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Large Battery Energy Storage Systems

John Benson's picture
Senior Consultant, Microgrid Labs

PROFESSIONAL EXPERIENCE: Microgrid Labs, Inc. Advisor: 2014 to Present Developed product plans, conceptual and preliminary designs for projects, performed industry surveys and developed...

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  • Jun 25, 2018


In October of last year I posted "Energy Storage Survey", and this is linked below. As its name suggests this earlier paper was a broad look at all forms of energy storage, which then focused down to batteries, and finally the dominant battery technology, lithium ion chemistries.

This paper takes that one step further, by focusing on large to very large battery energy storage systems (BESS) that are starting to transform our electric utility operations world-wide, and also creating increased energy economy and resilience among facilities.

2.System Components and Solutions

In the next section we will review major the providers of these BESS and some major projects. If I were writing about BESS providers a year or two ago, I would limit the discussion of BESS providers to battery manufacturers, but now two really major providers are emerging and neither is a battery manufacturer. This brings home, that a project consists of much more than batteries.


The components of a major project could consists of:

  • BESS experience (and thus qualification to provide a proposal and credibility)
  • Marketing of, and sales to the party (or parties) requiring the project
  • Negotiating a primary contract with the client and subcontracting project content to supporting subcontractors and suppliers
  • Obtaining permits for constructing the project
  • Financial engineering to provide cash-flow for the project implementation
  • BESS components, including, batteries, power electronics, transformers, enclosures, and other miscellaneous hardware
  • Application engineering to make the BESS perform contracted functions within the target grid
  • Frequently, long-term financing (generally for a power-purchase agreement)
  • Long-term warranty and support

Note that the last two bullets will expedite the project and reduce risk for the client.

If the proposing-organization provides most of the above components but does not happen to make the batteries, it still can be a credible solution-provider.

Also, in the last paper linked above, I made the argument that the rapidly expanding electric vehicle (EV) market is driving down the price of Lithium-Ion (Li-Ion) batteries, to where they are becoming the only viable technology for most projects, and this certainly applies to large projects. The flip-side of this is that there are several major battery manufacturers that are willing to provide only the battery subsystem for a project, thus the batteries themselves are becoming commodities. Indeed, as we will mention in the next section, a major project by a leading battery manufacturer used another manufacturer's batteries.

2.2.Unique Functions Provided by Large BESS

The applications below focus on providing transmission grids, distribution grids or large renewable projects with capabilities they cannot obtain from any other single component.

Network Stability: BESS have the unique ability to supply or absorb large amounts of power in an extremely short time. Other forms of dispatchable generation require many second to minutes to ramp whereas BESS can do this in milliseconds to a few seconds. During unanticipated events (like a major generating unit or transmission line tripping), large BESS can maintain stability when other assets cannot. This allows a grid to be safely run closer to its limit, increasing utilization. It also allows a very large facility to execute a bumpless transfer to internal power in the event of a power outage.

Rapid Deployment: Several recent emergencies demonstrated large BESS installations ability to be strategically deployed in a matter of a few months vs. years for new generation or transmission lines. This prevented or resolved black-outs and/or power-rationing.

Fast Network Restart: After natural or man-made disasters, restarting a large grid can require many days. By using strategically placed BESS, charged by renewables, this process can be accelerated, or in a very large facility, it can support facility operations until power to the grid is restored.

Mitigating Renewable Variability: The function can be performed in several ways as described below. Also see the earlier paper on storage linked above for a good explanation of these methods.

  • DC-coupled Photovoltaics (PV) plus Storage: Each PV "string" (of panels) produces a voltage in the range of 600 to 1,500 Vdc. This is in the same range as BESS use for the interface to their battery banks. The most efficient design for PV + storage is to DC-couple the two, then use a single inverter. The interface between the PV strings and the storage batteries still requires some power-electronics (DC-to DC convertor) between them to manage voltage and current, but overall DC-coupled PV + storage is the most efficient design.
  • Nearby Independent BESS plus Renewables: Storage that is used to mitigate wind or PV generation, when placed close to the renewable project (each asset with independent inverters) can both mitigate the variability and optimize the power flow into the grid, including the provision of frequency regulation and other ancillary services. While not as efficient a DC-coupled PV plus storage, it is still more effective than remotely located storage.
  • Large Remote BESS Performing Multiple Functions: As individual BESS projects become larger (hundreds of MW) it is reasonable to use them to perform multiple functions, including mitigating combined renewable variability in a large area.

    Lowest cost, when combined with PV: The cost of battery storage keeps falling. Between 2010 and 2016, the price across the industry fell 73%, from $1,000 a kilowatt-hour to $273 a kilowatt-hour. By 2020, it may drop to $145 a kilowatt-hour, and by 2025, to $69.5 per kilowatt-hour.[1]

Current cost of wind energy (PPA contracted in early 2017, with subsidy)[2] is around $38 per MWh, and this is projected to be reduced to $23 per MWh without subsidies in 2030 by using various advancements.[3] The price of PV in 2030 is projected to be $30 per MWh.[4]

Recent prices from PPAs for PV plus storage are in the $30 to $50 per MWh range (lower-48 U.S., with subsidies), which is competitive with most other sources. Wind is less predictable on a long-term basis, and thus economically-justified hybrid systems have not emerged (yet).

3.Large BESS Providers and Major Projects

In this section we will look at providers that have a demonstrated capability to deliver the largest BESS, and review a few projects from each. Each subsections below will review a provider, and these are in alphabetical order.


In the middle of (2017) two of the largest companies in the power supplier sector decided to combine forces in a new organization: Fluence. The two organizations are AES Corporation and Siemens. Both had prior BESS designs and references. The combined organization has three system designs:

  • Siestorage: from Siemens. This is specifically designed to address applications that require fast response, like ancillary frequency regulation services required for grid support.
  • Advancion: from AES. This is designed for long-service, reliability and expandability.
  • SunFlex: a new offering. This is specifically designed to augment photovoltaic generation. It uses DC-to-DC coupling to maximize efficiency and minimize costs.

Each partner brings a specific set of talents to the partnership as described below, but neither manufactures batteries. Instead they source the battery (storage) subsystem from leading suppliers.

AES brings:

  • The most storage references and a proven supplier of large BESS
  • Experience managing distribution utilities
  • Provision of various renewable and conventional generation projects for utilities, businesses and the commercial sector
  • A large backlog of existing booked projects

Siemens brings:

  • A leading supplier of major utility generation, transmission and distribution projects
  • Strong sales and marketing organizations throughout the world
  • A very strong financial organization
  • A major supplier of power electronics, like inverters and DC-to-DC converters, required for the above systems

Combined Fluence has over 500 MW of installed storage projects with 68 installations in 16 countries.[5] 

Major Fluence Projects: (installed or contracted)

Dec, 2017: 30 MW, 120 MWh Escondido energy storage project built by AES, and is one of the biggest lithium ion battery installations in the world. Built in about six months, it and a smaller, 7 MW battery provide daily ramping and peak shaving services for San Diego Gas & Electric.[6]

Various sources / dates: AES Distributed Energy will built a solar-plus-storage project on the Hawaiian island of Kauai that stands out both in capacity and power price. The AES facility will have 28 megawatts of solar photovoltaic capacity paired with 20 megawatts of five-hour duration batteries. This project is scheduled to be complete by the end of 2018, and the cast of energy will be $0.11 per kWh (very low compared to the current energy price in Kauai). AES DE will be the long-term owner and operator of the project.

October 17, 2017: AES Dominicana announced that it brought online 20 MW of new battery-based energy storage arrays at two sites in the Dominican Republic, which played a key role in maintaining grid reliability in September when Hurricanes Irma and Maria struck the island. The two 10 MW arrays, which were supplied by AES Energy Storage, are the first of their kind in Central America and the Caribbean. Located on sites in the Santo Domingo region, both arrays are providing critical grid reliability services for the island by improving the efficiency and contributing to the stability of the Dominican Republic’s interconnected national electricity system.[7]

Various sources / dates: In January 2018, AES and Siemens announced they received the necessary "approvals and authorizations" to proceed with a "100 MW/400 MWh" energy storage project in Long Beach, California, dubbed the Alamitos power center energy storage project. Said project will provide backup power to Southern California Edison in western Los Angeles. Construction for the Alamitos energy storage project will start in late 2018 and is targeted for completion by the end of 2020.

3.2.LG Chem

LG Chem is a major automotive battery supplier. Although LG Chem implemented several major BESS projects a few years ago, they have apparently pulled back from this market, and are now more focused on residential energy storage units. A few of their larger projects are covered below. The first "project" relates to a large supply agreement with AES Energy Storage (a.k.a. Fluence).

Dec 2015: Energy storage provider AES Energy Storage has signed a multi-year agreement with battery supplier LG Chem to provide 1GWh of lithium-ion battery capacity for AES’s energy storage systems, which an analyst has said could take around seven to eight years to install and be worth an estimated US$300 million. LG Chem’s battery modules are configured for AES’s Advancion grid-scale energy storage solution.[8]

June 2016: A 7 MW/3 MWh battery energy system powered by LG Chem batteries has been commissioned for S&C Electric Company, making it one of the largest solar and energy storage systems in the United States. Commercial operation of the system will be run by its owner Half Moon Ventures (HMV), a renewable energy company, and will be used primarily by the local municipal utility of the Village of Minster, Ohio. The BESS and 4.2 MW PV systems are installed in the service territory of the Village of Minster. The BESS provides four distinct revenue streams for HMV and the Village: frequency regulation; T&D cost deferral; power quality improvements; and peak demand shaving. The project is in the PJM Interconnection RTO.

Sep 2015: LG Chem has supplied a 1 megawatt/2 megawatt-hour energy storage system for a solar power station in Cedartown, Georgia, USA. A Southern Company and Electric Power Research Institute (EPRI) initiative, the project is evaluating the impacts of the energy storage system (ESS) in relation to load smoothing, peak shaving and voltage support. LG Chem provided the batteries and power conversion equipment; plus battery installation, commissioning and operations and maintenance of the system. Also involved in the project was ABB providing solar inverters.

3.3.NEC Energy Solutions

In August 2014 A123 sold its stationary battery business to NEC, and the title organization was formed. This firm has remained moderately active in the BESS market. The following are recent large projects.

March 2018: Ørsted offshore wind company, and Eversource transmission builder, announced on March 16 that their Bay State Wind partnership had signed a Letter of Intent to work with Massachusetts-based NEC Energy Solutions to develop an energy storage solution for the 800 megawatt (MW) Bay State Wind. Specifically, they are looking to combine the offshore wind farm with a 55 MW/110 MWh energy storage option, which upon completion would result in the world’s largest wind-paired energy storage system for commercial-scale energy.

Dec 2016: The Sterling, Massachusetts GSS® is the largest battery-based energy storage system installed in New England and the first utility scale project in Massachusetts. It will improve grid resiliency against weather-related power outages, while providing enhanced clean energy usage and cost savings for the town of Sterling. Specifications include T&D Support, 2 MW / 3.9 MWh, battery container w/integrated cooling, power conversion system, operational December 2016.[9]

April 2017: The latest project to be dubbed “Europe’s largest battery” will be a 50MWh project from Dutch energy supplier Eneco and Japanese conglomerate Mitsubishi Corporation in Jardelund, Germany. NEC Energy Solutions will supply and integrate the EnspireME battery system, which includes 48MW / 50MWh lithium-ion batteries, power conversion technology and controls. It is expected to be put into operation by the end of 2017.

3.4.NextEra Energy Resources

NextEra Energy, is the holding company for Florida Power & Light (FPL). They have been a renewable energy developer since 1997 (initially under the name FPL Energy). As of 2009 it changed the name of its renewable division to the title of this subsection, also in this year it was the largest wind and solar energy producer in the U.S. Currently it has over 2,000 MW (net) of solar projects and almost 13,000 MW (net) of Wind projects operating.

A couple of years ago NextEra Energy Resources (hereafter "NextEra") started deploying BESS, and currently they have more than 100 MW of these systems deployed. Like Fluence, they do not make batteries, nor any of the other major BESS components. They have deployed several independent BESS, and have started bidding (and winning) PV plus storage projects. At least one of the "independent" projects is deployed adjacent to one of their major wind projects (Golder Hills Wind in the Altamont Pass a few miles from where I live in Livermore, CA). See below for more details.

June 2018: Today, NextEra Energy Resources has more than 100 MW of operational energy storage, including the Lee DeKalb Energy Storage Facility in Illinois, and the Meyersdale and Green Mountain Energy Storage Facilities in Pennsylvania. These facilities are being used for frequency regulation.

May 2017: Tucson Electric Power will buy solar energy at a historically low price from a new local system large enough to power 21,000 homes. The project, which is being built by NextEra Energy, calls for a 100 MW solar array and a 30 MW, 120 MWh energy storage facility. These are expected to be in service by the end of 2019. Tucson Electric Power has signed a power purchase agreement for a solar-plus-storage system at "an all-in cost significantly less than $0.045/kWh over 20 years," according to a company official.

February 2016: NextEra Energy Resources recently won bids to develop three projects. One is the Golden Hills Battery Energy Storage System, a 30-megawatt (MW) battery project that will provide frequency regulation to the Pacific Gas & Electric system. The project, which will be located within the boundary of the recently commissioned Golden Hills Wind Farm in the Altamont Pass just east of Livermore, California, has a 10-year contract. NextEra is one of the largest project developers in the Altamont Pass region with over 200 MW of installed capacity (combined, in three projects).

Two projects: Parry and Elmira Battery Energy Storage Systems, are each 2-MW projects that are planned for Ontario, representing a new market for NextEra Energy Canada. The batteries for these projects will store energy produced during off-peak demand periods and re-inject that electricity into the system during times of peak demand, as instructed by Ontario’s Independent Electricity System Operator (IESO). These projects will provide four hours of peaking power during high demand periods.

Jan 2017: The NextEra Energy Resources energy storage team brought online 26 MW of utility-scale battery energy storage systems – the 16-MW Casco Bay in Maine and the 10-MW Pima project in Arizona.

June 2018: NV Energy’s awarded bids included two solar-plus-storage plants, all in Sierra Pacific Power Company’s service territory. Dodge Flat: NextEra will build a 200-megawatt solar plant coupled with a 50-megawatt/200-megawatt-hour storage system. Fish Springs Ranch: NextEra will build a 100-megawatt solar plant coupled with a 25-megawatt/100-megawatt-hour storage facility. Both projects are due online December 1, 2021.

Also the picture and caption below were in the referenced article.[10]

The NV Energy contracts (bottom right) continue the trend of low solar prices, which have fallen comfortably below the price of gas generation. (Image credit: GTM Research)


Tesla is the leading EV supplier in the U.S., and from their initial manufacture of LiIon batteries (in conjunction with Panasonic) they started offering large-scale BESS. They currently have the record for the largest BESS project (probably until Fluence delivers the Alamitos project), albeit using another manufacturer's batteries. Also, in their recent share-holder meeting, Tesla announced: "…it has deployed 1 gigawatt-hour of energy storage globally. In less than one year from the date of the 2018 shareholder meeting (6/5/2018), said Elon Musk (Tesla CEO), Tesla will have installed its next 1 gigawatt-hour."

See below for more information on Tesla's large BESS Projects to date.

Various sources (see below): Elon Musk will kept his promise to deliver a large-scale Powerpack system to the government of South Australia in 100 days. The BESS is a 100 MW/129 MWh Powerpack system which is paired with global renewable energy provider Neoen’s Hornsdale Wind Farm near Jamestown” in the Australian state.

Less than a month after Tesla unveiled a new backup power system in South Australia, the world's largest lithium-ion battery is already being put to the test. And it appears to be far exceeding expectations. In the past three weeks alone, the Hornsdale Power Reserve has smoothed out at least two major energy outages, responding even more quickly than the coal-fired backups that were supposed to provide emergency power.

Tesla's battery last week kicked in just 0.14 seconds after one of Australia's biggest plants, the Loy Yang facility in the neighboring state of Victoria, suffered a sudden, unexplained drop in output, according to the International Business Times. And the week before that, another failure at Loy Yang prompted the Hornsdale battery to respond in as little as four seconds — or less, according to some estimates — beating other plants to the punch. State officials have called the response time “a record,” according to local media.[11]

A Tesla representative confirmed a report carried by Japanese newspaper Nikkei, which said the EV and stationary energy storage maker is using battery cells made by South Korean supplier Samsung SDI for the Hornsdale Power Reserve. Nikkei had said the reason for supply decision was Tesla CEO Elon Musk having promised to deliver the finished 100MW / 129MWh project in South Australia within 100 days of contracts being signed, and Samsung appeared to be the surer bet to meet the required schedule.[12]

Jan 2017: Mira Loma, California — Tesla cut the ribbon on a massive 20MW/80MWh battery storage facility in the Southern California desert, 60 miles east of Los Angeles on Monday. The Powerpack project, a joint venture with local electricity provider, Southern California Edison (SCE), will support grid operation during peak hours and improve the integration of renewable energy resources.

March 2017: Tesla will power the Hawaiian island of Kauai with solar panels and its giant battery packs. The project consists of a 17-megawatt photovoltaic solar array on 50 acres adjacent to an existing power plant owned by Kauai Island Utility Cooperative (KIUC). The installation will include a 52-megawatt-hour battery system. Tesla will sell power from the project to KIUC under a 20-year power-purchase agreement.

“The most interesting thing about this project is that it’s firm solar power,” said Peter Rive, founder and CTO of SolarCity (now Tesla). “That’s a new and important class of utility-scale solar power system. The batteries will store all the energy produced by the solar array, and then dispatch it to the grid as needed.”

Furthermore, KIUC noted that this is “only slightly more than the cost of energy from KIUC’s two existing 12-megawatt solar arrays, whose output is available only during the day.” Under the agreement, KIUC will purchase power for 14.5 cents per kilowatt-hour -- considerably less than the utility currently pays for comparable diesel generator capacity.

February 2017: In November, Ta'u (one of the outer islands in American Samoa) saw the completion of a new solar-powered microgrid, which shifted the entire island’s energy generation from 100 percent diesel fuel to 100 percent solar. The solar project was installed by SolarCity, a California-based company recently purchased by Elon Musk’s Tesla. The $8 million project was funded by the U.S. Department of Interior and the American Samoa Power Authority (ASPA).

Located on seven acres of land on the northern coast of the island, the system includes 5,328 solar panels, generating 1.410 megawatts of electricity. The energy can be stored in 60 Tesla Powerpacks—large batteries that allow Ta'u to stay powered for up to three days without any sunlight.

The final Tesla project may point the way towards the future.

The state of South Australia has announced that it will create a network of thousands of solar-powered homes, using Tesla solar panels and Powerwall batteries, Reuters reports. Initial phases of the plan are already underway and will eventually expand to as many as 50,000 homes, creating the “world’s largest virtual power plant,” according to premier Jay Weatherill.[13]

“Our energy plan means that we are leading the world in renewable energy and now we are making it easier for more homes to become self-sufficient,” Weatherill said. “We will use people’s homes as a way to generate energy for the South Australian grid, with participating households benefiting with significant savings in their energy bills.”

Installation of the 5kW solar panels and Tesla batteries has already begun on 1,100 public housing properties, with 24,000 more to follow. After that, the program will be opened up to as many as 50,000 South Australian homes over the next four years.

The panels and batteries are being supplied at no cost to homeowners, backed by a multi-million-dollar grant and a loan from a taxpayer renewable energy fund. The program will be financed through the sale of excess energy generated by the solar power grid.


[1] Adele Peters, FastCompany, "Tesla has installed a truly huge amount of energy storage", June 2018.

[2] Ryan Wiser, Mark Bolinger, Lawrence Berkeley National Laboratory, "2016 Wind Technologies Market Report", sponsored by DOE-EERE, August 2017,

[3] Katherine Dykes, Maureen Hand, Tyler Stehly, Paul Veers, Mike Robinson, and Eric Lantz

National Renewable Energy Laboratory, "Enabling the SMART Wind Power Plant of the Future Through Science-Based Innovation", August 2017,

[4] DOE, Solar Energy Technology Office, The SunShot 2030 Goals,

[5] Fluence Web Site,

[6] Gavin Bade, Utility Dive, Project of the Year: SDG&E's Escondido energy storage project, Dec 2017,

[7] Steven Goldman, Fluence Web Site, Dominican Republic’s First Energy Storage Arrays Help Island’s Grid to Prevent Blackouts, October 17, 2017,

[8] Tom Kenning, Energy Storage News, " LG Chem’s 1GWh ‘largest supply contract’ with AES", Dec 2015,

[10] Julian Spector, Greentech Media (GTM), "Nevada’s 2.3-Cent Bid Beats Arizona’s Record-Low Solar PPA Price" June 2018,

[11] Brian Fung, Washington Post, " Tesla’s enormous battery in Australia, just weeks old, is already responding to outages in ‘record’ time", December, 2017,

[12] Andy Colthorpe, Energy Storage News, " Tesla using Samsung cells in South Australia as ‘100 days’ countdown begins", October, 2017,

[13] Mark Austin, Digital Trends / Yahoo, "Tesla and Australia will turn 50,000 homes into a virtual solar power plant", Feb 4, 2018,


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