Developed by researchers from the SPECIFIC Innovation and Knowledge Centre and COATED M2A programme at Swansea University, the material is said to be easily scalable and can be sized and shaped to fit multiple applications. Findings from the research, carried out in collaboration with Bath University, have been published in the Journal of Materials Science.
The process starts with the dissolving of sodium alginate in water, followed by the addition of expanded graphite. Gelation can be achieved by transferring the solution into a mould for freezing. After being kept at - 20°C for over two hours, beads are formed and transferred to a saturated calcium chloride solution. An alternative method uses a drop-cast technique, with the mixture being dropped into thermochemical calcium salt, causing gelation on contact.
Once sufficient salt diffusion has occurred, the synthesised beads are filtered and dried at 120°C. The new spherical beads are said to boast increased salt capacity, achieving up to four times greater energy density than a vermiculite carrier developed previously at SPECIFIC. This is facilitated by their efficient packing in a fixed bed that maintains good airflow. As a result, the new material can achieve the same heat energy storage capacity in just a quarter of the volume.
In a statement, Jack Reynolds, research lead at Swansea University, said: "The ability to recover and store otherwise-wasted heat from various sources, including industrial operations and the summer sun, presents an exciting opportunity in the quest for sustainable and affordable energy resources. Our new heat storage material marks a significant step forward in realising this potential."
Dr Jonathon Elvins, senior technology transfer fellow and co-author, added: "To explore new applications for this latest technology, we are preparing for a trial at Tata Steel UK’s Trostre steelworks to investigate ways of capturing waste heat from industrial processes for use elsewhere."
The research at SPECIFIC Innovation and Knowledge Centre and COATED M2A was funded by the European Regional Development Fund through the Welsh Government, the European Social Fund via the Welsh Government, EPSRC, and Tata Steel UK. It was also supported by the Industrial Decarbonisation Research and Innovation Centre.
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