This is very cool. A great way to store energy without batteries, without firing up coal plants. We already have a large pumped hydro generation plant in Socal (the Lake Hodges complex), and this operates on the same principle. Charge the system at night when electrical rates are low, then discharge power into the grid when rates are high, typically starting at 2pm. It’s simple energy arbitrage on a huge scale. In Socal our peak rates are above $0.45 per Kwh, and lowest rates are around $0.18 per Kwh. That’s a big spread.

And with Goldman Sachs investing in this, you can bet it has some real positive ROI. Sweet.