Thermophysical properties of low cost lithium nitrate salts produced in northern Chile for thermal energy storage

Highlights

The composition of the salt is altered after corrosion processes as well as purity.

Thermal stability, viscosity and the storage capacity are affected.

Lithium nitrate salts present a higher energy storage density.

Abstract

In recent years, lithium containing salts have been studied for thermal energy storage (TES) applications because of their excellent thermophysical properties. In solar power plants, lithium is seen as a way to improve the properties of state-of-the art molten salts used today. Lithium nitrate is a good candidate for sensible heat storage, because of its ability to increase the salt mixture’s working temperature range. In the present research, thermophysical properties characterization of lithium nitrate containing salts, produced in Chile, have been carried out. Corrosion evaluations at 390 ° and 565 °C for 1000 h were performed for low chromium steel T22 and stainless steels (AISI 430 and AISI 316), respectively. Chemical composition of the salts including identification of corrosion products and impurities was determined and an estimation of the Chilean production costs is reported. The study shows a loss of thermal properties after the corrosion tests. The heat capacity was reduced, possibly caused by the formation of oxides at high temperatures. The partial thermal decomposition of the salt was probably produced by the incorporation of corrosion products from the steel.

Keywords

  • Molten salts;
  • Lithium nitrate;
  • Thermal energy storage;
  • Concentrated solar power

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