Liquid Metal Batteries for Grid Storage?

An MIT-born start-up is trying to make the technology cost-competitive:

A 40-foot trailer loaded with 25 tons of liquid metals may be the solution to the renewable-energy industry’s biggest challenge: making sure electricity is available whenever it’s needed.
A Boston-area startup founded by MIT researchers is working to turn this new concept into a commercially viable product, liquid-metal batteries that will store power for less than $500 a kilowatt-hour. That’s less than a third the cost of some current battery technologies.
The technology promises an alternative to the massive pumped-water systems that make up 95 percent of U.S. energy-storage capacity. At that price, developers will be able to build wind and solar projects that can deliver power to the grid anytime, making renewable energy as reliable as natural gas and coal without the greenhouse-gas emissions.
“If we can get liquid-metal batteries down to $500 a kilowatt-hour, we’ll change the world,” Donald Sadoway, chief scientific adviser at Cambridge, Massachusetts-based Ambri Inc., said in an interview....
"To make it dirt-cheap you have to make it out of dirt,” he said. Earlier versions used molten magnesium and antimony, separated by a layer of salt, to store and release electricity. Those materials only worked at temperatures that were too high to sustain and didn’t produce enough voltage. Sadoway and his team tested more than 1,000 cells with dozens of alloys and salts to find one that’s commercially viable.
They will compete against lithium-ion batteries, the same technology used in laptop computers and electric cars, which are becoming more common for grid-storage. AES Corp., the largest operator of power-storage systems, said yesterday it’s now selling them to utilities and renewable-energy developers, for about $1,000 a kilowatt...
 Sadoway expects Ambri’s liquid-metal batteries to be competitive with pumped-hydropower systems. The most common form of storage involves pushing water to an uphill reservoir when electricity demand is low, and releasing it to run hydropower generators when more energy is required. Some facilities exceed a gigawatt, but they can only be built in areas with suitable topography.
There’s about 23.4 gigawatts of pumped-hydro capacity in operation in the U.S., compared to about 304 megawatts of battery storage, according to the U.S. Energy Department.

Economical storage for renewable sources is a must.  Hopefully this is a potential solution.