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Paving the way to a truly sustainable solar panel recycling industry

UNSW Research Fellow Dr Rong Deng is on a mission to see all of the materials extracted from used solar panels and turned into new solar panels, or other high value products.

This feature article is an extract from ACAP 10 years - Creating a Pipeline of Opportunities.

Dr Rong Deng doesn’t like the term ‘waste bomb’ when referring to the one million tonnes of household solar panels that’ll reach their end of life by 2030. She prefers to characterise them as a rich and growing source of re-usable materials for making new panels, or other high value products.

Deng, who was recognised in Forbes Asia’s 30 under 30 Healthcare and Science list, is on a mission to revolutionise the sustainability of the solar industry in time for the coming tsunami of retiring solar panels.

In early 2024, with the support of ACAP, Deng delivered a ground-breaking white paper that will guide the Australian PV industry towards circular, cost-effective solar panel end-of-life management in the next 10 years.

To date, solar panel recycling processes have been expensive and ineffective. There’s a lack of specialist infrastructure, and aside from the aluminium frames, the materials are often contaminated and have limited second life uses.

And unlike in the EU, in Australia there’s currently no requirement on the industry to take responsibility for old panels. As a result, commercial-scale recycling is largely non-existent.

The challenges of recycling solar panels

By design, solar panels are a fused, watertight, weatherproof sandwich of glass, metals, semiconductors and plastics. This is critical for generating electricity for up to 25 years, but it means they’re difficult to separate.

Removing the aluminium frame and the electrical junction box is as far as most current recycling goes. The glass is hard to separate from the solar cells and is sometimes shredded to be sold as lowgrade contaminated granules.

The remaining valuable materials – the silicon wafer, silver and copper – are more difficult to extract, particularly in a pure re-usable form. No current commercial recycling process deals with these, so they With the support of ACAP, Deng delivered a ground-breaking white paper that will guide the Australian PV industry towards circular, cost-effective solar panel end-of-life management. Infrastructure funding 78 are either sent to landfill or used as a filler in concrete or bricks.

Solar’s silver problem

Silver, the most conductive metal on earth, is an integral and expensive part of a solar panel. It collects and conducts the electricity produced by the excited electrons in the silicon wafer.

Deng says, “Silver consumption in the photovoltaic industry is currently about 10% of the world’s supply of silver. But if annual PV installation expands 5-10 times, then we’re using all of the world’s silver and we’ll run out of the world’s reserves in just two decades.”

In the EU, PV manufacturers are required to recycle used panels and recover at least 80% of their mass. As such they recover the bulk materials – glass, aluminium and low grade, contaminated silicon. Not all of the silver (the most valuable of the materials) and copper are recovered.

Solar panels contain 5-10 times less silver than when they were made 20 years ago, but the massive scaling of the industry in the next decades means silver supply is a serious problem.

The imperative to recycle

In 2022, the world reached 1 terawatt of installed solar, but leading solar power experts have predicted that if the world is to meet its decarbonisation goals, about 75 terawatts or more of globally deployed PV will be needed by 2050.

Here in Australia, by 2050, it’s estimated we’ll be grappling with 2 to 3 million tonnes of solar panels at the end of their working life.

There are compelling benefits from recycling solar panels, including:

• preventing depletion of silver reserves

• avoiding landfill and toxic emissions from the lead and fluorine

• creating revenue and circular business models through the re-sale of valuable aluminium, copper, silver and silicon

• avoiding the energy and other environmental impacts of producing raw materials for new panels.

The imperative to innovate and improve material sustainability is on the industry right now. And, Deng says, with the massive scaling of the industry, the economic feasibility of full materials recovery also improves.

The research

With the aim of achieving the highest level of materials recovery, circularity and cutting current recycling costs by 50%, Deng and her team comprehensively reviewed the technologies, opportunities and challenges of recycling silicon solar panels (80% of the PV market).

This included projecting the volumes and flow of retiring panels; the complex logistics of recovering small numbers of panels on the rooftops of millions of houses all over the country; and identifying optimal locations for large scale recycling.

They looked at the composition of the panels and how these have changed over time. They searched for next-use markets and secondary applications for the extracted plastics and glass to build circular business models (recovered silver and aluminium have a large market demand).

“These waste panels should be viewed as a big reservoir of materials ... to be supplied back into manufacturing.”

Critically, Deng’s team comprehensively reviewed all emerging silicon solar PV recycling processes and technologies currently in the lab or in pilot phase around the world. They compared the equipment, the costs, the quality of materials extracted, the advantages and disadvantages and the potential for improvement for large scale application. Gaps, trends and opportunities for further research and development were identified.

Excitingly, Deng and her team have identified two promising breakthrough recycling technologies that have the potential to improve the efficiency and lower the costs of separating and sorting the materials.

The importance for the industry

Deng’s white paper will help the industry develop recycling standards and regulations, including a Product Stewardship Scheme for Photovoltaic Systems that will involve the whole supply chain in taking responsibility for PV systems through to their end of life and developing an efficient and innovative domestic PV recycling industry.

Deng says, “These waste panels should be viewed as big reservoir of materials, if we recycle them properly from now on, we can supply materials back into manufacturing, stopping and reducing digging into the earth, and achieving a circular economy for the PV industry, making PV truly sustainable.”

“The industry is active, we are keen to leverage our expertise and skills to collaborate with industry partners to develop better tools, technologies, and standards.”

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