Virtual Power Plants for Grid Resilience: A Concise Overview of Research and Applications

The power grid is undergoing a transformation from synchronous generators(SGs) toward inverter-based resources(IBRs). The stochasticity, asynchronicity, and limited-inertia characteristics of IBRs bring about challenges to grid resilience. Virtual power plants(VPPs) are emerging technologies to improve the grid resilience and advance the transformation. By judiciously aggregating geographically distributed energy resources(DERs) as individual electrical entities, VPPs can provide capacity and ancillary services to grid operations and participate in electricity wholesale markets. This paper aims to provide a concise overview of the concept and development of VPPs and the latest progresses in VPP operation, with the focus on VPP scheduling and control. Based on this overview, we identify a few potential challenges in VPP operation and discuss the opportunities of integrating the multi-agent system(MAS)-based strategy into the VPP operation to enhance its scalability, performance and resilience.

Intelligent Fractional-Order Controller for SMES Systems in Renewable Energy-Based Microgrid

An autonomous microgrid that runs on renewable energy sources is presented in this article.It has a supercon-ducting magnetic energy storage(SMES)device,wind energy-producing devices,and an energy storage battery.However,because such microgrids are nonlinear and the energy they create varies with time,controlling and managing the energy inside them is a difficult issue.Fractional-order proportional integral(FOPI)controller is recommended for the current research to enhance a standalone microgrid’s energy management and performance.The suggested dedicated control for the SMES comprises two loops:the outer loop,which uses the FOPI to regulate the DC-link voltage,and the inner loop,responsible for regulating the SMES current,is constructed using the intelligent FOPI(iFOPI).The FOPI+iFOPI parameters are best developed using the dandelion optimizer(DO)approach to achieve the optimum performance.The suggested FOPI+iFOPI controller’s performance is contrasted with a conventional PI controller for variations in wind speed and microgrid load.The optimal FOPI+iFOPI controller manages the voltage and frequency of the load.The behavior of the microgrid as a reaction to step changes in load and wind speed was measured using the proposed controller.MATLAB simulations were used to evaluate the recommended system’s performance.The results of the simulations showed that throughout all interruptions,the recommended microgrid provided the load with AC power with a constant amplitude and frequency.In addition,the required load demand was accurately reduced.Furthermore,the microgrid functioned incredibly well despite SMES and varying wind speeds.Results obtained under identical conditions were compared with and without the best FOPI+iFOPI controller.When utilizing the optimal FOPI+iFOPI controller with SMES,it was found that the microgrid performed better than the microgrid without SMES.

Comparative Analysis of Reaction to Fire and Flammability of Hemp Shives Insulation Boards with Incorporated Microencapsulated Phase Change Materials

Nowadays buildings contain innovative materials,materials from local resources,production surpluses and rapidly renewable natural resources.Phase Change Materials(PCM)are one such group of novel materials which reduce building energy consumption.With the wider availability of microencapsulated PCM,there is an opportunity to develop a new type of insulating materials,combinate PCM with traditional insulation materials for latent heat energy storage.These materials are typically flammable and are located on the interior wall finishing yet there has been no detailed assessment of their fire performance.In this research work prototypes of low-density insulating boards for indoor spaces from hemp shives using carbamide resin binder and cold pressing were studied.Bench-scale cone calorimeter tests were conducted to evaluate fire risk,with a focus on assessing material flammability properties and the influence of PCM on the results.In this research,the amount of smoke,heat release rate,effective heat of combustion,specific extinction coefficient,mass loss,carbon dioxide yield,specific loss factor,ignition time of hemp straws samples and samples of hemp straws with 10%and without PCM admixture were compared.There is a risk of flammability for PCM and their fire reaction has not been evaluated when incorporating PCM into interior wall finishing boards.The obtained results can be used by designers to balance the potential energy savings of using PCM with a more complete understanding and predictability of the associated fire risk when using the proposed boards.It also allows for appropriate risk mitigation strategies.

Energy Economic Dispatch for Photovoltaic-Storage via Distributed Event-Triggered Surplus Algorithm

This paper presents a novel approach to economic dispatch in smart grids equipped with diverse energy devices.This method integrates features including photovoltaic(PV)systems,energy storage coupling,varied energy roles,and energy supply and demand dynamics.The systemmodel is developed by considering energy devices as versatile units capable of fulfilling various functionalities and playing multiple roles simultaneously.To strike a balance between optimality and feasibility,renewable energy resources are modeled with considerations for forecasting errors,Gaussian distribution,and penalty factors.Furthermore,this study introduces a distributed event-triggered surplus algorithm designed to address the economic dispatch problem by minimizing production costs.Rooted in surplus theory and finite time projection,the algorithm effectively rectifies network imbalances caused by directed graphs and addresses local inequality constraints.The algorithm greatly reduces the communication burden through event triggering mechanism.Finally,both theoretical proofs and numerical simulations verify the convergence and event-triggered nature of the algorithm.

Hybrid Ensemble-Learning Approach for Renewable Energy Resources Evaluation in Algeria

In order to achieve a highly accurate estimation of solar energy resource potential,a novel hybrid ensemble-learning approach,hybridizing Advanced Squirrel-Search Optimization Algorithm(ASSOA)and support vector regression,is utilized to estimate the hourly tilted solar irradiation for selected arid regions in Algeria.Long-term measured meteorological data,including mean-air temperature,relative humidity,wind speed,alongside global horizontal irradiation and extra-terrestrial horizontal irradiance,were obtained for the two cities of Tamanrasset-and-Adrar for two years.Five computational algorithms were considered and analyzed for the suitability of estimation.Further two new algorithms,namely Average Ensemble and Ensemble using support vector regression were developed using the hybridization approach.The accuracy of the developed models was analyzed in terms of five statistical error metrics,as well as theWilcoxon rank-sum and ANOVA test.Among the previously selected algorithms,K Neighbors Regressor and support vector regression exhibited good performances.However,the newly proposed ensemble algorithms exhibited even better performance.The proposed model showed relative root mean square errors lower than 1.448%and correlation coefficients higher than 0.999.This was further verified by benchmarking the new ensemble against several popular swarm intelligence algorithms.It is concluded that the proposed algorithms are far superior to the commonly adopted ones.

OPTIMAL DYNAMICAL BALANCE HARVESTING FOR A CLASS OF RENEWABLE RESOURCES SYSTEM

An optimal utilization problem for a class of renewable resources system is investigated. Firstly, a control problem was proposed by introducing a new utility function which depends on the harvesting effort and the stock of resources.Secondly, the existence of optimal solution for the problem was discussed. Then, using a maximum principle for infinite horizon problem, a nonlinear four-dimensional differential equations system was attained. After a detailed analysis of the unique positive equilibrium solution, the existence of limit cycles for the system is demonstrated. Next a reduced system on the central manifold is carefully derived, which assures the stability of limit cycles. Finally significance of the results in bioeconomics is explained.

A SOLVABLE ONE-DIMENSIONAL ALLOCATION DECISION MODEL OF RENEWABLE RESOURCES

In the paper, the determinate atlecation decision model and the probabilistic allocation decision model of a kind of renewable resource are separatly studied by means of dynamic programming, and the optimal allocation policy is given under some special conditions.

Tapping Renewable Energy Resources -with A Combined Capacity of 1236 MW as Target for the Year 2000

China began the research and development of renewable energy generation since 1970s, in particular in the Eighth Five-year Plan period, the State made closer attention to the research and development of renewable energy, therefore the technical level, application scale and economic, social benefits have seen greater progress. The combined capacity of renewable energy generation reached 100 MW at the end of 1994. And it is planned a combined capacity of 1236 MW will be targeted for the year 2000.

China puts more money in renewable energy resources

In 2010, over 300 billion yuan ($47.31 billion) are invested in renewable energy sources in China, outranking every other country. Hence, China has become one of the world’s biggest investors in renewable energy sources.

Studies on the Evolutionary Laws and Maintaining Mechanism of Renewability of the Yellow River's Water Resources

The Yellow River has a vast catchment area and historically it is the mother river of the Chinese nation. Now it serves as one of the main theatres for the on-going national campaign to develop China's western hinterland.……

Optimizing Decision-Making of A Smart Prosumer Microgrid Using Simulation

Distributed renewable energy sources offer significant alternatives for Qatar and the Arab Gulf region’s future fuel supply and demand.Microgrids are essential for providing dependable power in difficult-to-reach areas while incorporating significant amounts of renewable energy sources.In energy-efficient data centers,distributed generation can be used to meet the facility’s overall power needs.This study primarily focuses on the best energy management practices for a smart microgrid in Qatar while taking demandside load management into account.This article looked into a university microgrid in Qatar that primarily aimed to get all of its energy from the grid.While diesel generators are categorized as a dispatchable distributed generation with energy storage added to handle solar radiation from the sun and high grid power operating costs in the suggested scenario,wind turbines and solar Photovoltaic(PV)are classified as non-dispatchable distributed generators.The resulting linear math issues are assessed and displayed in MATLAB optimization software using a mixed-integer linear programming(MILP)strategy.According to the simulation results,the suggested energy management strategy reduced the university microgrid’s grid power costs by 38.8%,making it an affordable solution which is somehow greater than the prior case scenario’s 23%savings.The installed solar system capacity’s effects on the economy,society,and finances were also assessed,and it became clear that the best option for the smart microgrid was determined that would be 325 kW of solar PV,25 kW of wind turbine,and 600 kW of diesel generators,respectively.Given the current situation,university administrators are urged to participate in distributed generators and adopt cutting-edge designs for energy storage technologies due to the significant environmental and financial benefits.

Graphene-Based Active Tunable Metasurfaces for Dynamic Terahertz Absorption and Polarization Conversion

Simultaneous broadband absorption and polarization conversion are crucial in many practical applications,especially in terahertz communications.Thus,actively tunable metamaterial systems can exploit the graphene-based nanomaterials derived from renewable resources because of the flexible surface conductivity and selective permeability of the nanomaterials at terahertz frequencies.In this paper,we propose a graphene-based active tunable bifunctional metasurface for dynamic terahertz absorption and polarization conversion.The graphene ring presents a certain opening angle(A)along the diagonal of the xoy plane.When A=0°,the proposed metasurface behaves as a broadband absorber.Numerical results show the feasibility of achieving this polarization-insensitive absorber with nearly 100%absorptance,and the bandwidth of its 90%absorptance is 1.22 THz under normal incidence.Alternatively,when A=40°after optimization,the proposed metasurface serves as a broadband polarization convertor,resulting in robust broadband polarization conversion ratio(PCR)curves with a bandwidth surpassing 0.5 THz in the reflection spectrum.To tune the PCR response or the broad absorption spectrum of graphene,we change the Fermi energy of graphene dynamically from 0 to 0.9 eV.Furthermore,both the broadband absorption and the linear polarization conversion spectra of the proposed metasurface exhibit insensitivity to the incident angle,allowing large incident angles within 40°under high-performance operating conditions.To demonstrate the physical process,we present the impedance matching theory and measure electric field distributions.This architecture in the THz frequency range has several applications,such as in modulators,sensors,stealth,and optoelectronic switches.THz wave polarization and beam steering also have broad application prospects in the field of intelligent systems.

Progress and Prospects of Hydrogen Production: Opportunities and Challenges

This study presents an overview of the current status of hydrogen production in relation to the global requirement for energy and resources.Subsequently,it symmetrically outlines the advantages and disadvantages of various production routes including fossil fuel/biomass conversion,water electrolysis,microbial fermentation,and photocatalysis(PC),in terms of their technologies,economy,energy consumption,and costs.Considering the characteristics of hydrogen energy and the current infrastructure issues,it highlights that onsite production is indispensable and convenient for some special occasions.Finally,it briefly summarizes the current industrialization situation and presents future development and research directions,such as theoretical research strengthening,renewable raw material development,process coupling,and sustainable energy use.

Selective oxidation of biomass derived 5-hydroxymethylfurfural to 2,5-diformylfuran using sodium nitrite

A mild and simple process for the effective oxidation of 5-hydroxymethylfurfural（HMF） into 2,5-diformylfuran（DFF） has been developed using Na NO2 as the oxidant. Some important reaction parameters were investigated to optimize the oxidation of HMF into DFF. It was found that the reaction solvent was very crucial for this reaction. Trifluoroacetic acid was the best solvent for the oxidation of HMF into DFF by Na NO2.Under the optimal reaction condition, almost quantitative HMF conversion and high DFF yield of 90.4% were obtained after 1 h at room temperature.

Covalent modification of multiwalled carbon nanotubes with a low molecular weight chitosan

Covalent modification of shortened multiwalled carbon nanombes （MWNTs） with a natural low molecular weight chitosan （LMCS） was accomplished by the nucleophilic substitution reaction. The LMCS modified MWNTs （MWNT-LMCS） were characterized by FTIR, solid-state ^13C NMR, and XPS spectroscopies, thermogravimetric analysis, and transmission electron microscopy. The results revealed that amino and primary hydroxyl groups of the LMCS participated mainly in the formation of the MWNT-LMCS conjugates. The MWNT-LMCS consists of 58 wt.% LMCS, and about four molecular chains of the LMCS were attached to 1000 carbon atoms of the nanotube sidewalls. As a novel derivative of the MWNTs, the MWNT-LMCS not only solved in DMF, DMAc and DMSO, but also in aqueous acetic acid solution.

Homogeneous modification of carbon nanotubes with cellulose acetate

An efficient strategy that comprised shorten, chain extension, active groups introducing and homogeneous reaction tactics, was adopted to modify multiwalled carbon nanotubes （MWNTs） with cellulose acetate （CA）. Specially, by utilizing 2,4,6-trichloro- 1,3,5-triazine, a reactive intermediate of the MWNTs （MWNT-triazine） was obtained. Suitable solubility of the MWNT-triazine helps make the homogeneous modification become reality. Detailed characterizations further verified that reaction between chloride atoms in the MWNT-triazine and hydroxyl groups in the CA had contributed to the formation of MWNT-CA conjugates. The novel MWNT-CA consists of carbon （76.3%）, oxygen （18.4%） and nitrogen （5.3%）. With a nanotube-attached CA content of 42.8 wt%, the MWNT-CA is readily soluble in DMSO, NMP, DMF and DMAc. Confirmation of the CA-based modification route might lead to studies aiming for specific sorption and isolation.

Activation of commercial Pt/C catalyst toward glucose electro-oxidation by irreversible Bi adsorption

The effect of irreversibly adsorbed Bi on commercial Pt/C catalyst toward glucose electro-oxidation re- action （GOR） in different electrolytes （acidic, neutral, alkaline） is studied. Bi is successfully deposited on Pt/C from Bi3＋ containing acidic solution from 0 to 90% coverage degree. The stability of the Bi layer in acid and alkaline corresponded to previous studies and started to dissolve at 0.7 V and 0.8 V versus re- versible hydrogen electrode （RIIE）, respectively. However, in neutral phosphate buffer the layer showed remarkable stability to at least 1.2V versus RHE. Bi modification at low （20%） and high （80%） coverage showed the highest increase in the activity of Pt/C toward GOR by a factor up to 7 due to the increased poisoning resistance of the modified catalyst. The effect of poisoning was especially reduced at high Bi coverage （80%）, which shows that adsorbate blocked by Bi through the third-body effect is effective. Finally, with or without Bi modification GOR on PtIC was most active in alkaline conditions.

Microstructure and Properties of Woodceramics Prepared from Lignin-modified Phenol-formaldehyde Resin

Novel woodceramics were successfully fabricated by enzymatic hydrolysis lignin （EHL） modified phenol-formaldehyde resin and woodpowders. The microstructure of woodceramics was investigated by FT-IR, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The effects of EHL-modified PF resin on the properties of woodceramics, such as the weight loss ratio, volume shrinkage ratio, open porosity, bending strength and compressive strength, were studied. The experimental results showed that EHL modified woodceramics had a uniform porous structure. EHL-modified PF resin played an important role in the properties of woodceramics. With the increase of EHL-modified PF resin content, the open porosity, weight loss ratio and volume shrinkage ratio of woodceramics increased, but the bending strength and compressive strength decreased.

Building a Highly Stable Ultrathin Nanoporous Layer Assisted by Glucose for Desalination

Although nanoporous membranes are of great interest in desalination,it is still challenging to construct highly permeable nanoporous membranes with excellent rejections for an efficient desalination process.In this work,highly permeable nanoporous membranes were built from renewable resources,assisted by the versatile functions of glucose and dopamine,with coupling reactive groups via interfacial reaction with 1,3,5-benzenetricarbonyl trichloride(TMC).The small molecules(0.66 nm)of glucose,which have high hydrophilicity,can diffuse into the membrane for an effective reaction to ensure structural integration.Our novel ultrathin(~44 nm)nanofiltration(NF)membrane exhibits ultra-high Na_(2)SO_(4)flux and excellent rejection of Na_(2)SO_(4)(66.5 L·m^(-2)·h^(-1),97.3%)and MgSO4(63.0 L·m^(-2)·h^(-1),92.1%)under a pressure of 5 bar(1 bar=10^(5)Pa)which is much superior to the performance of natural-product NF membranes.The membrane demonstrates excellent long-term stability,as well as tremendous acid-base and alkali-base stability and high anti-pollution capacity.The designed membrane materials and architecture open a new door to biopolymer-based separation membranes beyond existing membrane materials.

Liquefaction of Kraft Lignin at Atmospheric Pressure

Kraft lignin was liquefied using polyethylene glycol#400(PEG)and glycerol(G)in a weight ratio of 80/20(w/w)and sulphuric acid(SA)as catalyst under atmospheric pressure at 160ºC.The three independent variables:reaction time(60,80 and 100 min),percentage of lignin(15,20 and 25%,w/w),and catalyst concentration(0,3 and 6%,w/w),were varied resulting in 27 experimental runs.The effect of these reaction conditions on the properties of the polyols was evaluated.The statistical analysis showed that only“the percentage of lignin”did not influence the properties of the liquefied products,however,reaction time and catalyst load were important parameters.The resulting liquefied products were characterized by FTIR analysis.