Solar energy is good news for planet Earth, but solar panels are not as climate-friendly as they should be. Researcher Martin Bellman is using the waste of "black gold" solar panel production to make new panels.
Solar energy is clean energy. Pure and simple. But things get more complicated when it comes to getting the raw materials needed to make solar cells. Not only do most of these raw materials come from China, but a third of them are lost in the manufacturing process.
"But these materials can be recovered as part of the manufacturing process," says Martin Bellman. "And maybe it will allow us to create a new solar industry in Europe," he said. Bellman is a senior business developer at SINTEF Industry and leads an international solar panel manufacturing project called Icarus. Solar panels currently provide 60% of global renewable energy growth.
From quartz to crystalline silicon
Bellman explains how solar cells start with the mineral quartz, which is used to make ultra-pure silicon. First, silicon is melted in a crucible and silicon crystals or ingots are extracted.
"The cavity forms a kind of cylinder that slowly pulls the silicon out of the shell and grows and expands," says Bellman. "It is then cut to make blocks with square sides, which are cut into thin slices, or wafers, as we researchers call them," he said.
A typical wafer is only 0.13 millimeters (13 micrometers) thick, and these wafers are used to make solar cells.
But all these sawmills produce a lot of sawdust. It's like chopping wood. part of the wood is lost during sawing. The same thing happens when you look at a silicon rod, even if you're using a thin diamond wire. Some material will always be lost in the form of "silicone dust".
Dead balance 35%
"We lost 35% of the silicon as black dust," says Bellman.
The researcher aims to use this powder, which he calls the new black gold.
"Today, we just dusted it off," says Bellman. What the Icarus project is doing is mainly finding ways to get dust back into the value chain and using it to make silicon chips and solar cells,” he said.
The dust is collected in a molten sludge mixture, which also contains contaminants from the sawing process, such as oxygen, carbon, nickel, iron and aluminum.
"This metal-contaminated silicon is not suitable for solar cells," said Bellman.
That's why he's working with colleagues on the Icarus project to find a way to decontaminate silicon dust so it can be recycled as a raw material for new solar cells. What we think of as waste today can be used for other products, such as electric car batteries. Many colleagues are experimenting with various methods to separate silicon from contaminated mixtures.
Pan-European Project
Of course, the aim is to make better use of raw materials, which in turn will be better for the environment and climate. But also the stated goal is that Europe should achieve greater self-sufficiency.
"Europe's solar panel industry used to be bigger than it is now, but everything was shifted to China," said Bellman. “Currently, we are very dependent on raw materials in Asia, and silicon is no exception. We plan to use silica powder to reduce our dependence on China," he said.
Bellman hopes the Icarus research project will become a new industrial base, possibly also in Norway. Norwegian energy is clean and in this context a huge advantage.
Silicone can be recycled, etc
The advantage of the Icarus project is that the researchers plan to recycle the quartz caps by melting the silicon before turning it into crystals.
"The melt breaks up as it cools in the furnace," says Bellman. “Every time you melt quartz, you have to get a new vessel and throw away the old one. Our goal is to use it as a feedstock for silicon carbide production," he said.
Silicon carbide is used in the electronics industry, among other things, and electric cars are one of the many products that contain this material.
"Normally we use what's called high-purity quartz to make silicon carbide, but it's very expensive," says Bellman. "Our idea was that we could replace high-purity quartz with crater waste, which is basically very high-purity quartz," he said.
The Icarus project is also looking at recycling waste graphite as a feedstock for use in batteries, among other things.
"High-purity graphite can also be cast," says Bellman. "It is used in furnaces where silicon crystals are extracted, but over time it has to be replaced as it loses its properties. Currently, the Icarus project works with graphite waste to recycle it," he said.
quote : New solar panels from waste solar cells (28 Nov 2022). Retrieved December 4, 2022, from https://techxplore.com/news/2022-11-solar-panels-panel.html.
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