Assessing the performance of novel molten salt mixtures on CSP applications

Abstract

The use of molten salt mixtures as a storage medium in Concentrating Solar Power (CSP) plants has been shown to have a significant impact on increasing the reliability of CSP plants and reducing the levelized cost of energy. In this context, the present work presents the implementation of a detailed simulation procedure that contemplates different design considerations for the Rankine cycle to maximize its efficiency according to the temperature constraints established by utilizing different molten salt mixtures. To achieve this, three commercial CSP plant configurations were considered: an indirect coupling using parabolic trough collectors (PTC) with thermal oil as field heat transfer fluid (HTF) and molten salts as the storage medium, a direct coupling of PTC using molten salt as HTF and storage medium, and a central receiver plant (solar tower). The analysis considers the integration strategy between the solar system and the thermal storage, where all of those configurations considered the integration of the two-tank (hot/cold) approach. The analysis enables the development of an accurate estimation of the economic performance of changing the HTF in CSP plants, as well as the assessment of the parasitic consumption due to freezing protection systems, the effect of increasing the current field temperature, and the effect on the plant’s capacity factor. The results show that the improvement in conversion efficiencies associated with salt mixtures operating at higher temperatures induces a higher electricity generation; however, such improvement is not compensated by the material change costs within the specified considerations.