From the addition of a large contribution of renewable resources (e.g., wind, solar), there has been an increase in the application of Battery Energy Storage Systems (BESS) on the Bulk Power System BPS. In recent years, the use of BPS-connected battery energy storage has quadrupled from 214 MW (2014) to 899 MW in the USA (2019), and NERC anticipates that the capacity could exceed 3,500 MW by 2023.

Figure 1: United States BPS-Connected Battery Energy Storage Power Capacity (July 2020)

As of September 2020, the United States and Canada had over 37 GW of rated power in energy storage (not only BESS) with 90% coming from pumped hydro. The remaining 10% is from lithium-ion, thermal storage, compressed air, flywheel, lead batteries, and flow batteries.

Figure 2: Electric Storage Capacity in the United States and Canada, by Type of Storage Technology

Applications of Battery Energy Storage for the Grid BESS are a well suited technology to provide short-term grid contingency support (tens of seconds) but also long-term energy support/reserve (up to four hours). The main applications of BESS -shown in Figure 3- are:

• Voltage support: Generating facilities are required to provide reactive power to the grid - BESS can provide the reactive needed to support grid voltage stability on the transmission system.
• Inverter-Based Resources (IBR) Energy Capacity Firming: Renewable energy resources, such as wind plants and solar PV, are variable energy resources as their “fuel source” is inherently variable. BESS can support renewable energy resources by providing energy during times of intermittent or expected unavailability.
• Peaking Capacity & Peak Shaving: BESS can discharge energy at the peak loading conditions to meet the peak demand as well as provide peaking generation capacity replacing the need to use high cost natural gas plants that have historically been dispatched during peak seasons. Furthermore, BESS can ameliorate congestion issues and serve as a substitute for peak shaving.
• Energy Arbitrage: BESS can take the advantage of different energy market prices by charging battery during low price hours and discharging during peak price hours.
• Transmission and Distribution Upgrade Deferrals: When the peak electricity demand exceeds the existing electricity grid’s transmission and distribution capacity, BESS can reduce grid congestion and improve overall transmission and distribution.
• Blackstart Capability Following a power system blackout, a BESS can be a potential blackstart resource as the stored energy lasts hours and can provide initial start-up power for itself and other generation facilities.

Figure 3: Main Battery Applications in the Grid.

Figure 4. Applications Served by Utility-Scale Batteries at Renewable Hybrid Facilities (2018).

Electricity Storage Technologies There are many electricity storage technologies at or near commercial viability with many more at various stages of development. This area is rapidly evolving and a summary of the categories in current technologies are mechanical, electrochemical, thermal, electrical, and chemical, as shown in Figure 5.

Figure 5: Classification of Storage Technologies

Lithium-Ion and Flow Batteries Advances in technology and materials have greatly increased the reliability, output, and density of modern battery systems, and economies of scale have reduced the associated cost. Two emerging technologies in electric energy storage are: Lithium-Ion and Flow Batteries, these two electrochemical technologies offer a more robust and adaptable energy grid. The fastest growing technology is the lithium-Ion market, which is largely driven by the electric vehicle (EV) market.

The cost of batteries is projected to continue to fall over the medium to long-term. However, the rate of decrease is likely to vary significantly by battery technology as shown in Figure 6.

Figure 6: Estimated Levelized Capital Costs of Battery Storage

Lithium-Ion Lithium-ion is the dominant storage technology because of its moderate cost, high efficiency, and long lifetime. These characteristics make lithium-ion batteries well suited for the frequency regulation market.

Flow Batteries (FB) Unlike solid-state batteries, flow batteries store energy in liquid chemicals that are pumped through a reaction area for charging and discharging. This has the advantage of enabling the storage capacity to be increased by increasing its reservoirs. The present day vanadium redox flow battery (VRFB) is the most used. Other technologies include iron and zinc-bromine FB.

Table 1: Advantages & Disadvantages of Li-ion and Flow Batteries

BESS are projected to grow at an increasing pace across the North American footprint as shown in Figure 1 and the impact they can have on the future sustainable energy grid is substantial. As renewable energies continue to grow BESS can enhance grid reliability by offsetting resource variability and providing essential reliability services, such as voltage support and frequency. Moreover, advances in technology and decreasing costs are already promoting BESS growth.

If you want to dive deep on these topics you can acces to NERC's report here and an Energy Storage Grand Challenge Roadmap published on December 2020 by the US Department of Energy.

These topics and a detailed vendor landscape from rising technologies will be further discussed on our Renewables & Storage: Grid Scale Storage forum on April 1. We are looking forward to see you there and discuss with us the technologies and different opportunities in the field!