Solar power after the sun goes down is possible and usable if the power can be stored.   This is being described as a game-changer for the solar industry.

An artist's rendering by SolarReserve

“The two farms being planned by SolarReserve of Santa Monica, Calif., would store the sun’s energy in molten salt, releasing the heat at night when it could be used to drive a turbine and generate electricity. Two utilities, NV Energy in Nevada and Pacific Gas and Electric, Northern California’s biggest utility, would buy the power.

The sun’s intermittent nature has made large-scale solar farms most useful as so-called peaker plants that supply electricity when demand spikes, typically in the late afternoon on hot days. But the ability of SolarReserve to store the sun’s energy for use at night would be a step forward in technology.”

These plants can hold between 7 and 12 hours of power storage.  It works with salt, but I wish they had discussed more in detail how it works.  (See the link below.)

“The solar farm features a 538-foot-tall concrete tower topped by a 100-foot receiver that contains millions of gallons of molten salt. The Rocketdyne division of United Technologies developed the molten salt technology and has licensed it to SolarReserve.

Huge fields of mirrors called heliostats focus the sun on the receiver, which heats the salt to 1,050 degrees. The liquefied salt flows through a steam-generating system to drive the turbine and is returned to the receiver to be heated again.”

Molten salt storage is discussed here.

Read more here