Tech Insights

Examining the Role of ESSIs and Databases in Battery Energy Storage Systems

May 12, 2023 by Rakesh Kumar

Energy storage system integrators develop and sell battery-powered energy storage systems. They are key to the growth of energy storage systems in terms of designing better products and finding new ways to use them. 

Most of the time, energy storage system integrators (ESSI) design and sell energy storage systems. ESSIs either buy the battery packs, the power conditioning system, the auxiliary system, and the software that controls the system or make them themselves. Then, these parts are put back together inside the containers. 


Energy Storage Systems Integrators

ESSIs design battery energy storage system (BESS) solutions ranging from hundreds of kW to a few MW in terms of power and energy ratings and are a key part of the growth of energy storage systems to make a better product and look for new ways to use it. 


Li-ion-based battery energy storage system

Li-ion-based battery energy storage system rated up to 3.1 MW/MWh. Image used courtesy of IEEE Open Journal of the Industrial Electronics Society


Energy Storage Market Players

Energy industry research and consulting firm Navigant Research says that Fluence, Nidec ASI, Tesla, RES, Powin Energy, Greensmith, LG CNS, NEC Energy Solutions, NextEra Energy Resources, and Doosan GridTech are the main players in the utility-scale ESSI market. Some other companies that put together energy storage systems are ABB, Alfen, General Electric, and Schneider Electric. 

Some of the biggest companies on the market today that make battery cells are A123Systems, CATL, Electrovaya, Fiamm, Johnson Control, LG, Panasonic, Saft, Samsung, and Toshiba for lithium-ion based technologies; CellCube, Primus Power, Rongke Power, UniEnery Technologies, and Vionx Energy for flow batteries; and NGK Insulators for sodium sulfur batteries.


Battery Energy Storage Database

Regarding BESS installations and pilot projects, National Technology & Engineering Sciences of Sandia, LLC (NTESS), which runs Sandia National Laboratories for the U.S. Department of Energy/National Nuclear Security Administration, keeps a database on energy storage installations. This database has information about energy storage installations worldwide, including power and energy rating, location, applications, owner, storage technology, and status. 

Out of 466 projects, only active installations using electrochemical technology and a power rating less than or equal to 5 MW were included. 

The two pie charts in Figure 1 show that the chosen projects are analyzed to find out what services the storage and electrochemical technologies provide. 

In Figure 1(a), what stands out is that there is no one use case dominating BESS applications.  The most common use of battery energy storage systems is electric bill management, energy time shifting, frequency regulation, microgrid capability, shifting renewable generation, and securing renewable capacity. 

Figure 1(b) shows that lithium-ion technologies are the most common solution. Figure 2 shows that BESS are often used as multi-functional systems and are usually involved in both commercial and technical services.


Storage applications (a) and technologies (b)

Figure 1. Storage applications (a) and technologies (b). Image used courtesy of IEEE Open Journal of the Industrial Electronics Society


Percentage of BESS installations performing technical and commercial services

Figure 2. Percentage of BESS installations performing technical and commercial services (a) and the number of services that each installation performs (b) Image used courtesy of IEEE Open Journal of the Industrial Electronics Society


Frequency Containment Reserves

Along with general information about battery-based storage projects, this article examines a project where BESS was tested for frequency control. In this situation, TenneT B.V., a Dutch transmission system operator (TSO), ran a pilot project to see how frequency containment reserves (FCR) could be provided by combining energy from different sources, such as energy storage. Several aggregated pools that provide FCR to the Dutch market were tested as part of the pilot. 

Lead-acid and lithium-ion batteries were tested in the aggregator pools. The minimum bid size went from 1 MW to 100 kW, and participants had to send in bids every week for the following week. The management system of a battery affects how well it works. The FCR provision was not affected. 

The pilot shows that all assets were technically able to provide FCR, and the main problems were measuring frequency and setting up a way for the TSO and aggregators to talk to each other. TSO's minimum power step requirements might be hard for battery energy storage systems to meet. Shortening the bidding period and simpler measurements would make it easier for aggregators to participate in the FCR market.


Enhancing Battery Energy Storage Systems 

Energy storage systems could improve the grid in numerous ways if the battery storage system’s technical and economic performance were enhanced. 

Three-level and modular converters could be more efficient and reliable, have more power density, and cost less than two-level converters, which are most commonly used in commercial products. Even though three-level and multi-level topologies have been studied a lot in other applications, how using a better converter topology affects the technical performance of a storage system and how much it costs to own haven’t been demonstrated. 

The main factors preventing the use of battery energy storage systems are high initial costs and questions surrounding where this money will come from. The combination of various services can enhance BESS's profitability. Most running installations provide more than one service and often aim for both technical and market-related goals, such as voltage regulation, network upgrade deferral, microgrid capabilities, and black starts, as well as energy arbitrage, frequency regulation, and demand response, as shown in Figure 1(a). 


More Research Needed

More research must be done to determine how best to provide multiple services from the same storage unit. A too-simple battery model can cause excess capacity loss due to poor scheduling. More research into short-term scheduling and network planning is critical for models that accurately depict battery performance and lifespan while not adding more runtime. 


This post is based on an IEEE Open Journal of the Industrial Electronics Society research article.