In the 1930s, the Hoover Dam transformed the American West through powering millions of homes and businesses. Now, the dam may get a second life as a giant battery to store excess solar and wind energy. The plan is to equip the dam 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.