‘Trainsmission’: An Old New Idea

Introduction — Solar by Train?

In a world where electricity is the currency of both information and energy aspirations, a key question is how best to move electrons. In December 2024, SunTrain announced its proposal for a Wireless Alternative Train Transport (WATT) project — a plan to transport energy from solar farms in southern Colorado to centers of use such as Denver and the Front Range, via batteries loaded onto rail cars. Calling its approach to electrification “trainsmission,” the company envisions mobile power, with electricity delivered where and when it is needed without long, high-voltage power lines.

But is moving energy by rail really a new concept? Within the U.S., coal has been transported from mines to centers of use via railroads since well before the advent of electrification. Even today, “trainsmission” is the primary method for delivering coal to power plants across the country. Despite the evolution and expansion of long-distance, high-voltage transmission (HVT) networks, and the interconnection of HVT systems across the country, moving coal by rail to generating facilities continued throughout the 20th century and still today. In 2023 railroads transported nearly three-fourths of coal delivered to power plants even as coal-fired power generation has declined by two-thirds since 2007.

Rail became a vital connection between coal fields, mines, and distant energy-hungry cities and industrial centers. Much like coal, solar and wind resources also tend to be located far from energy customers. For these same reasons, SunTrain is looking at shipping solar energy in battery-hauling trains.

Energy systems entail supply and value chains. Supply chains encompass logistics — from production to transportation, delivery, and end use with storage occurring at various points across linked functions. The accrual in value of a good — electricity in this case — occurs as it is produced, transported, and delivered to final customers, where additional value is also created. The higher the cost of supply (fuels, generation technologies, logistics) relative to the market value of a final good (demand for electricity), the less attractive the economics. Energy infrastructure projects are driven by the differences in price signals between energy supply source and point of demand. The larger the difference, or differential between a base price and what customers are willing to pay, the easier it is to originate investment. The transport hurdle is not an easy one to surmount. Intense competition can exist across different strategies — for instance, transporting fuels (like coal) for generation as opposed to transporting electrons (electricity). Electricity is not easily stored, adding further complications.

Whether coal by rail or natural gas by pipeline, a substantial amount of primary energy is moved in the form of fuels to power plant locations, where it is used to generate secondary energy in the form of electricity. Physical storage of energy fuels until they are used can be accomplished in various ways, such as coal piles held at power stations or mines, underground natural gas storage connected to pipelines, water held in reservoirs behind hydroelectric dams, and so on. From electric power generation plants to customer load centers the distances can be much shorter, reducing the need for long-distance power lines.

The advent of large, grid-scale wind and solar projects has raised the bar on expensive HVT projects. Wind (onshore and offshore) and solar, along with geothermal, marine, and other emergent energy resources for power generation are location-specific and thus immobile. Wind and solar also are highly variable intermittent resources, making electricity generated from them nondispatchable. The availability of wind and solar energy resources cannot be controlled and to achieve stable grid operations, technical interventions or other energy sources are needed, at a cost.[1] When it comes to these energy resources, storing and moving electrons becomes a paramount hurdle for building resilient supply chains and robust value chains. 

Looking Back — Coal and Water by Wire

Sir Henry Bessemer, inventor of the Bessemer process for making steel from pig iron, is credited with introducing the concept of “coal-by-wire.” He coined the phrase in an April 18, 1882, letter to The London Times, titled “Easter and the Coal Question.” In it, he discussed the idea of generating hydroelectric power at Niagara Falls and transmitting it over several hundred miles via copper wire to supply electricity to industrial plants and homes that, in those days, were dependent on direct coal use.

His astonished readers were struck by the prospect of tapping into energy created by distant falling water, potentially at a fraction of the cost of coal. The story was covered by papers, magazines, and journals on both sides of the Atlantic. At the time, Bessemer’s phrase meant simply that an energy user, say a factory, could run a machine with electricity generated at a far-off location, rather than operating a steam engine onsite by burning the coal that was almost always delivered by train. Bessemer’s ultimate goal was to reduce the cost of steel for his major customers — including, within a few years, the nascent auto industry — and the expense of shipping coal via rail was a ready target.

Bessemer’s projection of long-distance electricity transmission preceded Thomas Edison’s introduction of a comprehensive electric lighting system at Pearl Street Station by several months. Niagara Falls power reached industrial centers 13 years later. Transport of electricity over hundreds of miles had to wait until the 1910s as utilities adopted technologies that allowed for high-voltage transmission (HTV) of electricity across longer and longer distances.

In the early 1900s, concerned about dwindling coal supplies, engineers looked to HVT coupled with mine-mouth coal-fired power generation as a substitute for coal transport via railroad. While utility executives sought to avoid labor strikes on rail lines, progressives endorsed mine-mouth plants as a way to reduce urban smoke pollution, and mine owners considered opportunities to burn coal waste. Because abundant coal supplies had underpinned industrial success in the 19th century, some argued that long- distance HVT, paired with hydroelectric power, could tip the economic balance in the 20th century. Still, utility owners and central station managers were not always convinced that coal-by-wire was more energy efficient than coal by train.[2]

Challenges Posed by Geography

Geography posed challenges to both coal transport and electricity transmission. One quote from 1917 suggests that building and operating long-distance HVT was not a simple proposition: “As a fitting start in its field of service to man, this mighty energy that has lain dormant in the West Virginia hills for ages is shot at lightning speed to the top of a 165-foot tower, across that picturesque yet industrious, complacent and docile yet at times turbulent and unmanageable Ohio River, climbing steep rocky hills, down over fertile valleys, through farm lands, woodlands, towns and villages to a city teeming with industry, there to serve its master, man, at the touch of a button to perform wonders undreamt of by our fathers who fought the Indians and cleared the forests of this great section of our country.”[3]

Construction of HVT Networks

After experiencing energy shortages during World War I — particularly coal shortages resulting from competing demands, weather-related rail disruptions, and labor strikes — engineers proposed, and Congress debated, large HVT systems to advance the concept of coal-by-wire. Known as “Superpower” and “Giant Power,” these proposals were never formally adopted.[4] Instead, individual utilities built interconnected systems across increasingly larger regions of North America. By the 1960s, most power customers in the United States were linked to giant networks of HVT lines.

The 1973 Oil Shock and Western Coal Mines

The debate about rail transport versus coal-by-wire revived during the 1970s, as Congress limited the use of oil and gas for power generation. These decisions were a consequence of erroneous perceptions of fuel shortages following the Arab oil embargo in 1973 and subsequent oil price shock. A long period of low oil prices during the 1960s had discouraged drilling in the U.S., leaving the country vulnerable to disruptions. Additionally, regulation of natural gas prices since the 1950s had impacted supply of that fuel, especially for delivery in interstate markets.[5]

As investment surged into large, but remote, coal mines in the Western states, utilities sought more efficient ways to turn coal into delivered electricity. The rapid expansion of coal production across the West reignited traditional tensions over rail transport. The owners of stranded coal from Western mines loathed being captive to railroads, which they claimed were charging monopoly rates for freight.

Enormous coal unit trains of 100 or more cars disrupted communities and local traffic — unit trains carry a single commodity to one destination without stops, reducing both time and cost by avoiding car switching. Meanwhile large-scale projects such as the Navajo Mine/Four Corners, Navajo Nation, and San Juan power stations, which delivered electricity via HVT to customers across the fast-growing Southwest, presented an attractive model for energy and economic development.[6]

Objections to Energy Infrastructure

Not everyone was on board with the coal-by-wire solution. In one notable case, a coalition of rural cooperatives invested in a mine-mouth plant in North Dakota and a new 400-kilovolt DC transmission line to carry the electricity to the Minneapolis-St. Paul metroplex. This project promised to deliver cheaper power to the Mid-Continent Area Power Pool, a network serving utilities in seven midwestern states. The associated air pollution from the power plant would be separated by hundreds of miles from population centers across the region. But landowners along the route of the power line objected strenuously. Farmers, after exhausting all legal methods for opposing the HVT line, took to gathering at night around newly installed pylons and pulling them down. Eventually, the power plant operated, the line was built, and coal was delivered by wire to customers across the network.[7]

Objections to energy infrastructure have become commonplace in the 21st century. Landowners, local communities, and environmental activists have questioned the wisdom of building new energy transmission routes — from gas and oil pipelines to electric transmission lines. High-voltage transmission is widely considered to be the most difficult infrastructure to approve and site.

In the meantime, trains can transport coal and oil, and ships can transport liquified natural gas providing highly-desired optionality. In this context, optionality refers to the contractual right — not obligation — to make strategic choices. For businesses, it includes the flexibility to expand capacity, buy or sell assets, or optimize operations — such as choosing cargo destinations based on shifting market conditions. As noted at the outset, despite the expansion of long-distance HVT networks and the interconnection of systems across the country, moving coal by rail to generating facilities continues today.

Looking Ahead — New Possibilities?

Using existing rail infrastructure instead of building expensive new HVT lines is core to the concept of rail-borne batteries, or trainsmission, for moving electricity. The growing demand for wind and solar power, often generated in remote locations, has created significant HVT challenges. Efforts to build new transmission lines to connect prospective solar and wind farms to population centers have been largely unsuccessful.

Across the U.S., numerous HVT projects have failed, particularly those intended to support intermittent wind and solar resources. Opponents often point out limitations in these proposals, such as the inclusion of electricity from conventional sources — coal, natural gas, and nuclear — as well as concerns about the lack of off-ramps, or local access nodes, for communities along HVT routes. Some also cite potential harm to area ecosystems.[8]

High-voltage transmission projects face economic and financial pressures that require continuous utilization to generate cash flows sufficient to amortize their substantial investments. For 2023, within the Texas Interconnected System, wind and solar combined generated 27% of the electricity — delivered to customers by wire, while coal generated 13% — delivered to power plants by train. The larger share of power, 52%, is generated from natural gas delivered to power stations by pipelines, with underground storage of gas to help balance supply and demand. The 7% of generation from nuclear is fed by uranium fuel assemblies typically transported by truck.

The roughly $7 billion Texas Competitive Renewable Energy Zones (CREZ) initiative stands out for adding 3,600 miles of HVT lines to support 23 gigawatts of new wind capacity. The cost of the CREZ lines was spread across the entire Texas market, a feat not easily accomplished and hard to duplicate. Importantly, the Texas CREZ lines can accommodate any generation source, playing an essential role in maintaining grid reliability and operating a competitive wholesale power market.[9]

Many Questions to Consider

Could a concept like trainsmission enable access to electric power from remote, intermittent energy sources like wind and solar? For that matter, could a SunTrain facilitate carriage of electricity from any source that is remote from customer loads? If existing rail lines can be utilized, clear advantages include avoiding the wait for new HVT lines, gaining flexibility to route electricity based on demand, and providing short-term backup power. Yet, the idea raises a host of questions and some new dilemmas:

• How long will it take to charge rail-borne batteries, in particular from intermittent wind and solar, and can enough batteries be charged quickly enough to support the economics of rail-borne battery stored energy?
• How much stored electricity can a single train carry, and how does that compare to the cost of moving a similar amount of energy on HVT lines?
• Given that commercial batteries currently provide about six hours of discharging, and given transportation time and delays, can cost-effective, long duration batteries be developed and used?
• How much electricity can rail-borne batteries provide when they reach destinations, and for how long? Would rail-borne batteries be most useful for very short-term peak demand or short-term emergencies?
• Can trains be deployed efficiently to areas experiencing electricity shortages, given that transmission lines deliver power almost instantly?
• How many locations along existing rail lines can support battery connections to local grids?
• What challenges exist in establishing electricity corridors along existing rail routes?
• Which state and federal agencies would oversee interstate trainsmission, and how might regulation affect the economics of this type of energy transportation?
• What technical and logistical issues must be addressed?

Many hurdles must be navigated, including: battery design and chemistry; battery materials and manufacturing supply chains; management of alternative energy technologies waste; and safety. Safety considerations include  community and state acceptance of unit train impacts as well as the economic effects of emerging battery safety practices. The economics of battery energy storage systems (BESS) for power grids are dictated in part by measures such as spacing between battery cells to prevent thermal runaway incidents and packaging of battery cells for proper containment. These will likely apply to proposed battery trains as well.

Conclusion — On the Right Track?

The brief history presented here of building electric power value chains raises a fundamental question: What are the most efficient, cost-effective energy sources and transportation modes — and what are the complex tradeoffs? The answer, of course, is that it depends. It depends on the energy source and generation technology, the distances involved, how projects are financed, and many other factors.

In the past, large-scale, dispatchable power sources such as Niagara Falls, coal, natural gas, and nuclear more easily justified long-distance, high-voltage transmission than intermittent sources like wind and solar do today. Fuels such as coal, natural gas, and uranium can be transported in myriad ways or converted to electricity and delivered via wire. Energy storage batteries introduce new possibilities and challenges. Bessemer’s 19th-century notion reflects the enduring tension between competing ideas and trade-offs in energy value chains and logistics — a dynamic that continues to evolve in new forms today.

Notes

[1] Gürcan Gülen et al., “Competitiveness of Renewable-Generation Resources,” Bureau of Economic Geology’s Center for Energy Economics, Jackson School of Geosciences, The University of Texas at Austin, April 2018, http://bit.ly/45zIBWP.

[2] For a history of development of electric power systems in the United States, see Julie Cohn, The Grid: Biography of an American Technology (MIT University Press, 2017).

[3] “Windsor-Canton Transmission Line,” Practical Engineer 21 (1917): 258.

[4] For a 21st-century engineering perspective, see Joseph J. Cunningham and John Paserba, “Superpower: Regional Coordination a Century Ago [History],” IEEE Power and Energy Magazine 23, no. 3 (2025): 99–105, https://dx.doi.org/10.1109/MPE.2025.3540755. See also, Cohn, The Grid.

[5] Michelle Michot Foss, “Natural Gas Pricing in North America,” in The Pricing of Internationally Traded Gas, edited by Jonathan P. Stern (Oxford Institute for Energy Studies, 2012), 85–144.

[6] Based on past work on Western energy development by Michot Foss, including while coordinating the Energy and Minerals Field Institute, Colorado School of Mines, 1982–85.

[7] Paul David Wellstone and Barry M. Casper, Powerline: The First Battle of America's Energy War (University of Minnesota Press, 2003).

[8] Based on past work by Michot Foss including a forum on HVT projects held in Washington, DC, Jan. 26–27, 2010, and research and monitoring to date.

[9] For a comprehensive look at the challenges to integrating wind and solar on electric power grids, see Peter R. Hartley et al., “ERCOT and the Future of Electric Reliability in Texas” (Houston: Rice University’s Baker Institute for Public Policy, February 7, 2024), https://doi.org/10.25613/EP4G-KW61.

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