High Temperature, Raman Spectroscopy Based, Inline, Molten Salt Composition Monitoring System for Concentrating Solar Power Systems

One of the key recommended research activities in a recent DOE development roadmap for next generation CSP plants (CSP Gen3) was to develop an in-situ molten salt composition/chemistry monitoring system. In-situ, real time, online monitoring is the first step in carefully controlling the salts’ composition which is key to achieving thermal performance and reducing corrosion kinetics and grain boundary attack. Salt chemistry stability is a key technology enabler, as system and component design is tied to accurate and reliable thermal properties, and impacts salt- handling protocols (i.e., melting, purification, and ullage gas), and operation of critical subsystems (TES, system sizing, receiver, heat trace, valves, pumps, and primary heat exchanger). Ideally such a system would need to be: capable of measuring a range of molten salt compositions at target operational temperatures (CSP Gen 3 as high as 800oC); capable of detecting contaminants at relevant concentrations; and rugged/reliable enough for use in industrial settings. Sporian Microsystems has previously developed inline, real time, gas and liquid composition monitoring systems for DOD based on Raman Spectroscopy, and has developed a range of high temperature (1000-1800oC) sensor technologies for the energy industry, and specifically for CSP HTF/TES fluid monitoring applications. While these prior sensor systems were built for different applications, in principle the technologies should be similarly useful for monitoring molten salt composition at high temperatures. Thus, the long term-objective of the proposed effort is to leverage Sporian’s prior work on Raman Spectroscopy and high temperature sensors to realize a Raman based, high temperature capable, molten salt/HTF composition/contaminant monitoring system. Work will be done through collaboration between Sporian Microsystems and the National Renewable Energy Laboratory (NREL The phase I effort will include: working with DOE national labs and industry stakeholders to define system requirements; evaluating and defining revised hardware/electronics architectures and designs, and proof of principle testing/demonstration using benchtop scale prototype hardware. The proposed sensor has the potential to improve the efficiency, reliability, and economic viability of CSP systems. This, in turn, will help realize the full potential of CSP to provide clean, sustainable electric power and to enhance America’s energy independence. These harsh environment composition monitoring systems could have a variety of additional applications for nuclear power generation, fossil fuel power generation, concentrating solar fuels, and transportation systems.