In traditional pumped hydro storage facilities, electric pumps move water uphill, into a natural or manmade body of water. Then, when electricity is needed, that water is released and flows downhill past a turbine, generating electricity. Quidnet’s approach instead pumps water down into impermeable rock formations and keeps it under pressure so it flows up when released. “It’s like pumped hydro, upside down,” says CEO Joe Zhou. Quidnet started a six-month test of its technology in late 2...

Lithium-ion batteries have some emerging competition: Sodium-based alternatives are starting to make inroads. Sodium is more abundant on Earth than lithium, and batteries that use the material could be cheaper in the future. Building a new battery chemistry is difficult, mostly because lithium is so entrenched. But, as I’ve noted before, this new technology has some advantages in nooks and crannies.  I’ve been following sodium-ion batteries for a few years, and we’re starting to see the c...