Untersuchung elektrochemischer Messverfahren zur in-situ Analyse von Salzschmelzen

Abstract

The generation of dispatchable renewable energy sources into the existing power grid is one of the most important aspects of research, today. Concentrating solar power coupled with thermal energy storage plays a significant role in this field since it can store surplus energy from solar resources and provide thermal and/or electric energy when needed. A frequently used storage material is Solar salt, consisting of 40 wt% KNO3 and 60 wt% NaNO3. The molten salt is operated between 290 to 560 °C. At and above 560 °C the thermodynamic decomposition is no longer negligible since formation of increased amounts of corrosive species due to reactions with tank materials and toxic nitrogen oxides is observed. An analysis of the resulting species is therefore necessary to ensure long-term efficiency and safety of operational power plants utilizing molten salts. This thesis attempts to identify electrochemical methods which would principally allow for in-operando analysis of molten salts instead of applying post-analytical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods were explored extensively for this purpose. More precisely, this thesis investigated potential electrode materials and conducted tests to identify appropriate electrochemical parameters. This included the investigation of the influence of temperature and measurement conditions. Finally, the selected materials and settings were used to investigate the influence of alternating voltage on the molten salt. In summary, this research investigates the applicability of the electrochemical measurement methods in molten solar salt with the aim of applicability in concentrated solar power plants (CSP).