Report on innovative techniques for molten salts high temperature measurements

The present report is concerned with the description of the improvement of measurement techniques for molten salts as heat transfer fluid (HTF) and sensible thermal energy storage (TES) media at elevated temperatures (up to 700 °C). For concentrating solar power (CSP), the standard medium for TES is a mixture of Sodium Nitrate and Potassium Nitrate. The thermal stability of this mixture limits the operation temperature (about 560 °C). At higher temperatures alternative TES media, such as chlorides or carbonates, are required. This document aims for elevated TES operation up to 700 °C using an alternative molten mixture based on a ternary chloride salt mixture. In order to monitor the salt chemistry specifically an adapted measurement technique based on an electrochemical technique was developed. This allows for the extension of the measurement possibilities compared to known methods