Incorporation of controllable supercooled phase change material heat storage with a solar assisted heat pump: Testing of crystallization triggering and heating demand-based modelling study

Abstract

In short to long-term heat storage, the heat loss of common phase change material (PCM) systems is a big problem where heat is lost continuously to the ambient environment and is thus wasted, even when the system is not in use. Controllable supercooled PCM in the proposed system offers a solution to this problem. Latent heat is only released when the supercooled PCM is triggered to induce crystallization, so it can be stored at ambient temperature. To control the release of heat, the installation will be constructed as a group of PCM storage units, each with its own trigger, which can be activated according to the heating demand of a building perhaps over several days. The proposed versatile PCM energy storage system can play an essential role in synchronizing energy demand and supply, on a short to long-term basis (days/weeks). In this study, an electrical triggering mechanism is constructed and tested in the laboratory to control the crystallization of the PCM. The PCM temperature increased from 20 °C to 56.4°C in 20s after triggering. After validation of controllable crystallization and melting time, a solar-assisted heat pump coupled with supercooled PCM storage units was simulated considering the heating demand profile of an eco-house in Nottingham, UK. The charging time of the PCM tank was found 6.5h when 8 cm diameter PCM tubes were adapted. During discharging period, the hot water supply temperature was achieved at higher than 43 °C, considering the one-day heating profile of the building.