An Overview of Battery Storage Systems

With increasing decarbonization measures and incentives for sustainable sources, battery storage systems represent emerging (and solid) alternatives in reducing dependence on diesel generator sets and controlling the seasonality of renewable sources. This is because Battery Energy Storage Systems (SAEB) or Battery Energy Storage System (BESS) allow the collection of electrical energy, from renewable or non-renewable sources, and the optimized distribution of stored energy, based on the objectives of the installation project. [1]

One of the main characteristics of the technology is related to the versatility and diversity of possible applications. Thanks to the development of new electrochemical cells, developments in the manufacturing process, and advances in power converter control strategies, today, it is possible that storage systems can be inserted inside and outside the energy distribution and transmission system, at various energy storage and supply capacity scales (from kWh to MWh). [2]

The applications of a storage system depend on certain characteristics, such as the implementation architecture, the storage capacity, the associated power converters, the available recharge periods and sources, and the predefined energy dispatch dynamics. Once established in design, a single storage system can perform different functions. Each level of application (residential, commercial, industrial, or utility) has its own characteristics and different uses of battery storage systems. Some of the most common applications of storage systems are: Peak Shaving, Load Shifting, backup, power booster, and microgrid. [3]

LIST OF APPLICATIONS:

• Load displacement.
• Solar power smoothing.
• Peak shaving.
• Backup.
• Microgrid.
• Charging stations.
• Black start.
• Power quality.
• Ancillary services.

• Peak Shaving: Overdemand fines are one of the biggest villains of Group A consumer units. In storage systems with real-time monitoring of the conventional grid, there is the possibility of parameterizing and limiting the power delivered by the utility. When close to the established limits, the battery bank assumes a portion of the load necessary to maintain network demand within the contracting limits.
• Load shifting: Many installations have a load utilization profile that does not allow photovoltaic generation systems to perform well (low self-consumption) and/or that, even with countermeasures, still present significant load demands at peak times. Load shifting consists of charging the battery bank with excess energy from photovoltaic systems (or other renewable sources) or with the utility itself, provided that, outside of peak hours; and discharging the storage system, at times of low availability, to service the loads partially or completely.
• Backup: The design of storage systems and the choice of storage cells, in general, consider long periods of autonomy (from 3 hours to 12 hours). In the event of faults in the distribution system or scheduled maintenance, the system is able to maintain the operation of critical loads, as long as there is sufficient stored energy (about 20% to 30% of the total capacity of the battery bank), without the loads identifying the transition between the sources.
• Power booster: Often, expansions of production lines and the acquisition of machinery represent such significant changes in the load profile that changes are necessary in the input pattern of the consumer unit. The burden of the changes is the responsibility of the project, takes time and requires a series of steps before the energy utility. With an operation similar to the displacement of load and the Peak Shaving, power reinforcement focuses on servicing loads that exceed the capacity of the consumer unit. Meeting the portion of demand that the current network infrastructure does not support, through the battery bank, allows for the delay of reinforcement investments and facilitates changes in the plant of interest.

Most of the applications only occur, as a result of the structure of the battery energy storage system. Each part of the system has one or more functions that, together, make applications possible and guarantee the reliability of the system. [4]

The main components of a storage system are: Storage modules, Battery Management System, Power Conversion System, Energy Management System, Protection and Encapsulation Systems.

• Storage modules: Storage modules are comprised of battery cell arrays and represent the system's effective storage elements. The modules are connected in series and/or in parallel, generally arranged in racks, until the desired storage capacity is obtained.

• Battery Management System (BMS): The battery management system acts to maintain the useful life of electrochemical cells, by monitoring key parameters, such as the temperature at the terminals, the voltage of the cells, and the current in the Strings, and ensures that the system operates under appropriate conditions while charging or discharging the batteries. The current state of charge (SoC), or available energy stored in batteries, and the percentage of useful life of the modules (SoH) are also estimated.

• Power Conversion System (PCS): The power conversion system interfaces the storage system with the loads and with the other energy sources available in the plant. It determines the specifications of the power supplied and the network requirements of the application. Energy conditioning takes place via different power converters that, depending on their characteristics, allow the bi-directional or unidirectional flow of energy. In cases that require galvanic isolation, transformers are also part of the power conversion system.

• Energy Management System (EMS): The energy management system controls the power flow, determining the moments of charging and discharging the battery bank, with strategic decision-making based on performance or profitability optimization functions and on the parameters, in real time, of the storage system and the energy market.

• Protection systems: The protection systems operate under abnormal system conditions and ensure that there is no damage to equipment and/or people during maintenance or possible operating failures. Within a storage system, electrical surge protection systems, decoupling systems, fire detection and suppression systems, ventilation systems, and temperature control systems are present. In some cases, camera monitoring systems are also applied.

• Encapsulation: Most storage systems are allocated in containers that allow the system to be assembled, commissioned, and shipped safely to installation sites, in addition to protecting the system against weather and other harmful agents.

Currently, storage systems are being used to strengthen autonomous electrical energy distribution systems, both direct current and alternating current, adding stability and quality to energy dispatch for long periods, and thus increasing the useful life of machines and equipment. With the increasing advances in the production processes of emerging technologies and converters with increasingly complete control strategies, the expectation is that, in the coming years, storage systems will be active with a significant impact on the national energy system, as is already the case elsewhere in the world.

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REFERENCES

[1] S. Bouckaert, A. F. Pales, C. McGlade, U. Remme, and B. Wanner,”Net Zero by 2050: A Roadmap for the Global Energy Sector”, tech. rep., International Energy Agency, 2021.

[2] T. L. Fantham and D. T. Gladwin,”Impact of cell balance on grid scale battery energy storage systems”, Energy Reports, vol. 6, pp. 209—216, 2020. 4th Annual CDT Conference in Energy Storage Its Applications.

[3] M. Chamana, I. Mazhari, B. Parkhideh, and B. H. Chowdhury,”Multimode operation of different pv/bess architectures in a microgrid: Grid-tied and island mode,” in 2014 IEEE PES TD Conference and Exposition, pp. 1—5, 2014.

[4] P. Unahalekhaka and P. Sripakarach,”Reduction of Reverse Power Flow Using the Appropriate Size and Installation Position of a BESS for a PV Power Plant,” in IEEE Access, vol. 8, pp. 102897-102906, 2020.