Hasil untuk "Energy industries. Energy policy. Fuel trade"

Xiaohui Yan, Shiqing Liu, Yongjian Su et al.

Free radicals are a class of reactive substances produced during the operation of proton exchange membrane fuel cells (PEMFCs), which have a great impact on the durability of PEMFCs. Previous research on the fuel cell degradation mechanism mainly focused on the degradation of the membrane electrode assembly (MEA) in high Pt loading PEMFCs, especially the chemical degradation of proton exchange membrane (PEM). However, there are significant differences in the characteristics and performance of PEMFCs with low and high Pt loading especially under the high current density, which is mainly due to the oxygen transport process in cathode catalyst layers (CCLs). Currently, few relevant research has explored the impact of chemical degradation on oxygen transport in the cathode of low-Pt PEMFCs. Therefore, this work investigates the effects of free radical attack on the structure of ionomer films, the local oxygen transport process and the evolution of the ionomer coated Pt/C structure in CCLs through physicochemical characterizations, electrochemical measurements and molecular dynamic simulations. Our research found that free radical attacks decreased the electrochemical active area of CCLs, but it also temporarily improved the cell performance at high current densities. Furthermore, molecular dynamics simulations demonstrated that the ionomer exhibited higher oxygen self-diffusion and a more relaxed structure after degradation.

Phan Anh Duong, Hokeun Kang

Shaoming Han, Cheng Qian, Nawal Abdalla Adam et al.

This study examines the impact of financial inclusion on bank stability across 36 emerging economies, utilizing bank-level data from over 1,500 commercial banks spanning the period 2004 to 2023. Despite the recognized benefits of financial inclusion, its influence on banking stability remains complex and context dependent. The research employs advanced econometric methodologies, including fixed-effects models, Driscoll-Kraay standard errors to address heteroskedasticity and cross-sectional dependence, and system Generalized Method of Moments (GMM) estimation to control for endogeneity and dynamic effects. The findings reveal that financial inclusion generally enhances bank stability and positively influences operational efficiency and funding stability. However, during periods of lax financial regulations or excessive government intervention, banks may engage in riskier behaviors, potentially undermining stability. Key results indicate that (1) robust economic growth and stable policy environments amplify the positive effects of financial inclusion on bank stability, (2) excessive government control may foster risk-taking behaviors, (3) strong financial conditions mitigate adverse impacts, (4) financial inclusion improves risk management and operational efficiency, and (5) effective regulatory frameworks are pivotal in leveraging financial inclusion for sound banking operations. These insights suggest that policymakers in emerging markets should carefully balance the promotion of financial inclusion with safeguards that maintain financial stability.

Hassan Al Garni, Arunachalam Sundaram, Anjali Awasthi et al.

A major design challenge for a grid-integrated photovoltaic power plant is to generate maximum power under varying loads, irradiance, and outdoor climatic conditions using competitive algorithm-based controllers. The objective of this study is to review experimentally validated advanced maximum power point tracking algorithms for enhancing power generation. A comprehensive analysis of 14 of the most advanced metaheuristics and 17 hybrid homogeneous and heterogeneous metaheuristic techniques is carried out, along with a comparison of algorithm complexity, maximum power point tracking capability, tracking frequency, accuracy, and maximum power extracted from PV systems. The results show that maximum power point tracking controllers mostly use conventional algorithms; however, metaheuristic algorithms and their hybrid variants are found to be superior to conventional techniques under varying environmental conditions. The Grey Wolf Optimization, in combination with Perturb & Observe, and Jaya-Differential Evolution, is found to be the most competitive technique. The study shows that standard testing and evaluation procedures can be further developed for comparing metaheuristic algorithms and their hybrid variants for developing advanced maximum power point tracking controllers. The identified algorithms are found to enhance power generation by grid-integrated commercial solar power plants. The results are of importance to the solar industry and researchers worldwide.

Yu Miao, Alexandre Yokochi, Goran Jovanovic et al.

Non-thermal plasma as a tool in chemical reaction engineering has been studied for many years. The temperature of electrons in non-thermal plasma far exceeds other particles, which leads to its high efficiency. Besides the well-studied destruction of volatile organic compounds (VOCs), the reaction environment generated by non-thermal plasma is also suitable for the activation of many significant gas-phase chemical reactions, e.g., as methane coupling, reduction of carbon dioxide, ammonia synthesis, nitrogen fixation, as well as some liquid phase chemical reactions such as the treatment of contaminated water. Material synthesis is another target field of non-thermal plasma. Plasma in micro scale with several enhanced properties makes it an even more promising tool for plasma-chemical processing. This work summarizes different types of non-thermal plasmas and their performance in commonly studied chemical reactions. The advantages gained by generating non-thermal plasma in micro scale with constricted spaces, reduced timescales, and micro-/nano-structured electrodes are also discussed.

Yang Liu, Fangqi Chen, Xiaojie Liu et al.

To reduce the heat island effect brought by conventional asphalt roofing products with high solar absorption, we propose a category of self-cleaning and self-cooling composited roofing tile (CRT) made of old corrugated containers (OCC) and tung oil inspired by traditional Chinese oil-paper umbrellas, which can be fabricated at scale and easily recycled for roofing applications. Compared with asphalt shingles, CRTs can improve the solar reflection due to the randomized structure of the cellulose microfibers, contributing to a significant temperature difference of ∼13.2 °C. In addition, they have a high thermal emissivity of 0.93 in the atmospheric window, radiating great amounts of heat into the cold outer space (∼ 3 K). The top layer tung oil film smeared on the OCC pulp fibers transforms the roofing tile from a waterabsorbing to a waterproofing state and significantly enhances the mechanical strength, contributing to a stable thermal performance in outdoor applications. Furthermore, dyed CRTs can selectively reflect visible light for desired colors and effectively reflect near-infrared light to reduce solar heating, which synchronously achieves roof cooling and aesthetic variety. These cheap, eco-friendly, and multifunctional roofing tiles can provide a value-added path for OCC recycling, which may inspire more radiative cooling composites purely from recycling waste towards an energy-saving and sustainable society.

Bojan Ivanović

Stabilnost na male poremećaje, koja se još naziva statička stabilnost ili modalna analiza, se bavi stabilnošću sistema u slučaju malih poremećaja kao što su promene u potrošnji ili proizvodnji na satnom i dnevnom nivou. Prednost ove vrste analize je njeg globalni karakter jer daje sve sopstvene vrednosti matrice stanja sistema, odnosno polove, u okviru jednog sistemskog proračuna. Postojanje samo jednog pola sistema sa pozitivnim realnim delom ukazuje na nestabilan sistem. Mera relativnog učešća određene promenljive stanja, vezane za određeni generator, i određenog pola sistema dobija se računanjem faktora učešća. Sortiranjem faktora učešća za sve polove sistema u opadajući redosled i uspostavljanje korelacije sa tačno određenom promenljivom stanja nekog generatora dobija se povratna sprega do generatora koji su dominantni uzročnici postojanja polova sistema sa pozitivnim realnim delom. U radu se prikazuje izračunavanje sopstvenih vrednosti sistema i uspostavljanje korisničke povratne sprege do generatora uzročnika pojave nestabilnog pola. Uspostavljanje ove povratne sprege i eliminacija nestabilnog pola sistema promenom parametara generatora je demonstrirana na primeru realnog distributivnog sistema ogranka Leskovac sa preko 2500 čvorova i priključenih više od 40 sinhronih generatora.

M.F.B. Stodt, J. Kiefer, U. Fritsching

Flame spray pyrolysis (FSP) is a technique for the synthesis of metal oxide nanoparticles by combusting precursor solutions in a spray flame. The combustion of certain precursor solutions is known to lead to severe droplet disruptions (μ-explosions) in the spray flame that are linked to the synthesis of homogeneous and phase-pure nanoparticles. In this work, a broad spectrum of suitable subsonic operating conditions for the synthesis of iron oxide nanoparticles by FSP is investigated to understand the influence of the jet Reynolds number and turbulence on the onset of μ-explosions and droplet dynamics in spray flames. In order to enable a coherent comparison between differently operated spray flames using an iron(III) nitrate nonahydrate solution, the gas-to-liquid mass ratio and, hence, the oxygen/fuel ratio have been kept constant in order to identify the influence of flow conditions on the droplet dynamics. From the analysis of the droplet sizes in the spray and in the spray flame, it is found that in all combusting sprays, the droplet sizes convert from unimodal (after atomization) to bimodal droplet size distribution (DSD) due to the presence of μ-explosions. The occurrence and evolution of the bimodal DSD reveal that high jet Reynolds numbers result in narrower DSD and in a sharper separation of both DSD probability peaks (modal values). A straightforward 1-step kinematic model is presented to describe the conversion of unimodal to bimodal DSD considering the evaporation of droplets as well as the disruption of droplets to mimic the effect of μ-explosions. The temporal evolution of droplets in FSP is investigated by spatially resolved velocity data that reveal the formation of a temporal self-similarity. The resulting iron oxide nanoparticle size decreases with increasing jet Reynolds number. The turbulent mixing and residence times in the flame, primarily set by the jet Reynolds number, are identified as key design parameters for FSP.

Vineet P. Chandran, Bhim Singh

Abstract This work presents the operation and control of a pico‐hydro‐solar photovoltaic (PV)‐battery energy storage (BES)‐based isolated renewable energy system (RES) feeding 3‐phase 4‐wire loads. For voltage regulation, to maintain frequency, and power quality improvement in this system, a 4‐leg VSC is used. The BES is connected to the DC‐link of the voltage source converter (VSC) through a bidirectional converter (BDC), which regulates the DC‐link voltage and controls the charging and discharging current of the battery. An advanced perturb and observe (AP&O)‐based MPPT control technique with drift free operation and capability to operate in the derated mode is adapted in this work. The VSC connected to PCC, injects or absorbs power from this system based on the difference of power between generation and the load. The modified complex co‐efficient filter (MCCF)‐based control technique monitors the power quality of this RES system and 4 leg VSC provides the source neutral current compensation. This control algorithm is used to extract the amplitude of the fundamental load current component with improved dynamic response, DC offset elimination and higher order harmonics removal capability. The ability of the presented control strategy for power quality improvement, power management, load balancing and neutral current compensation is reported in this work.

Hongjie Jia, Huiyuan Wang, Yan Cao et al.

Abstract In modern society, system integration that enables multiple subsystems to function as one is emerging in various fields like industry, commerce, and infrastructure. Although it has been proved that integration value could be tapped to the maximum with controllable cost by optimising the integration schemes in certain fields, there is still a lack of a general method for modelling and analysing the process of system integration. To address this need, this paper proposes an analysis framework of system integration. The concepts of integration object, integration strategy, integration time, integration cost and integration value are introduced to describe the integration process. Further, three optimisation models of the local optimisation (OPT1), phase optimisation (OPT2) and integration optimisation (OPT3) are constructed. The proposed framework can also supervise and compare the performance of intermediate processes of different integration schemes. Two case studies in the commerce and energy fields are analysed to illustrate the function of the proposed framework.

董彦军, 王晓甜, 马红明 et al.

电力负荷具有非线性和时序性的特点，为了深入研究各特征变量对于电力负荷预测的重要性，进而获得更高的电力负荷预测精度，提出了基于随机森林（random forest，RF）算法及长短期记忆网络（long short-term memory，LSTM）的混合负荷预测模型。首先根据时间日期因素及气候因素建立高维特征数据集作为随机森林模型的输入，通过随机森林算法筛选出重要特征量，并使其与历史负荷结合作为LSTM模型的输入，经过粒子群算法对LSTM模型进行参数寻优后得到RF-LSTM混合模型及负荷预测结果。使用该方法对河北电网某台区的电力负荷进行预测，结果表明该混合模型的预测精度比未经特征变量筛选的传统单一的随机森林算法、LSTM模型以及BP神经网络更为理想。

Milorad Zakić, Goran Kvaščev

U ovom radu je obrađena jedna relativno nova metoda za procenu mesta nastanka kvara na vodu, koja se bazira na primeni neuralnih mreža. Kako bi se izvršila provera efikasnosti ove metode, u programskom paketu MATLAB/Simulink je formiran model jednostavnog EES-a, koji čine dve visokonaponske mreže (ekvivalentirane Tevenenovim generatorom) povezane 100 km dugačkim dalekovodom. Pomoću ovog programskog paketa su simulirani različiti tipovi kvarova na različitim pozicijama na vodu. Vrednosti faznih struja i međufaznih napona koje generišu ovi kvarovi predstavljaju podatke koji se dovode na ulaz neuralne mreže. Na osnovu ovih ulaznih veličina i izlazne vrednosti koja je jednaka stvarnom rastojanju mesta kvara od početka voda (odnosno pozicije lokatora kvara), moguće je izvršiti obučavanje neuralne mreže. Obučavanje neuralne mreže je izvršeno pomoću softverskog alata nntool (eng. Neural Network Toolbox), koji je sastavni deo programskog paketa MATLAB.

Alena Worschech, Uli Schlachter, Henning Wigger et al.

Flexible energy plants are one of the key requirements for future energy systems with high levels of fluctuating renewable energy. In the course of the transition to sustainable energy systems, regulatory frameworks and tax systems should promote carbon-reduced flexible power plants in a timely manner.This paper considers hybrid systems consisting of battery energy storage systems (BESS) and Power-to-Heat (PtH) modules which can contribute to a more flexible energy system by providing Frequency Containment Reserve (FCR). Contrary to many papers, this contribution explicitly focuses on taxes for FCR providing power plants, which are incurred annually or based on energy consumption. Additionally, regulatory frameworks are investigated, meaning requirements for FCR provision and conditions for energy trading. The effects of these factors on the economic efficiency of hybrid power plants providing FCR are analysed.The regulatory framework conditions and tax systems from three countries are analysed: Germany, France and Austria. For each of these countries four scenarios are simulated in which the net present values (NPV) are calculated considering the corresponding national tax systems and framework conditions. Additionally, operational strategies using the degrees of freedom (DoF) are examined regarding their influence on the economic performance.The comparison shows a huge influence of taxes on the profitability of the hybrid system. Framework conditions mostly play a minor role in this context. Compared to a benchmark scenario with uniform framework conditions and without taxes, on average the NPV decreases more rapidly considering taxes (−107 k€ in France to −710 k€ in Austria) than considering country specific framework conditions (−122 k€ in France to −308 k€ in Austria). Since framework conditions mostly determine the size of the battery capacity, they primarily affect the investment costs. Additionally, the longer the time slices and the earlier the gate closure is, the more often the hybrid systems violate requirements for FCR provision.

Ivan Vujović, Željko Đurišić

Trendovi centralizacije telekomunikacione i računarske opreme radi postizanja ekonomskih benefita, odnosno implementacije tehnoloških inovacija i novih tehničkih rešenja dovode do potrebe izgradnje sve većih Data Centara (DC-a). Povećanje veličine objekta DC-a, odnosno broja rekova sa opremom koji se implementiraju unutar DC-a, kao i broja uređaja koji omogućavaju pravilnu funkcionalnost te opreme, prati neminovno povećanje potrebne količine električne energije za napajanje. Za DC-e koji zahtijevaju veliku količinu električne energije isplativa je izgradnja sopstvenih, obično obnovljivih izvora energije (OIE). Tada su OIE primarni, a ElektroEnergetski Sistem (EES) služi kao sekundarni i redundantni izvor napajanja. U radu je predstavljena ideja za realizaciju DC-a koji se, preko EES-a, primarno napaja iz OIE. Generisana električna energija iz OIE se prenosi u EES upotrebom razvodnih postrojenja (RP-a) visokog napona, a DC napaja iz EES-a preko RP-a niskog, srednjeg i visokog napona. Za realizaciju jednog takvog objekta potrebno je obezbijediti adekvatne uslove koji se odnose na geografsku poziciju, dostupnost lokacije sa stanovišta pristupa, kao i mogućnosti elektroenergetskog, odnosno telekomunika-cionog povezivanja. Na osnovu sprovedenih istraživanja potencijala OIE, raspoložive putne, elektroenergetske i telekomunikacione infrastrukture, u ovom radu su analizirani uslovi razvoja DC-a na lokaciji kod Beograda i to u blizini Transformatorske Stanice (TS) „Beograd 20“. Predloženo rešenje, sa aspekta napajanja DC-a, uključuje izgradnju vjetroelektrane, solarne elektrane i elektrane na deponijski gas, kao i pratećih RP-a. Predviđeno je telekomunikaciono povezivanje objekta sa mrežom EES-a i drugim važnim telekomunikacionim centrima. Ove konekcije se ostvaruju preko optičkih kablova, postavljenih uz elektroenergetske vodove i kablove, a gdje to nije moguće, postavljene samostalno. Prikazan je dizajn unutrašnjosti DC-a i urađeni proračuni potrebne količine električne energije za napajanje opreme i uređaja u objektu. Na osnovu toga je izvršen proračun potrebnog kapaciteta OIE, kao i proračun pripadajućih RP-a. Dato je i rešenje optičkog povezivanja unutar objekta DC-a. Na kraju rada izvršena je uopštena procjena investicionih i ekonomskih aspekata izgradnje ovakvog DC-a.

Manfred Benthaus

Abstract Global trends in the development and use of electricity utilities and assets are practically irreversible. In industrialized nations, capacity factors have grown so large that users may expect freely available electrical potential energy at all times and in almost all locations. Economically capitalizing on this trend means maximizing energy provision and use to boost gross domestic product growth rates. Electricity is now a basic indicator of social development; it is to the cultural-technological dimension what breathing air is to the physiological-biological dimension, the implication being that sustainable development of provision systems has become a matter of international concern. This article presents a decision basis for the design of sustainable national electrical energy supply systems, incorporating country-specific boundary conditions in the form of user requirements to be specified by users. The basis is a solution space of technologically possible systems, obtained by combining generalized user requirements and physical limitations to generate the solution states. As all technological options for the system are brought under consideration, this approach represents a comprehensive comparative analysis. The decision process ensues by assigning to each solution state a set of (newly defined) system risk factors. Particular consideration is given to evaluating the system’s ability to meet the user requirements, i.e., interruption-free provision. The central benchmark is the technological-economic availability. From this is obtained a sustainability boundary, the boundary between quantifiable and unquantifiable economic loss potentials. This article deliberately avoids referencing specific technological solutions, with the justification that the basis of the user’s decision should be independent of technological considerations. The sole exception is a reference to the currently used technology, which forms the starting point.

黄杰, 薛峰, 张鹏飞 et al.

电网输配电网损引发的间接碳排放已被我国部分试点碳市场纳入管控。参与碳市场对电网企业而言是机遇也是挑战，电网作为服务低碳能源转型的减排平台，其网损水平并不完全取决于自身管理能力，网损水平的波动使得电网企业暴露于碳市场履约风险之下。前期已基于支持向量机方法，采用2012～2016年能源主管部门披露的某省有关数据，构建了网损统计分析模型。进一步根据某省发展规划构建多个未来发展假想场景，根据试点碳市场规则，对2017～ 2020年期间某省电网网损水平和碳排放配额仓位进行态势推演。基于碳排放配额仓位推演结果，进一步评估了配额跨期使用、碳抵消机制使用、碳市场灵活交易等碳资产管理措施在不同假想场景下的风险防控效果，提出了电网企业在具备不同技术条件和风险偏好时的碳资产管理策略。最后，针对现行电网行业碳排放配额分配方案，指出仍需进一步量化评估电网的减排平台作用，制定更为科学的配额分配方案。

Anusuiya Singh, Anil Kumar Patel, Mukund Adsul et al.

Lignocellulosic (LC) biomass is abundantly available as a low-cost resource on the Earth. LC conversion into energy carriers is the most accepted alternative energy production policy because it is non-competitor to food or feed. LC ethanol has brought cellulases to the forefront which was otherwise lost in oblivion during last decades. LC biomass can be converted into value added products or into sugars by various routes, e.g., thermo-chemical, chemical, or biological methods. Biological route via enzymes is one of the most eco-friendly and feasible method. Both fungi and bacteria are known to degrade biomass. Fungi have been greatly exploited for cellulase production due to their inherent properties of secreting extracellular cellulase. These microorganisms are known as cellulase producers for many decades, however, to bring the enzymatic biomass conversion to an economically feasible status, extensive research efforts have been made in last decade to enhance cellulase titers. Mutations and genetic interventions along with bioprocess development have played a very important role for enhancing cellulase production. This review will present a critical overview of the on-going research towards improving cellulase production for biofuel industry via genetic modification, which will include mutation and genetic engineering employed to exert changes at genetic level in microorganisms.

John A. Mathews, Hao Tan, Michael J.B. Moore et al.

Alfredo Behrens