The $3 Billion Plan to Turn Hoover Dam Into a Giant Battery

https://www.nytimes.com/interactive/2018/07/24/business/energy-environment/hoover-dam-renewable-energy.html

Hoover Dam helped transform the American West, harnessing the force of the Colorado River — along with millions of cubic feet of concrete and tens of millions of pounds of steel — to power millions of homes and businesses. It was one of the great engineering feats of the 20th century.
Now it is the focus of a distinctly 21st-century challenge: turning the dam into a vast reservoir of excess electricity, fed by the solar farms and wind turbines that represent the power sources of the future.
The Los Angeles Department of Water and Power, an original operator of the dam when it was erected in the 1930s, wants to equip it with a $3 billion pipeline and a pump station powered by solar and wind energy. The pump station, downstream, would help regulate the water flow through the dam’s generators, sending water back to the top to help manage electricity at times of peak demand.
The net result would be a kind of energy storage — performing much the same function as the giant lithium-ion batteries being developed to absorb and release power.