"Thousands of buildings across the United States are staying cool with the help of cutting-edge batteries made from one of the world's simplest materials," reports the Washington Post — ice.

When electricity is cheap, the batteries freeze water. When energy costs go up, building managers turn off their pricey chillers and use the ice to keep things cool. A typical building uses about a fifth of its electricity for cooling, according to the International Energy Agency. By shifting their energy use to cheaper times of day, the biggest buildings can save hundreds of thousands of dollars a year on their power bills. They can also avoid using electricity from the dirtiest fossil fuel plants. In places where the weather is hot and energy prices swing widely throughout the day — for instance, Texas, Southern California and most of the American Southwest — buildings could cut their power bills and carbon emissions by as much as a third, experts say...

When every building is blasting its air conditioner at the same moment on a hot day, power companies often fire up backup generators, known as peaker plants, which are generally extra pricey and polluting. If utilities avoid using peaker plants, they'll pollute less and save money. Last year, the Energy Department struck a tentative $306 million loan deal with the ice-battery-maker Nostromo Energy to install its systems in 193 California buildings to make energy cheaper and cleaner while lowering the state's blackout risk.
"The batteries themselves are huge..." the article acknowledges, citing one in New York City that uses 100 parking spot-sized tanks "which collectively make 3 million margaritas' worth of ice each night... But that's starting to change." (And they believe new smaller designs "could bring the batteries into smaller buildings and even houses.")

Wherever they can squeeze into the market, ice batteries could be a cheaper and longer-lasting option than the lithium-ion batteries that power phones, cars and some buildings because their main ingredient is water, experts say. The pricey chemicals in a lithium-ion cell might degrade after 10 years, but water never wears out.

And according to the article, one company has already installed ice batteries in over 4,000 buildings...

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