High Operating Temperature Liquid Metal Heat Transfer Fluids
The University of California, Los Angeles (UCLA), along with partners at the University of California, Berkeley, and Yale University, under the 2012 Multidisciplinary University Research Initiative (MURI): High Operating Temperature (HOT) Fluids funding opportunity, is investigating the use of metal alloys as a heat transfer fluid (HTF) in concentrating solar power (CSP) systems operating at temperatures in excess of 800°C. By allowing higher temperature operation, CSP systems can achieve greater efficiencies and thereby reduce the overall cost of electricity production.
The research team is working to identify a metal alloy with the following properties:
- A freezing point below 100°C
- Stable at temperatures greater than 800°C
- Low corrosion of stainless steel and high-nickel content alloys
- A heat capacity greater than 2 megajoules per meter cubed Kelvin (MJ/m3K)
If these and other project targets are met, this fluid has the potential to be used in both current and next-generation CSP technologies.
The UCLA-led project team is using a novel material synthesis system to rapidly screen metal alloys with the desired thermophysical properties. The search space is being defined through thermochemical modeling efforts, then being further refined by measurements taken with the rapid screening tools. The project team is using a combination of modeling and experimental tools, including high temperature corrosion flow loops, to verify that the metal alloys identified can meet all the needs of a CSP plant.
The superior transport properties of liquid metals, including low vapor pressure, high thermal conductivity, and relatively low viscosity, make them a natural candidate for many thermal applications. The project team is using an advanced multi-target co-sputtering system to create massive compositional libraries in thin-film forms and employ high-throughput characterization methods to rapidly screen candidate liquid metals. These combinatorial experiments are being tightly integrated with thermochemical modeling to efficiently identify the most promising compositional spaces as well as to validate and improve material databases. A critical challenge in utilizing liquid metals at elevated temperatures is undesired reactions with structural materials. Systematic computational thermodynamics modeling and experimental tests are being conducted to develop effective corrosion mitigation strategies.