Transactive energy management for optimal scheduling of interconnected microgrids with hydrogen energy storage

In recent years, renewable energy sources (RESs) have attracted substantial attention due to carbon-free and cost-effective advantages that have made them one of the main sources of energy generation in the modern structure of the power grid. This paper proposes the stochastic day-ahead scheduling model for optimal energy management of renewable-based microgrids. In this paper, each microgrid is equipped with 100% RESs including the PV system and wind turbine for full pollutant-free energy generation while the hydrogen energy storage (HES) system is used for alleviating the intermittences of the RESs aiming to dynamically balance the energy during a day. To model the fluctuations such as day-ahead market price in the microgrids, the autoregressive integrated moving average and fast forward selection methods are exerted for scenario production and reduction, respectively. Transactive energy as a sustainable and reliable technique is considered for controlling and coordinating energy sharing among the microgrids and the energy network for dynamic energy balancing in the deregulated environment. For energy management in the demand-side, the price and load response schemes are presented, aiming to revise the consumers' patterns in energy consumption in line with balancing energy and minimizing the microgrids’ energy cost. The effectiveness of the suggested model is validated using the modified IEEE 24-bus case study. The realistic modeling of the system based on the proposed model has led to an 8.51% increment in energy cost.     

Nanosized ammonia borane for solid-state hydrogen storage: Outcomes,limitations, challenges and opportunities

Ammonia borane NH₃BH₃ (AB), a material for solid-state hydrogen storage, can be nanosized by confinement into the porosity of a scaffold like mesoporous silica, carbon cryogel, graphene oxide, ZIF-8 as a metal organic framework, poly (methyl acrylate), boron nitride and manganese oxide. In doing so, nanosized AB is destabilized and shows better dehydrogenation properties than bulk AB in terms of temperature, activation energy, enthalpy and kinetics. Such improvements are due to the confinement-driven nanosizing effect, but not only. A catalytic effect may also have a contribution and, in some cases, it even overpasses the nanosizing effect. These effects are explained in detail herein. The present review aims at reporting the outcomes of the AB confinement strategy to help understand the advantages and to identify the limitations which are still not adequately defined. Based on this analysis, the challenges ahead are listed and discussed, and it appears that there are new opportunities to explore. Though nanosized AB is not mature enough for implementation, it has the potential to be developed further. Avenues worth exploring are given.     

Review and clustering of optimal energy management problem studies for industrial microgrids

The optimal energy management problem of microgrids is an agenda item for the energy field. Especially industrial microgrids, whose energy demand is high and uninterruptible, need to be managed by a holistic view of optimization. Technical researches in this field are to be enriched with the literature review that looks through various angles. In the scope of this paper, the research literature is reviewed deeply and analyzed with the aim of presenting the gaps. Articles written in English, in the period of 2010 to 2019 have been revised thoroughly. By eliminating the search results, 105 relevant articles have been determined. Objective(s), criteria for analysis, processes included, power source(s), storage system, other system components and methodology of each article have been studied. The literature has been summarized, it has been seen that solar, wind, and diesel sources are used in about 82%, 55%, and 16% of articles, respectively. Then, they have been clustered using self‐organizing maps. Nine clusters have been obtained which separate the articles clearly. Especially, three of them which have fewer data have been analyzed. Clustering results have been interpreted and utilized to show the research openings. Achievements of this study will lead the scientific research that will fill in the gaps.     

Optimal configuration for photovoltaic storage system capacity in 5G base station microgrids

Base station operators deploy a large number of distributed photovoltaics to solve the problems of high energy consumption and high electricity costs of 5G base stations. In this study, the idle space of the base station’s energy storage is used to stabilize the photovoltaic output, and a photovoltaic storage system microgrid of a 5G base station is constructed. Aiming at the capacity planning problem of photovoltaic storage systems, a two-layer optimal configuration method is proposed. The inner layer optimization considers the energy sharing among the base station microgrids, combines the communication characteristics of the 5G base station and the backup power demand of the energy storage battery, and determines an economic scheduling strategy for each photovoltaic storage system with the goal of minimizing the daily operation cost of the base station microgrid. The outer model aims to minimize the annual average comprehensive revenue of the 5G base station microgrid, while considering peak clipping and valley filling, to optimize the photovoltaic storage system capacity. The CPLEX solver and a genetic algorithm were used to solve the two-layer models. Considering the construction of the 5G base station in a certain area as an example, the results showed that the proposed model can not only reduce the cost of the 5G base station operators, but also reduce the peak load of the power grid and promote the local digestion of photovoltaic power.     

Compact energy storage: Opportunities and challenges of graphene for supercapacitors

碳纳米储能材料发展迅速,质量容量性能不断刷新。但通常碳纳米材料的密度较低,导致其体积比容量有限,在很多时候很难将材料水平上的优异性能反映到最终的器件上。发展高体积能量密度储能材料,在器件水平上实现致密储能,对推动储能材料和器件的实用化至关重要。作为其它sp2碳质材料的基本结构单元和一种柔性二维材料,石墨烯通过组装可以实现纳米结构致密化,在致密储能方面具有先天优势。本文以石墨烯在超级电容器中的应用为主,分别从材料、电极、器件3个层次讨论了实用化储能器件的设计原则,梳理了高体积能量密度碳基储能材料的研究进展,重点介绍了高体积容量碳电极材料的致密化设计理念,强调了从器件角度考虑储能材料设计的重要性,并对致密储能面临的机遇和挑战作了分析。     

Minimizing the energy cost for microgrids integrated with renewable energy resources and conventional generation using controlled battery energy storage

This paper presents a methodology to minimize the total cost of buying power from different energy producers including renewable energy generations particularly within the context of a microgrid. The proposed idea is primarily based on the controlled operation of a battery energy storage system (BESS) in the presence of practical system constraints coupled with our proposed cost optimization algorithm. The complex optimization problem with constraints has been solved using the well-known concept of dynamic programming. The methodology has been assessed using actual power and price data from six different power generation sites and cost reduction has been calculated for a number of BESSs by varying their energy and power capacities. Twofold benefits of the proposed methodology lie in minimizing the total cost along with the constraint-based efficient operation of the BESS. Simulation results depict that the given power demand at a particular region can be fulfilled properly at all times using a BESS and multiple power generation.     

光伏制造业:现状、前景及研究需求(四)

产品多样性使得分析c-Si状况更为复杂,但c-Si修正后的椭圆区也在格林最初提出的边界上。天合太阳能公司在2010第二季度报道晶体硅电池的光电转换效率在15%～22%之间,生产成本低至1.10美元/Wp。椭圆区上的箭头代表此技术的预期潜力。最大盈利需通过减少Si需求进一步降低制造成本,并提升组件效率趋近于25%。两者相结合可使成本降低到0.5美元/Wp。然而,FirstSolar公司的出现带来的一个结果就是c-Si工业已经具备快速响应、降低成本的能力。此外,重要的是硅并不需像CdTe一样去解决那么多问题。一旦     

Hydrogen energy,economy and storage: Review and recommendation

The hydrogen economy is a proposed system where hydrogen is produced and used extensively as the primary energy carrier. Successful development of hydrogen economy means innumerable advantages for the environment, energy security, economy, and final users. One major key to wholly develop hydrogen economy is safe, compact, light and cost-efficient hydrogen storage. The conventional gaseous state storage system as pressurized hydrogen gas and liquid state storage system pose safety and cost problems to onboard applications; therefore, they do not satisfy the future goals for a hydrogen economy. Fortunately, solid-state storage systems based on metal hydrides have demonstrated great potentials to store hydrogen in large quantities in a quite secure, compact, and repeatedly reversible manner and thus, becoming increasingly attractive option for hydrogen applications. However, techno-economic feasibility of hydrogen storage systems is yet to be realized as none of the current metal hydrides fulfill all the essential criteria for a practical hydrogen economy, mainly because of low hydrogen storage capacity, sluggish kinetics and unacceptable temperatures of hydrogen absorption/desorption. This article gives a brief review of hydrogen as an ideal sustainable energy carrier for the future economy, its storage as the stumbling block as well as the current position of solid-state hydrogen storage in metal hydrides and makes a recommendation based on the most promising novel discoveries made in the field in recent times which suggests a prospective breakthrough towards a hydrogen economy.     

Two-layer robust optimization framework for resilience enhancement of microgrids considering hydrogen and electrical energy storage systems

This paper presents a two-layer framework for improving the resilience of a 118-bus active distribution network consisting of four microgrids, which includes hybrid storage systems, electric buses (EBs), and the direct load control (DLC) program. In the proposed model, the uncertainties of RESs generation, demand, and EBs’ mobility are considered, and the robust optimization approach is used to tackle them. In the first layer, the planning of each microgrid is done separately and the energy purchase/sale request is sent to the control center. Then in the second layer, the control center performs the planning of the main network according to the requested program of the microgrids. Note that in this layer, the control center is able to rearrange the distribution feeder and send EBs to vital points of the network. Finally, the validity of the proposed model is evaluated through the implementation on seven case studies and the results show that the presence of hydrogen and electrical storage devices reduces forced load shedding (FLS) by 45.03% and 12.19%, respectively, during emergency situations. In addition, the results indicate that robust planning and the use of EBs for network recovery increase the resilience index by 3.35% and 3.98%, respectively.     

Optimal day-ahead energy planning of multi-energy microgrids considering energy storage and demand response

Due to the environmental and economic advantages of combined heat and power (CHP) units, their use in power grids has expanded. The entry of CHP into power systems increases the complexity of the economic power flow problem. This complexity is due to the introduction of multiple constraints into problem. A mere electricity supply is not optimal in today's networks, and energies such as heat, power and gas must be planned and managed simultaneously as an energy hub. Therefore, in this paper, an intelligent multi-energy microgrid (MG) consisting of power generation units, CHP units and gas units is modeled for day-ahead energy management (DAEM). The economic distribution problem focuses on the amount of power generation, heat and gas of the units in the system. In contrast, the total generation cost of the system is minimized, and all the equality and inequality constraints of the problem are observed. The proposed microgrid includes various energy-dependent equipment such as CHP units, gas boilers, electricity-to-gas units, power and heat storage units and electric heat pumps. Also, price-based load management was included to reduce costs due to the transfer of information between the consumer and the generator in the context of smartization. Since the above problem is difficult to solve due to various constraints and decision parameters, a newly developed optimization method based on water flows was proposed. The simple movement of water flows on the ground is efficient and optimal and always follows the shortest and fastest path to reach the deepest point. In the proposed algorithm, simple movements of water in routing, a change of direction and even the creation of rapids and vortices were simulated as various mathematical operators. Finally, the proposed model and method were examined in different scenarios. The numerical outcomes demonstrated that, the proposed modeling framework is superior to hub-based multi-carrier microgrid models in terms of power system security. The sensitivity of operational expenses to changes in initial values of energy storage systems (ESS) and thermal storage system (TSS) is proved that the cost of operation reduces as the baseline values of ESS and TSS are reduced to 0.2% of the maximum capacity. Because DAEM performance is less flexible when the primary values are reduced by 0.2% of the maximum value, the system running expenses increase marginally.     

An improved particle swarm optimisation for unit commitment in microgrids with battery energy storage systems considering battery degradation and uncertainties

Using electric storage systems (ESSs) is known as a viable strategy to mitigate the volatility and intermittency of renewable distributed generators (DGs) in microgrids (MGs). Among different electric storage technologies, battery energy storage (BES) is considered as the best option. In unit commitment (UC) module, the set of committed dispatchable DGs along with their power, power exported to/imported from macrogrid and status and power of ESS units are determined. In this paper, BES degradation is considered in UC formulation and an efficient particle swarm optimisation with quadratic transfer function is proposed for solving UC in BES‐integrated MGs, while the uncertainties of demand, renewable generation and market price are considered and dealt with robust optimisation. UC is formulated as a multi‐objective optimisation problem whose objectives are MG operation cost and BES degradation. The resultant multi‐objective optimisation problem is converted into a single‐objective optimisation problem and the effect of weight factors on MG operation cost and BES lifecycle are investigated. The results show that by consideration of BES degradation in objective function, BES lifecycle increases from 350 to 500 and the minimum depth of charge increases from 5.5% to 34%; however, MG operation cost increases from $8717 to $8910.2. The results also show that by consideration of uncertainties, MG's operation cost increases by 8.22%.     

Harnessing electricity storage for systems with intermittent sources of power: Policy and R&D needs

A central challenge for grid operators is matching electricity supply to demand, especially when the electricity supply is composed in part of intermittent resources. Several system options could help balance electricity supply and demand given different mixes of intermittent, baseload and load-following generation capacity; of these, electricity storage is especially interesting. If electricity storage could be deployed widely, grids of any size could sustain a wide range of profiles of intermittent and baseload power. Currently, most installed electricity storage worldwide is pumped hydro. Flywheels, compressed air and batteries represent interesting technologies that could provide grid-scale storage, especially if technology costs come down. A significant amount of storage R&D worldwide is appropriately focused on lowering these costs, but more is needed. Ultimately, storage will only achieve high levels of penetration if it can compete for service provision in electricity markets, and policy adjustments are needed in many countries to ensure this is the case.     

光伏制造业:现状、前景及研究需求(三)

四TW级/年制造的材料可获取性随着太阳电池制造年产量即将达到1TW,将使光伏行业面临原料是否充足的问题。Te和In这两种核心原料已引起人们广泛关注,它们分别是铜和锌矿冶炼时的副产品。Te和铂族元素一样同属于稀土元素,然而随着人们对Te角色认识的变化(批评到节约,再到寻求替代),致使对其资源的评估存在着广泛的争论和极大的不确定性。主流     

冰蓄冷系统研究新进展

介绍了不同冰蓄冷系统研究的新进展 ,并着重介绍一种新的冰蓄冷技术—过冷水动态制冰技术及与冰蓄冷空调系统有关的低温送风技术 ,以及蓄冷技术应用与峰谷分时电价之间的内在联系。最后 ,对于未来冰蓄冷研究提出几点建议     

Reversible chemical hydrogen storage in borohydrides via thermolysis and hydrolysis: Recent advances,challenges, and perspectives

Efficient hydrogen storing alternatives are now been pursued for decades. Solid storage systems are currently highly researched due to high volumetric densities at low temperatures and pressure. Still, no developed systems have satisfied even close to the targets given by The United States Department of Energy (DOE) 2020. Although various systems have reported good outputs at nearly room temperatures. The boron-based hydrides (BBHs) are the typical materials. They show a maximum of four reacting B–H bonds and hence have high volumetric densities of hydrogen. The majority of the research has been dealing with dehydrogenation through thermolysis and hydrolysis. This article critically reviews different BBHs for effective hydrogen storage. The first materials reviewed are ammonia borane, lithium borohydride, and sodium borohydride. However, their progress declined in the past few years due to incomplete reactions, elevated dehydrogenation temperature, and purity of hydrogen produced. To overcome these issues, new materials using suitable dopants have been developed since 2000. These materials display enhanced operations along with few drawbacks. Regenerability and numerous other stability factors have been intensively analyzed in this review. Also, different strategies for a system to operate at room conditions have been critically discussed. The findings suggest that BBHs are potential candidates in the field of hydrogen storage, but their applicability highly depends upon the regenerability and recyclability of byproducts.     

Review on thermal energy storage with phase change: materials,heat transfer analysis and applications

Thermal energy storage in general, and phase change materials (PCMs) in particular, have been a main topic in research for the last 20 years, but although the information is quantitatively enormous, it is also spread widely in the literature, and difficult to find. In this work, a review has been carried out of the history of thermal energy storage with solid–liquid phase change. Three aspects have been the focus of this review: materials, heat transfer and applications. The paper contains listed over 150 materials used in research as PCMs, and about 45 commercially available PCMs. The paper lists over 230 references.     

Modeling of biomass-to-energy supply chain operations: Applications,challenges and research directions

Reducing dependency on fossil fuels and mitigating their environmental impacts are among the most promising aspects of utilizing renewable energy sources. The availability of various biomass resources has made it an appealing source of renewable energy. Given the variability of supply and sources of biomass, supply chains play an important role in the efficient provisioning of biomass resources for energy production. This paper provides a comprehensive review and classification of the excising literature in modeling of biomass supply chain operations while linking them to the wider strategic challenges and issues with the design, planning and management of biomass supply chains. On that basis, we will present an analysis of the existing gaps and the potential future directions for research in modeling of biomass supply chain operations.     

Development of an optimization model for the feasibility analysis of hydrogen application as energy storage system in microgrids

Hydrogen can be used as an Energy Storage System (ESS) in a microgrid allowing to store surplus generation of variable renewable sources for later use. Research in the area mainly refers to the sizing of the components, however few studies evaluate the optimal technology selection and operation of microgrids using hydrogen as ESS. In this work, a model to determines optimal selection and to dispatch of Distributed Energy Resources (DER) allowing to evaluate the viability of hydrogen application as ESS in a microgrid is developed. The model is implemented in GAMS, using mixed integer linear programming, and applied in a hypothetical microgrid using as input data load profiles and commercial data available in literature. The results indicate the economical and environmental benefits of DER adoption, but the currently high investment costs make it infeasible to adopt hydrogen into a microgrid. However, when considering environmental costs and market prospects, the adoption of this technology became a good alternative, improving the energy management and reducing the total annual cost of the microgrid by 14.1%.     

Materials challenges in CO2 capture and storage

Abstract

To achieve deep reductions in CO₂ emission from power generation, technologies for CO₂ capture and storage are required to complement other approaches such as improved fuel use efficiency, the switch to low carbon fuels, and the use of renewable and nuclear energy. Three main options currently exist for CO₂ capture: removal of CO₂ from the flue gas; removal of carbon from the fuel before combustion; and oxyfuel combustion systems that have CO₂ and water, which can be separated by condensation, as principal combustion products. On the transport and storage side, the materials issues arise from corrosion and may be solved by drying and purification of the CO₂ stream. On the capture side, there are few specific issues regarding the materials used in technologies such as chemical absorption of CO₂ in an appropriate solvent (usually amines). The high temperature membranes used to separate oxygen from nitrogen in oxyfuel combustion systems raise materials issues in relation to ionic conduction, thermal and mechanical stability and lifetime when integrated in boilers, fluidised beds and gas turbine systems. The performance of systems integrating ceramic oxygen separating membranes is largely dependant on operating temperature, so the behaviour of these materials at ever higher temperatures is a real technical challenge. Membranes can also be used instead of chemical absorption for the separation of CO₂ and hydrogen in fuel de-carbonisation.