Use of polyethylene glycol for the improvement of the cycling stability of bischofite as thermal energy storage material

Abstract

Bischofite is a by-product of the non-metallic mining industry. It has been evaluated as phase change material in thermal energy storage, but it shows little cycling stability, therefore in this paper the mixture of bischofite with an additive was studied. Since polyethylene glycol (PEG) is a PCM itself, in this paper PEG (with different molecular weights) is used as additive in a PCM (bischofite) to improve its thermal behaviour. Results show that adding 5% PEG 2 000 to bischofite gives a more cycling stable PCM without affecting its melting temperature neither decreasing significantly its heat of fusion. This research shows that mixing an inorganic PCM with an organic additive can be a good option to improve the thermal performance of the PCM.

The authors would like to acknowledge the collaboration of the company SALMAG. The authors acknowledge to FONDECYT (grant N 1120422), CONICYT/FONDAP N 15110019, and the Education Ministry of Chile Grant PMI ANT 1201 for the financial support. This work was partially funded by the Spanish project ENE2011-22722. Dr. Luisa F. Cabeza would like to acknowledge the Generalitat de Catalunya for the quality recognition 2014-SGR-123. Andrea Gutierrez would like to acknowledge for her doctorate scholarships to the Education Ministry of Chile (ANT 1106) and CONICYT/PAI N7813110010.