Some rail companies are starting to equip their freight trains with “mobile containerized batteries” to rely less on fossil fuels, but the batteries could also be used to back up the electric grid, according to researchers at the Lawrence Berkeley National Laboratory in a study published in June 2023 in the journal Nature Energy.

The researchers examined the potential to use the U.S. rail system as a nationwide backup transmission grid over which containerized batteries, or rail-based mobile energy storage (RMES), are shared among regions to meet demand peaks, relieve transmission congestion and increase resilience.

“Nations will become increasingly reliant on electricity grids as they pursue decarbonization, making reliability a top policy priority,” according to the report. “We show that sharing flexible, multi-purpose RMES assets across regions and sectors is a viable, cost-effective strategy for enabling a reliable and resilient clean energy future.”

Rail transportation has “tremendous” weight capacity to deliver large battery assemblies, according to the study. A single train can carry 1 gigawatt-hour of battery storage, roughly equivalent to the carrying capacity of 1,000 semi-trucks, and large-scale mobile containerized battery pilots are already underway for freight propulsion.

The researchers found that RMES is a feasible reliability solution for low-frequency, high-impact events, such as the 2020 California blackout and the 2021 Texas winter storm. Sometimes such emergency events can be predicted several days in advance—“well over the amount of time necessary for RMES scheduling and shipment,” they wrote.

RMES could move among regions for “days, weeks or months at a time” and serve most low-frequency, high-impact events, which in addition to extreme weather emergencies, can also include major price spikes caused by supply-demand imbalances and annual peak-demand events, the researchers wrote.

Deploying RMES for all these types of events could save the power sector upwards of $300 per kilowatt-year compared to new transmission lines, and $85 per kW-year compared to stationary battery capacity, according to the study.

As with stationary generators, RMES reduces risk by providing enough physical capacity in each operating region during tight supply conditions—but reduces total investment requirements, the researchers wrote.

“As with transmission lines, RMES reduces risk by diversifying a region’s access to generating capacity, but utilizes existing infrastructure to avoid the financial and logistical expense of transmission expansion,” according to the report. “Additionally, RMES can provide redundancy along existing transmission paths, which is valuable for reducing failures in critical infrastructure.”

Although there are no technical barriers preventing RMES from being utilized in the power sector—analogous business models exist for electric school buses—currently there are issues concerning interconnection logistics and costs, as well as electricity regulation, according to the study.

“While strategic siting could reduce interconnection hurdles, further work is needed to assess market-specific interconnection opportunities and simulate feasibility based on freight operations data,” the researchers wrote. “Revising state and federal regulatory frameworks would be needed to include RMES assets in reliability markets and planning processes.”