The electric grid in the United States is currently under multiple evolving pressures. The growing demand for power, driven by the increased adoption of electric vehicles and the transition from gas to electric energy in buildings, is putting a strain on the grid. Additionally, the effects of climate change are leading to more frequent and extreme weather events. While events like the 2020 heatwave and resulting rolling blackouts in California were relatively uncommon in the past, they are now occurring more frequently. Therefore, utilities need to be prepared to handle such situations.
A recent study conducted by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory suggests that batteries installed on trains could provide a flexible and cost-effective solution for backup power during these challenging events. Previous research had already indicated that rail-based energy storage could contribute to meeting the country’s daily electricity demands. However, the Berkeley Lab researchers aimed to explore whether train-mounted batteries could efficiently and affordably supply backup power during extreme events, while also considering the feasibility within the existing U.S. rail network.
Jill Moraski, the lead author of the paper and a graduate student at the University of California Berkeley, highlighted the uncertainties surrounding the occurrence and severity of extreme supply shortages. Nevertheless, the study revealed that the U.S. rail network has the capability to transport energy to locations experiencing such events, and implementing this approach could be more cost-effective than constructing new infrastructure.
The paper titled “Leveraging rail-based mobile energy storage to increase grid reliability in the face of climate uncertainty” was recently published in the journal Nature Energy.
A ready resource in freight rail
The inspiration for the study originated from Amol Phadke, a staff scientist at Berkeley Lab and co-author of the research. While observing a long freight train passing by a railway crossing, he pondered the number of batteries such a massive train could carry and how their utilization for emergency backup power could make a significant impact. A rough calculation revealed an astonishing capacity, potentially capable of supplying power to every household in Berkeley for several days.
The United States is currently constructing long-distance transmission lines and installing stationary battery banks to meet electricity demand and establish backup power capacity. However, the study sought to explore additional and complementary technologies. Researchers at Berkeley Lab recognized the enormous potential of trains, which have the capacity to transport gigawatt-hours of battery storage, but had not been thoroughly considered in terms of integration with the electric grid.
With the largest rail network in the world, spanning approximately 140,000 miles (220,000 kilometers), the study examined historical freight rail flows, costs, and scheduling constraints. The objective was to determine if railroads could be utilized to transport batteries during high-impact events, as grid operators typically receive advance notice of several days to a week before extreme weather occurs.
The analysis concluded that mobile energy storage could be efficiently transported between major power markets along existing rail lines within a week, without disrupting freight schedules. This finding highlights the potential feasibility and viability of leveraging the U.S. rail network for enhancing grid reliability during extreme events.
What about stationary options?
The researchers conducted a cost analysis comparing the deployment of batteries on rail for infrequent events with the investment costs associated with stationary energy storage and transmission lines. They found that for distances of approximately 250 miles (400 kilometers) or shorter, which is roughly equivalent to a trip from Los Angeles to Las Vegas, rail-based energy storage could be more cost-effective than constructing stationary battery banks to address supply gaps that occur during less than 1% of the total hours in a year.
In cases where transmission lines are used frequently at these shorter distances, they remain a cost-effective option compared to rail-mounted batteries. However, as the travel distance increases to over 930 miles (1,500 kilometers), such as a journey from Phoenix to Austin, rail-based energy storage becomes cheaper than transmission lines for low-frequency events. The study concludes that this alternative approach could save the power sector more than 60% of the total cost of a new transmission line or 30% of the total cost of stationary battery storage.
The study highlights New York State as an example where rail-based mobile energy storage could be a suitable solution due to its robust freight capacity and existing transmission constraints between upstate clean energy generation and downstate load centers. In other scenarios, it may be beneficial for multiple states to share the additional capacity provided by a rail-based battery bank.
The researchers suggest that this resource does not necessarily need to be concentrated in one region. Instead, it can function similar to an insurance policy, where the coverage is spread across different geographic regions to mitigate risks effectively.
A train of thought worth following
The authors of the study acknowledge the presence of regulatory and infrastructure challenges. The United States currently lacks adequate interconnections to effectively transfer power from the train-based storage to the grid. Furthermore, the current electricity markets do not have a framework in place for approving, pricing, and regulating a mobile energy asset like they do for traditional power plants. Policy revisions would be necessary, and deployment efforts would need to leverage existing interconnections where feasible, such as repurposing retired coal plants that already possess rail lines and interconnection rights.
The researchers believe that there are additional opportunities to quantify the advantages of rail-based mobile energy storage beyond the scope of their current study. This could involve considering larger territories, a decarbonized grid, and future climate conditions. They emphasize that integrating energy storage across the rail network should not be seen as a substitute for crucial infrastructure such as transmission lines but rather as a valuable complement.
“While our paper provides a high-level overview of how rail-based mobile energy storage can benefit the current grid in today’s climate,” Moraski explained, “as we envision a future with increased electrification, greater fluctuations in renewable energy, and more frequent extreme events, the case for incorporating rail-based energy storage into the energy mix may become even more compelling.”