Adhesives could play a key role in reducing carbon footprint of renewable energy

Amid growing calls for higher performance adhesives to drive forward the renewable energy sector, their ability to extend the life of equipment and aid in their dismantling are proving just as valuable.

Indeed, a key research focus is on such adhesives’ debonding qualities. Current adhesive solutions challenge renewable energy equipment recycling processes because they keep dissimilar materials together during dismantling.

“The development of alternative energy sources is inconceivable without adhesive bonding,” said an October 2022 report (1) from Bremen, Germany-based research institute Fraunhofer IFAM, working with FEICA, the Association of the European Adhesives & Sealants Industry: “Adhesive bonding is what makes modern systems for alternative energy production and their reliable large-scale energy generation possible in the first place.” It cited the sealing of solar cells, adhesive solar films, lightweighting of turbine rotor blades, construction of magnetic cores for electric motors from electro-packaging sheets, sealing of battery cells, thermal management of batteries with thermally conductive adhesives and fuel cell sealing as benefits adhesives could bring to the sector.

The potential market for these adhesives is significant. The global renewable energy market was valued at USD1.1 trillion in 2023 and is projected to reach USD2.5 trillion by 2033, at a CAGR of 8.5% during the forecast period, said Pune, India-based market research company Allied Market Research (2).

A 2021 report by researchers from the universities of Leicester, Edinburgh and Birmingham, published in the academic journal Green Chemistry, published by the Royal Society of Chemistry, said adhesives’ help in recovering renewable energy equipment was especially important because of shortages in essential minerals required for such technology (3): “The solution to these issues lies with adhesive design, as easy debonding or degradation would facilitate disassembly and allow higher value outputs from recycling.”

One of the report’s authors, Professor Andrew Abbott, professor of physical chemistry at the University of Leicester, told PPCJ: “Much of the value in recycling is in recovering thin layers of metals such as silver and copper required to conduct the electricity produced. It is the removal of the EVA [ethylene-vinyl acetate], which is the main recycling challenge.

“Polymers, in the forms of plastic or adhesives, are often the major fraction of end-of-life materials and they can have several roles such as structural integrity, enabling flexibility, toughness or making the device watertight,” he noted.

So, adhesives are an essential element of ‘design for recycle’ concepts aiding end-of-life dismantling, he said.

An alternative technology now being developed, he stressed, is a debondable adhesive which contains modified polymers with a section which can break when activated by a specific stimulant. These could be UV-light, heat, electrical field, magnetic field or chemical switches.

“A variety of triggers need to be created to deal with the expected operational conditions of the devices. A debondable trigger based on UV stimulus would clearly be useless for a photovoltaic device and a thermal debonding mechanism would not work for a device which gets hot during normal service,” he stressed. As a result, specific debondable triggers such as ultrasound with brittle thermoset adhesives could be useful as debonding could be targeted and rapid.

“Debondable adhesives would also significantly extend product lifetimes if units were replaceable. They have a major role to play,” said Prof Abbott.

Dr Matthias Popp, group leader adhesive formulation, adhesives and polymer chemistry, at Fraunhofer IFAM, agreed and told PPCJ “debonding on demand” and the utilisation of wind turbine equipment after their service life is “an important topic”.

He said: “In terms of sustainability, we are increasingly trying to design adhesive bonds in such a way that they not only hold, but can also be released again,” adding that lightweight construction with plant fibres in combination with bio-based epoxy resins and adhesives is also “an interesting field” for study.

And from a commercialisation standpoint, Frank Billotto, senior manager strategic marketing, with USA chemical major DuPont told PPCJ that debonding was already a product focus for his company: “From a deconstruction standpoint we have innovations aimed at lending themselves to the deconstruction of the module that provide second life re purposing.”

His DuPont colleague Tyler Auvil, R&D technical manager, told PPCJ: “Demand for higher performing adhesives is only increasing and engineers rely on them more and more. There is a growing use of adhesives in the design of parts.”

And he said customers were increasingly asking for the plant-based content of adhesives to be quantified to prove their environmental credentials and track the carbon footprint of products throughout their life cycle.

Both DuPont executives cited a new adhesive, BETAFORCE, developed using bio-based materials plus room temperature curing capabilities that avoid the use of high-temperature curing ovens.

In addition, they said, its hydrophobic nature “opens up the possibility of being used in wind turbines” as well as the housing for EV batteries.

In other renewable energy sectors, solar film producer Heliatek, from Dresden, Germany, has introduced a new adhesive solar cell – HeliaSol. Its adhesive backing which can be used on any surface, converting it into a potential energy source.

Initially aimed at irregular shaped roofs, the films are now being installed on cylindrical storage tanks with further applications in the pipeline, a spokesman told PPCJ.

He said: “Even though solar energy is already widespread, approximately 98 percent of the world’s roofs remain untapped for solar production. With our films, we intend to bridge this gap, especially for structures requiring lightweight or waterproof solutions.

Sven Krusche, assistant – sales and marketing at Heliakek said: “It boasts an exceptionally low carbon footprint of less than 10g CO2e per kilowatt-hour generated, making it significantly greener than conventional silicon-based solar modules.

“The implications are profound: every building can become a net-zero energy structure, powered entirely by clean energy.”

Chemistry technology company OXECO, based in Oxford and adhesives producer Scott Bader, from Northamptonshire, both UK-based, have teamed up to generate another adhesive solar option with a product that allows flexible solar panels to bond to a range of commercial building roof structures and can survive a category five hurricane.

A lack of structural integrity to support the weight of traditional, glass-faced solar panels has been a major hurdle to take-up, they claimed.

Now their SEMPRABOND product, a chemical surface adhesive treatment, can enable lightweight, flexible solar panels to be used instead: “By solving this issue we have removed a major barrier to the solar energy revolution and can greatly accelerate the move to net-zero,” said Vassilis Ragoussis, OXECO CEO.

Adhesives – it would appear – could enrich the circular energy economy at all stages from infrastructure inception to dismantling.

By Sarah Gibbons