Save our solar … the narrow road to economic PV recycling
To harvest the sun’s power you must maximise your exposure to it. Any tree will tell you that. It’s why they have broad canopies made up of thousands of flat receiving devices called “leaves”. Humans caught on to this as a great way to turn the sun’s rays into electricity and, as they always do, commercialised it. The photovoltaics industry thus spawned has since become a shining hope in humanity’s struggle against emissions produced by polluting forms of generation.
But there is a problem.
The panels manufactured in their billions to energise economies have a lifetime of 30 years or so – although some say less (and some say more). Considering an average lifespan of 30 years, it is expected that by 2047 Australia will have accumulated more than 800,000 tonnes of discarded PV modules, according to a 2019 study out of Macquarie University in Sydney. Most of that huge pile of purple oblongs will consist of glass (about 68%) and aluminium (about 14%), followed by copper and steel.
Because of the recent rapid acceleration of the buildout of large-scale solar the volume of decommissioned panels will balloon by mid-century. “With regards to all PV penetration scenarios in the electricity generation market until 2030, Australia is estimated to face around 1 to 8 million tonnes of decommissioned PV until 2060,” write Macquarie researchers Sajjad Mahmoudi, Nazmul Huda and Masud Behnia.
The only problem is that solar panels are built tough. They have to be, to last decades in the wind and rain and sun and snow. It’s not that easy to take them to pieces again. But as they multiply across the planet the value of the materials locked in PV modules will become substantial.
If the recovery of the end-of-life PV raw materials is managed well, the Macquarie researchers estimate $1.2 billion of value can be realised. It’s enough of a lure to set researchers on a path to figuring out how best to pull PV panels to pieces. Where to begin?
A first step, says Richard Corkish, chief operating officer at the Australian Centre for Advanced Photovoltaics at the University of NSW, is to develop a triage system to select end-of-life paths for modules in the field: this one has some life left in it, this one’s cactus, etc. “Trying to make that [triage assessment] quick and cheap and automated is a strong area of our interest,” he says. “It’s something of fairly low value – and end-of-life item – so you really can’t invest too much in deciding what to do with it.”
The triage approach would make use of automated imaging tools, including photoluminescence and electroluminescence testing, strong areas for UNSW. The next stage is to develop standards, rules, guidelines and policies about managing retired panels. The logistics of delivering stacks of panels around the country is an important cost consideration. “If it’s too expensive to carry them around then it’s just not going to be done.”
Finally, it’s time to pull them to pieces – the hard part.
The PV industry excels at layering components in a module to maximise their durability in the elements – rain, sand, snow, hail, saltwater, bird poo – for decades. All this effort in the manufacturing process to prevent delamination makes it hard for the person who needs to separate them.
Once the aluminium frames and junction boxes are pulled off to be respectively sent to recycling and into the normal electronic waste stream, it’s time for the hard part.
There are three main approaches recyclers can take to separating materials: thermal, chemical and mechanical – with the optimal process likely involving a mixture of the three, Corkish says.
One technique that looks hopeful is the “hot knife”, developed in Japan, where a blade separates the glass from the adhering encapsulant. That should leave you with an unbroken sheet of glass, possibly suitable for reuse, although “the value of [it] is still a bit unclear to me,” Corkish says. Glass used on PV panels is heat-treated and laminated so that it will shatter, similar to a car windscreen. This means it cannot be resized. Whether there will always be a market for glass sheets sized to yesteryear’s PV technology is a long call. As manufacturers chop and change wafer sizes it’s hard to imagine it.
“At the moment it’s not easy to imagine putting [the glass] back into the PV manufacturing stream,” Corkish says, “unless we end up with a range of stable formats in size.”
Once the glass is off, you’re left a sandwich of polymer, solar cells and backsheet which can be put through a thermal or chemical separation process.
A thermal process trialled by Corkish’s UNSW colleague and lecturer Jose Bilbao is pyrolysis, or heating in the absence of oxygen, where exhaust containing fluorine from the backsheet is captured. A “gentler” thermal path is also being considered where the backsheet is first removed. A third option is to remove the backsheet when the glass is still intact. All three options – thermal, chemical, mechanical – will be looked at for separating the rest, including the cells.
“We’re looking to get the cells out unbroken, and potentially reusable,” Corkish says. “That’s the goal.”
Having handled a few wafers in his time, and assessed their fragility, your correspondent is surprised. Reusable? What happened to the notion they were at the end of their lives? “Yes,” says Corkish, “but the reason these panels are at the end of their lives is not necessarily the cells.”
Module failure is mostly a result of water entering through cracked glass or compromised encapsulants and affecting interconnections. Cells do degrade over their lifetime, primarily as a result of boron and oxygen combining, he says, and research at UNSW is pointing to a method to undo the degradation process. “You might even have a cell that’s better than the one you started with.”
A cell that’s not reusable might still have another life as a wafer, once all the metal is stripped off. Or it might be worth reusing the silicon, once it’s been melted or crushed. “If we can have gentle processes that can get the unbroken wafers out then all the paths are open to us,” he says. “That’s where we’d like to start.”
Silver contained in the printed contacts on cells deemed unfit for reuse is also well worth retrieving.
All recycling options need to be measured against environmental and financial criteria, he says. “We want processes that are both cheap and clean.” If a solution is found that is a better option than landfill, the job’s done. If not, then it’s off to the tip. “We’re very conscious that recycling isn’t necessarily wonderfully better than not recycling.”
Considering the continued and increasing adoption of solar, the material benefits of recycling are plain as day, says Bilbao, a lecturer in the School of Photovoltaic and Renewable Energy Engineering at UNSW. “When you start scaling up the amount of production that we need for solar cells in the future, then we need as much material as we can recover,” he says.
A shortage of silver, for example, has been flagged as a possible roadblock for the production of PV modules, to say nothing of the sunk cost of the energy used to purify silicon in ageing PV systems. “The amount of energy used to produce that wafer is about 70% of total emissions of the module,” he says. “If we can recycle that cell we are cutting the amount of emissions by a big portion.”
Tomorrow’s modules may prove easier to dismantle and recycle, he says, as manufacturers are slowly realising the importance of designing for more than one life. “And it will happen faster if there is more regulation,” Bilbao says.
It’s a different story in Europe, where EU regulations stipulate that panel manufacturers must finance the cost of collection and recycling. A plant operated by waste management firm Veolia in Rousset, southern France, separates all materials using a mechanical process, where about two-thirds of glass is recovered to be used in glass-making, the framework is sent to an aluminium refinery, plastic is sent to a cement works and separated silicon goes to the precious metals sector. Cables and connectors are crushed and sold as copper shot. The plant opened two years ago and processes about 2,000 tonnes of material a year, with ambitions to increase to 4,000 tonnes a year.
Back in Australia, the possibilities of recycling PV have drawn the attention of a couple of young entrepreneurs. In Sydney, Timothy Dawson started looking at the recycling problem about four years ago and has started collecting and storing panels at a facility in Exeter, south-west of Sydney. Dawson has seen what’s happening at Veolia’s facility in France and bought a de-framing machine in preparation for setting up a similar operation. “That’s the path we’ve been heading down,” the PV Industries founder and director tells EcoGeneration. A larger de-framing machine is on its way from Europe.
Victoria has prohibited the disposal of panels in landfill as part of its e-waste ban. “That’s great,” says Dawson, “but you need a system to support that. At the moment there is no-one in the country who can recycle these panels in their entirety.”
Product stewardship schemes, similar to some that exist for TVs and computers, are an industry-led alternative being looked over by state and federal governments. PV Industries is sorting out a deal with two other businesses in the waste sector that will see it expand its capabilities, Dawson says. Meanwhile it is testing a few methods of processing PV modules with expectations of having a pilot plant in operation by the end of this year.
Dawson expects to settle on a mechanical process to begin with and further down the line adapt a combination of different types of processes. This could include commercialisation of a process developed in the laboratory at UNSW. “If and when that becomes available, we’ll have the rights to use that technology,” he says.
“The silicon is the tricky part,” Dawson says. “It’s the final piece of the puzzle. All the other materials have their markets and are quite easy to sell or give to manufacturers, but the silicon is trickier.”
A major goal of the UNSW project, then, is to develop markets that use silicon in the manufacturing process – and that can be satisfied with the quality of silicon recovered.
“It’s early days in the technology front,” Dawson admits, before declaring he is hopeful the research he is involved with can beat Veolia’s solution used in France. “We think we can improve on that process. The thing with the French technology is that by immediately cutting and crushing you’ve made your job to separate the different pieces a lot harder. We’re trying to separate one material at a time rather than all at the same time.”
The next stage for PV Industries is to establish a commercial plant capable to taking the first volleys of retired panels that is sure to swell to a tidal wave of purple rectangles as systems reach the end of their lives.
In a country this size, Dawson is well aware logistics will play a huge part in the operation’s success.
Many installers are accumulating used panels that still have some life in them. Those they can’t flog on Gumtree are stacking up in workplaces or garages – and they are becoming a problem. “They can’t get rid of them,” he says. “There is not a large market for them.” They’ll have to pay, say, $20 a panel to have them taken away, he says, depending on location. That price should come down as the volume of clapped-out panels balloons. “I think we’ll be ready,” he says.
If the UNSW solution isn’t commercially feasible, Dawson says PV Industries can improve on the Veolia process, with help anticipated from various state and federal grants.
Tearing PV panels apart and selling the parts sounds like hard work. Will companies that succeed in the venture make money? “Definitely,” Dawson says. “There’s already an appetite in the market to pay for it.” System owners will be willing to pay for disposal, he reckons, so their green credentials can remain unquestioned.
Not everyone agrees. Energy blogger Ronald Brakels reckons the value of recovered materials makes recycling uneconomic, without some sort of financial or legal incentive. “It would be nuttier than a lumpy chocolate bar to put a charge on solar panels now to cover the cost of their recycling before putting a price on carbon emissions,” Brakels says. “The amount of time the Earth can tolerate a heap of yet-to-be-recycled solar panels is a lot longer than it can tolerate increasing greenhouse gas levels.”
Until such time as recycling becomes super cheap and efficient the best thing to do to limit waste is improve the lifespan of solar panels so fewer end up as waste early, he says, “and fortunately that has been happening”.
If change is going to happen it will be because someone is willing to put in the effort to spell out the benefits and get the industry on side. This will require a shift in attitudes.
“People see [PV panel] recycling as expensive as opposed to dumping them, but it’s actually not,” says Clive Fleming, director of Reclaim PV Recycling. “All it needs is a bit more of a network setup and a bit more inclusion of the whole industry to make it a viable option.”
Fleming’s heard it said here and there that the recycling of solar modules is not a viable business. “That’s actually not true,” he says. “They’re basing that on small-scale studies rather than the factual elements that exist, that are realistically the transport costs. Once you can reduce those costs it is very viable to do recycling.”
Installers (or de-installers, when it comes to pulling old solar arrays off rooftops) can hold on to panels at their own premises until they have a few pallet-loads to make pick up cheaper, Fleming says, then arrange for Reclaim PV to collect from a work site or transport the panels themselves to Reclaim PV’s warehouses in Brisbane or Adelaide.
Once the panels are collected it’s time to reverse the manufacturing process and collect the primary ingredients. It’s not as simple as it sounds when you’re looking at spindly metal connections and brittle wafers, all sandwiched and laminated between sheets or glass and glued to rugged backsheets.
Fleming has looked at many options for separating the materials in a PV module and settled on a thermal process, using a furnace designed in collaboration with and manufactured by an Australian company.
“We target the different temperatures of each element, which allows us to unlock them from each other,” he says. “I can’t go into too much detail; it’s a bit of a trade secret.”
Fleming is aiming to recover intact glass panels and unbroken solar cells, although he admits this is difficult. “The glass comes out in shards but we want to do it so they come out in whole pieces, so we can re-use that, if we can. The solar cells come out in smaller broken bits, but we want to refine the process so they come out as whole solar cell parts.” Glues and backsheets are consumed in the thermal process.
The Adelaide and Brisbane facilities can separate 150,000 panels a year when operating at full capacity. “Our system is very modular,” he says, suggesting that a surge in demand can simply be met by adding more furnaces at the existing sites or opening further locations.
Once the aluminium frames are removed, the busbars pulled out and the shards of glass piled up, the fragments of the PV cells go into a wet process.
The wet process includes two stages, where the silver and aluminium contained in the solar cells is removed and, in the next stage, the silicon cells are refined further to make them reusable or prepared for use in silicon manufacturing.
The wet process is still a work in progress, Fleming admits, as he waits for enough decommissioned PV panels to pile up to make the costly process worth the investment. “That’s down the track a bit, once the feedstock increases,” he says. “It’s a chemical process to extract value from the cells and refine the cells further.”
Once impurities are stripped away from the cells, the silicon is transformed into a valuable commodity. Fleming won’t be drawn into a detailed breakdown of the chemicals used in the wet process. “Maybe down the track but not right now,” he says.
The business was born in 2014 in expectation of an inevitable wave of retirement of ageing solar arrays. Owners of systems will be happy to have banked years of energy savings, but when it comes time to rip panels off rooftops they are disinclined to see the value in having them carted off. The same goes for installers. Collection is the biggest cost in the process, Fleming says, and it’s important that the industry understands the cost of disposing of panels should be factored into budgets.
It is simply not on to send them to the tip.
It’s a tough message to get across, he says. “An installer might contact us and say I have 20 panels to get rid of, and we say, no worries, it’ll be about $600 and we’ll pick them up – and they say, no, I’m not paying that.”
As Reclaim PV works on its network of collection options and state governments ponder moves to follow Victoria’s ban on PV panels in landfill, he says recycling will reach the point of being priced about the same as the gate fees at a dump.
Collection costs about $30 a panel, he says. In regions where local collection arrangements are in place the cost of collecting 20 panels could fall to $200, or $10 a panel. Drop-offs to a collection point will cost less, say $150 in that case, and delivery to a Reclaim PV warehouse in Adelaide or Brisbane might incur a $50 fee. “The cost comes down, which we see as a huge advantage for installers.”
Fleming and his team have put plenty of work into putting together a network of partners willing to accept drop-offs in key regions and centres around the country, he says, and the company is working on an agreement with a silicon manufacturer to take refined wafer material.
As larger and larger PV systems enter their twilight years in the decades ahead Fleming sees Reclaim PV working on becoming a combined decommissioning and recycling partner. “When it gets to that point it will be a different business,” he says. When that time comes, he expects the business’s transport links to have reached a level of sophistication where costs will be attractive.
In China, the manufacturing epicentre of PV, recycling is slowly creeping up the R&D agenda. During a trip to the Xining headquarters of Chinese solar company SPIC, a subsidiary of HHDC, in December last year EcoGeneration was shown materials extracted from PV panels using what was cursorily described as a crushing process. The SPIC technician involved in the project couldn’t share too much information, as it was a work in progress, but the company’s showroom display included bowls of backsheet fragments, whispy strands of busbar conductors and granular silicon to show it was serious about tackling the problem.
In Australia, the Australian Renewable Energy Agency (ARENA) is offering up to $15 million in funding towards research that aims to address end-of-life issues for solar PV panels, as well as increasing their efficiency and lowering their cost. ARENA is interested in the economics of recycling including better upfront design, increasing the value of recovered materials or even innovations for re-using components in new panels.
Without funding, the UNSW team is at very early stages of research. Corkish says he’s been talking to ARENA for more than three years about the importance of the work. When he spoke to EcoGeneration in July it was felt a decision from ARENA on a bid for funding for research into recycling PV was imminent. “Work in advance of that has been small,” he says, although some undergraduate students have set themselves on the task with typical relish.