Multi discharge assessment of non-eutectic mixture PCM as excellent candidate for medium temperature thermal storage operation

Abstract

Mixing polyol-based phase change material (P-PCM) to form non-eutectic mixture (NEM) is performed to reduce the impact of poor crystallization of sorbitol (STL) and high supercooling of mannitol (MTL). A series of experimental evaluations is designed based on various discharge methods commonly used for the application of thermal energy storage (TES) systems. It is the main novelty of this work, as the modification of the TES material is evaluated under different discharge methods, providing more detailed outcomes to understand the impact of material modification and operational conditions on the performance of the TES system. The finding indicates the charging capacity for the produced NEM varies between 430.8 – 486.1 Wh, which is higher than STL (386.2 Wh). Forming NEM with 25 wt% MTL offers a reliable rating charge, which enhances 10.1% than MTL. Active discharge with air yields the highest rating at 1.29°C/min for NEM, which improves under passive operation with liquid by 43.7% relative to STL. Improvement on the solidification mechanism indicates positive outcome according to the average increment of water temperature outlet with maximum improvement around 13.1°C. Rapid discharge by flowing water through the external wall of TES container produces a higher temperature outlet, which improves between 18.5 - 21.3°C. Detailed observation of the heat release profile demonstrates a significant impact on the solidification behavior, implying that the formation of NEM has a better freezing mechanism than the base material. The finding opens up new opportunities to use NEM as a reliable solution to improve the usability of P-PCM for TES systems.