Large Energy Storage Systems Research Articles

Boron-Doped Ni-Rich Layered Cathodes with Enhanced Cycling Stability

Lithium-ion batteries (LIBs) are emerging as one of the most promising power sources for portable devices, as well as electric vehicles (EVs) and large energy storage systems (ESS), owing to their high energy density and excellent cycle life. However, the application of LIBs in EVs to reduce CO2 emissions in internal combustion engine vehicles (ICEVs) involves some critical technical challenges, such as the driving range, safety, and cost concerns due to the properties of LIBs.1-3 For this reason, research interests and industrial efforts have focused on developing low-cost, high-energy, and safe cathode materials, which are the main component determining LIB performance and cost. Transition metal layered oxides belonging to the LiNixCoyAlzO2 (NCA) or LiNixCoyMnzO2 (NCM) family, which can increase their intrinsic capacity (above 200 mAh g-1) by increasing Ni content, are emerging as promising new cathode materials.4 However, the intrinsic drawbacks of Ni-rich cathodes, such as low Li intercalation stability over extended cycles, should be improved. In this study, we present the first successful boron doping strategy for a Ni-rich cathode material with very high Ni content. For the boron doping, we used a simple method where only a small amount of B2O3 was added during the calcination process. In addition, the structural and morphological stability of the boron-doped Ni-rich NCM cathode material was investigated before and after testing to evaluate the improved electrochemical performance; specifically, the significantly enhanced cycle performance. Thus, we conclude that the boron doping strategy is an effective and simple way to mitigate the poor stability problem of Ni-rich cathode materials for high-energy and stable LIBs. References D.-W. Jun, C. S. Yoon, U.-H. Kim, Y.-K. Sun, Chem. Mater. 2017, 29, 5048.J. H. Lee, C. S. Yoon, J.-Y. Hwang, S.-J. Kim, F. Maglia, P. Lamp, S.-T. Myung, Y.-K. Sun, Energy Environ. Sci. 2016, 9, 2152.S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett. 2017, 2, 196.4. K.-S. Lee, S.-T. Myung, K. Amine, H. Yashiro, Y.-K. Sun, J. Electrochem. Soc. 2007, 154, A971.

大規模蓄電池システムの高効率有効電力指令配分手法に関する考察

大規模蓄電池システムの高効率有効電力指令配分手法に関する考察

Environmental impacts of electricity generation for Graciosa Island, Azores

The Graciosa project combines a large scale battery energy storage system with renewable electricity generation from wind power and photovoltaics in a hybrid power plant to reduce the environmental impacts caused by the previous electricity generation by 100 % Diesel combustion on Graciosa Island, Azores. The goal of this contribution is to assess and compare the selected environmental impacts related to the electricity generation of the previous and the new system by using Life Cycle Assessment. To accomplish this goal, all energy and material flows that occur during production, use and recycling/disposal of the electricity generating systems are quantified and evaluated. The results of the Life Cycle Assessment show a reduction of environmental impacts of approx. 43% due to the transformation to the hybrid electricity supply system with high shares of renewable energies (65%). In the new electricity supply system, the majority of environmental impacts (>60%) is still caused by the remaining Diesel based electricity generation. Environmental impacts, which are associated with the construction of the large scale battery energy storage system, account for only 6% of total impacts. Wind power and photovoltaics account for 18% and 14%, respectively.

Zero‐voltage switching modular equalization system for series super‐capacitor string

This paper presents a zero‐voltage‐switching modular equalization for series super‐capacitor string in a large energy storage system. The zero‐voltage working scheme is analyzed based on Power Simulation (PSIM) to verify its validity. An equalization system test for 16‐super‐capacitor cells is conducted under voltage‐imbalanced conditions. The power flow model, switching patterns, and zero‐voltage gap are discussed. The simulation and experimental results are presented, indicating that the equalization not only inherits the advantages of traditional inductor‐based super‐capacitor equalization system, but also brings some merits, such as flexible, low switching loss, and highly modularized.

Overcoming Solar PV Intermittency using Demand Response Management in Buildings

Singapore’s National Climate Change Policy is aimed to make energy usage in Singapore more efficient, reduce pollution and expand the nation’s green spaces. Part of the plan is to promote the integration of solar photovoltaics (PVs) on rooftops of high-rise HDB residential and commercial buildings. This initiative contributed to the significant growth in the integration of solar PV systems in the last few years. However, large-scale integration of solar PVs will put at risk the reliability and stability of Singapore’s power system due to its intermittent nature. The intermittency problem of solar PV, typically in the range of minutes, will become very significant in Singapore as the installations of PV systems continue to increase. Conventionally, large energy storage systems are deployed as an energy buffer to compensate for the deficit or surplus of power supplied by solar PV systems. However, the high capital and maintenance costs as well as large space requirement for energy storage systems makes this an unfavorable option for building owners. This paper proposes a solution that utilizes the centrifugal fans in building air conditioning and mechanical ventilation (ACMV) system to dynamically compensate for the deficit or surplus of power supplied by solar PVs. For example, the developed solution will reduce the load demand of fans in the ACMV system equal to the drop of solar generation by controlling the speed of the fan. This will ensure that the amount of power supplied by the grid to the building will remain the same (as before the drop of solar generation) and thus no impact on the grid stability. However, since ACMV system is directly linked to building occupant comfort/health, the proposed solution will also include battery management and priority-based load shedding programs to provide support when room temperature (air conditioning) or CO level (ventilation) is above regulatory limit.

Investigation of using molten salt as heat transfer fluid for dry cooled solar parabolic trough power plants under desert conditions

This research aims mainly at further investigate technical options to reduce the cost of electric power production from concentrating solar power plants in hot arid regions. The work also aims to minimize water consumption due to its scarcity in such regions by means of investigating the utilization of dry cooling option. However, dry cooling system increases the parasitic power consumption of the power plant and this is bound to reduce the overall system efficiency. In arid regions, this loss in efficiency is compensated by the abundance of solar radiation that results in a better solar field efficiency. Furthermore, this study investigates the effect of using alternative heat transfer fluid in the solar circuit instead of synthetic oil. For this purpose, an optimization of a solar parabolic trough power plant coupled with dry cooling system has been performed using the simulation software “SAM”. The optimization is carried out by varying the solar field size, the thermal energy storage system, the size of the power block (steam turbine) and the type of the heat transfer fluid. This was done in order to find out the best combination that gives lowest power production cost. The power plant was simulated in two steps with different combinations; while “Therminol VP I” was used in the first step, as heat transfer fluid, in the second step, “Therminol VPI” was replaced by “Molten Salt”. The obtained results prove that plants with large solar fields (solar multiple of 2) and large thermal energy storage systems (7.5 full load hours) perform better and can generate power at lower costs compared with smaller plants. The investigation of alternative heat transfer fluid shows that molten salt is more cost effective than synthetic oil in parabolic trough power plants. The obtained Levelized Cost Of Electricity of the best power plant optimized configuration is 17.24 c€/kWhe and 13.8 c€/kWhe, for plants with “Therminol VP I” and “Molten Salt” as heat transfer fluid, respectively. The optimization results with “Molten Salt” as heat transfer fluid show excellent results regarding the dry cooled solar power plants. This show good technical and economic potentials in future designs.

Reliability Evaluation of Large Scale Battery Energy Storage Systems

This paper analyzes the reliability of large scale battery storage systems consisting of multiple battery modules. The whole system reliability assessment is based on the reliability evaluation of system components including individual battery modules and power electronic converters. In order to evaluate the reliability of a battery module, a reliability model based on the state of health of individual battery cells is introduced. The state of health of a battery cell is calculated based on the capacity fade of the cell using a weighted Ampere-hour throughput method. A universal generating function-based method is then introduced to evaluate the reliability of the battery module. The reliability model of dc/ac power electronic converters is also presented in this paper. The reliability analysis is conducted for battery storage systems with different system configurations and management strategies, and the influence of system configuration on the reliability of battery system is studied. Comparative studies are conducted for a classic battery energy storage system (BESS) and a reconfigurable BESS (RBESS) to demonstrate the advantages of having a reconfigurable system topology. The comparison results show that the proposed RBESS has higher system reliability and more power outputs than the classic BESS.

Efficient optimization of a longitudinal finned heat pipe structure for a latent thermal energy storage system

Phase Change Materials (PCMs) are gaining importance in energy storage applications. However, many PCMs are poor thermal conductors and thus can benefit from the optimal use of appropriate fins. This work introduces a PCM-fin structure optimization framework. Typically, the non-linear solidification process increases the complexity associated with solving the mathematical equations for the PCM-fin structure optimization problem, making it computationally expensive. In this paper a modeling approach called Layered Thermal Resistance (LTR) model is extended and developed in 2D cylindrical geometry in order to enable efficient PCM-fin structure optimization. The finned LTR model represents the nonlinear transient solidification process by analytic equations. This significantly reduces the computational cost associated with optimization. A finned heat pipe structure modeled by the finned LTR approach is optimized based on minimizing cost while meeting operational requirements. The optimal results imply that thinner fins result in lower system cost and that there is a thickness limit for the fins to be economically welded on a heat pipe. The finned LTR model also gives the optimal cost of material usage for a large scale latent thermal energy storage system in terms of dollars per kilowatt and it was found that the system cost is slightly lower by using carbon-steel as the construction material for the heat pipes and fins than by using Al 6061.

Renewable energies for Graciosa Island, Azores – Life Cycle Assessment of electricity generation

The Graciosa project combines a large scale battery energy storage system with renewable electricity generation from wind power and photovoltaics in a hybrid power plant to reduce the environmental impacts caused by the previous electricity generation by 100 % diesel combustion on Graciosa Island, Azores. The results of a Life Cycle Assessment show a reduction of environmental impacts of approx. 43 % due to the transformation to the hybrid electricity supply system with high shares of renewable energies (65 %). In the new electricity supply system, the majority of environmental impacts (> 60 %) is still caused by the remaining diesel based electricity generation. Environmental impacts, which are associated with the construction of the large scale battery energy storage system, account for only 6 % of total impacts. Wind power and photovoltaics account for 18 % and 14 %, respectively.

Benefits of battery energy storage system for system, market, and distribution network – case Helsinki

This study presents the first performance results of a large battery energy storage system (BESS) that is connected to a medium-voltage distribution network and used simultaneously by multiple stakeholders. This study presents the background of the purpose of a BESS as part of the Nordic power system and markets, and the functionalities it is able to perform. The first test cases ran in the fall 2016 included simultaneous controls of frequency, reactive power, and voltage according to the requests from transmission and distribution system operators. The results showed that the first functions of the BESS performed were successful. Valuable experience has also been reached when observing, e.g. the energy capacity limits of the batteries.

The development of techno-economic models for large-scale energy storage systems

The development of a cost structure for energy storage systems (ESS) has received limited attention. In this study, we developed data-intensive techno-economic models to assess the economic feasibility of ESS. The ESS here includes pump hydro storage (PHS) and compressed air energy storage (CAES). The costs were developed using data-intensive bottom-up models. Scale factors were developed for each component of the storage systems. The life cycle costs of energy storage were estimated for capacity ranges of 98–491 MW, 81–404 MW, and 60–298 MW for PHS, conventional CAES (C-CAES), and adiabatic CAES (A-CAES), respectively, to ensure a market-driven price can be achieved. For CAES systems, costs were developed for storage in salt caverns hard rock caverns, and porous formations. The results show that the annual life cycle storage cost is $220–400 for PHS, $215–265 for C-CAES, and $375–480 per kW-year for A-CAES. The levelised cost of electricity is $69–121 for PHS, $58–70 for C-CAES, and $96–121 per MWh for A-CAES. C-CAES is economically attractive at all capacities, PHS is economically attractive at higher capacities, and A-CAES is not attractive at all. The developed information is helpful in making investment decision related to large energy storage systems.

Potassium-Based Dual Ion Battery with Dual-Graphite Electrode.

A potassium ion battery has potential applications for large scale electric energy storage systems due to the abundance and low cost of potassium resources. Dual graphite batteries, with graphite as both anode and cathode, eliminate the use of transition metal compounds and greatly lower the overall cost. Herein, combining the merits of the potassium ion battery and dual graphite battery, a potassium-based dual ion battery with dual-graphite electrode is developed. It delivers a reversible capacity of 62 mA h g-1 and medium discharge voltage of ≈3.96 V. The intercalation/deintercalation mechanism of K+ and PF6- into/from graphite is proposed and discussed in detail, with various characterizations to support.

Selection of container materials for modern planar sodium sulfur (NaS) energy storage cells towards higher thermo-mechanical stability

Sodium sulfur (NaS) cell is recognized as a promising candidate for advanced grid-scale large energy storage systems (ESS). In this work, we study the impacts of planar NaS cell container materials on the accumulation of residual stresses in the cell joints and solid electrolyte during the cell assembly and operation processes. Concentration of such thermo-mechanical stress in these vulnerable areas in the modern NaS cells can lead to catastrophic cell failures, which can present a huge challenge for developing large planar NaS cells towards commercial deployment. Here, we employ the finite-element analysis (FEA) computational technique to quantitatively assess the thermo-mechanical stress accumulation using prototype planar NaS cells. Relevant experimental procedures with corresponding thermal cycling conditions for the cell assembly, operation, and maintenance processes are incorporated into the FEA model. The influences of Al alloy (Al3003), stainless steels (STS304 and STS340), and iron-nickel-cobalt superalloy (KOVAR) on the residual stress accumulation are tested and thoroughly discussed. The computation results show that high stress concentration can be developed in the cell joint area. Through the comprehensive computational analysis, it is suggested that applying smaller CTE (less than ∼12×10−6K−1) alloys is necessary to secure the thermo-mechanical stability of NaS cells that can be implemented in a large scale ESS.

Frequency Control in Isolated/Islanded Microgrids Through Voltage Regulation

This paper presents a frequency control mechanism for an isolated/islanded microgrid through voltage regulation. The proposed scheme makes use of the load voltage sensitivity to operating voltages and can be easily adopted for various types of isolated microgrids. The proposed controller offers various advantages, such as allowing the integration of significant levels of intermittent renewable resources in isolated/islanded microgrids without the need for large energy storage systems, providing fast and smooth frequency regulation with no steady-state error, regardless of the generator control mechanism. The controller requires no extra communication infrastructure, and only local voltage and frequency is used as feedback. The performance of the controller is evaluated and validated through various simulation studies in the PSCAD/EMTDC software environment based on a realistic microgrid test system, using small-perturbation stability analysis to demonstrate the positive effect of the proposed controller in system damping.

(Invited) Safety of Aged Lithium-Ion Cells

Lithium-ion batteries have been introduced into large stationary energy storage systems. In recent years, used automotive batteries are being repurposed for use in stationary energy storage systems. It is of significant importance to understand the hazards associated with used cells and batteries and also determine the changes that occur to the cell components such as cathode, anode, separator and electrolyte. Under this study, cells were cycled to various levels of capacity loss and subjected to safety tests such as external short and overcharge. The cell cycling protocol included cycling the cells to the full end of charge and end of discharge voltages as well as reduced end of charge and end of discharge voltages. Cells were removed at 10%, 15% and 20% capacity loss and subjected to external short and overcharge tests. Cells were also cycled under hybrid electric vehicle usage profiles and at different temperatures to characterize the changes.

Redox-Active Hybrid Materials for Pseudocapacitive Energy Storage

We aim to show the exciting development of sustainable pseudocapacitive hybrid materials for small and large scale electrochemical energy storage systems.1–5 In our approach, we combine redox-active organic molecules with suitable carbon nanostructures and/or highly conductive metal carbides (MXenes) to improve the conductivity of organic materials. These combinations result in high energy and power density pseudocapacitive electrodes with improved cyclability. Using experimental and simulation techniques, we will discuss the interfacial organic-inorganic interactions, charge storage mechanisms, and preferred molecular orientations of organic molecules at the interface. We will also highlight the remaining challenges and future opportunities for improvement in nanostructured hybrid materials for the electrochemical energy storage. 1. M. Boota et al., Adv. Mater., 28, 1517–22 (2015) 2. M. Boota, K. B. Hatzell, E. C. Kumbur, and Y. Gogotsi, ChemSusChem, 8, 835–843 (2015). 3. M. Boota, C. Chen, M. Bécuwe, L. Miao, and Y. Gogotsi, Energy Environ. Sci., 9, 2586–2594 (2016). 4. M. Boota et al., ChemSusChem, 8, 3576–3581 (2015) 5. K. B. Hatzell, M. Boota, and Y. Gogotsi, Chem. Soc. Rev., 44, 8664–8687 (2015)

Evaluating and comparing profitability of bulk storage systems in unit commitment and optimal power flow operation frameworks

An energy storage system (ESS) is a promising tool for improving the power system's technical and economical functionalities. This device possesses diverse applications in terms of system operation and planning. One of the main applications of the ESS in the power system operation, specially a large scale unit, is defined as load leveling. To this end, in the literature, various ESS models are integrated into two main power system operation frameworks, i.e., optimal power flow (OPF) and unit commitment (UC). But the question is that in which framework the obtained benefit from the load leveling by ESS is maximum and why. In other words, should ESS units schedule before generating unit commitment (UC) or after OPF and how. In this context, this paper performs three works. First, it proposes OPF and UC frameworks integrated with large scale ESS units. Second, the proposed models are implemented with identical parameters. Third, the obtained results are considered with respect to various outcomes, especially operation cost. This study is implemented on an IEEE 24 bus RTS system. The simulation results are analyzed and compared with respect to various parameters, and relevant conclusions are drawn based on the results.

Characteristics of large thermal energy storage systems in Poland

In District Heating Systems (DHS) there are significant fluctuations in demand for heat by consumers during both the heating and the summer seasons. These variations are considered primarily in the 24-hour time horizon. These problems are aggravated further if the DHS is supplied by a CHP plant, because fluctuations in heat demand adversely affect to a significant degree the stable production of electricity at high overall efficiency. Therefore, introducing Thermal Energy Storage (TES) would be highly recommended on these grounds alone. The characteristics of Large (i.e. over 10 000 m 3 ) TES in operation in Poland are presented. Information is given regarding new projects (currently in design or construction) that apply TES technology in DHS in Poland. The paper looks at the methodology used in Poland to select the TES system for a particular DHS, i.e., procedure for calculating capacity of the TES tank and the system to prevent water stored in the tank from absorbing oxygen from atmospheric air. Implementation of TES in DHS is treated as a recommended technology in the Polish District Heating sector. This technology offers great opportunities to improve the operating conditions of DHS, cutting energy production costs and emissions of pollutants to the atmosphere.

大型蓄電池システムによる周波数制御方式の開発

大型蓄電池システムによる周波数制御方式の開発

Demand response strategy management with active and reactive power incentive in the smart grid: a two-level optimization approach

High penetration of distributed generators (DGs) using renewable energy sources (RESs) is raising some important issues in the operation of modern po­wer system. The output power of RESs fluctuates very steeply, and that include uncertainty with weather conditions. This situation causes voltage deviation and reverse power flow. Several methods have been proposed for solving these problems. Fundamentally, these methods involve reactive power control for voltage deviation and/or the installation of large battery energy storage system (BESS) at the interconnection point for reverse power flow. In order to reduce the installation cost of static var compensator (SVC), Distribution Company (DisCo) gives reactive power incentive to the cooperating customers. On the other hand, photovoltaic (PV) generator, energy storage and electric vehicle (EV) are introduced in customer side with the aim of achieving zero net energy homes (ZEHs). This paper proposes not only reactive power control but also active power flow control using house BESS and EV. Moreover, incentive method is proposed to promote participation of customers in the control operation. Demand response (DR) system is verified with several DR menu. To create profit for both side of DisCo and customer, two level optimization approach is executed in this research. Mathematical modeling of price elasticity and detailed simulations are executed by case study. The effectiveness of the proposed incentive menu is demonstrated by using heuristic optimization method.