Molten Salt as a Heat Transfer Fluid in a Linear Fresnel Collector – Commercial Application Backed by Demonstration

Abstract

Abstract Motivated by the need of thermal storage, Novatec decided in 2012 to put the major product development focus on the development of the direct molten salt technology, applying molten salt directly as a heat transfer fluid (HTF)in Fresnel collector solar fields. After an intense engineering phase, Novatec started the experimental testing of molten salt specific issues in 2013. Several small-scale demonstrators with a cumulated pipe length in the order of 1 to 30 m have been built to gain first experience with salt-specific challenges such as Joule heating and salt freezing and re-melting. End of 2013, a demonstrator consisting of all piping and process components that will be used in future direct molten salt plants has been built, including over 550 m of solar receiver and connection piping. This paper presents the major challenges of future large-scale direct molten salt plants from today's perspective and how they were addressed experimentally including the testing results. To conclude: So far, all previously expected challenges related to the use of molten salts in Novatecs solar collector pipes have been experimentally tested. As a result, no point of concern for the use of molten salt as HTF was found. Even if freezing occurs, which likely can be avoided by night circulation or draining, measures have been proven to safely re-thaw the salt again. The testing was performed with HITEC® salt mixture.