I have read many discussions on the Fool boards concerning energy storage and battery technology. One method of storing energy that I have not seen discussed is pumped storage. I have no expert knowledge but it would seem a natural fit with large scale solar, for example.
One needs to distinguish between disruptive and sustaining technologies. A disruptive technology will obsolete old ways of doing things and be a big boost for the companies providing the new technologies. On the other hand, sustaining technologies will be used by incumbents to improve their operations.
Pumped storage is of the sustaining kind, good for pump makers but nothing revolutionary to invest in.
Wrong board. You will get more traction on the METAR board, or the Climate Change board.
Short answer, to expensive, too much turn around loss, and slow response time to loads.