The article touches on the battery that is being used:
> In one case, it takes advantage of negative prices by being paid to pump large volumes of water into a mountain lake in Austria. When prices are higher, the company releases the water, using turbines to generate electricity.
Pump the water up when the power is cheap, use the stored water in a hydro dam when the power is expensive. The storage capacity is quite significant and while not as fast to respond to the grid as batteries, its substantially faster than other power generation systems when wind or solar power generation dips.
> In one case, it takes advantage of negative prices by being paid to pump large volumes of water into a mountain lake in Austria. When prices are higher, the company releases the water, using turbines to generate electricity.
This is Pumped Storage hydroelectricity - https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
Pump the water up when the power is cheap, use the stored water in a hydro dam when the power is expensive. The storage capacity is quite significant and while not as fast to respond to the grid as batteries, its substantially faster than other power generation systems when wind or solar power generation dips.