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Renewable energy developers in the US are facing a bottleneck of epic proportions as they jockey for limited space on the nation’s aging network of long distance transmission lines. Building new transmission infrastructure would help, but a Sisyphus-level permitting process and a web of legal challenges await any who dare propose such a thing. If only someone could figure out how to leverage the nation’s copious rail freight resources for wind and solar energy transmission — oh, wait…
Renewable Energy On Rails, What A Concept
If you’re thinking some clever soul has proposed loading large batteries onto freight cars, stuffing them full of renewable energy, and shipping them out to energy-thirsty locations, run right out and buy yourself a cigar. The US startup SunTrain has been developing just such a concept.
SunTrain cites a 2023 transmission study from the US Department of Energy, which indicates that the US will need to double its current transmission network by 2040, to reach 115,000 gigawatt-hours. Meanwhile, the nation’s freight rail system already racks up more than 100,000 miles’ worth of capacity, and then some.
“Running on almost 140,000 route miles, the U.S. freight rail network is widely considered the largest, safest, and most cost-efficient freight system in the world,” explains the US Department of Transportation.
The idea is to leverage spare railway capacity, some of which has been created by a steep drop in the use of coal for power generation. Instead of mile-long trains full of coal, SunTrain proposes deploying freight trains as high-capacity, rolling energy storage systems. The company is aiming for a train length of 7,000 feet, which it states is about the same length as a typical coal train.
The SunTrain system can also make use of grid connections at the site of former coal power plants. “While the transmission grid is already close to capacity, the railroad grid is not. SunTrain can move gigawatt-hours of renewable energy – a single SunTrain can deliver the energy of two nuclear plants operating for an hour – across the existing rail network to where and when it is needed,” SunTrain explains.
The Long Road To Renewable Energy On Wheels
That thing about two nuclear power plants remains to be seen, but SunTrain is off to a good start. Last week the company provided an update on its plans for deploying a grid-scale demonstration in Colorado, following a successful run of tests on a 750 kilowatt-hour train. The test train completed more than 6,500 miles on Union Pacific railways in California.
The next step is a 20-car, grid-connected train totaling 384 megawatt-hours, ferrying renewable energy from a former coal power plant to another former coal site 125 miles away, where it will be discharged to the grid. The goal is to reduce emissions from gas-fired peaker plants by capturing wind and solar energy that would otherwise be curtailed due to oversupply, and shift it to a location where it can be used during periods of peak demand.
“The results of this grid-connected pilot would remove the last major hurdles slowing the development of full-scale 1.9 GWh, 100-car systems,” SunTrain enthuses.
Who’s Gonna Pay For All This?
There being no such thing as a free lunch, SunTrain is applying for a grant from ARPA-E, the cutting edge funding office of the Energy Department, to help cover the estimated $125 million cost of the 20-car pilot project. In addition, SunTrain is laying plans to partner up with one of the Energy Department’s laboratories and collaborate with a leading utility, both to be named later so keep an eye out for more news on that score.
Want to get in on the action? SunTrain just launched a campaign through the crowdfunding site Republic, where the company notes that it can potentially get a full-sized SunTrain up and in two years. Even if the timeline doubles, that would beat the estimate of 10-20 years to get a new transmission line in the ground.
Take the Grain Belt Express, for example. The 800-mile, multi-state renewable energy transmission line jumped off the drawing board in 2010, only to land neck deep in a swamp of opposition from local officials and property owners.
Last summer the project finally seemed to be moving forward, at least forward enough to earn conditional approval for a $4.9 billion loan guarantee from the Energy Department’s Loan Programs Office. That’s enough to cover a 578-mile section of the project rom Kansas to Missouri.
Other transmission lines have fallen by the wayside, the proposed 175-mile Clean Path renewable energy transmission line in New York being one example. It met a dead end last month. Stakeholders in the project are reportedly seeking other solutions to solve transmission bottlenecks in the state.
More Renewable Energy For The USA
In terms of getting more renewable energy into the hands of more energy consumers, SunTrain also teases out some interesting advantages over stationary energy storage systems, such as flexibility and swap-ability. “Stationary storage projects require grid access with over 1086 GW of proposed projects stalled in the connection queue in 2024,” the company also observes. “SunTrains can be deployed as soon as they are complete.”
One potentially sticky wicket is safety, which is a significant concern when one is sending 7,000 feet worth of batteries onto the rails. For a solution, SunTrain has turned to lithium-iron-phosphate batteries engineered by the Canadian firm TROES. Although the LFP formula has a lower energy density than the more familiar lithium-ion platform, the extra weight of a typical LFP battery is not a deal-breaker for rail transit. LFP also batteries make up the difference in safety and cost-effectiveness.
For the record, SunTrain notes that diesel-electric locomotives will be doing the heavy lifting to haul its mobile renewable energy storage units around, until new battery electric and/or fuel cell electric locomotives appear in force.
The mobile energy storage model could also dovetail with other new railway decarbonization technologies. The startup Parallel Systems, for example, has been working on a network of autonomous electric rail cars that can operate independently or in platoons, without any help from locomotives.
On the renewable energy side, one example is the Swiss firm Sun-Ways. The startup is developing removable solar panels that can be laid between railroad tracks and picked up when rail work is needed. Railway stakeholders are also eyeballing the potential for outfitting locomotives and rail cars with solar panels, so stay tuned for more on that.
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Photo (cropped): SunTrain is planning a new mobile energy storage system that collects renewable energy where available and ships it where needed, using existing railways instead of transmission lines (courtesy of SunTrain).
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