Effect of phase separation and supercooling on the storage capacity in a commercial latent heat thermal energy storage: Experimental cycling of a salt hydrate PCM
Journal article, 2020

Latent heat storage technologies offer process benefits like daily peak shaving. In this work a commercial storage design for storing cold thermal energy has been studied using a laboratory prototype containing 168 kg of a commercial salt-hydrate phase change material (PCM). The storage was charged and discharged with subsequent cycles at different mass flow rates over a fixed temperature range and duration. It was found that the PCM TES design exhibits phase separation and increased supercooling with continuous cycling. Both phenomena lead to a gradual decrease of the effective storage capacity. With later cycles only the bottom part stores latent heat, while the top and middle parts of the storage remain liquid. The results were repeatable and are consistent with T-History measurements of samples from the PCM TES before and after cycling. It is likely that the PCM itself does not suffer from incongruent melting. Instead, the phase separation is likely to occur due to a segregation of different liquid phases across the height of the storage. It was found that T-History measurements alone are not able to predict this behavior. Moreover, it is shown that phase separation in the storage can be reversed by increasing the PCM temperature and mechanical mixing of the liquid phase. This phase separation has to be prevented in future work in order to achieve stable performance with the studied storage design.

Phase Separation

Thermal Energy Stoage



Phase Change Material



Pepe Tan

Chalmers, Architecture and Civil Engineering, Building Technology

Patrik Lindberg

ÅF Pöyry AB

Kaia Eichler

ÅF Pöyry AB

Per Löveryd

Akademiska Hus

Pär Johansson

Chalmers, Architecture and Civil Engineering, Building Technology

Angela Sasic Kalagasidis

Chalmers, Architecture and Civil Engineering, Building Technology

Journal of Energy Storage

2352-152X (eISSN)

Vol. 29 101266

Demonstration plant for cold storage in phase change materials

Swedish Environmental Protection Agency (NV-07079-16), 2017-01-01 -- 2018-06-30.

Evaluation and optimization of a heat storage with phase change materials for better energy management in buildings - field studies, modeling and laboratory experiments

Swedish Energy Agency (39695-1), 2015-01-01 -- 2017-12-31.

Optimized design and operation of thermal energy storage with phase change materials. Demonstration of a PCM cold storage for an office building

Swedish Energy Agency (39695-3), 2019-03-15 -- 2020-12-31.

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Other Materials Engineering

Energy Systems

Building Technologies



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