This paper proposes a wind power probabilistic model (WPPM) using the reflection method and multi-kernel function kernel density estimation (KDE). With the increasing penetration of renewable energy sources (RESs) into power systems, several probabilistic approaches have been introduced to assess the impact of RESs on the power system. A probabilistic approach requires a wind power scenario (WPS), and the WPS is generated from the WPPM. Previously, WPPM was generated using a parametric density estimation, and it had limitations in reflecting the characteristics of wind power data (WPD) due to a boundary bias problem. The paper proposes a WPPM generated using the KDE, which is a non-parametric method. Additionally, the paper proposes a reflection method correcting for the boundary bias problem caused by the double-bounded characteristic of the WPD and the multi-kernel function KDE minimizing the effect of tied values. Six bandwidth selectors are used to calculate the bandwidth for the K... [more]

In this paper, the results of an experimental study on hydrogen production at a tungsten discharge electrode with negative polarity in the DC electrolysis of a typical 10 wt% Na2CO3 aqueous solution in three operational regimes (the Faradaic, transition, and plasma-driven solution electrolysis (PDSE)) are presented for the first time. To focus the study on hydrogen production, a flowing inert gas (argon) was used to transport the gas mixture produced at the discharge electrode and prevent any other potential chemical reactions. The results showed that the highest hydrogen production rate of 0.147 g(H2)/h was achieved in the cathodic PDSE regime at the applied DC voltage of 198 V. However, the energy yield of hydrogen production of 0.405 g(H2)/kWh obtained at the applied voltage range of 141−170 V in the PDSE regime was lower than that obtained in the Faradaic regime (0.867 g(H2)/kWh) at 28 V. The energy balance of hydrogen production in the cathodic PDSE regime for the typical aqueous... [more]

Diesel engines are one of the most popular reciprocating engines on the market today owing to their great thermal efficiency and dependability in energy conversion. Growing concerns about the depletion of fossil resources, fluctuating prices in the market, and environmental issues have prompted the search for renewable fuels with higher efficiencies compared with conventional fuels. Fuel derived from vegetable oils and animal fats has comparable characteristics to diesel fuel, but is renewable, despite being manufactured from various feedstocks. Nevertheless, the direct use of these fuels is strictly prohibited because it will result in many issues in the engine, affecting engine performance and durability, as well as emissions. To make biofuels as efficient as fossil fuels, it is essential to alter their characteristics. The use of emulsification techniques to obtain emulsified biofuels is one of the many ways to modify the fuel characteristics. Emulsification techniques allow for a d... [more]

The dynamic viscoelastic theory of soil−pile interaction dominates the initial impedance calculation during the pile dynamic design and analysis. Further, it provides a firm theoretical ground for the wave propagation simulation, which could be the basis of seismic analysis and some geotechnical testing approaches. This review traces the development history and key findings of viscoelastic soil−pile interaction theory and expounds on the advantages and limitations of various theoretical advances in terms of dynamic design and wave propagation modeling. The review consists of three sub-divisions, which are the longitudinal, horizontal, and torsional viscoelastic soil-pile theories. The development and implement of multi-phase soil constitutive equations, multi-dimensional soil−pile interaction modeling methods, pile−soil−pile mutual interactions in pile groups, and the fluid−structure interaction problems in offshore piles are especially remarked and concluded. Finally, the shortcomings... [more]

Climate change has been turning into a climate crisis. Thus, we live in an era in which it is important to carry out the promise of 2050 carbon neutrality worldwide. South Korea is a country with a very large private education market. As the online education market has also recently expanded rapidly, interest in the electricity consumed by educational institutions is growing. One way to reduce the power consumption of private educational institutions, which is expected to gradually increase, is to replace the existing power system with a hybrid energy system based on renewable energy. This study aims to investigate an optimized renewable-energy-based hybrid system to supply adequate power to private educational institutions in Korea. We propose an optimal system using the HOMER (Hybrid Optimization Model for Electric Renewables) program. The result is that when private educational institutions adopt a hybrid renewable energy system, the renewable fraction is negligible in the grid-conn... [more]

Frequency stability is an important factor for the safety and stability of the power system operation. In a traditional power system, the operation stability is ensured by the inertia response, primary frequency modulation, and secondary frequency modulation. In recent years, in order to achieve the goal of carbon neutralization and carbon peaking, China has made great efforts in new energy development. With large-scale new energy connected to the power grid, the proportion of traditional conventional synchronous units has gradually declined. At the same time, a large number of power electronic devices have been used in the power grid, which led to the capability decline of the inertia response and primary frequency modulation. For example, the East China Power Grid has experienced a sharp frequency drop in such an environment. In order to solve the above problems, the operation principle and control mode of various new energy resources are analyzed in this paper. Moreover, the process... [more]

A high-performance and scalable lipase immobilization method using a dipping and jet break-up technique was reported for the production of microcapsule biocatalysts with an entrapped cascade of lipase enzyme. The lipase from Candida antarctica (CALb) recombinant Aspergillus oryzae and from the vegetal of Jatropha curcas L. (var. Sevangel) in Morelos State of Mexico were entrapped by mixing with a sodium alginate biopolymer at different concentrations. The obtained microcapsules were hardened in a CaCl2 solution, aiming at developing Ca2+ alginate microbeads with sizes mostly from 220 to 300 μm. The relationship between the process variables with the shape and size of the alginate drops before and after the gelation was established with aid of optical image analysis. The results showed that a critical Ohnesorge number (Oh) > 0.24 was required to form spherical microencapsulated beads. The biodiesel production via esterification/transesterification reaction was performed using the crude... [more]

The dependence of road transport on fossil fuels and its contribution to greenhouse gas (GHG) and pollutant emissions are main concerns leading to the need for shifting toward alternative energy sources and, namely, electromobility. The current paper aims to identify the key determinants affecting the consumer adoption of electric vehicles (EVs), focusing on private passenger cars. Toward this purpose, a systematic review of recent international literature is conducted in order to identify motivators and barriers, which are then categorized following the PESTLE (Political−Economic−Social−Technological−Legal−Environmental) approach. Based on the review results, main policy implications and recommendations are discussed. A main conclusion is that the recent literature highlights a wide array of determinants, without converging as to which ones are the most influential regarding EV adoption by consumers. Another conclusion is that the environmental aspects are less important for consumers... [more]

The rising share of renewable energy in the energy mix brings with it new challenges such as power curtailment and lack of reliable large-scale energy grid. The forecasting of wind power generation for provision of flexibility, defined as the ability to absorb and manage fluctuations in the demand and supply by storing energy at times of surplus and releasing it when needed, is important. In this study, short-term forecasting models of wind power generation were developed using the conventional time-series method and hybrid models using support vector regression (SVR) based on rolling origin recalibration. For the application of the methodology, the meteorological database from Korea Meteorological Administration and actual operating data of a wind power turbine (2.3 MW) from 1 January to 31 December 2015 were used. The results showed that the proposed SVR model has higher forecasting accuracy than the existing time-series methods. In addition, the conventional time-series model has hi... [more]

The paper presents the experimental research on the thermal management of a 150 W LED lamp with heat sink inside a synthetic jet actuator. The luminous flux was generated by 320 SMD LEDs with a nominal luminous efficacy equal to 200 lm/W mounted on a single PCB. Characteristic temperatures were measured with three different measurement techniques: thermocouples, infrared camera, and an estimation of the junction temperature from its calibrated dependence on the LED forward voltage. The temperature budget between the LED junction and ambient as well as the thermal resistance network was determined and analyzed. The energy balance of the LED lamp is presented along with the values of the heat flow rate and heat transfer coefficient in different regions of the LED lamp surface. For an input power supplied to the SJA equal to 4.50 W, the synthetic jet dissipated approximately 89% of the total heat generated by the LED lamp. The heat from the PCB was transferred through the front and rear s... [more]

Different renewable energy resources and energy demands between parks lead to waste of resources and frequent interactions between the regional distribution grid and the larger grid. Hence, an optimal dispatching scheme of the regional integrated energy system group (RIESG), which combines the power-to-gas (P2G) and inter-park electric energy mutual aid, is proposed in this paper to solve this problem. Firstly, for the park integrated energy system (PIES) with various structures, the coupling matrix is used to describe the input-output relationship and coupling form of multiple energy sources in the energy-hub (EH), which linearizes the complex multi-energy coupled system and is more conducive to the solution of the model. Secondly, the electrical coupling relationship of the system is improved by adding P2G to enhance the system’s ability to consume renewable energy. Moreover, the installation cost of P2G is introduced to comprehensively consider the impact of the economic efficiency... [more]

Sub-synchronous oscillation is one of the most challenging issues in modern power systems with a high proportion of wind power. Interactions among the wind turbines are key factors causing the oscillations. This paper aims to propose a method to quantify the interactions among N permanent-magnet-synchronous-generator (PMSG)-based wind turbines by transfer functions and analyze the influence of the interactions on the system stability. We derived different terms of the self- and en-stabilizing functions to describe different interactions caused by different wind turbines analytically. Meanwhile, the parameter sensitivity of this method is proposed to analyze the impact of the system and control parameters on the interactions and the system stability. Examples and simulations are given to show the effectiveness of this method.

Electric Vehicles (EVs) replace fossil fuel vehicles in effort towards having more sustainable transport systems. The battery of an EV is recharged at a charging point using electricity. While some recharging will be required at locations where vehicles are normally parked, other recharging could be necessary at strategic locations of vehicular travel. Certain locations are suitable for EV charging station deployment, others are not. A multi-stage decision analysis methodology for selecting suitable locations for installing EV charging station is presented. The multi-stage approach makes it possible to select critical criteria with respect to any defined objectives of the EV charging station and techno-physio-socio-economic factors without which the EV charging station could not be deployed or would not serve its designated purpose. In a case, the type of charging station is specified, and a purpose is defined: rapid EV charging stations intended for public use within and across border... [more]

Seaweeds represent a promising and sustainable feedstock for biofuel production which raises increasing research interests. Their high availability, easy fermentable composition, and good degradation potential make them a suitable candidate for alternating fossil fuels as an advantageous energy resource. This comprehensive review aims to summarize and discuss data from the literature on the biochemical composition of seaweeds and its potential for biomethane and biohydrogen production, as well as to investigate the effect of the common pretreatment methods. Satisfactory yields comparable to terrestrial biomass could be obtained through anaerobic digestion; concerning dark fermentation, the challenge remains to better define the operating conditions allowing a stable production of biohydrogen. Finally, we propose a potential energy production scheme with the seaweed found by the Caribbean Islands of Guadeloupe and Martinique, as well as current techno-economic challenges and future pros... [more]

The article presents and compares two different control methods for a permanent magnet synchronous motor (PMSM) for diesel−electric ship propulsion. The main focus of the article is on control optimization, which allows improving energy efficiency by reducing reactive power in the mechatronic propulsion system. The first method consists in modifying the commonly used field-oriented control (FOC) strategy to ensure zero reactive power in the inverter−PMSM system. Since a characteristic of ship propulsion systems, unlike those used on land, is the step load on the propulsion motor, the system’s performance in dynamic states is particularly important. Unfortunately, control strategies based on FOC do not take into account the dynamics of the system, since they apply only to steady states. Therefore, the authors of this paper, based on control theory methods, proposed an approach that also optimizes control in dynamic states, while minimizing reactive power in the steady state. The analyti... [more]

Methanol crossover is an important factor affecting the performance of direct methanol fuel cells (DMFCs). In this work, a novel membrane electrode assembly (MEA) is designed and prepared by adding a layer of graphene aerogel (GA) between the carbon powder microporous layer and the catalytic layer, which optimizes the methanol transport and improves the output performance of DMFC at high methanol concentrations. Compared to conventional carbon powder, the addition of GA increases the tortuosity of the anode in the through-plane direction; hence, methanol is diluted to a suitable concentration when it reaches the catalyst. The maximum power density of the novel MEA can reach 27.4 mW·cm−2 at a condition of 8 M methanol, which is 234% higher than that of the conventional electrode. The test results of electrochemical impedance spectroscopy (EIS) indicate that the addition of GA does not increase the internal resistance of the novel MEA and that the mass transfer resistance at high concent... [more]

This study analysed a novel re-liquefaction system integrated with a fuel supply system (FSS) for an LPG carrier to conventional systems. The re-liquefaction system and FSS were installed independently in a conventional LPG carrier, while those systems were combined in the novel system. The condensed LPG in the re-liquefaction system was directly transferred to the FSS without the cooling and expansion process in the novel system. 84,000 m3 LPG carrier equipped with a 10 MW engine at normal continuous rating (NCR) was selected as a target ship. Aspen HYSYS ver.12.1 was employed for process simulation. The results showed that the energy consumption for the novel system was reduced by 38%. The energy for re-liquefaction was decreased because the flow rate recirculated was decreased, and the energy for FSS was reduced as the temperature of the stream supplied to the FSS was relatively high in the novel system. A sensitivity analysis was conducted to investigate the effect of the parameter... [more]

Energy security and the reduction of greenhouse gases such as carbon dioxide are two major crises facing the world today. Using carbon dioxide to develop unconventional oil and gas resources is a positive way to reduce greenhouse gas emissions, which can significantly alleviate global energy security issues. This study systematically introduces the prerequisites for CO2 to extract crude oil and CO2 to be safely and effectively stored. Under high temperature and high pressure, the rock properties of deep reservoirs are completely different from those of atmospheric conditions in the two-phase porous media environment of crude oil and high salinity formation water. The research progress on the phase behavior, mutual solubility, CO2 storage potential and mechanism between supercritical CO2 and crude oil, formation water and reservoir are reviewed in detail. In addition, CO2 leakage will inevitably occur during long-term geological storage, the proper estimation and evaluation of the risk... [more]

Ecosystem destruction is one of today’s significant challenges due to fast industrialisation and an increasing population. It takes several years for solid trash, such as plastic bottles and super-market bags, to decompose in nature. In addition, plastic disposal techniques such as landfilling, reuse, and incineration pose significant threats to human health and the environment. In this paper, we investigated whether the impact of mixing biodiesel with waste oil from recycled plastic on the resulting fuel mixture’s yields better physical and chemical properties. Consequently, pyrolysis is one of the most advantageous and practical waste disposal methods as it is both environmentally benign and efficient. Pyrolysis is the high-temperature thermal breakdown of solid waste to produce pyrolytic oil. The pyrolytic (plastic) oil produced is converted to a hydrocarbon-rich pyrolytic fuel. Similar to diesel and gasoline, pyrolytic fuel has the same calorific value. Internal combustion engines... [more]

Increasing the penetration of variable energy resources (VER) can reduce the inertia and frequency response performance of power systems supported by replacement synchronous power generation. Therefore, it is necessary to manage the VER penetration limit in power systems for stable operation and to increase the operability to the desired level. This study proposes a method to evaluate and quantify the effect of increasing the penetration limit of VER by controlling a battery energy storage system (BESS). The BESS can provide a fast response, but frequency response performance varies depending on the operating conditions. In the proposed quantification method, various control methods of a BESS, operating conditions of the power system, and penetration conditions of additional VER were analyzed, and the effect of the BESS on increasing the penetration limit of VER was evaluated. This evaluation and analysis enabled the selection of the BESS operating conditions to achieve the target VER... [more]

In this paper, we consider spatially and technologically diversified portfolios of renewable energy resources (RES) on a European scale. These portfolios efficiently allocate wind and solar production capacity with a view on matching load and restricting conventional generation capacity in each country. We investigate the composition of optimal portfolios taking into account the existing cross-border transmission capacity as well as future expansion scenarios. For the purposes of our analysis, we develop several multi-criteria optimization models and apply them to a rich dataset of daily electricity load, RES capacity factors, and transmission capacity constraints for 32 European countries during the period 2010−2015. By exploring different scenarios for the composition of efficient portfolios and cross-border network connectivity, we quantify the effectiveness of the resource aggregation strategy in terms of reducing the energy production deficit or surplus in each country. Empirical... [more]

This work is aimed at developing a stand for tuning the fuel system of an internal combustion engine based on two electromagnetic retarders connected to the driving wheels of a car to simulate a load, and a microprocessor-based torque control system for each brake. In accordance with the terms of reference from the specialists of the automotive service center, such a stand should provide two main modes of operation: (1) stabilization of the speed of the drive wheels in the entire range of loads (fuel supply); (2) engine acceleration and deceleration according to linear tachograms in the range from minimum to maximum speed to determine the dependence of engine power and torque on speed. The purpose of this research is the synthesis of controllers, testing, the choice of the structural scheme, and the parameters of the control and data processing system in the stand for the precision tuning of internal combustion engines. Based on a preliminary analysis of the system, taking into account... [more]

Hydrogen is a key enabler of a sustainable society. Refurbishment of the existing natural gas infrastructure for up to 100% H2 is considered one of the most energy- and resource-efficient energy transportation methods. The question remains whether the transportation of 100% H2 with reasonable adaptions of the infrastructure and comparable energy amounts to natural gas is possible. The well-known critical components for refurbishment, such as increased compressor power, reduced linepack as well as pipeline transport efficiencies, and their influencing factors were considered based on thermodynamic calculations with a step-by-step overview. A H2 content of 20−30% results in comparable operation parameters to pure natural gas. In addition to transport in pipelines, decentralized H2 production will also play an important role in addressing future demands.

The partial recovery of kinetic energy during braking allows the vehicle’s battery to be additionally charged and thus extends the range of an electric vehicle. Because of the different operating strategies of the braking energy recovery system, it is important to understand the factors influencing the level of recovered energy. The driving conditions at the place of use have a direct impact on the energy efficiency of an electric vehicle. The purpose of this paper was to analyze the energy recovered during braking in different driving conditions. The tests were based on the parameters of actual trips made along urban and suburban routes, and express roads. The collected actual speed profiles were used for the simulation studies. AVL cruise vehicle simulation software was used in the study. Simulation tests revealed that the levels of energy recovered during braking in an electric vehicle were the highest in urban conditions. The amount of energy recovered during urban driving can acco... [more]

To understand the change in overburden structure after coal seam group mining, we investigated the overburden characteristics and bearing capacity of abandoned coal mines in a coal seam group. We provide a theoretical basis for the construction and utilization of a coal mining subsidence area under a complex geological environment. This paper takes the construction project of Zhongtie Huizhi Square in Zhangqiu District, Jinan City, Shandong Province as the engineering background. According to the occurrence conditions of the study area, theoretical analysis, similar simulation, numerical simulation, and engineering practice verification are used. The overburden structure characteristics of abandoned mines in a shallow-buried coal seam group were studied. The results show that the development height of the water-carrying fractured zone after the mining of the 3#, 4#, and 9# coal seams is 17 m, 19.5 m, and 27.1 m, respectively, which shows that the height of water flow in the fractured z... [more]