April 16, 2013
Imagine pumped-storage hydropower, but with railroad cars on tracks instead of water in pipes, and what you’ve got is the brainchild of a California start-up.
Santa-Barbara-based ARES North America is proposing to use weighted railroad cars on tracks to create grid-scale energy storage needing no water, no hazardous materials, no fossil fuels and producing no emissions.
According to the company, ARES [Advanced Rail Energy Storage] “is a rail-based technology that stores energy by raising the elevation of mass against the force of gravity and recovering the stored energy as the mass is returned to its original location.”
In other words, the technology uses off-peak energy -- preferably generated by renewable resources -- to run a full-scale electric locomotive, pulling four flat cars loaded with concrete on railroad tracks up a hill to an upper rail yard. There the unit would remain until it was called upon to return its stored energy to the grid. Then, when the energy is needed, the four-car unit would be released back down the hill to a lower rail yard, and its motion would be used to spin a generator.
Each four-car unit could generate about 2 MW over 30 minutes, with as little as a few seconds of notice by a grid operator, and the system is infinitely scalable, from about “100 MW with 200 MWh of storage capacity up to large 2-3 GW regional energy storage systems with 16-24 GWh of energy storage capacity,” according to the company.
The system, of course, would need sloped terrain on which to lay the tracks. “A 6- to 8-percent grade is our sweet spot,” said ARES CEO James Kelly, an energy industry veteran who worked for Edison International for 38 years, most recently overseeing Southern California Edison’s 50,000-square-mile grid as its senior VP of transmission and distribution.
Kelly told Energy Prospects West that in the western United States, “there are a tremendous number of good sites,” and the ideal terrain is alluvial fan topography, typically formed by sediment deposited by water draining down a canyon from mountainous terrain onto a flatter plain below.
That type of topography often occurs in arid areas with great wind and solar resources, he added.
The system is also “light on the land,” he said. “There’s little environmental impact -- just railroad tracks. You can just pull up the tracks, rake it out, throw out some grass seed and you’ll never know we were there.”
The ARES system differs from pumped-storage hydro in that it doesn’t require the damming of water resources -- often in arid regions -- and doesn’t require boring pipes through rock. Because of this, ARES doesn’t trigger the federal permitting required of dams, and doesn’t have the complicated environmental and water-management issues that contribute to pumped-storage hydro’s typically 10- to 15-year permitting cycle.
According to Kelly, an ARES system would take about 12 to 18 months to permit -- about the same amount of time it would take to permit a railroad track. And the cost of an ARES system would be 50 to 60 percent cheaper than a similarly-scaled pumped-storage hydro project -- which tends to be much cheaper than other storage technologies, such as batteries and flywheels.
Kelly told Prospects that he views the ARES system as something complementary, not in competition, with batteries and flywheels, because of the difference in the scale ranges of the technologies. And ARES technology has an average efficiency of about 85 percent, compared to 75 percent for pumped-storage hydro.
And because of its scalability and ability to respond to requests for generation within seconds, he said he views the technology as ideal for providing balancing services to regional grid operators, such as the California ISO.
According to the U.S. Department of Energy, more than 100 GW of new storage capacity will be needed in the U.S. by 2030, to integrate all the renewable energy required by state and national goals.
Within the next few weeks, Kelly said, the company will be unveiling a demonstration project with a scaled-down locomotive and about a thousand feet of track near the Tehachapi Pass wind farm in Kern County, Calif., “purely as a test bed.” Then, later this year, ARES will install its first commercial, 50-MW phase in southern Nevada’s Nye County, where there are thousands of renewable energy projects proposed or under various stages of development.
The Nye County project will be developed in cooperation with Valley Electric Association, which joined the Cal-ISO in January of this year.
“The project is a natural fit for us, partly because of the terrain, and also because of the 1.4 GW of generation proposed in our service area,” said Valley Electric CEO Thomas Husted. Husted said most of the projects are photovoltaic and solar thermal under development by independent power producers.
He said when ARES approached Valley Electric a year ago, it was “a Eureka moment for us. The simplicity of the application is just absolutely beautiful.
“We’ve seen a lot of projects come and go over the past several years, and this one really excites us,” he said.
- Penelope Kern