PUEBLO, Colo. — SunTrain, a San Francisco company, is designing a method to transport power by rail, moving containerized batteries between solar and wind farms in Colorado to existing rail-served power plants in the Denver area.
The concept is that batteries, inside standard 20-foot containers and loaded onto 89-foot railcars, are charged at originating solar and wind farms and transported on existing Union Pacific and BNSF Railway tracks for delivery to power plants, where the energy is discharged from the containers and transported to the grid using those power plants’ infrastructure.
The first-of-its-kind model introduces a new type of commodity to be transported across freight railroads, side-stepping the challenging regulatory and capital-intensive process of building new transmission lines between solar farms and the rest of the electrical grid, allowing rail to serve as the conduit for the movement of renewable energy from its source directly to the grid.
Each one of SunTrain’s 20-foot containers holds 40 tons of batteries, each producing about 4.8 megawatt-hours. Each 89-foot railcar carries 120 tons of batteries, producing 19.2 megawatts per hour. This is enough energy to power 1,000 homes for a day. SunTrain plans to invest in a fleet of 20 railcars, moving in two blocks of 10 railcars each.
“Eventually, we will be transitioning to boxcars. where we likely use a 40-foot or 50-foot boxcar,” says Christopher Smith, SunTrain’s chief technology officer, who founded the company in 2021. “We’ll make use of the additional height of that boxcar as well as using the Type F plate, so that we can cut down on the redundancy. We don’t want four individualized batteries to be wired together.”
The switchover to boxcars is still a few years away, but the company has started designs and engaged railcar manufacturers on the concept. The main priority currently is getting the project up and running between the two Colorado locations.
The batteries will be charged at the Comanche Generating Station near Pueblo, Colo., which hosts both the state’s largest coal-fired power plant and adjacent solar farm. The batteries will tap into energy generated by the solar panels for delivery to Denver-area power plants.
SunTrain is collaborating with Xcel Energy, Colorado’s largest electric utility, to deliver the battery storage to its Cherokee Generating Station as soon as next year. Located about 10 miles north of Denver, the Cherokee station is a coal-fired power plant converted to natural gas in 2017. When batteries roll onto the plant’s property, it will be the first time the plant has seen rail since unit coal trains stopped arriving in 2017.
While transmission lines connect the southeastern Colorado solar farms with the Cherokee plant and the rest of the electrical grid, Smith says there are few options to store that renewable energy generated by wind and solar, and existing transmission lines do not have the capacity to distribute the additional energy. Xcel Energy is working on a $1.7 billion project to build 550 miles of transmission lines between Pueblo, Colo., and Denver, but the project is moving slowly and has faced scrutiny by the Colorado Public Utilities Commission over broader cost and deliverability concerns.
With rail lines in place between the originating and destination locations, one of the only infrastructure needs is installing wayside charging and discharging equipment. Smith says all four batteries on each 89-foot railcar can charge simultaneously and the process can take as little as four hours, using rail-mounted chargers on adjacent tracks or installed along the track. As the fleet size grows, each railcar will continue to charge simultaneously. Discharge times are comparable and the hardware used to charge and discharge the batteries is already being used in the battery-charging sector and was modified only slightly for rail use, according to Smith.
SunTrain has also developed a plan with Union Pacific and BNSF Railway that explains the commodity type and ensures that battery storage is assigned the appropriate commodity classification, similar to how a tank car’s contents are identified. Smith says the company and its railroad partners have presented the information to the Federal Railroad Administration and Association of American Railroads.
Smith says SunTrain is using similar batteries already in use on diesel-electric and battery-powered locomotives today, which have undergone rigorous vibration, impact, and temperature tests in different environments.
“We are going to make sure our batteries meet all of the same certifications, with the added bonus that our batteries are not operating [in use] over the freight railroad network,” says Smith.
SunTrain’s proximity to the AAR’s Transportation Technology Center near Pueblo, Colo., provides convenience for additional demonstrations and testing in front of industry partners and regulators.
SunTrain sees additional opportunities to replicate the business beyond the Denver-Pueblo corridor, looking at similar options in California, Nevada, and Texas. The company envisions one day moving 100-car-unit trains of battery storage across the U.S., connecting renewable energy sources with electrical grids without burdening those existing systems.
To date, SunTrain has raised about $3.2 million dollars to develop the technology and prove its concept. Its prototype has been demonstrated at California ports in Long Beach, Oakland, and San Francisco before moving to Colorado.
Asked how the idea for SunTrain came to fruition, Smith says he was hiking with friends in Alaska in the summer of 2020 when they saw an Alaska Railroad train pass by enroute to Fairbanks, Ala., carrying various types of energy products.
“A section of the train went by carrying shipping containers, [and] I incorrectly identified the shipping containers as batteries … That afternoon, I’m like ‘wow, it’s pretty cool they are putting batteries on trains, because that actually makes a lot of sense,’ but then I soon discovered that not only were those not batteries, is that there are no batteries or electricity … moving over the freight railroad network.”
After a lot of research and getting acquainted with railroads, Smith, who has more than a decade of experience in the management of renewable power projects, decided to launch SunTrain in 2021. Less than four years later, the company is getting closer to bringing a new type of renewable energy to rails.
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