Conventional Energy Storage Systems Research Articles

Comparative characteristics of power delivery and temperature between conventional and hybrid energy storage systems in UAVs

Comparative characteristics of power delivery and temperature between conventional and hybrid energy storage systems in UAVs

Investigation of a novel combined ab- and ad- sorption based thermal energy storage and upgrade system

This paper presents a novel sorption-based cycle combining energy storage with energy upgrade to store low-grade heat for long periods and transform it on demand to usable energy at elevated temperatures. The system consists of an ammonia-water absorption system coupled to a resorption thermal transformer using manganese chloride and calcium chloride as the working pair with an ammonia absorbate. The absorption and adsorption systems are charged by separating the constituent sorbent-sorbate pairs, and they remain separated during the transition season. The discharge consists of a two-stage sorption process between the two systems. This work presents a transient thermodynamic model and analysis of the two-stage sorption system. For a typical solar thermal energy input of 106 °C during charging, and ambient temperatures of 5 °C and 25 °C in the winter and summer, respectively, the system is capable of discharging at an average elevated temperature of 62 °C with an energy storage efficiency of 27 %. This system is capable of simultaneously producing heat at a lower temperature by varying the mass flow rate through the high-temperature salt. The energy storage density of the combined system under different conditions is between 71 and 185 kJ kg−1. In comparison with other conventional single-stage thermal energy storage systems, this combination of absorption and adsorption-based storage provides a higher coefficient of performance for a comparable temperature output.

High-Voltage, Long Term-Stable and Wearable Zinc-Ion Hybrid Batteries with Gel Biopolymer Electrolytes

We are on the eve of the energy transition towards the phase-out of coal, electromobility and renewable power supply. Lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs) are complementary energy storage devices supporting this technological change. They have dominated the commercial market of power sources, serving as energy supplies for various technologies ranging from daily electronics and gadgets through electric vehicles to management systems of the intermittent electric grid. However, conventional energy storage systems present some challenges regarding operational safety, the expected increase in production costs, the risk of limited availability of raw natural resources, and universal waste disposal.1,2 Zinc-ion rechargeable power sources, including batteries and hybrid supercapacitors, are a promising alternative to commercial LIBs and EDLCs.3,4 This technology integrates attractive features, such as high gravimetric and volumetric theoretical capacity, low cost, high safety, and environmental friendliness. Nevertheless, the widespread adoption of zinc-ion systems for powering commercial devices still faces challenges related to electrode design, the risk of liquid electrolyte leakage, rigid construction, and the presence of synthetic polymer-based components. This research attempts to address the aforementioned shortcomings by exploring the concept of biopolymer-based zinc-ion systems.Herein, we present zinc-ion hybrid batteries employing gel biopolymer electrolytes. Batteries and dual-ion hybrid batteries of aqueous Zn-ion technology operate according to similar mechanisms, differing on the catholyte side. In Zn-ion batteries, zinc ions are involved in the reactions on both electrodes, whereas hybrid systems have cathodes adopted from alkaline metal-ion technologies, operating according to intercalation/deintercalation processes of monovalent cations, e.g., Li-ion, Na-ion, K-ion, etc.5 As observed, hybrid devices are feasible with fast kinetics, good stability, and flat and high discharge voltage plateau. The application of gel electrolytes additionally improves their performance on the anode side, facilitating Zn stripping/plating processes due to homogeneous current distribution and flat Zn deposition. Generally, the presented idea emerges as a promising strategy, offering an efficient, safe, low-cost, non-combustive, flexible and sustainable technology. Particular attention is paid to overcoming LIB performance and environmental limitations whilst developing wearable features through innovative biobased technological improvements.References(1) Mauler, L.; Duffner, F.; Zeier, W. G.; Leker, J. Battery Cost Forecasting: A Review of Methods and Results with an Outlook to 2050. Energy Environ. Sci. 2021, 14 (9), 4712–4739.(2) Simon, P.; Gogotsi, Y.; Dunn, B. Where Do Batteries End and Supercapacitors Begin? Science (80-. ). 2014, 343, 1210–1211.(3) Wang, Y.; Sun, S.; Wu, X.; Liang, H.; Zhang, W. Status and Opportunities of Zinc Ion Hybrid Capacitors: Focus on Carbon Materials, Current Collectors, and Separators. Nano-Micro Lett. 2023, 15 (1), 78.(4) Tang, B.; Shan, L.; Liang, S.; Zhou, J. Issues and Opportunities Facing Aqueous Zinc-Ion Batteries. Energy Environ. Sci. 2019, 12 (11), 3288–3304.(5) Shi, Y.; Chen, Y.; Shi, L.; Wang, K.; Wang, B.; Li, L.; Ma, Y.; Li, Y.; Sun, Z.; Ali, W.; Ding, S. An Overview and Future Perspectives of Rechargeable Zinc Batteries. Small 2020, 16 (23), 2000730. Figure 1. Work concept. Figure 1

Advanced Hybrid Polymer/Ceramic PEO-SnF2 Protective Mechanism for Sodium Metal Anodes

In the face of mounting global energy requirements and pressing environmental issues, the scientific community turned to lithium-metal batteries, celebrated for their superior capacity and efficiency. However, challenges arising from the scarcity and increasing costs of lithium have redirected research efforts towards sodium batteries. Sodium metal anodes, with their remarkable theoretical specific capacity of ~1166 mAh/g, low anode potential of -2.714 V vs standard hydrogen electrode, and cost benefits, are increasingly recognized as promising candidates for conventional energy storage systems. Notwithstanding their advantages, the unstable and fragile solid electrolyte interphase (SEI) due to the spontaneous reaction between metallic Na and a liquid electrolyte remains a significant limitation. As this SEI layer expands, it hinders ion transport, causing increased polarization and diminishing the battery's energy efficiency. Specifically, during the plating process, Na ions are deposited beneath the SEI layer, causing significant expansion. This expansion fractures the fragile SEI, allowing dendrites to grow through these defects. As these dendrites grow, they can pierce the separator, posing a risk of short-circuiting the battery. While numerous studies have proposed designs for protecting sodium metal interphase, to overcome these challenges, this study amalgamates mechano-electrochemical protective strategies to enhance sodium metal anode stability, offering groundbreaking solutions to these challenges.Central to our exploration were tin fluoride (SnF2) and silicon nitride (Si3N4), both established as effective in generating robust artificial SEI layers on the sodium metal surface. These layers, rich in NaF and NaxN respectively, demonstrated a notable improvement in cycling performance, effectively suppressing dendrite growth and enhancing the battery's cycling stability by nearly 3.5 times compared to bare sodium anodes.Building upon these foundational insights, a novel approach was conceptualized: a hybrid protective mechanism combining polyethylene oxide (PEO) with the presence of SnF2 as an additive, is particularly efficacious. This combination was specifically chosen to provide chemical stability, morphological conformality, and mechanical flexibility to accommodate the mechano-electrochemical instability upon sodiation/desodiation processes. Through this novel strategy, we aimed to amalgamate the strengths of both components, ensuring optimal outcomes. This composite artificial SEI under a 0.25 mA/cm2 current density, delivers a cycling performance 10 times superior to bare sodium metal and survived up to 1800 hours of cycling. Impressively, at a high current density of 0.5 mA/cm2, the hybrid system still performed much better than its untreated counterpart and continued cycling for up to 800 hours of cycling. The synergy of PEO and SnF2 remarkably minimized electrolyte decomposition, inhibited dendrite formation, and stabilized Na plating/stripping processes, all of which consolidated its promise for sodium metal battery technology.

Economic evaluation of the second-use batteries energy storage system considering the quantification of environmental benefits

The number of retired batteries from electric vehicles continues to grow, which not only puts pressure on battery recycling but also leads to environmental pollution. By replacing the conventional batteries with the second-use batteries in configuring the energy storage system, the investment cost can be effectively reduced, and the issue of retired batteries disposal can be alleviated. In view of this, the paper investigates the quantification of the environmental benefits of second-use batteries, and comprehensively evaluates the second-use batteries energy storage system (SUBESS) in terms of environmental and economic benefits. The energy storage configuration model aimed at maximizing annual net income is developed, and the improved particle swarm optimization algorithm is applied to determine the optimal capacity and power in a photovoltaic (PV) pilot area. Under the same capacity condition, several evaluation indexes are used to compare the economics of the SUBESS with the conventional batteries energy storage system (CBESS). The results show that: (1) Compared to end-of-life disposal of batteries, secondary utilization will yield greater environmental benefits. (2) When the cost per unit capacity of the SUBESS is lower than 63.99 % of the CBESS, the economy of the SUBESS is better than that of the CBESS. Finally, targeted suggestions are made to further promote the scale development of the retired batteries secondary utilization industry. The research results not only validate the economic feasibility of the SUBESS but also have significant environmental benefits, which can provide a reference for potential investors.

Design an energy storage system for a 1 MW photovoltaic powerplant based on compressed-gas-refrigeration for buildings cooling and ice production

An energy storage system was designed for a 1 (MW) photovoltaic solar power plant. This power plant is located in a university campus in the hot desert region, which requires continuous cooling of its buildings consists of a large number of classrooms. Due to the desert nature of the region, it was not possible to use conventional energy storage systems based on pumped-hydro; because in considered climate, it is not possible to provide a large volume of water and compensate for the evaporated water. Therefore, an energy storage system based on compressed gas refrigeration was used. The effect of system parameters including the maximum pressure on its performance including COP, total space can be cooled, ice making capacity and also the required volume for high-pressure vessel was studied. The effect of using different gases including air, nitrogen, ammonia, carbon dioxide and argon as the working fluid was studied. Also, the effect of the mixture of nitrogen and carbon dioxide and different molar percentages of them on the performance of the system was studied. The results showed that the designed energy storage system can well supply the cooling load of the university building where the solar power plant is located.

Hybrid energy storage system for electric motorcycles: Technical and economic analysis

This paper presents the multiple energy storage system usability for electric motorcycle focused on hybrid topology. This study focuses on evaluating the cost-effectiveness of a hybrid energy storage system (HESS) for e-motorcycles over a 10-year period by considering the number of battery replacements instead of solely the initial system price. The motorcycle studied in this manuscript, is a recreational electric motorcycle utilized as an experimental test bench in EV-SCHS laboratory at the OJEN company. The 10-year equivalent price of the energy storage system includes both the initial purchase cost and the cost of battery replacements over the system's lifespan. A battery life model is essential for estimating the frequency of replacements over the 10-year period. Incorporating ultracapacitors (UC) in the HESS enhances power specifications, leading to improved acceleration and regenerative braking capabilities. This reduces battery current and extends battery life, resulting in fewer required replacements and lower overall system costs over the 10-year period. The study findings demonstrate that optimally-sized HESS configurations offer favorable power specifications, with the 10-year equivalent price of HESS being $3466 lower than that of conventional energy storage systems, despite the initial price of HESS being $833 higher.

Modeling and Simulation of Single Flow Zinc–Nickel Redox Battery Coupled with Multi-Physics Fields

Metallic zinc (Zn) presents a compelling alternative to conventional electrochemical energy storage systems due to its environmentally friendly nature, abundant availability, high water compatibility, low toxicity, low electrochemical potential (−0.762 V vs. SHE), and cost-effectiveness. While considerable efforts have been devoted to enhancing the physical and chemical properties of zinc-ion battery materials to improve battery efficiency and longevity, research on multi-physics coupled modeling for a deeper understanding of battery performance remains relatively scarce. In this study, we established a comprehensive two-dimensional model for single-flow zinc–nickel redox batteries to investigate electrode reactions, current-potential behaviors, and concentration distributions, leveraging theories such as Nernst–Planck and Butler–Volmer. Additionally, we explored the distribution of the velocity field using the Brinkman theory in porous media and the Navier–Stokes equations in free-flow channels. The validated model, informed by experimental data, not only provides insights into the performance of the battery, but also offers valuable recommendations for advancing single-flow zinc–nickel battery technology. Our findings offer promising avenues for enhancing the design and performance of not only zinc–nickel flow batteries, but also applicable for other flow battery designs.

Analysis of Supercapacitors in Renewable Energy Systems for Managing Power Fluctuations

Environmental decarbonization drives the world to find better ways to generate and store energy. Sustainable energy in the form of solar and wind is explored with the use of conventional energy storage systems (batteries) to close the gap. Green energy generation is weather-dependent, leading to power output fluctuations, and the short-term variability in irradiance adversely affects the system’s energy output and reliability. Standalone operation of a generating system necessitates a storage energy unit that manages transient loading and effectively shares power between the load and energy storage. This article presents an approach to managing energy fluctuations when renewable energy sources fluctuate, this occurs when short-term variability in irradiance, and transient loading occurs. The approach uses supercapacitors as a short-term energy storage solution. The proposed configuration has the following key advantages: effective power sharing, rapid charge, and discharge cycles in supercapacitors result in voltage restoration under transient conditions. The performance of the system is confirmed in MATLAB/Simulink. The proposed study confirms that integrating supercapacitors with PV systems does provide significant power oscillation management when sudden variations occur in renewable sources. A practical test was performed using smaller components following the same concept, and the results supported the hypothesis. The results show that the output voltage is managed when oscillation in irradiance occurs. This is seen in the simulation without supercapacitors when the output voltage fluctuates between 100 and 450 V within the first second of the simulation; however, with the introduction of SC, the voltage becomes stable and maintains an output of 620 V within 0.02 seconds. This is further supported by the experimental outcomes where almost 50% of the solar panel is covered and the output voltage is maintained.

Cryptocurrency mining as a novel virtual energy storage system in islanded and grid-connected microgrids

Renewable electrical energy (such as: solar and wind energies) generation in microgrids (MGs), is gaining attention to reduce greenhouse gas emissions. Microgrid operators (MOs) aim to create self-sufficient, environmentally sustainable grids, increasing the capacity of renewable energy sources (RESs) by up to 100%. Despite of the benefits of this trend, challenges arise from non-controlled characteristics of these power generations and their seasonal variations, causing fluctuations and renewable energy curtailment. Although the technical solutions; such as: the demand response (DR) programs, and the conventional electrical energy storage systems (EESSs) can help, however those may face limitations in countries with high seasonal energy generation and consumption variations. This paper introduces cryptocurrency mining loads (CMLs) as innovative virtual energy storage systems (VESSs), named cryptocurrency energy storage systems (CESSs). It proposes a structure to store excess renewable energy in cryptocurrency units (CCUs) like Bitcoin (BTC). CESSs can be charged during off-peak intervals and, conversely, they discharge during high-demand periods to reduce the overall operational cost of MGs. Furthermore, it presents a new energy management system (EMS) formulation for the optimal operation of MGs in the presence of CESSs, providing an opportunity to generate additional electricity from RESs and to mitigate renewable energy curtailment. This paper explores the optimal operation conditions of both islanded and grid-connected MG with the proposed CESS. Utilizing a dataset from an island in Finland as a practical MG, its effectiveness is demonstrated through several case studies. The results of one case study in this paper demonstrate that the proposed CESS can decrease the operating cost of the MG by about 46.5%. Additionally, it is showed that by application of CESS the renewable energy curtailment is significantly reduced, and approached zero.

Risk-averse bi-level planning model for maximizing renewable energy hosting capacity via empowering seasonal hydrogen storage

Renewables (i.e., solar and wind power) in the Nordic area have highly seasonal characteristics, which severely restrict the wide development of renewables since they can be excessive in summer but insufficient in winter with intermittent outputs. The conventional battery energy storage system (BESS) with short-term adjustment functionality cannot eliminate the seasonal imbalance of renewables. In this regard, a risk-based bi-level planning model is presented to maximize the hosting capacity (HC) of renewables through configuring seasonal hydrogen storage (SHS) and BESS. Specifically, the upper level applies a multi-objective scheme to maximize HC and minimize the investment cost simultaneously. In turn, the lower level is driven by maximizing the profits of the distribution system operator (DSO) with the implementation of price-based demand response (PBDR). Due to forecasting errors of renewables and load resulting from intermittent output and random behaviors, a stochastic programming (SP) method is developed to address and adapt multiple uncertain fluctuations. Moreover, the conditional value-at-risk (CVaR) is introduced to measure the effect of the risks raised by multiple uncertainties on system operation. Finally, numerical studies are employed to verify the effectiveness of the proposed model. Compared to the cases without considering PBDR and SHS, the total renewable energy HC in the proposed model is increased by 2.30 MW and 0.37 MW, respectively, while the yearly cost benefit of DSO is enhanced by 28063.2 US$ and 17823.7 US$, respectively. The promising results demonstrate the empowerment of SHS can promote the cross-seasonal consumption of renewables, effectively maximizing the HC and improving the economic operation of distribution systems.

Enhanced electrocatalytic conversion of tellurium with MnO hollow nanospheres modified hierarchical n-doped carbon nanosheets in high-performance aqueous Zn-Te battery

Rechargeable aqueous zinc batteries (AZBs) are increasingly recognized as an alternative to conventional energy storage systems due to their environmentally safe nature, abundant zinc resources, and high theoretical capacity. However, the intercalation or surface redox mechanisms limit the development of AZBs cathode materials due to low specific capacity and energy density. The tellurium-based (Te) materials with conversion mechanisms are promising cathode materials for AZBs. Nevertheless, the slow kinetics are detrimental to the increase in specific capacity and energy density for Zn-Te battery. Therefore, a hierarchical structure of manganese oxide (MnO) hollow nanospheres loaded on nitrogen-doped carbon nanosheets (MnO@NC) was rationally designed and used as Te hosts (Te/MnO@NC) for Zn-Te battery. This hierarchical structure facilitates the loading of more Te species. Meanwhile, the MnO hollow nanospheres can expose more active sites, which can promote the kinetics of Te redox reactions thereby lowering the reaction energy barrier. The Te/MnO@NC cathode exhibits high specific capacity and high energy density (429 mAh g−1 and 407 Wh Kg−1 at 0.1 A g−1). Additionally, the conversion mechanism was investigated by systematic characterization and density functional theory (DFT) calculations. This study presents a new design platform for developing AZBs with high specific capacity and energy density.

Coupled thermo-hydro-mechanical modeling on geothermal doublet subject to seasonal exploitation and storage

Combining the conventional high-temperature aquifer thermal energy storage system with the common geothermal reservoir development system is a potential alternative to increase energy access, but effects of natural parameters like fracture aperture and reservoir permeability and development parameters like flow rate and injection temperature on the efficiency of energy exploitation and storage have seldomly been investigated. In this study, three assessment parameters and three evaluation criteria were defined to evaluate the sustainability and efficiency of deep geothermal reservoirs with seasonal energy exploitation and storage, and a robust approach of optimizing the development parameters was proposed by combining numerical reservoir model, experimental design and surrogate model, and multiple response optimization method. Based on a case study of the geothermal doublet in Tsinghua University, China, the robustness and reasonability of the developed optimization method were demonstrated. The results show that the optimal development parameters can not only maximize the total recoverable energy and effective recovery efficiency, but also satisfy the requirements of sustainably developing deep geothermal reservoirs. The recoverable heat energy can increase about 20% by adding artificial thermal storage into geothermal reservoir development. Therefore, it is strongly recommended to add energy storage into the future geothermal reservoir development system.

I-Sare. The Future Grid.

This paper presents a real implementation of hierarchical control scheme for a smart grid equipped with voltage source converters, attached to renewable and conventional energy generators and storage systems based on ultracapacitors, flywheel and batteries, which is able to assume the demand of domestic, commercial, industrial and electric vehicle demanding current loads up to 400 kw in islanded mode or connected to the main grid. The hierarchical control used is implemented in the central control system and in each of the converters connected to the intelligent grid, in order to distribute the control over all the elements involved in the generation of energy. For this purpose it is used a distributed communication architecture based on EPICS to manage all the information generated. This micro grid, called i-Sare, was developed during the 2012 and beginning of 2013, and will be operational in Donostia (Gipuzkoa) at the end of 2013. In this paper real test results are presented to demonstrate the effectiveness of the control and the communication architecture used in iSare.

Development of Liquid Organic Hydrogen Carriers for Hydrogen Storage and Transport.

The storage and transfer of energy require a safe technology to mitigate the global environmental issues resulting from the massive application of fossil fuels. Fuel cells have used hydrogen as a clean and efficient energy source. Nevertheless, the storage and transport of hydrogen have presented longstanding problems. Recently, liquid organic hydrogen carriers (LOHCs) have emerged as a solution to these issues. The hydrogen storage technique in LOHCs is more attractive than those of conventional energy storage systems like liquefaction, compression at high pressure, and methods of adsorption and absorption. The release and acceptance of hydrogen should be reversible by LOHC molecules following favourable reaction kinetics. LOHCs comprise liquid and semi-liquid organic compounds that are hydrogenated to store hydrogen. These hydrogenated molecules are stored and transported and finally dehydrogenated to release the required hydrogen for supplying energy. Hydrogenation and dehydrogenation are conducted catalytically for multiple cycles. This review elaborates on the characteristics of different LOHC molecules, based on their efficacy as energy generators. Additionally, different catalysts used for both hydrogenation and dehydrogenation are discussed.

Development of High Electrochemical Performance-Reliability TiO2 Nanoparticle-Mulberry Paper Based Supercapacitor

The paper-based energy storage systems with lightweight, thin and large scalability have been attracted much attention in the field of next generation research. Along with the advantages of these papers, they have excellent flexibility and wettability, so they have high power density even under mechanical bending and twisting deformation, making them suitable for wearable devices. However, conventional paper has limited electrochemical stability due to its low chemical resistance and decomposition in organic or acidic electrolytes.Mulberry paper can be an outstanding alternative for overcoming the limitations of conventional paper-based energy storage systems. Mulberry fibers form a stronger mechanical network and are longer than conventional paper fibers, so they have excellent chemical strength. Therefore, in this study, a supercapacitor with high electrochemical performance and reliability was produced based on mulberry paper.As high electrochemical performance active materials, TiO2 nanoparticle and graphene oxide nanocomposites were used. A TiO2 nanoparticle was coated on a mulberry paper substate, graphene oxide was coated, and heat treatment was performed at 700℃ under nitrogen atmosphere for 3 hours. Mulberry paper was carbonized to increase areal energy density. It was strongly fixed by the reduced graphene oxide to maintain the flexibility of carbonized mulberry paper and prevent the delamination of the TiO2 nanotube without protection layer.Therefore, it is suitable for wearable energy storage systems because it can maintain excellent charge-discharge cycle reliability and flexibility carbonized mulberry paper by improving areal energy density from carbonized mulberry paper and metal oxides and preventing the delamination of the metal oxide.

Performance study of the supplemental combustion type compressed air energy storage system

Compressed air energy storage technology is considered to be the most promising energy storage technology, but it has not been applied commercially on a large scale, partly because of the low system efficiency, with the existing efficiency being about 70%. To improve the round trip efficiency of the system, this paper proposes a supplementary combustion compressed air energy storage system based on adiabatic compressed air energy storage. The system adds supplementary combustion equipment to increase expansion machines’ inlet air temperature by burning fuels such as syngas, hydrogen, and natural gas to increase the power generation of the system. The thermodynamic performance analysis has been conducted through the thermodynamic model of the system, and the effects of parameters such as compressor discharge temperature, supplementary combustion, and air-fuel ratio on the system performance have been further investigated. The research results show that the efficiency of the system is improved by nearly 6% compared with the conventional adiabatic compressed air energy storage system. Meanwhile, the system’s round-trip efficiency can be further increased by appropriately raising the compressor discharge temperature and supplemental combustion quantity.

Integrating wind energy and compressed air energy storage for remote communities: A bi-level programming approach

The integration of compressed air energy storage and wind energy offers an attractive energy solution for remote areas with limited access to reliable and affordable energy sources. This study presents a design approach for an energy system comprising wind turbines, compressed air energy storage, and diesel generators. The proposed method is based on bi-level programming, enabling the simultaneous optimization of the size and operation of the system while considering the interaction between them. Detailed mechanical design and configuration of the compressed air energy storage system are considered, including the number and size of compressors and turbines, valves, recuperator operating conditions, etc. In contrast with conventional compressed air energy storage systems, operating once a day for peak shaving, the proposed compressed air energy storage system aims to mitigate wind fluctuations. Therefore, it would operate under partial load conditions most of the time, and as a result, the system's off-design modeling is also considered. The results indicate that the proposed system is a promising, cost-effective, reliable energy solution for remote areas, significantly decreasing the average daily total cost and CO2 emissions by 69 % and 76 %, respectively. Additionally, by studying the system's performance under both design and off-design conditions, it is concluded that considering the off-design conditions is critical to ensure a more realistic performance of the system as the system is less likely to utilize the compressed air energy storage in low charging and discharging opportunities.

A data-driven rolling optimization control approach for building energy systems that integrate virtual energy storage systems

The virtual energy storage system (VESS) is an innovative and cost-effective technique for coupling building envelope thermal storage and release abilities with the electric and heat power conversion characteristics of an air conditioner; this system provides building energy systems (BESs) with adjustable potentials similar to those of conventional battery energy storage systems (BESSs). However, the VESS is a dynamic system, and uncertainties in the outdoor temperature and solar irradiance are difficult to accurately predict, which impacts the quantification accuracy of VESSs; these characteristics challenge the BES control scheme economy and the thermal comfort of occupants. To solve this crucial issue, a data-driven rolling optimization (RO) control approach for a BES that integrates a VESS is proposed. First, a BES state space model integrating the VESS is created to reflect the VESS adjustable potential and dynamic characteristics. Based on the above model, while aiming at a small BES data sample size, a support vector machine (SVM) is combined with RO to correct the day-ahead quantification errors of the VESS adjustable potential and enhance the economical operation and thermal comfort of the BES that integrates the VESS in uncertain environments. Comparative simulations validate the effectiveness of this VESS modelling and data-driven RO control approach.

Optimal Electric Vehicle Fleet Charging Management with a Frequency Regulation Service

Electric vehicles are able to provide immediate power through the vehicle-to-grid function, and they can adjust their charging power level when in the grid-to-vehicle mode. This allows them to provide ancillary services such as frequency control. Their batteries differ from conventional energy storage systems in that the owner’s energy requirement constraint must be met when the vehicles participate in a frequency control system. An optimization problem was defined by considering both the owner satisfaction and frequency control performance. The main contribution of the proposed paper, compared to the literature, are (1) to keep the total available energy stored in the batteries connected to a charging station in an optimal region that favors the frequency regulation capability of the station and the proposed QoS and (2) to consider the optimal region bounded by the efficiency thresholds of the charger to allow for maximum regulation power. The problem is expressed as a multi-criteria optimization problem with time-dependent references. The paper presents an energy management strategy for frequency control, describes a concept of an optimal time-dependent state of charge for electric vehicle charging demands, and considers the power dependence of the electric vehicle charger efficiency. Finally, the simulation results are presented via Matlab/Simulink to prove the effectiveness of the proposed algorithm.