Solar-powered plastic recycling at real-world scale
Researchers demonstrate how to use the power of the sun to turn plastic waste, such as drinks bottles, into clean hydrogen fuel at a scale large enough to be genuinely useful in the real world using a scalable approach.
The researchers, from the University of Cambridge, have previously demonstrated that a solar-powered reactor can convert plastic waste into clean hydrogen fuel and valuable industrial chemicals, but only at laboratory scale.
Now, they have shown a clear path for converting this technology to a commercial scale, in outdoor, real-world conditions.
While previous demonstrations have used a small reactor (catalyst) about 25cm square, the new device is significantly larger – about one metre square – which they tested under natural sunlight outside Cambridge’s Chemistry Department. This is the first time that this technology has been successfully used in outdoor conditions using scalable techniques.
Instead of generating electricity like a conventional solar panel, the Cambridge devices drives a chemical reaction that converts waste into useful products while converting water to release clean hydrogen.
Earlier versions of the solar-powered panels required high temperatures, harsh chemicals, or complicated manufacturing processes. Typically, this involved small particles suspended in solution and deposited onto a substrate.
“When we started trying to scale this technology up, we quickly found out that what seems simple on a small scale is not simple at all when you’re trying to make it at scale,” said co-first author Ariffin Bin Mohamad Annuar, from Cambridge’s Yusuf Hamied Department of Chemistry. “We can’t really have giant vats of solution to make these panels – it’s just not practical at scale.”
“If we’re really going to change the way we deal with the twin problems of plastic pollution and clean energy generation, we’ve got to develop a very scalable way to make these photocatalyst materials and reactors — and show that they really work outdoors,” said Professor Erwin Reisner, who led the research.
The new panels can be assembled at room temperature without specialist equipment: first the light-absorbing material is sprayed onto a glass panel, and then the panel is coated with specially designed molecules containing cobalt and zirconium.
Co-author Professor Dominic Wright’s team, also from the Department of Chemistry, did the work to make the molecular precursor material. These precursors were then used by Reisner’s team for loading into a sprayer– like a household paint sprayer – so that the coating could be sprayed directly onto a glass panel.
“What surprised me was, after all the optimisation, just how simple it is,” said Mohamad Annuar. “We just have this huge panel, we spray our catalyst on it, put it into our solution, put it under the sun, and it produces hydrogen and other valuable chemicals just from plastic waste. It’s just simple and scalable.”
The researchers showed the reactor works on materials ranging from cellulose to PET plastic bottles: the kind used for fizzy drinks. They also carried out a cost analysis to show what it would realistically take to scale the technology up commercially, which they say is a first for this type of research.
The spray-coating method developed by the Cambridge researchers dramatically reduces the cost to produce the reactors, which is vital to producing them at scale. However, the researchers say they still need to improve the durability and efficiency of the reactors before they are ready for commercial production.
A patent for the technology has been filed with Cambridge Enterprise, the University’s innovation arm. The research was supported in part by the UK Department of Science, Innovation and Technology, the Royal Academy of Engineering, and Petronas. Erwin Reisner is a Fellow of St John’s College, Cambridge. Ariffin Bin Mohamad Annuar is a Member of Clare College, Cambridge.
University of Cambridge
