Application of solar thermal energy to metallurgical processes

Concentrated solar thermal (CST) processing of minerals to produce metals has been shown to be technically feasible but has not yet been commercialized. Significant developments have been made in improving the concentration of solar flux into different reactor designs. Large research groups, such as the Paul Sherrer Institute (PSI) have moved beyond the proof-of-concept studies that dominated many of the studies in the late 20th century by developing systems above 10kW power and production rates above a few kilograms per hour. Over the last 20 years, research groups in Switzerland, Israel, USA, Japan, Germany and Australia have demonstrated the use of concentrated solar flux for processing of a range of oxide materials to produce metal products, with Paul Scherrer Institute and the Weizmann Institute of Science testing a range of materials in CST reactors of up to 300kW power, productions rates of 50kg/h and thermal efficiencies above 30%. There remain significant issues associated with the location of the CST plant relative to the ore processing plants, energy storage and hybridization, integration with existing metallurgical processes, productivity, and maintenance that are important considerations in developing commercial CST technologies but the biggest barrier to commercialization is the high capital cost associated with mirror systems and general CST infrastructure. The heliostat field contributes to the majority (typically 40–50%) of the capital cost of a solar thermal metallurgical system. Improved thermal efficiency of the reactor plays a major role in bringing down the capital cost, so optimizing the reactor design to minimize heat loss remains a major priority. Addressing the issues of production scale, lowering the capital cost of CST infrastructure, and integration into existing metallurgical infrastructure are key challenges that need to be addressed before solar thermal processing melting and smelting of metals can be commercialized.