Railways can be a major ‘utility player’ for backup power, says new study

Simultaneously, the US electric grid faces mounting pressures. The demand for electricity from the grid is increasing as people adopt electric cars and construction energy is converted from gas to electricity. At the same time, climate change is driving more extreme weather. Events like the 2020 heat wave that caused rolling blackouts in California are relatively rare, but they are happening more frequently—and utilities need to be prepared for them.

New research points to a flexible, cost-effective option for backup power in case trouble strikes: batteries on trains. A study by the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) shows that rail-based mobile energy storage is a viable way to ensure reliability during extraordinary events.

Previous research has shown that, in principle, rail-based energy storage could play a role in meeting the country’s daily electricity needs. The Berkeley Lab researchers wanted to take the idea further to see whether rail-generated batteries could cost-effectively provide backup power for extreme events – and whether the scenario was feasible on the existing US rail network.

“There is a lot of uncertainty about when extreme supply shortages are going to occur, where they will be, and how extreme they might be,” said Jill Morasky, a graduate student at the University of California Berkeley, a researcher at Berkeley Lab. Lead author of the paper. “We found that the US rail network has the potential to bring energy when these events occur, and it may cost less than building new infrastructure.”

The paper, “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 idea for the study came to Berkeley Lab staff scientist and study co-author Amol Phadke while he was watching a long freight train pass by at a railway crossing. He started counting the cars and counted more than 100 in that one train.

“A thought struck me – how many batteries could such a large train carry? If they were to be used for emergency backup power, how significant would their contribution be?” Phadke writes in a briefing on the study. “A quick, back-of-the-envelope calculation revealed an astonishing capacity, potentially enough to power every home in Berkeley for a few days.”

To meet electricity demand and build capacity for backup power, the US is building long-distance transmission lines and installing stationary banks of batteries.

“While both of these resources are essential, we wanted to explore additional, complementary techniques,” said Natalie Popovich, Berkeley Lab research scientist and co-author of the study. “We have trains that can carry one gigawatt-hour of battery storage, but no one has thought in a cohesive way about how we can connect this resource to the electric grid.”

The US rail network is one of the largest in the world, covering approximately 140,000 miles (220,000 km). The study looked at historical freight rail flows, costs and scheduling constraints to see whether railways could call on battery transport 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 approaching.

The analysis found that mobile energy storage could travel between major electricity markets along existing rail lines in under a week without disrupting freight schedules.

What about static options?

The researchers compared the cost of deploying batteries on rails for low-frequency events with the investment costs of stationary energy storage and transmission lines. In cases where trains need to travel a distance of about 250 miles (400 kilometers) or less – roughly equivalent to a trip from LA to Las Vegas – comparisons have been made to building stationary battery banks to fill rail-based energy storage. Might make more sense cost-wise. Supply gaps that occur during less than 1% of the total hours of the year.

Over those short distances, transmission lines remain cost-effective compared to batteries on rails if they are used frequently. When travel distance exceeds 930 miles (1,500 km)—say, travel from Phoenix to Austin—railroad becomes cheaper than transmission lines for low-frequency events. This third option could save the power sector up to 60% of the total cost of a new transmission line or 30% of the total cost of stationary battery storage, the study concludes.

The study points to New York State, with its strong freight capacity and current transmission bottlenecks 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, it may make sense for multiple states to share excess capacity from a rail-based battery bank.

“It’s not necessarily a resource that needs to be in an area,” Morasky said. “It can work similar to an insurance policy, where you cover risks for a wider geographic area.”

a train of thought worth following

Regulatory and infrastructure barriers exist, the authors note. The US lacks adequate interconnection to extract power from the train and essentially plug it into the grid. And existing electricity markets have no framework for approving, pricing and regulating mobile energy assets the way they do for traditional power plants. Policies will need to be revised, and efforts to deploy storage will need to capitalize on existing interconnections where possible, such as eliminating coal plants that have existing rail lines and interconnection rights.

The researchers see more opportunities to measure the benefits of rail-based mobile energy storage beyond the scope of the current study, taking into account larger areas, a decarbonized grid and future climate conditions. They stress that the expansion of energy storage into rail networks is not a replacement for critical infrastructure such as transmission lines, but can be an important complement.

“Our paper gives a top-level overview of how rail-based mobile energy storage can benefit today’s grid in today’s climate,” Morasky said. “As we look to a future with greater electrification, more fluctuating renewable energy, and more frequent extreme events, the case for adding rail-based energy storage to the mix could become even stronger.”