Li (Emily) Liu, an associate professor of nuclear engineering and engineering physics at Rensselaer Polytechnic Institute, has been selected by the U.S. Department of Energy Solar Energy Technologies Office (SETO) to receive a $1.8 million award to study high-temperature molten-salt properties and corrosion mechanisms. The award is part of a $72 million funding program to advance concentrating solar power (CSP) research, a power plant technology that could reduce the cost of solar energy. CSP systems supply solar power on demand through the use of thermal storage. CSP technologies use mirrors to reflect and concentrate sunlight onto receivers that collect solar energy and convert it to heat. Thermal energy can then be used to produce electricity via a turbine or heat engine driving a generator. Types of CSP technologies include power towers, mirrored dishes, and linear mirrors. The Generation 3 Concentrating Solar Power Systems (Gen3 CSP) funding program will build on prior research for high-temperature concentrating solar thermal power technologies. Projects will focus on developing components and integrated assembly designs with thermal energy storage that can reach high operating temperatures, with a target of at least 700 °C, which would boost the efficiency and lower the cost of the electricity. Molten salt is used both as a heat transfer fluid and as a thermal energy storage medium in a power tower CSP system. "The molten salt mixture is both nontoxic and inert, and it can deploy inexpensive and scalable thermal storage, thereby enabling cost-effective 24-hour electricity generation using only solar energy," Liu said. However, molten salts, which contain impurities such as oxygen and moisture, can be very corrosive at high temperatures and can eat away the common alloys used to produce the heat exchangers, piping, and storage vessels in CSP systems. Liu's research aims to fill the knowledge gaps in salt properties and gain a fundamental understanding of corrosion mechanisms, which will help guide the selection of salts and containment materials for CSP systems. Liu and her project collaborators will use state-of-the-art technologies to develop in situ corrosion kinetics and salt property measurements. "The salt chemistry, as well as its corrosion, must be understood before the system and component design because the material choice may differ with the salt properties identified," Liu said. The researchers are developing four innovative and in many cases first-of-their-kind approaches in their study of molten salts, including in situ transmission electron microscopy, neutron reflectometry of molten salt and alloy cells, macroscopic electrochemical studies, and vibrational spectroscopy analysis and modeling.
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