As recyclers work out the best way to pull apart PV panels and reuse the raw materials, system owners are throwing them out before their time is up, writes Jeremy Chunn.
Solar energy comprised more than 12 per cent of the National Electricity Market in 2021 and its share of the work is growing.
Other than cloud cover, what can go wrong? A few things.
Solar modules are built to last 25 years, but as output efficiency has leapt ahead, owners of rooftop systems are replacing older panels with much more powerful new ones. When you factor in large-scale installations with hundreds of thousands of panels, the wave of unwanted modules on the horizon looks huge.
The International Energy Agency expects about 78 million tonnes of raw materials will be bound up in retired PV modules by 2050.
Although the materials used to make them are abundant – apart from silver – PV panels are blindingly difficult to pull apart for those materials to be used again.
In Australia, Victoria has already banned solar panels from landfill, and Minister for the Environment Sussan Ley has told the industry she wants a commitment to panel recycling by mid-2022 or regulations will be introduced.
Solar recycling is a problem that won’t go away.
Hard to disassemble
The PV recycling sector is wobbling on baby legs. The problem is working out how to cleanly and cheaply breach the ethylene vinyl acetate (EVA) encapsulant that holds everything together behind the glass and in front of the backsheet.
Lots of different methods have been tried: thermal, mechanical and combinations of both. The “hot knife” method, pioneered in Japan, sees the glass sliced off in one piece. Another method gnaws away the glass so the silicon can be decontaminated and reused.
Other methods involve grinding everything into bits and separating metals using chemical processes. But which method will set the standard?
“We don’t know yet – it’s unclear, to be honest,” says Dr Richard Corkish, chief operating officer of the Australian Centre for Advanced Photovoltaics at the University of NSW (UNSW).
He says one tricky aspect of using a thermal solution is dealing with the lead – a toxic metal – in solder. In cadmium telluride modules, the issue is how to separate cadmium, a toxic heavy metal.
Nonetheless, the PV recycling sector is heating up. In Melbourne, Lotus Energy has proudly shared video of panels being fed into a shredder at a new facility in the city’s north.
Also in Victoria, infrastructure company Ojas is working with University of Melbourne and RMIT on the design of a facility that will use European technology to recover glass, silicon and polymers. Their hunch is that ground glass can replace some sand in concrete.
Other players are further ahead. PV Industries co-founder Timothy Dawson can’t share much detail about the separation process his company has settled on other than saying the mechanical process “maximises the value of the recovered materials and limits contamination”. The trick is to separate panels “piece by piece”, he says, so glass and wafers are parted.
“We looked at some off-the-shelf options and traditional recycling processes, such as shredding,” says Dawson.
“They’re OK, but not great, and they’re expensive.”
It’s a long road for aspiring PV recyclers. Dawson has flown to faraway destinations to check out methods that, although impressive, have left him uncertain about their commercial viability.
“That’s the question we face, and that’s when we decided to pursue our own recycling technology and process,” he says.
Second time around
Like all other PV recycling methods, aluminium frames, junction boxes and cables are sent into well established recycling streams.
“The glass is the tricky part,” says Dawson.
So much glass is already collected by councils that there is an oversupply, but it is contaminated by labels, fag butts and sugary swill. With the help of researchers from UNSW, Dawson wants to find uses for glass from PV panels and buyers who will value it.
Silver will absolutely need to be recovered from PV panels as the amount needed to enable forecast deployment of solar is more than can be mined on Earth, according to some estimates. Manufacturers need to use less of the semiprecious metal, or not use it at all, as is the ambition of Sydney company SunDrive, which has opted for copper instead.
It isn’t enough to recover silicon or silver. To be used again in solar they must be extremely pure. A reverse electroplating technique developed at UNSW results in silver of 99.99 per cent purity, which isn’t pure enough.
There are mutterings that some recyclers send ground-up panels away to be used as road base. If it’s true, that doesn’t solve the problem, says Dawson.
“It’s really important that everyone maximises the value of those materials,” he says.
“If we were to shred them, is that helpful? Can we recover those materials to be used in an efficient way?”
Researchers at UNSW are looking at architectural uses for low-iron glass used in solar panels, such as shop counters and balustrades on balconies. The NSW Government’s Circular Solar Grants program in 2021 handed almost $1 million to Solar Professionals, a company that wants to see glass from panels used in greenhouses.
Capable of so much more
A sad fact is that PV systems are being retired with plenty of life in them.
“There might not be very much wrong with them at all,” says Corkish.
Australian Standards updates mean replacement of an older, non-compliant inverter can lead to an entire system being replaced. Colleagues at UNSW are trying to work out how many panels are being decommissioned before their 25-year lifetimes.
Until that’s known, Corkish says, “we’re making assumptions about when the waste stream is coming and how big it’s going to be”. It might end up bigger and earlier than expected.
The time it takes to test unwanted panels so they may be directed towards reuse will need to be sped up. A major development is photoluminescence testing that can be carried out in daylight.
“I would have sworn on a stack of bibles it was impossible, but they’re doing it,” says Corkish.
The idea of putting older panels back to work rather than slinging them into landfill has gained traction in the form of the Circular PV Alliance, a group of clean energy goalkickers that includes the full spectrum of technical skills.
The alliance is working on a testing protocol that will decide what can be reused and whether refurbishment is an option. The ultimate step is to work with industry on a certification standard for second-life panels.
Manufacturers on the sideline
Reclaim PV Recycling has operations in Adelaide and Brisbane, where panels are separated using pyrolysis (heating) to undo glues, shed backsheets and release the cells from the contacts and glass. A chemical process follows, where silicon, lead, copper and silver are recovered from the cells, with the silicon sold to a manufacturer.
PV panels are made to last decades so they don’t surrender their vital parts easily. If wafers could be extracted unharmed, they could be reprinted and returned to use.
“Ideally, that’s what we would like to achieve,” Reclaim PV Recycling director Clive Fleming tells EcoGeneration. “It’s our secondary goal.”
However, it could be a bridge too far because the silicon used to make cells in the past will be below the standards required today. On top of that, older, smaller wafers won’t fit today’s formats.
Fleming says some manufacturers agree to pay for recycling, whereas others prefer to continue to pay to send panels to the dump. He has no idea why.
“The manufacturers that are onboard know the importance of displaying support [for recycling],” he says.
At Reclaim PV, panels that turn up for recycling but still work OK are tested then badged as safe for sale in a secondary market or offered to charity. It’s a step up from shipping unwanted and untested panels off to countries only for the recipients to discover half of them don’t work.
“I see that as a problem for the nation taking them,” says Fleming, adding it’s a problem for everyone if they go to landfill.
Too good to waste
Most of a PV panel is super-high-clarity glass made using sand with very low iron content. Some of that sand likely comes from Australia, and it was only until about 13 years ago that low-iron glass was made here.
Glass from solar panels is too good to be turned into jam jars, says Corkish.
“If we had an industry making low-iron glass in Australia, we’d have a market for low-iron glass from old modules,” he says.
Manufacturers are thinking ahead about designing for recycling, and funnelling R&D into easily disassembled modules.
“Perhaps we can make modules that come apart more easily or on demand,” says Corkish.
“There are a lot of people thinking about these problems. We certainly, absolutely, have not given up.”
The environmental cost of recycling will slowly fall as the energy used to retrieve and refine materials is supplied by renewables. Almost all the cost of making new silicon, for example, is down to the coal burnt to power production and refining.
“There is a lot of light at the end of a few dark tunnels,” says Corkish.