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THIS CONTINUES a discussion of energy-storage concepts, begun here at SimanaitisSays. The New York Times, June 3, 2017, “The Biggest, Strangest ‘Batteries’ ” is a primary source, along with my usual snooping around the Internet.

Yesterday, we discussed two options: pumped-hydro energy storage, akin to conventional hydro, but with human-crafted topography; and compressed air as the medium stored. Today, I describe four other options.

Molten Salt.

Molten Salt Stockpiling the Sun’s Rays. During the heat of the day, energy from 10,300 solar panels melts a salt into a 1000-degree Fahrenheit liquid that retains its heat. Through heat exchange, this liquid runs steam-generated turbines producing electricity—even for hours after the sun goes down.

Crescent Dunes Solar Energy Facility. Image from

The Crescent Dunes Solar Energy Facility in Tonopah, Nevada, about 200 miles northwest of Las Vegas, features ten hours of molten-salt storage of 1.1 Gigawatt-hours, which is 2.75 times the size of the largest of battery projects, which top out at around 400 Megawatt-hours.

Train Laden with Rubble.

Rail Energy Storage. This one is akin to pumped hydro, but without the water. When energy is abundant, rail cars with heavy loads are motored up a grade and parked there. When demand warrants, these cars roll back down, their wheels driving electric generators.

ARES, a proposed rail-energy storage concept for Pahrump, Nevada. Image from

The company ARES Nevada has U.S. Bureau of Land Management approval to install a rail-energy storage facility in Pahrump, Nevada, about 30 miles east of Death Valley. When released on the grade, the train is designed to reach full capacity within 15 seconds and produce enough energy to run 14 average homes for a month.

Spinning Wheels Powering a Crane.

Flywheel energy storage. A large electric crane requires a great deal of juice in lifting a load, but only for short bursts. However, it can also be fashioned to generate considerable energy when lowering a load. A spinning flywheel acts as a motor/generator, storing the energy of the crane’s lowering a load and expending it when another is raised.

Matson Inc.’s crane on Kodiak Island, Alaska, generates part of its own energy supply; it receives another part from a nearby wind farm. Image by Margaret Kriz Hobson from

Such hardware is part of Matson Inc.’s crane on Kodiak Island, Alaska. Its efficiency enhances the island’s electricity grid, about a quarter of which is wind-generated.

An Ice Maker Chilling a Building.

Enhanced air conditioning. As in many places, nighttime electricity in New York City is less expensive than during the day. The office building at 1 Bryant Place uses this off-peak electricity to chill a mixture of water and glycol to around 27 degrees Fahrenheit. This mixture is then pumped through two miles of tubing coiled inside an array of 750-gallon water tanks.

The water in the tanks freezes, thus storing energy in the form of ice. The next day, the glycol mixture is pumped out of the coils and into a closed-circuit heat-exchange air-conditioning system. It helps chill the building for as many as ten hours during the day, when electricity is more expensive.

It’s worth emphasizing that these “strange” options of enhancing renewable energy storage aren’t at all Rube Goldberg. They’re already in use. ds

© Dennis Simanaitis,, 2017

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