A Circular Economy

From PV modules to rubber soles

In a typical linear economy, resources are taken, turned into products, and then discarded once those products are no longer fit for purpose. A circular economy, on the other hand, is a regenerative process; resources are reused for as long as possible, continually being recovered and recycled as each service life comes to an end.

What does the circular economy mean for the photovoltaic (PV) solar industry? Isn’t solar already inherently sustainable? While solar energy offers a sustainable – and economic – alternative to electricity generated from fossil fuels, the industry is relatively young. This means that the volume of panels that have reached the end of their operational lives isn’t as high as it will be in a few years. The International Renewable Energy Agency estimates that just five countries – China, the US, Japan, India and Germany – will generate between 60 million tonnes (mt) and 78 mt of waste from PV panels by 2050. And, as with any highly competitive industry that is mainly focused on cost, long-term planning to mitigate the impact of large volumes of decommissioned panels is not an obvious priority.

The fact is that PV panels are manufactured using valuable resources, including glass, plastics, rubber laminates, metals and semiconductor material such as crystalline silicon or Cad-Tel (CdTe). While these components are brought together to generate clean solar electricity for 25 years or more, they also lend themselves to high-value recycling – each component has worth and can be reused when separated from the others at the end of the module’s service life. Effectively managing this process and shaping it into a regenerative one will allow the solar PV industry to embrace the circular economy.

Enthusiasm for the concept is not quite unanimous across the industry, but important benchmarks have already been set. Even as you read this article, someone somewhere is walking around in shoes whose soles contain rubber that was originally used to laminate a thin-film PV module. Elsewhere, someone is pedalling a bicycle, grasping handles whose rubber was similarly sourced. Likewise, high quality containers are being produced from glass sourced from decommissioned PV modules.

What do they all have in common? A high-value recycling programme which is unique to the module manufacturing industry in terms of its scale and innovation.

Recycling recovery rate of more than 90 per cent – While the automotive sector manages to recycle 75 per cent of the weight of an average vehicle, and the information technology industry manages a recycling ratio of 45 per cent. This not only translates into commonly used glass, rubber and plastic products, but also creates a regenerative source of our semiconductor material – CdTe. With a recovery rate of more than 90 per cent, just 1 kg of our semiconductor can be reused 41 times to generate 2 GWh of clean energy, while displacing 1,100 metric tonnes of carbon dioxide over 1,230 years, before it becomes insufficient to coat one of our panels. Significantly, the semiconductor is itself a stable compound produced from the by-products of zinc and copper mining; it safely sequesters these materials, their unique, combined semiconductor properties used to create high performance modules.

Decouple growth from resource depletion

But even this is not enough. While there have been extensive investments in high-value recycling technology, the objective is to close the loop and eventually be able to produce highquality recycled glass with all the optical properties that are essential to the performance of our modules.

And the question we often get asked is, why is this important? First, driving a circular economy will be critical to the PV industry’s long-term resource resilience. In fact, a recent assessment conducted by the European Commission confirmed the need for secondary resource strategies to be put in place for materials that are fundamental to the PV industry: silicon, silver and indium. The absence of these strategies could create bottlenecks in the deployment of low-carbon technologies, the study concluded. Secondly, the industry cannot hide behind the “clean” label in the long run, especially as larger volumes of panels are decommissioned. Every year, Earth Overshoot Day – the date on which humanity’s resource consumption for the year exceeds the planet’s capacity to regenerate those resources that year – moves earlier, and earlier. As solar energy shakes off the “new energy” tag and becomes a ubiquitous element of the global energy generation portfolio, the industry must step up and address its responsibilities, ultimately striving to decouple its growth from the reality of resource depletion.

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