As the price of solar power plummets, the uptake of solar panels and rooftop solar is booming. The more this surge accelerates, the easier it will be to mitigate climate change.
But the materials and processes needed to build solar panels (or PV, photovoltaics) are not carbon-free. Research from the University of New South Wales (UNSW) points out that the aluminium in solar panels will need to be made sustainably to minimise panels’ emissions.
“Lots of people get focussed on silicon, and they talk about the silver,” says Professor Alison Lennon, a researcher at UNSW and chief scientist at Sundrive Solar.
“But when you actually install a PV system, the modules have got to have frames. And then you’ve got to put the modules onto the roof, and often there’s a tilt, and there’s a lot of aluminium that goes in all that railing.”
Other parts of the kit, such as the casings for inverters, are also often best made with light, waterproof aluminium.
Unlike more precious metals, there isn’t a predicted shortage of aluminium. But the researchers caution that aluminium needs to be found and purified in more sustainable ways than it currently is.
“There’s actually quite a lot of aluminium in the Earth’s crust,” says Lennon.
“In Australia, we have enormous amounts of aluminium resources, or bauxite. It’s more a matter of the global-warming potential of refining all that bauxite into aluminium, because it requires so much energy.”
Currently, a lot of the world’s bauxite is refined in China, using fossil-fuel power. Lennon says localised aluminium production, particularly in Australia, could be much less carbon intensive.
“We have a number of refineries to produce alumina, and we have four smelters to convert the alumina to aluminium,” she says. “All our smelters are in renewable energy zones or already using hydroelectricity.”
Refining aluminium here would be better for both the economy and our emissions. Moreover, aluminium is very easy to recycle, making the end-of-life handling for solar panels far more straightforward.
Lennon is lead author on a paper published in Nature Sustainability, which examines the aluminium demand for solar panels.
According to the International Technology Roadmap for PV, the world is going to need more than 60 terawatts of solar PV to reach net zero emissions.
“At the moment, we have about 800 gigawatts of PV, globally,” says Lennon. That’s roughly 1.3% of the required amount.
The team’s analysis used data from Chinese predictions on the amount of aluminium which will become available for recycling to determine how much aluminium would be needed to be mined from bauxite each year to satisfy this solar spike.
It found that, in a worst-case scenario, this aluminium demand could be responsible for an additional overall 3500 megatonnes of CO2 equivalent in the atmosphere by 2050.
But there is also a low-carbon path for aluminium production. If effort is made to recycle all the aluminium currently in use (a relatively simple industrial process), and research is done into further ways to decarbonise the production, aluminium could be responsible for less than 1000 megatonnes of CO2 overall by 2050.
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Lennon says Australia has potential to lead in this best-case scenario.
“There needs to be some discussion about whether we should actually be making our own PV modules in Australia,” she says. “There are economic reasons for doing so. I imagine there are energy security reasons for doing so as well.”
Setting up this industry would require “quite significant government investment”.
“But the other aspect, which is linked, but could also be independent, is really trying to provide incentives for the aluminium industry to rapidly decarbonise.”
This involves using renewable energy in smelters, and investing in research to take additional emissions out of the process.
This is all achievable, according to Lennon.
“I see aluminium as an easy case,” she says.
“Do we want to start producing silicon ingots here? That’s a lot more complex. That’s a lot further down the path.
“But there is already an existing aluminium industry in this country.”