Thermal characterisation of binary sodium/lithium nitrate salts for latent heat storage at medium temperatures

Philip Eames,Dan Zhou

doi:10.1016/j.solmat.2016.08.017

Abstract

Latent heat storage in molten salt mixtures has been considered as a promising method for medium temperature solar thermal storage and industrial waste heat storage. The binary sodium/lithium nitrate salt mixture is one of the potential candidate materials. However there is limited information on their thermal performance except for their phase diagrams. In this paper, two binary salts, NaNO3–LiNO3 (46–54%) and NaNO3–LiNO3 (40–60%), were investigated to assess their suitability for medium temperature heat storage. The thermal properties and long term stability under multiple cycles of each binary salt pair were investigated using Differential Scanning Calorimetry (DSC). The chemical stability at elevated temperatures was tested using a Thermogravimetric Analyser (TGA). Both binary salts analysed have suitable melting temperatures (just under 200°C) with relatively high latent heat values (>220kJ/kg), both exhibiting good thermal and chemical stability.

Highlights

Thermal energy storage, including sensible heat and latent heat storage, plays a key role in solar thermal energy and industrial waste heat storage
This paper presents and analyses the binary salts of NaNO3–LiNO3 (46–54%) and NaNO3–LiNO3 (40–60%), which are studied to assess their potential to be used for latent heat storage applications
From the tests undertaken by Maeso and Largo [22], the eutectic point occurred at 45% NaNO3 and 55% LiNO3 with a melting temperature of 201 °C

Summary

Introduction

Thermal energy storage, including sensible heat and latent heat storage, plays a key role in solar thermal energy and industrial waste heat storage. It has been considered as one of the most promising technologies for improving the effective use of available sources of heat when time of generation and demand do not match. Latent heat storage using PCMs has a bigger potential compared to sensible heat storage for some applications due to its high heat storage density within a narrow temperature range. Many researchers have provided comprehensive reviews of the use of PCMs in solar thermal energy applications for the low temperature and high temperature heat storage. Most of the researchers have not focused on the medium temperature range

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