The Gemasolar Concentrating Solar Power plant, under construction by Torresol Energy in Sevilla, Spain, with help from Outokumpu, features technological breakthroughs in solar heat reception and storage systems. Gemasolar incorporates 2650 heliostats, tracking reflectors, situated around a central tower. They concentrate the sun’s rays onto a receiver placed at the top of the tower, which is capable of absorbing 95% of the heat energy. Molten salts acting as the working fluid are passed through the receiver and become heated to be used to generate water vapor for steam turbines that drive electric generators. With 17MW of nameplate power, Gemasolar will generate enough electricity to power 30,000 homes. Gemasolar will be fitted with a heat storage system where the hot molten salts are stored in special tanks at temperatures exceeding 500C. This system will allow Gemasolar to operate for up to 15 hours without solar radiation. SENER, a Spain-based engineering and technology group and a 60% owner of Torresol Energy have developed the new technology. Outokumpu specialists provided SENER with information about the grade’s behavior at 550C and above, the corrosion and stress relief tests to be applied, and welding procedures – even alternatives to 347H. Outokumpu’s early and deep involvement in the Gemasolar project was instrumental for Outokumpu to secure the stainless steel supply for the hot salts tanks, consisting of 347H plates. The contract for the fabrication of the largest tank, 23m in diameter and 14m high, went to the Barcelona-based tank fabricator Emypro. This tank continues successful cooperation between Emypro and Outokumpu in building many industry-leading storage tanks in Spain in recent years.