Procedures for testing valves and pressure transducers with molten salt

Abstract

Thermal energy storage has been identified as an effective method for improving the capacity of concentrating solar power plants. The most commonly-used storage media is molten salt (also known as solar salt) comprising 60%w NaNO3 – 40%w KNO3. However, their specific features such as material incompatibilities, high surface tension and a high solidification point (which is around 240 °C) can create technical issues and systematic failures in hydraulic components and instruments where the molten salt flows. The current standard procedures for testing hydraulic components, such as valves and pressure transmitters, do not take into account their real behavior under the working conditions and type of fluid used in these commercial thermal storage systems.This study reports the results of a specific set of tests for commercial globe valves and pressure transmitters operated at high temperature in molten salt thermal energy storage systems in CSP facilities. These tests were performed using two experimental devices, BES-I and BES-II, designed specifically for the task and constructed at the Plataforma Solar de Almeria (PSA), which belongs to the Spanish Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT). While BES-I can test components up to 3 MPa and 400 °C, BES-II can extend the working conditions up to 4 MPa and 600 °C.To support the proposed tests, some experimental results for a globe valve and a pressure transmitter are presented and discussed. The tests are conducive to improving component design and allowing manufacturers to adapt their products for operation in molten salt thermal energy storage systems.