Modular converter system for low-cost off-grid energy storage using second life Li-ion batteries

Lithium ion batteries are promising for small off- grid energy storage applications in developing countries because of their high energy density and long life. However, costs are prohibitive. Instead, we consider 'used' Li-ion batteries for this application, finding experimentally that many discarded laptop cells, for example, still have good capacity and cycle life. In order to make safe and optimal use of such cells, we present a modular power management system using a separate power converter for every cell. This novel approach allows individual batteries to be used to their full capacity. The power converters operate in voltage droop control mode to provide easy charge balancing and implement a battery management system to estimate the capacity of each cell, as we demonstrate experimentally.Comment: Presented at IEEE GHTC Oct 10-14, 2014, Silicon Valle

Grid energy storage device (ESD).

Master of Science in Electrical Engineering. University of KwaZulu-Natal, Durban 2016.Abstract available in PDF file

Reaction Mechanisms for Long-Life Rechargeable Zn/MnO 2 Batteries

Rechargeable aqueous Zn-ion batteries (ZIBs) are very promising for large-scale grid energy storage applications owing to their low cost, environmentally benign constituents, excellent safety, and relatively high energy density. Their usage, however, is largely hampered by the fast capacity fade. The complexity of the reactions has resulted in long-standing ambiguities of the chemical pathways of Zn/MnO 2 system. In this study, we find that both H + /Zn 2+ intercalation and conversion reactions occur at different voltages and that the rapid capacity fading can clearly be ascribed to the rate-limiting and irreversible conversion reactions at a lower voltage. By limiting the irreversible conversion reactions at â1.26 V, we successfully demonstrate ultrahigh power and long life that are superior to most of the reported ZIBs or even some lithium-ion batteries

The Allocation of Micro-grid Energy Storage System Considering Controlling Parameter

This research proposes a novel method of how to integrate controlling parameters, voltage and frequency, into to the energy storage system (ESS) allocation in a microgrid with renewable sources. The goal is to use the sensitivity analysis to find the most effective bus where the ESS should be in-stored to minimize the fluctuations both in terms of voltage and frequency. Indicators, such as SAIDI and SAIFI, are used to measure system reliability after the optimum size and location of ESS are determined

A Novel Solid Oxide Redox Flow Battery for Grid Energy Storage

In this work we report proof-of-concept of a novel redox flow battery consisting of a solid oxide electrochemical cell (SOEC) integrated with a redox-cycle unit. The charge/discharge characteristics were explicitly observed by operating between fuel cell and electrolysis modes of the SOEC along with “in-battery” generation and storage of H2 realized by an in situ closed-loop reversible steam-metal reaction in the redox-cycle unit. With Fe/FeO as the redox materials, the new storage battery can produce an energy capacity of 348 Wh/kg-Fe and round-trip efficiency of 91.5% over twenty stable charge/discharge cycles. This excellent performance combined with robustness, environmental friendliness and sustainability promise the new battery to be a transformational energy storage device for grid application

GRID ENERGY STORAGE IN POWER SUPPLY SYSTEMS

The quality of power supply is one of the key components of the reliability of the power system, and depends on many parameters, which are maintained within acceptable limits using various devices. These devices include grid energy storage devices, which are able to equalize irregularities in the supply of electricity, act as an uninterruptible power supply, and also as an energy accumulator in case of emergencies.Качество электроснабжения является одним из ключевых компонентов надежности энергосистемы и зависит от множества параметров, поддержание которых в допустимых границах осуществляется с использованием различных устройств. К таким устройствам можно отнести сетевые накопители электроэнергии, которые способны выравнивать неравномерности подачи электроэнергии, выступать в роли бесперебойного источника питания, а также в роли аккумулятора энергии на случай аварийных ситуаций

Power Balancing Control for Grid Energy Storage System in Photovoltaic Applications — Real Time Digital Simulation Implementation

Abstract: A grid energy storage system for photo voltaic (PV) applications contains three different power sources i.e., PV array, battery storage system and the grid. It is advisable to isolate these three different sources to ensure the equipment safety. The configuration proposed in this paper provides complete isolation between the three sources. A Power Balancing Control (PBC) method for this configuration is proposed to operate the system in three different modes of operation. Control of a dual active bridge (DAB)-based battery charger which provides a galvanic isolation between batteries and other sources is explained briefly. Various modes of operation of a grid energy storage system are also presented in this paper. Hardware-In-the-Loop (HIL) simulation is carried out to check the performance of the system and the PBC algorithm. A power circuit (comprised of the inverter, dual active bridge based battery charger, grid, PV cell, batteries, contactors, and switches) is simulated and the controller hardware and user interface panel are connected as HIL with the simulated power circuit through Real Time Digital Simulator (RTDS). HIL simulation results are presented to explain the control operation, steady-state performance in different modes of operation and the dynamic response of the system

Analysis of reversible solid oxide cell technology for grid-energy storage and synthetic natural gas production with CO2

Reducing electricity related carbon emissions requires movement toward renewable energy technologies such as wind and solar, which is challenging due to their inherent intermittency. Electrical energy storage (EES) is expected to play a critical role in enabling greater penetration of renewables, but current technologies suffer from capacity limitations and high cost. Reversible solid oxide cells (ReSOCs) are an electrochemical energy conversion technology that can provide high efficiency and cost effective storage at both distributed and grid scales. This presentation discusses the fundamentals of ReSOC operation and compares the performance, cost, and net carbon emissions of ReSOCs employed in traditional EES systems with that of ReSOCs integrated with natural gas pipeline infrastructure and captured carbon dioxide. ReSOCs are ceramic electrochemical devices that can be used to either produce power from fuel when electricity is needed (fuel cell mode), or produce fuel from electricity when excess energy is available (electrolysis mode). By leveraging C-O-H reaction chemistry and operating at intermediate temperatures (600oC), these cells can be mildly exothermic in both operating modes, eliminating the need for external heat input or high over-potential operation during electrolysis. Storage of fuel (H2, CO, CH4) and exhaust (H2O, CO2) in tanks at the distributed scale and large caverns at the grid scale allows ReSOC systems to provide stand-alone EES services. While previous work has quantified performance and cost of ReSOC energy storage systems at both distributed and grid scales, this work focuses on ReSOC systems that couple natural gas pipelines as a fuel source and captured carbon dioxide as a co-electrolysis feedstock. ReSOCs are well suited for both carbon capture and synthetic fuel production. In fuel cell mode, ReSOCs consume fuel and oxygen and produce water, CO2, and excess air. Because fuel oxidation occurs via oxygen transport across the ReSOC electrolyte, separation of carbon dioxide from the exhaust stream can be achieved without concern for nitrogen. In electrolysis mode, internal methanation can be promoted to both provide heat for co-electrolysis of water and CO2 and to produce methane. Coupling ReSOC systems with natural gas pipelines and piped or tanked CO2 allows for both electricity generation with carbon-rich exhaust and for scalable carbon utilization given a source of CO2 and excess renewable electricity. However, it is unclear how such a system should be designed and operated in order to provide cost competitive electricity and synthetic natural gas, while maintaining low net carbon emissions. This work explores system design concepts, performance, cost, and net carbon emissions of a 50 MWe ReSOC system integrated with natural gas pipelines and stored CO2, and compares to ReSOCs used as flow-battery energy storage systems. Preliminary modeling results predict a fuel cell mode LHV efficiency of 56%, an electrolysis mode LHV efficiency of 62.6%, and system cost of 700$/kW. Additionally, it is observed that the stack and air-side components (heat exchangers, compressors, expanders) can be compatible in both modes of operation, reducing cost. The compatibility of condensers, heat exchangers, and compressors used for fuel and exhaust processing, however, depends strongly on the relative pressures of natural gas and carbon dioxide sources and sinks. Additional ways of reducing cost and net carbon emissions are also investigated and presented