rotating EMG-TENG. The summary explains the application of EMG-T... [more]

As the decarbonisation of heating and cooling becomes a matter of critical importance, it has been shown that flooded mines can provide a reliable source of low-carbon thermal energy production and storage when coupled with appropriate demand via an appropriate heat transfer technology. This paper summarises the potential resource represented by a long legacy of mining operations, the means heat can be extracted from (or rejected to) flooded mine workings, and then considers the risks and challenges faced by minewater geothermal energy (MWG) schemes in the planning, construction, and operational phases. A combination of site visits, interviews and literature reviews has informed concise, updated accounts for many of the minewater geothermal energy systems installed across the world, including accounts of hitherto unpublished systems. The paper has found that a number of previously reported MWG schemes are now non-operational. Key risks encountered by MWG schemes (which in some cases ha... [more]

The paper describes the cascaded voltage and current control for a bidirectional DC/DC converter in Dual Active Bridge (DAB) topology. The typical DAB converter circuit was extended by additional current filters, which allow it to operate in application fields with high requirements on current ripples. The core concept of the presented solution is usage of the modified Single Phase Shift (SPS) modulation, which allows to compensate for the DC-bias current occurring in dynamic states and provides a settling time of half switching cycle during transients. Its features were utilized to build a simplified dynamic model of the converter. The linear Proportional-Integral (PI) controllers are used in both voltage and current control loops. Based on the developed dynamic models, the tuning rules for both controllers were derived. In both cases, a number of the tuned parameters were reduced from two to one (which can present a great practical value for application engineers). The proposed solut... [more]

The use of photovoltaic (PV) systems as the energy source of electrical distributed generators (DG) is gaining popularity, due to the progress of power electronics devices and technologies. Large-scale solar PV power plants are becoming the preferable solution to meet the fast growth of electrical energy demand, as they can be installed in less than one year, as compared to around four years in the case of conventional power plants. Modular multilevel inverters (MMIs) are the best solution to connect these large-scale PV plants to the medium-voltage (MV) grid, due to their numerous merits, such as providing better power quality, having higher efficiency, providing better reliability, and their scalability. However, MMIs are still progressing and need some improvement before they can be implemented safely in the industrial, medium, and high voltage networks. The main purpose of this paper is to review the present MMIs topologies when used in PV applications. The review aims to present a... [more]

This paper proposes an energy management system (EMS) for battery storage systems in grid-connected microgrids. The battery charging/discharging power is determined such that the overall energy consumption cost is minimized, considering the variation in grid tariff, renewable power generation and load demand. The system is modeled as an economic load dispatch optimization problem over a 24 h horizon and solved using mixed integer linear programming (MILP). This formulation, therefore, requires knowledge of the expected renewable energy power production and load demand over the next 24 h. To achieve this, a long short-term memory (LSTM) network is proposed. The receding horizon (RH) strategy is suggested to reduce the impact of prediction error and enable real-time implementation of the EMS that benefits from using actual generation and demand data on the day. At each hour, the LSTM predicts generation and load data for the next 24 h, the dispatch problem is then solved and the battery... [more]

One of the most important milestones in the history of hydropower is the invention of the Kaplan turbine. It is a machine stemming from the Francis turbine, which Viktor Kaplan was originally trying to improve. However, it gradually developed into the creation of a completely new solution of an impeller with an axial flow rate and adjustable blades. The first patent relating to the new invention dates from 1913. Shortly afterwards, the Kaplan turbine became the most widely used type of device for the use of low heads and variable flow rates. That meant a significant expansion of the potential of economically usable hydropower. The article briefly introduces the history of turbine development. The overall picture is then completed by a few less-known historical documents.