Session: 06-03 Novel Reactors and Processes

Paper Number: 110773

110773 - Solar Hydrogen From Water Splitting Using Liquid Metal Oxidation/reduction Cycles H2pr Electrochemistry System Development 

This research investigation will assess the experimental development of a CSP-based thermochemical water splitting system. Approximately 300 thermochemical water splitting cycles accessible to CSP integration have been proposed, however after decades of research only seven cycles have been developed beyond proof of concept, with even fewer demonstrated at kW solar reactor scales. This work reviews the development of an H2 production reactor system that will demonstrate a hydrogen production process based on a simple stoichiometric metal/metal oxide water-splitting cycle operating at temperatures between 673-1073 K. This will be contained within a liquid metal solution utilizing molten salt electrolysis instead of thermolysis to reduce oxides. The test system encapsulates the redox chemistry within a binary liquid metal alloy. Unique chemical and physical properties of the alloy make it a highly effective heat transfer fluid, reaction medium, and electrical conduit. This facilitates integration of solar industrial process heat as well as electrolysis hardware. We further postulate that a large-scale plant based on this concept can operate and produce hydrogen at a lower cost than water electrolysis at similar scale. The thermochemical hydrogen production stage investigated here will be a closed loop, LMS-circulating system capable of producing 1-10 slpm of hydrogen by continuously processing 3-30g/min M. Preliminary results show that the in order to meet this hydrogen production goal, it would require that approximately 1 liter (1 kg) of water and 3.5 kg of Zn reacted over the aimed operational time. This translates to successfully reacting 28.6 g/min (4.321 mL/min) of Zn with 7.927 ml/min of water. With an expected reaction efficiency of 60%, the reaction vessel must contain 13.2 ml/min of water and 7.2 ml/min of Zn.

Presenting Author: Kenneth Armijo Sandia National Laboratories

Presenting Author Biography: Dr. Kenneth Armijo is a systems engineering staff member who leads molten salt and molten alkali metals R&D at the National Solar Thermal Test Facility (NSTTF). His research interests are in alternative energy technologies and sustainability, as they pertain to scientific and technological innovation, business and policy. Dr. Armijo holds a Ph.D. in Mechanical Engineering from the University of California, Berkeley with minors in Energy and Resources, and business credentials in Management of Technology from Berkeley's Haas School of Business. Dr. Armijo also received a Masters in Science in Mechanical Engineering from U.C. Berkeley. Presently, Dr. Armijo’s research in concentrating solar power (CSP) consists of system design for high-temperature (>720 °C) thermodynamic and commercial R&D systems, employing ternary chloride molten salts and alkali metals (sodium) as the heat transfer fluid. He is the test site Principle Investigator (PI) for multiple U.S. Dept. of Energy (DOE) projects in CSP that also includes pumped thermal energy systems. His research has also consisted of falling particles for centralized concentrating solar receivers and solar reactors for industrial process heat applications and climate change mitigation technologies. He also leads research activities pertaining to solar Stirling Engine applications as well as for solar reactor R&D and high-flux materials characterization. Dr. Armijo also serves as a lead Test Director for high-temperature materials research for Aerospace applications, such as Re-Entry and Hypersonic vehicles.