Seaweed heat storage material set for steelmaking trial

ENGINEERS at Swansea University, UK have developed a heat storage material made from seaweed that they will now test at Tata Steel to see how well it can capture waste heat from industrial operations.

The new thermochemical material is made using alginate, a polymer produced by seaweed. The team has created beads using the material which capture heat and can be made to release it using humid air.    

Jack Reynolds, who led the research as part of his doctorate 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."

Jonathon Elvins, senior technology transfer fellow and co-author of the paper discussing the development of the new beads, said: "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 beads are made by dissolving alginate in water and adding expanded graphite to increase surface area and thermal conductivity. The beads can be created by either transferring the solution to a mould, freezing them, and transferring them to a saturated calcium chloride solution. Or using a drop-cast technique, with the mixture being dropped into thermochemical calcium salt, causing gelation on contact. Once enough salt has diffused into the beads they are filtered and dried.

Reynolds said: “The beads are made up of 80% calcium chloride salt and that is the thermally-active material. When we apply a humid air stream that contains water to the beads a reaction takes place where we form a hydrated salt and this gives out heat energy. On the reverse, when we put heat energy in from something like industrial waste heat, this breaks down the chemical bonds releasing water and that is when we store our heat energy potential for the next cycle.”

The team reports that the increased salt capacity helps achieve four times greater energy density than a vermiculite material it previously developed. This is helped by efficient packing in a fixed bed that maintains good airflow.

Coming industrial trials will look to gather more information on how many cycles the material can be used for, and the maximum temperature at which the materials can be charged.

The work is part of a collaboration between Swansea’s Specific programme, which works to scale up and commercialise energy technologies, its Coated M2a doctoral training centre focused on functional industrial coatings, and the University of Bath, UK.