It is a design that allows solar power to deliver electrical power more when it is needed, rather than only peaking with the sun.
More info at:
http://www.solarreserve.com/what-we-do/csp-technology/
http://www.solarreserve.com/what-we-do/csp-projects/crescent-dunes/
Seems like a little spot of global warming, too. But that's OK as long as algore can make a buck with it.