Solar Two (SII) completed successful operations in the spring of 1999 and demonstrated advanced molten-salt power tower technology. It proved that solar energy could be collected and stored on a large scale. The 10 MWe SII power plant operated over a wide range of conditions and demonstrated that electrical power could be generated and dispatched at night during peak demand periods reliably and cost effectively. The experience gained from designing and operating SII is being applied to the design of the next generation commercial Solar Power Tower, 15 MWe Solar Tres (S III) to be located near Cordoba, Spain. The S III design criteria have been developed incorporating the SII lessons learned and a conceptual design is being prepared. Design innovations impact all SIII system elements and result in: • Molten-nitrate salt thermal storage capacity for 24 hour a day of full electrical energy production. • Thermal Storage raises annual plant capacity factor from 20–22% for SII to over 60% for SIII. • Improved plant availability with a 6% improvement in overall annual plant efficiency. • Improved receiver thermal efficiency by 3%. • Significant reductions in capital and operating costs. This paper provides an overview of the technological innovations in SIII resulting from Solar II experience.