High carnallite-bearing material for thermochemical energy storage: Thermophysical characterization

Abstract

Thermochemical energy storage has a high material-related energy density and low energy losses over time compared to sensible and latent energy storage. Considering economic and ecological aspects, there is a great opportunity in using low cost or even waste materials from the mining industry, as thermochemical energy storage medium. In this study, a systematic analysis of a high carnallite-bearing material, comparable to the natural waste, for thermochemical energy storage was performed. The material displays gradual decomposition and poor reversibility of hydration reaction at temperatures above 150°C. However, the reversibility is significantly higher and the decomposition is slower between 100°C and 150°C under pH2O=25 kPa. The reversible behavior of hydration reaction of carnallite, between 100°C and 150°C, is stable for 15 cycles when the material is exposed at 150°C for short periods of time (t < 20 min). Following this path, any potential application of this material is definitely limited to low temperature thermal storage or thermal upgrade. Taking the low material cost into account one of the potential applications of this material could be in the context of long-term heat storage. For this purpose, the temperatures of dehydration can be below 150°C and the temperatures of rehydration close to 40°C.