Electric Exchange Research Articles

Theoretical investigation of rotating magnetocaloric effect in PrRu2

The magnetic anisotropy in the cubic ferromagnetic PrRu2 compound (TC = 34 K) is due to the crystalline electrical field interaction. Using a model Hamiltonian which includes the crystalline electrical field, exchange and Zeeman interactions we calculated the rotating magnetocaloric effect, considering the magnetic field changes along the three main cubic crystallographic directions 〈001〉, 〈011〉 and 〈111〉. The influence of the spin reorientation, along the field directions, on the magnetocaloric potentials were quantitatively obtained and discussed.

Harmonized and Open Energy Dataset for Modeling a Highly Renewable Brazilian Power System

Improvements in modelling energy systems of populous emerging economies are highly decisive for a successful global energy transition. The models used–increasingly open source–still need more appropriate open data. As an illustrative example, we take the Brazilian energy system, which has great potential for renewable energy resources but still relies heavily on fossil fuels. We provide a comprehensive open dataset for scenario analyses, which can be directly used with the popular open energy system model PyPSA and other modelling frameworks. It includes three categories: (1) time series data of variable renewable potentials, electricity load profiles, inflows for the hydropower plants, and cross-border electricity exchanges; (2) geospatial data on the administrative division of the Brazilian federal states; (3) tabular data, which contains power plant data with installed and planned generation capacities, aggregated grid network topology, biomass thermal plant potential, as well as scenarios of energy demand. Our dataset could enable further global or country-specific energy system studies based on open data relevant to decarbonizing Brazil’s energy system.

Fit for social innovation? Policy reflections for EU energy and climate policy making

Abstract Achieving climate-neutrality by mid-century and its intermediary reduction targets for 2030, notably the EU’s greenhouse gas emissions reduction of 55% by 2030, requires an accelerated transformation of our systems of production and consumption. In essence, such transformations are socio-technical change processes that require a combination of technological and social innovation. While it is widely acknowledged that ambitious climate and energy policies are needed to accelerate such transition processes, research and practise have largely focused on their importance for spurring technological innovation. In this research perspective, we argue that energy and climate policy making should pay more attention to social innovation as much needed additional puzzle piece for successful decarbonisation. Such social innovation is diverse, ranging from renewable energy cooperatives, to participatory incubation and experimentation, and crowdfunding as well as local electricity exchange. Based on a literature review that informed an EU policy dialogue bringing together policy makers, practitioners and researchers and followed up by a workshop with city administrations, twelve practical action points were co-created on how to better consider social innovation in energy and climate policy making in the EU (and beyond). We thereby hope to stimulate a broader discourse on the dual need for social and technological innovation for reaching climate-neutrality.

THE TECHNIQUES OF EXERCISING FUTURES AND FORWARDS BY THE HEDGING METHOD

Supply and demand are always supposed to be balanced due to certain limitations relating to electricity. Electricity prices fluctuate constantly and cannot be determined with complete certainty. The spot market price of electricity is a reflection of the continuous equilibrium among the production and supply of electricity. Due to uncontrolled exposure to the risk of the continual fluctuations of the spot market prices, market participants can incur financial losses. For this purpose, future and forwards have been introduced on the market. Owing to them, market risk can be hedged by employing the hedging method. Two types of such contracts exist: futures traded on electricity exchanges and forwards traded on over-thecounter markets. In this article, the descriptions, differences and application of these contracts are presented. A description of the hedging method and its application to futures is provided. At the end of the article, an application of a futures contract on the largest Middle European electricity exchange, EEX, is presented.

Modelling and optimal management of renewable energy communities using reversible solid oxide cells

The use of reversible solid oxide cells within a renewable energy community results a promising application which permits to balance the temporal mismatch between renewable energy production and users’ demand through hydrogen as energy vector. Differently from batteries and supercapacitors, this technology is characterized by a high stored energy density and a negligible daily self-discharge. Nevertheless, the system management is more complex requiring cell behaviour optimization and hydrogen storage control. Here this work proposes a control algorithm for reversible solid oxide cell operation coupled to renewable energy sources within a renewable energy community formed by an aggregation of fifteen residential customers. Based on forecasts of loads and renewable energy production, the proposed algorithm, a stochastic model predictive control, can optimize system operation aiming at economic benefit maximization. The transition between the fuel cell mode for power generation and the electrolysis mode for energy storage through hydrogen production was set considering the available renewable energy, the power demand of community members and the energy sell-back price in order to increase the auto-consumed amount as well as to favour the electricity exchange within the renewable energy community. Since the reversible solid oxide cell is the key-point in such a system, SIMFC-SIMEC (SIMulation of Fuel Cells and Electrolysis Cells), a physically based 2D model, allowed an effective prediction of cell behaviour deriving the efficiency of electricity and hydrogen production from local physicochemical feature and working parameter gradients on each stacked cell plane.

Electric field-induced ball-cactus-like CuCo2Sx(OH)y nano-heterostructure towards high-performance supercapacitors

Herein, a simple electric field-induced anion exchange process was raised to prepare a novel nanostructured CuCo2Sx(OH)y heterostructure based on CuCo2S4 nanosheets as a substrate.

Optimization of the Hydrodynamic Regime in the Flow Electrodializator Cell

Electrodialysis is a water treatment and wastewater treatment technology that uses an electric field gradient and ion exchange membranes to separate ions in aqueous solutions. Studies conducted using this technology have shown the influence of the hydrodynamic regime on the efficiency of the process, the rate of mass transfer and polarization concentration. The article presents experimental results, mathematical calculations and numerical modeling in the universal software system of analysis by the Ansys finite element method. Theoretical calculated results show a good correlation with the results of hydrodynamic processes in the apparatus obtained experimentally. The hydrodynamic regime in the channel of the electrodialyzer cell has been studied, the influence of the mesh geometry on the distribution of fluid flow over the membrane surface has been shown, and the change in flow velocity and pressure depending on the structure of the mesh has been described.

Topological properties of Xene tuned by perpendicular electric field and exchange field in the presence of Rashba spin–orbit coupling

Xene (X=Si, Ge, Sn) is a typical and promising two-dimensional topological insulator with many novel topological properties. Here, we investigate the topological properties of Xene tuned by a perpendicularly applied electric field, exchange field, and Rashba spin–orbit coupling (RSOC) using the tight-binding (TB) method. We show that in the presence of RSOC, the system can be converted from a quantum spin Hall (QSH) insulator into a conventional band insulator (BI) by a weak perpendicular electric field or into a quantum anomalous Hall (QAH) insulator by a weak exchange field. Additionally, a suitable combination of electric and exchange fields can give rise to a valley-polarized metallic (VPM) state. Furthermore, we explore the competition between the electric field and exchange field in tuning the topological states owing to the Rashba coupling effect. When the electric field is stronger than the exchange field, the system tends to be in a topologically trivial BI state; otherwise, it will be a QAH insulator. More intriguingly, for a fixed exchange field and RSOC, as the perpendicular electric field increase continuously from zero, the system undergoes multiphase (e.g. QSH-VPM-BI) transitions. This paves the way for designing multiphase transition devices through external single-field regulation.

Optimal integration of Vehicle to Building (V2B) and Building to Vehicle (B2V) technologies for commercial buildings

The advent of vehicle-to-building (V2B) technology provides an option to export electricity from the battery in electric vehicles (EVs) into buildings to assist in meeting building electric demands. However, there are some constraints on operating the EV fleets as flexible energy storage for buildings, including (i) stochastic and limited availability of EVs for building energy management; and (ii) necessity of bi-directional flow of EVs to operate in both V2B and building-to-vehicle (B2V) modes. Hence, these constraints and the changing degree of electric energy exchange provided by the different numbers of EVs could affect the building energy management system and the dynamic energy usage. The main objectives of this paper are to study the optimal configurations of the number of EVs interacting with a building by examining (1) the impact of different numbers of EVs on the daily electricity bills in a grid-connected commercial building microgrid, (2) the range of allowable EV numbers that enable optimal V2B capacity and reasonable charging loads for enhancing the cost-effectiveness of building energy management; (3) the role of different EV numbers in affecting the required stationary battery energy storage system (BESS) capacity in an isolated commercial building microgrid. It is observed that optimal building connected EV numbers are determined by EV driving patterns, seasonal solar output, building demand profiles, and the price of grid electricity. Thus, a scenario analysis is conducted to determine a range of suitable EV numbers in each scenario. Simulation results indicate that the optimal number of EVs varies greatly between summer and winter, as well as across different solar irradiance scenarios. In a case study where a building’s peak electric consumption is 30 kW and the PV system’s rated capacity is 50 kW, the allowable EV number, depending on the amount of available solar energy, varies from 8 to 29 in summer and changes from 2 to 15 in winter. These results could be used to suggest the optimal EV numbers based on the day-ahead solar energy forecasting, enabling day-ahead planning to either attract more vehicle owners to boost V2B capacity or to limit the number of integrated EVs in order to avoid a spike in total EV charging demand.

Decarbonizing residential energy consumption under the Italian collective self-consumption regulation

The recent Italian regulatory framework is promoting Collective Self-Consumption to play a key role in the energy transition. In fact, this new scheme allows sharing and exchange of electricity produced from Renewable Energy Sources (RES) among different end-users living in the same multi-family building block. In this context, this paper aims to perform an energy, economic and environmental assessment of creating a RES-based energy community formed by end-users located in the same residential building, taking into account the currently available incentive schemes. In particular, two different progressive scenarios have been analysed: the first one includes only a photovoltaic system to supply the aggregated electricity demand of the apartments, while a heat pump is further integrated in the second scenario for supplying and electrifying/decarbonizing also the space heating demand of the building. Available temperature and solar irradiance datasets at national level were then used to spread the analysis to the whole country, at different latitudes. Although differences exist at regional levels for the proposed scenarios, the results highlight how the RES-based Collective Self-Consumption scheme is economically profitable for Italian residential end-users with cost savings up to 32% and environmentally sustainable with carbon emissions reduction up to 60%. • Economic, energy and environmental analysis of PV and HP for Italian households. • Energy modeling considering solar radiation and air temperature variability with GIS. • The results highlight how the economic and environmental perspectives are positive. • The new regulatory framework concerning energy sharing improve RES diffusion.

Bi-level optimization of a near-zero-emission integrated energy system considering electricity-hydrogen-gas nexus: A two-stage framework aiming at economic and environmental benefits

Decarbonization is increasingly highlighted to realize emission peak and neutrality targets, while relevant low-carbon measures remain price high, especially for industrial end-users. This paper thus focuses on a specific design for park-level integrated energy systems with near-zero emissions. Solar photovoltaic and distributed wind power are applied as the main power supply together with the help of the local grid. The decarbonization sector is composed of power-to-gas (P2G) and carbon capture units where electrolyzers are separated from P2G and constitute the hydrogen subsystem together with hydrogen tanks and fuel cells. The system is also considered under the dynamic market environment where electricity, hydrogen, and emission exchanges are included. Then, the system behaviors are determined by an optimal operation model considering an uncertain power supply. Based on the stochastic operation, system configuration optimization considering economic and environmental objectives is constructed as a multi-objective integral model that is solved by an enhanced firefly algorithm in the first stage. Next, the optimal result is concluded according to subjective judgment and objective distribution in the second one. A case study in Gansu province, China is carried out to validate the system, and results indicate that 1) optimal result investing 5.285 million $ could avoid 7.4542 kilotons of emissions annually with a 20.1 % loss of self-power supply rate on average, 2) up to 51.72 kg of hydrogen fuels or 47.90 kg of gas could be generated besides daily load satisfaction, 3) carbon exchange incentive above 4.2 $/t could promote additional emission reduction.

Coverage hole optimization with a mobile sensor in wireless sensor networks for smart grid

The Smart Grid (SG) enables electricity and energy exchange between two ends of the grid. Wireless Sensor Networks (WSNs) are considered as an enabling communication technology for effective SG management. How well the target region is covered by a WSN indicates the service quality of the relevant implementation. Since effective monitoring is key to exploiting the benefits of the SG, maintaining the desired coverage level is critical in WSN for SG applications. However, some uncovered regions (coverage holes) might emerge due to several reasons such as improper localization or sensor malfunctioning. In this paper, we propose using a mobile sensor to cover such blind regions in a timely and hence energy-efficient way. First, we present a novel 0–1 mixed integer programming model without restrictive assumptions about the mobility pattern to find the shortest trajectory for the mobile sensor. Then we show that the problem is NP-hard with a polynomial reduction to the Traveling Salesman Problem. Consequently, we present an optimization-based heuristic, two heuristic-based algorithms, and a hybrid algorithm. We show that our heuristics are efficient as they find high quality solutions in a few seconds. We also observe that assumptions about the starting point of the tour and the potential set of stops significantly affect the final tour’s length.

THE PRINCIPLE OF EXERCISING OPTIONS ON THE ELECTRICITY MARKET

Continual price fluctuations are possible to hedge by using various financial instruments, including options. An option buyer buys the right to the settlement price of an underlying asset such as electricity. Due to the volatility of the asset price, the buyer is not obliged to exercise the option. In such a case, the buyer’s only loss is the purchased right or the option premium, which is equal to the option price. Mathematical models for option pricing have been developed in the last hundred years. These models were very popular during the 1970s, owing to the application of the Black-Scholes formula for the calculation of theoretical option prices. In this article, options are distinguished according to various criteria, specific exercising methods are described and the historical development of option pricing models is reviewed. An example of option exercising with closing out of the margins on the largest Middle European electricity exchange, EEX, is presented.

Electric-field assisted ion-exchange of innovative float glass

Electric field-assisted ion exchange process was carried out on an innovative soda magnesia silicate float glass by using a specifically realized equipment which allows to change the applied voltage and the polarity and to measure the flowing current.Parameters such as surface K/Na exchange rate, potassium penetration, inter-diffusion coefficient, residual stress and case depth were measured and correlated with the processing conditions. The results revealed a high propensity of the considered glass to be chemically strengthened and a beneficial effect of the applied electric field in terms of time and temperature. For treatment carried out at 410 °C potassium penetration depth in excess to 10 μm can be achieved in less than 5 min. By alternating the polarity, both sides can be homogeneously reinforced. When the duration of each single cycle at a certain polarity is increased, the potassium penetration depth increases although cycles longer than 10 min can be detrimental.

Optimal scheduling management of the parking lot and decentralized charging of electric vehicles based on Mean Field Game

As an intermediary for the interaction between the grid and electric vehicles (EVs), the parking lot aggregator not only facilitates the exchange of electricity between EVs and the grid, but also brings benefits to all participants. This paper proposes a linear quadratic (LQ) Mean Field Game (MFG) theory with a major player to optimal scheduling management of the parking lot and formulate optimal decentralized charging control strategies for a large number of EVs, to achieve the minimization of EVs charging cost while maximizing the profit of the parking lot, but these two problems are a set of coupled control problems. In addition to modeling the interaction between the parking lot and the EVs as a finite-time dynamic game problem, the Nash Certainty Equivalence (NCE) of related optimization problems is also proposed, and the corresponding solution algorithm is designed. The control effects of the proposed dynamic game problem on the charging cycle, as well as the effects of parameters change and electricity price fluctuations on charging control are illustrated through numerical simulations.

An overview of bidirectional electric vehicles charging system as a Vehicle to Anything (V2X) under Cyber–Physical Power System (CPPS)

Nowadays, EVs are rapidly increasing in popularity, and are accepted as the vehicles of the future all over the world. The most important components are their battery and charging systems. The energy capacity of EVs’ batteries has a significant potential to supply different energy requirements. Therefore, EVs must be designed in accordance with bidirectional power flow, and Electric Vehicle Supply Equipment (EVSE) should be upgraded as Electric Vehicle Power Exchange Equipment (EVPE). This power exchange infrastructure can be called Vehicle-to-Anything (V2X). V2X will also be the key solution for energy grids of the future that will turn into a much larger and smarter system with the help of emerging digitalization technologies, such as Artificial Intelligence (AI), Distributed Ledger Technology (DLT), and the Internet of Things (IoT). This study introduces a multi-layer Cyber–Physical Power Systems (CPPS) framework to explore the potential of V2X technologies allowing bidirectional charging. In addition, the impact of e-mobility is discussed from the V2X perspective. V2X has the potential to provide more practical use of electric vehicles and to bring advantages to the user in terms of both economy and comfort, thus accelerating the transformation of e-mobility and making it easier to accept.

PENGARUH VARIASI GAS PELINDUNG PADA TIG BRAZING ANTARA CEMENTED CARBIDE DAN BAJA KARBON TERHADAP KEKUATAN GESER DAN STRUKTUR MIKRO

Dissimilar metals have found wide use in electric power generation, electronics, reactors, nuclear, petrochemical, chemical industries, civil construction, vessels, and heat exchange as well as several other industries. TIG welding (Tungsten Inert Gas Welding) is a type of electric welding that uses tungsten as the electrode material that is not consumed. Brazing is a way of joining metal materials through a heating process with an adhesive or filler material that has a melting point below the material to be combined or connected. The main objective of this study was to determine the shear strength and microstructure of the weld area that was joined by the brazing method. From the results of the shear strength test, there is a comparison of the difference in the shear stress strength. The results obtained indicate that where the shear stress test at a flow rate of 5 liters/minute of protective gas gets the highest shear stress value of 108 N/mm2, compared to the shear stress test with a gas flow rate of 10 liters/minute, the shear stress value is equal to 97 N/mm2, but at the protective gas flow rate of 15 liters/minute the lowest shear stress value was 76 N/mm2. The results of the microstructure obtained the result that the protective gas flow rate of 15 liters/minute got the lowest value due to a decrease in the amount of Si elements, resulting in the lowest shear stress value.

Effect of charge and anisotropic diffusivity on ion exchange kinetics in nuclear waste form materials

Motifs of radionuclide absorption particles (absorbers or fillers) for the nuclear waste treatment usually have crystal structures with nano-sized tunnels for fast ion diffusion. On the other hand, the accumulation of ions generates an electric field which affects the ion diffusion. Therefore, the strong anisotropic kinetic properties and the electric field affect ion exchange kinetics, especially in an assembly of these particles which may block the fast diffusion tunnels for each other. In this work, we developed a mesoscale model to describe the effect of anisotropic kinetic properties and electric field on ion exchange kinetics. With the model we simulated the effect of anisotropic diffusivity, electrochemical potential, particle morphology, size and aggregation on ion exchange kinetics during batch experiments. It is found that (1) ion exchange results in charge accumulation inside the particle because different ions have different diffusivities and different diffusion driving forces. The electric neutrality is not preserved; (2) the electric field speeds up the slower diffusion ions (either uptake or release) and slows down the faster diffusion ions to reduce charge accumulation and maintains charge neutrality; (3) the ion exchange becomes very slow at the later stages because (a) diffusion driving force (electrochemical gradient, Cs+ concentration in the solution and Na+ inside the particle) continuously decreases, as observed in batch experiments; and (b) the diffusivity decreases due to the Cs+ concentration dependence of ion diffusivity. This can explain the observed experimental phenomena that the radionuclide capacity usually cannot be reached; (4) for needle-like particle and their clusters, both surface area and diffusion distance along the direction with the fastest diffusivities have significant impact on the ion exchange kinetics.

A zonal balanced market clearing method in AC/DC hybrid system considering inter-area electricity exchange

As the intra-provincial spot market matures and the inter-area electricity exchange increases in China, the market clearing method requires some exploration. This paper proposes a zonal balanced market clearing method in hybrid direct current/alternating current (AC/DC) systems considering inter-area electricity exchange. In each area, the independent operator carries out the intra-area market clearing. The operator of high voltage alternating current (HVAC) and high voltage direct current (HVDC) power transmission channels is responsible for safe system operation and the quotation for each area. According to the results of the areas’ market clearing and the transmission lines’ optimal power allocation, the operator updates the quotation until reaching the convergence conditions. The case studies demonstrate the feasibility of the proposed zonal market clearing method.

Dynamics of electricity exchange markets

Dynamics of electricity exchange markets