Travis Hoium for Motley Fool:  First Solar (NASDAQ: FSLR) has been one of the solar industry's leaders since the early 2000s, pushing costs lower and developing some of the largest solar power plants in the world. But until recently, it hasn't done much to add energy storage to its solar power plants.

That changed this week when the company announced it would build a solar-plus-storage plant for Pinnacle West Capital Corp. 's (NYSE: PNW) Arizona Public Service subsidiary. The plant will store the electricity it generates during the day for delivery during the high-demand period between 3 p.m. and 8 p.m., extending the clean energy hours for the grid .

First Solar's move into energy storage

The 65 MW solar power plant will be paired with a 50 MW, 135 MW-hr energy storage system. To put that into perspective, the system will be able to store solar electricity from the power plant after producing at full capacity for just over two hours, and then provide more than two and a half hours' worth of power at its full discharge rate. The plant is expected to be complete by 2021.  Full Article: