A new paper from researchers at Lawrence Berkeley National Laboratory details how railways could provide an energy storage network that offers a flexible option for backup power for the grid.
In the paper, Leveraging rail-based mobile energy storage to increase grid reliability in the face of climate uncertainty, published in Nature Energy, the researchers compared the cost of deploying batteries on rail cars for low-frequency events, such as weather related power outages, with the investment costs of stationary energy storage and transmission lines.
The study looked at historical freight rail flows, costs, and scheduling constraints to see whether railroads could be summoned to transport batteries for high-impact events, given that grid operators typically have at least a few days’ notice, and sometimes up to a week, when extreme weather is coming. The paper’s authors found that mobile energy storage could travel between major power markets along existing rail lines within a week without disrupting freight schedules.
In cases where the trains need to cover distances of about 250 miles or less, rail-based energy storage could make more sense from a cost perspective than building stationary battery banks to fill supply gaps that happen during less than 1 percent of the year’s total hours, the researchers found. At that range, transmission lines are more cost effective than rail lines, if the batteries are used more frequently, the researchers added.
When distances grow to more than 930 miles, rail transport of energy storage becomes cheaper than transmission lines for low-frequency events, the paper found. Bringing energy storage to weather-affected areas by rail could save the power sector upwards of 60 percent of the total cost of a new transmission line or 30 percent of the total cost of stationary battery storage, the authors concluded.
While both new transmission lines and banks of batteries to store energy will be needed to meet demand and provide backup power for a grid that is increasing powered by intermittent renewable resources, “we wanted to explore additional, complementary technologies,” Natalie Popovich, a Berkeley Lab research scientist and co-author of the study, said in a statement. “We have trains that can carry a gigawatt-hour of battery storage, but no one has thought in a cohesive way about how we can couple this resource with the electric grid.”
The paper cited New York State with its robust freight capacity and current transmission constraints between upstate clean energy generation and downstate load centers, as an example of where rail-based mobile energy storage could work well. In other cases, the authors said, it may make sense for multiple states to share the additional capacity from a rail-based battery bank.
“This is not necessarily a resource that needs to be in one region,” Jill Moraski, a graduate student at the University of California Berkeley, researcher at Berkeley Lab, and the paper’s lead author, said in a statement. “It can operate similar to an insurance policy, where you spread the coverage across risks for a wide geographic region.”
The authors acknowledged that regulatory and infrastructure hurdles exist. For instance, there are not adequate interconnections to take power off a train and plug it into the grid, nor are there approval processes, pricing regimes nor regulatory frameworks in place.
They also acknowledged that extending energy storage across the rail network is not a replacement for expansion of the existing transmission infrastructure, but it could be an important complement.
“Our paper gives a top-level overview of how rail-based mobile energy storage could benefit today’s grid, in today’s climate,” Moraski said.