Optimised Solar Thermal Storage System for Delivering Process Heat at Temperatures Above 160 C

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The core aim of the study is the development of a novel solar thermal energy storage system using phase change materials (PCM). PCM are a class of material which change phase when absorbing or releasing energy. They typically enter a liquid form when absorbing heat and solidify when the heat is extracted. PCMs have high thermal energy storage potentials due to the material property of latent heat capacity, the amount of energy absorbed or released when a material undergoes a phase change. The system aims to take advantage of the developments in concentrating solar thermal collector technology which deliver high temperatures and couple it with PCM heat storage. This study aims to use latent heat storage capability to store a relatively large amount of solar thermal energy and release the energy at the point of demand. The research will give specific attention to delivering temperatures and heating profiles suitable for mid-temperature range industrial processes.Detailed scientific objectivesDevelopment of PCM which enhances desirable properties such as thermal conductivity and melting temperatures. This activity will be carried out using computer simulation followed by experimental verification.Identify the factors affecting the thermal cycle stability and long-term (seasonal) storage capability of PCM and incorporate measures to mitigate the negative effects of thermal cycling and long-term storage. Thermal cycling stability is defined as the number of times a material can undergo heating and cooling cycles while maintaining its thermal properties. Initial investigation will be carried out through standard material characterisation tests followed by microscopy using scanning electron microscope (SEM). Degradation factors will be identified, followed by the application of corrective measures and the material will be re-tested. Development of a model to explain the phase change boundary movement during melting and solidifying and development of heat exchanger design with optimisations led by knowledge gained from the melting and solidifying model.NoveltyModel to understand, quantify and visualise the melting and solidifying process of PCM.PCM optimised to undergo more thermal cycles and degrade less when used for long-term energy storage.Development of a novel heat exchanger designed to take advantage of the melting and solidifying profile of PCM.An industrial scale, system design for storage and delivery of heat, using an optimised PCM as the storage medium.Benefit to societyWith industrial processes accounting for nearly 16% of national energy usage in the United Kingdom and over half of that energy coming from non-renewable sources, it is the hope of this study, to make solar thermal energy a viable alternative in an industrial setting, through improvements in storage technology and capability to deliver higher temperatures. The potential applications of the proposed work include processes in the food processing industry, tea industry and polymer manufacture.