The Gemasolar plant situated in Seville, Spain, is the first CSP plant in the world to sustainably operate  for 24 hours with a combined central receiver and molten salt system. The molten salt heat storage system allows for up to 15 hours of electricity generation without incoming solar rays. For more information on how the plant works click this link…http://sterg.sun.ac.za/files/2012/09/GEMASOLARPLANT1.pdf