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Gravity Train as Energy Storage

Energy grids running on renewable energy sources need storage. The most common way to store energy on a grid scale is through “pumped” hydropower, where the excess energy available during off-peak is used to pump and store water at a higher elevation, which can then be released to produce electricity as gravity pulls it down to a lower elevation again. The Taum Sauk Hydroelectric Power Station in Missouri works exclusively on pumped-storage. Pumped hydro is effective, but needs lot of water and a suitable site for storage. Can the same principles be applied without using water as the prime mover?

A California-based company called Advanced Rail Energy Storage (ARES) has come up with a unique land-based alternative that could provide grid scale energy storage using electric locomotives.

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ARES’ technology uses rail cars carrying heavy blocks of concrete that are pushed to the top of a grade using excess power from renewable energy plants during off-peak hours when electricity demand is low. When the grid requires energy to meet periods of high demand, the rail cars are released back down the hill, generating electricity through regenerative braking. The company says the system can respond to increases or decreases in demand in a matter of seconds, boasting a charge/discharge efficiency of 80 percent, and can deliver constant power for periods of up to eight hours.

After testing a pilot system on a 268-meter track in Tehachapi, California, the company has been granted permission by the Nevada Public Utilities Commission to construct the grid energy storage system in the mountains of Nevada, in the United States. In a few years from now, a fleet of automated 300-ton electric-traction-drive shuttle trains should be moving up and down a 7.2% grade slope providing 50MW of fast response power to help stabilize the California electricity grid. The 34 shuttle units on the ARES system will operate on a 9.2 km track with an elevation differential between top and bottom of 2100 feet (640 meters).

ARES CEO Jim Kelly said that the system can "be deployed at around half the cost of other available storage technologies. Just as important, ARES produces no emissions, burns no fuel, requires no water, does not use environmentally troublesome materials and sits very lightly on the land.”

The system is also highly scalable in power and energy ranging from a small installation of 100 MW with 200 MWh of storage capacity up to large 2 to 3 GW regional energy storage system with 16 to 24 GWh energy storage capacity.

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ARES Co-Founder William Peitzke standing next to pilot project vehicle

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Electrical system engineer Larry Howes checks the clearance between the ARES shuttle and the electric conductor rail as the shuttle makes it's way up a 9 percent grade at Victory Springs Ranch in Tehachapi.

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Open panels show the electronics of the ARES shuttle. ARES Founder and Director of Technology Development Bill Peitzke is at left and CEO Jim Kelly is at right.

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The ARES Tehachapi pilot track with the orange conductor rail on the left

Sources: ARES / Leonardo Energy / Blackle Mag / Gizmag

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