HP Multi-Tiered Output Control Strategy for Ees Required Capacity Reduction in System Frequency Regulation

Lithium-ion batteries are used for both stationary and mobile applications. While in the automotive industry standard profiles are used to compare the performance and efficiency of competing vehicles, a similar comparative metric has not been proposed for stationary battery energy storage systems. Because standard profiles are missing, the comparable evaluation of different applications with respect to efficiency, long-term behavior and profitability is very difficult or not possible at all. This work presents a method to create these standard profiles and the results are available as open data for download. Input profiles including frequency data, industry load profiles and household load profiles are transformed into storage profiles including storage power and state of charge using a holistic simulation framework. Various degrees of freedom for the energy management system as well as for the storage design are implemented and the results are post-processed with a profile analyzer tool in order to identify six key characteristics, these being: full-equivalent cycles, efficiency, depth of cycles, resting periods, number of changes of sign and energy throughput between changes of sign. All applications examined in this paper show unique characteristics which are essential for the design of the storage system. E.g., the numbers for annual full-equivalent cycles vary from 19 to 282 and the efficiency lies between 83% and 93%. With aid of this work in conjunction with the open data results, users can test and compare their own cell types, operation strategies and system topologies with those of the paper. Furthermore, the storage power profiles and state of charge data can be used as a reference for lifetime and profitability studies for stationary storage systems.

A CFD based methodology to design an explosion prevention system for Li-ion based battery energy storage system

This study presents a new operation optimization method for distributed energy resource (DER) units in islanded distribution networks (DNs) of Southeast Asia, a region featured by high solar irradiance, consistently high temperatures and unpredictable weather patterns. First, a holistic thermal model for stationary battery energy storage systems (ESSs) is proposed with a detailed analysis of internal cooling power consumption. Then, to deal with voltage fluctuations caused by intermittent photovoltaic (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{P V}$</tex>) power generation caused by the region's volatile weather, the PV inverter oversizing is modeled to enable reactive power support while accounting for inverter lifespan degradation. Finally, the entire optimization problem is modeled by two stage stochastic programming, and the solution approach based on model linearization and relaxation is developed. Simulation tests on an IEEE-34 bus three-phase DN demonstrate the effectiveness of the proposed method.

Due to economic expansion, population growth, and technological improvements contribute to rising energy demand, the self-consumption of locally generated electricity from photovoltaic (PV) systems is becoming an important application area for stationary battery energy storage systems (BESS). The optimized load schedule and battery capacity were employed in this research to reduce the customer's total cost. In many articles, a PV-BESS system was optimized using various optimization approaches. The Earthworm Algorithm (EWA) in MATLAB was used as the optimization method. Based on the result, the EWA BESS size optimized is 20.36 kWh, the total optimized cost is 45% less than the total unoptimized value, and the total EWA optimized cost is 7% less expensive than the total Cuckoo Search Algorithm (CSA) optimized cost. It was proven using statistical tools that the overall cost of an optimized and unoptimized PV-BESS system differs significantly, whereas the total cost of an EWA optimized, and CSA optimized system does not differ much.

A resilience-oriented optimal planning of energy storage systems in high renewable energy penetrated systems

Intermediate temperature NaCl-AlCl3-based Al-ion batteries are considered as a promising stationary energy storage system due to their low cost, high safety, etc. However, such a cheap electrolyte has a critical feature, i.e., strong corrosion, which results in the short cycle life of the conventional Al-metal anode and also limits the development of the NaCl-AlCl3-based Al-ion batteries. A noncorrosive electrolyte may be a good choice for addressing the above challenge, while it is difficult to obtain the electrolyte that has advantages of both noncorrosion and low cost. Therefore, here, we report a Ga-metal anode in the affordable NaCl-AlCl3 electrolyte for constructing a long-life stationary Al-ion energy storage system. This featured liquid metal anode shows good alloying and dealloying processes between metallic Ga and Al, as well as renders superior stability of the interface between the electrolyte and the anode (e.g., smoothly running for over 580 h at 2 mA cm-2). No-corrosion and no-pulverization problems appear in this novel liquid/liquid interface. Those advantages demonstrate that the liquid Ga-metal anode has a great promise for the improvement of the NaCl-AlCl3-based Al-ion batteries for large-scale stationary energy storage applications.

In order to reach sustainable consumption and production patterns at scale, the implementation of a circular economy (CE) and the corresponding circular business models (CBM) increasingly need to become competitive with linear alternatives. This is inhibited by a lack of customer focus when implementing circular projects today. To address this challenge, this study presents an in-depth study of a real-world project on repurposing electric vehicle batteries in stationary battery energy storage systems in Germany, which serves to investigate the role of market- and customer requirements in implementing CBM. By combining quantitative analysis based on secondary sources with primary qualitative data collected at different stages of the project, the study offers unique insights into the practical key tasks for ensuring economic viability of circular projects from a multi-stakeholder perspective. These are identified as: i) Develop the product platform, ii) assess multiple value streams, iii) leverage on resource value, iv) provide risk assurances on product quality, v) observe trends in targeted downstream markets, vi) acquire access to suitable financial capital and vii) carry out pilot projects under market conditions. By addressing these tasks, the value captured in terms of the contribution of repurposing to the reduction of battery life cycle cost is found to be 109€/kWh in the case investigated. Based on the findings, the study concludes that implementing circular projects requires companies to provide resource, time and technical expertise for coordinating the identified key tasks and achieve competitiveness with linear alternatives. For future research, we hence suggest further investigation of the use of customer-oriented methods for assessing and developing CBM, as well as required policy-action to ensure commercial viability of CE strategies in industry.

Electro.Aero has been supporting the emerging electric aviation industry for nearly a decade, including the development of chargers, electrical management systems, battery management systems and electric propulsion systems to numerous electric aircraft development projects. During that time, it was identified that the industry needed standardization, especially regarding the charging coupler, so the SAE AE-7D committee was founded by Joshua Portlock in 2018 to help standardize electric aircraft charging and energy management. The AS6968 standard for light conductive charging of electric aircraft was the first standard the committee worked on and is now approaching completion through this year. Furthermore, while the charging coupler standard was proving to be of high priority to the industry, there has also been a noticeable trend that typical airport hangars don't have sufficient electrical power to charge the growing power demands of future electric vertical take-off and landing (eVTOL) aircraft. Therefore, SmartHangar technology was developed, whereby the limited grid connectivity is supplemented by solar and stationary battery energy storage systems to help deliver the peak power demands of electric aviation charging, whilst also helping airports and vertiports transition to more self-sufficient sustainable energy.

To address regional blackouts in distribution networks caused by extreme accidents, a collaborative optimization configuration method with both a Mobile Energy Storage System (MESS) and a Stationary Energy Storage System (SESS), which can provide emergency power support in areas of power loss, is proposed. First, a time–space model of MESS with a coupled transportation network and power grids is constructed, as a MESS is more flexible than a SESS. Considering resilience and recovery, a minimization objective function for total cost, encompassing the hybrid energy storage investment cost, the power grid operation cost, and the load shedding penalty cost, is established. Moreover, considering SESS constraints and operational constraints, a hybrid configuration model is established. Then, considering the probability of extreme accidents, the scenario analysis method is used to address randomness, ensuring that the configuration results can be adapted to various scenarios. The proposed method can fully combine the time–space flexibility of MESS and the economic advantages of SESS, which can reduce the total cost and ensure the power system’s reliability. Finally, the effectiveness of the proposed method is verified by the improved IEEE33 system.

The presence of distributed generation (DG), represented by photovoltaic generation and wind generation, brings new challenges to distribution network operation. To accommodate the integration of DG, this study proposes a bi‐level optimisation model to determine the optimal installation site and the optimal capacity of battery energy storage system (BESS) in distribution network. The outer optimisation determines the optimal site and capacity of BESS aiming at minimising total net present value (NPV) of the distribution network within the project life cycle. Then optimal power flow (OPF) and BESS capacity adjustment are implemented in the inner optimisation. OPF optimises the scheduling of BESS and network losses. On the basis of optimal scheduling of BESS, a novel capacity adjustment method is further proposed to achieve the optimal BESS capacity considering battery lifetime for minimising the NPV of BESS. Finally, the proposed method is performed on a modified IEEE 33‐bus system and proven to be more effective comparing with an existing method without BESS capacity adjustment.

Compared with traditional stationary energy storage system (SESS), mobile energy storage system (MESS) has power transfer ability in both spatial and temporal dimensions. Thus, it can provide greater flexibility in power system auxiliary services. To simplify and clarify the optimal scheduling problem, a novel “virtual switch” indicator is defined to describe the scheduling of MESS and an equivalent reconfiguration method is proposed by analogy with distribution network reconfiguration. Based on the method proposed, the dynamic economic scheduling of MESS in distribution networks(DNs) can be formulated as a scenario-based stochastic optimization problem, where the uncertainties of traffic flow and renewable energy output are considered by generating scenarios using Monte Carlo simulation. The objective function is to maximize the profit of distribution network operator. The time and cost of MESS scheduling are transformed into those of virtual switch switching in distribution network reconfiguration. Therefore, the operation scheduling problem of a MESS is equivalent to a distribution network reconfiguration problem with a SESS and several virtual switches. In this way, a grid-traffic network coupling problem is simplified to a pure distribution network problem, which provides a novel way to solve the MESS scheduling problems. Finally, simulation results on the IEEE 33-bus distribution system and simple traffic network verify the validity and feasibility of the method proposed.

The transformation toward climate-neutral mobility (road, air and water transportation) and stationary energy storage systems is a fundamental task of the current generation. In some fields, such as electromobility or stationary storage, Li-ion cell technology has emerged as a potential enabler of this transformation. Nevertheless, research is ongoing regarding Li-ion cells to meet both technical and customer requirements, particularly in terms of range (energy and power density) and safety. In addition to novel cell formats, such as large-format cylindrical cells 21700 or 47xx with tabless design, current research is focusing on new active materials with high specific capacity such as silicon. The challenge resulting from the use of these materials is the high volumetric expansion caused by lithiation. This causes mechanical aging phenomena such as the Loss of Active Material (LAM), which can have a significant negative impact on the service life. This leads to a tradeoff between maximizing the energy density and longevity of the battery system. In addition to optimizing the electrode design, such as the use of nano-silicon or silicon oxide or additives that buffer the mechanical load, the operating strategy of cells in the application can be adapted to minimize degradation. The purpose of this work is to gain a deeper understanding of the (mechanical) aging behavior of cylindrical cells with silicon-containing electrodes and to experimentally investigate the dependence of aging rate on operating conditions.The Samsung 50S Li-Ion cell, which has a 21700 format with a capacity of 5 Ah, was selected for testing. This cell utilizes a blend of Graphite (Gr) and Silicon Oxide (SiOx) as negative electrode, paired with a nickel-rich Lithium-Nickel-Cobalt-Aluminum-Oxide (NCA) as positive electrode. The cell was initially characterized physically, chemically and electrochemically at full and half-cell level. After that, the cycle stability was evaluated under different operating conditions. For this purpose, a cell was disassembled, electrode material was removed and laboratory cells were constructed. The laboratory cells were used to measure the potential and the change of thickness during (de)lithiation using a dilatometer. The morphology and chemical composition were determined using SEM, EDX and Glow Discharge Optical Emission Spectroscopy (GDOES) measurements.In the subsequent aging studies, terminal discharge voltages and current rates were systematically varied to investigate the influence of silicon utilization. To evaluate the aging behavior, check-up routines were performed every 100 Equivalent Full Cycles (EFC) and at the beginning of the test, which included a discharge and charge pulse at 50 % SoC as well as a pseudo Open Circuit Voltage (pOCV) measurement at 1/20C in the charge and discharge directions. These data were used to determine aging mechanisms such as Loss of Lithium Inventory (LLI) and LAM using Differential Voltage Analysis (DVA) and OCV-fitting. These analyses provide important insights into a better understanding of aging processes taking place inside the cell. Selected cells were disassembled after cycling in a glovebox and aging effects were validated visually and with the help of SEM and GDOES. The characterization of the cell shows a typical tab design with one tab per current collector (1x1) and a capacity share of silicon of 25 % (1.25 Ah) based on DVA. The dilatometer measurements resulted in a change in thickness of the negative electrode of 14.3 % with a very pronounced hysteresis and a significantly lower expansion with an expansion of 3 % and hysteresis of the positive electrode. In the aging study, accelerated aging of the cells was observed above a certain Depth of Discharge (DoD). While the cells with a lower utilization of the available capacity (DoD=55 %, SoC range: 40 % - 95 %) still showed a State of Health (SoH) of 0.82 after 1,500 EFC (subsequently referred to as slow-aged), the cells with full utilization of the capacity (DoD=100) showed sudden death after 300-400 EFC (subsequently referred to as fast-aged). The post-mortem analysis highlighted aging patterns across the jelly roll of the negative electrode for the fast-aged cells, which can be divided into four areas: At the core of the jelly roll there was a clear detachment of active material, the adjacent area showed Li-plating stripes, which are in the same phi-coordinate of the tab. In the area of the tab (center of the jelly roll), imprints of the tab in the jelly roll were clearly visible, which underlines the mechanical influence of the tab. The outer area showed no noticeable abnormalities. With the help of GDOES measurements, it was confirmed that the strips were Li-plating. The slow-aged cells showed neither these characteristics nor Li plating in these areas. Figure 1

This paper presents an optimization model for determining the nominal capacity of an energy storage system is presented, which transfers excess amounts of electrical energy from solar power plants as part of a group of distributed generation power plants, based on the criterion of the minimum cost of supplying electricity to end consumers. The use of the developed optimization model allows to determine the optimal parameters of the energy storage system to achieve an economic balance between the excess amounts of electric energy of solar power plants that are transferred and the amount of restrictions on inverters that are subject to payment. Based on the developed method, based on the forecast level of electric energy consumption and statistical data on the level of electric energy production at wind and solar power plants for the territory of Ukraine, the installed capacity of the wind, solar, reserve power plant and the nominal capacity of the two-hour energy storage system were determined, which will provide the minimum levelized cost of energy of supplying to consumers during the entire period of commercial operation of a group of distributed generation power plants.

This study aims to show methods of determining the installation site and the optimal capacity of a battery energy storage system (BESS) to attain load leveling. The methods are based on the hardware characteristics of 20 kW/100 kWh and 1 MW/4 MWh prototype BESSs, which are already developed and are being developed, respectively. The candidate site of BESS installation is the secondary side of a distribution substation's main transformer (MTR). These tasks are performed by first classifying the load pattern of an MTR and comparing it to the load pattern of a total power system. If the load factor improves, then the location is determined to be a BESS installation site. Subsequently, the optimal BESS capacity for an MTR is determined using the given operation pattern, the charging/discharging characteristics and efficiency. Computational experimentation was performed on an actual distribution system in Korea. After determining the optimal capacity, the authors verified that installing the BESS on the selected MTR improved both daily and nightly load factors.

The electric vehicle contributes to reduce greenhouse gases emissions and get a greater integration of renewable energy. In this context, the implementation of urban buses implies the development of new grid infrastructures in order to carry out the electricity supply required by the charging stations. In order to optimize the size of these infrastructures and to have more power capacity, this contribution proposes the design and the sizing of a fast charging station with a stationary energy storage system (ESS) installed, to supply the energy of the buses that run on one of the lines of Pamplona (Spain). In this contribution, first, the power demanded by the charging point is measured at the fast charging station located at the Public University of Navarre. Second, three energy management strategies are developed with which to use ESS. Finally, the proposed energy management strategies are simulated with the measured data obtained. The results achieved in this contribution show that with a 40 kWh ESS, the power demanded from the grid can be reduced by a whole 70%, that is, from 250 kW to 74 kW. In addition, the power contracted in the electricity rate is reduced too.