Solar Trash — How Can We Keep Solar Panels Green?

They’re everywhere. On rooftops, powering devices, running neighbourhoods and so much more. Currently, there are just under 100 billion solar panels in use in the world! Don’t get too comfortable though — solar panels have a lifespan of around 25 years. This means that within the next decade, billions of solar panels will be reaching the end of their lifespan. What then?

Currently, around 90% of solar panels get sent to landfills. The remaining 10% gets recycled. By 2010, there were about 10 billion solar panels in use. This means that by 2035, at least that many will be at the end of their lifespan. Given the current landscape, 9 billion of these solar panels will be sent to landfills if nothing changes. It might even be a lot worse, with HBR (Harvard Business Review) economists saying that:

“By 2035, discarded panels would outweigh new units sold by 2.56 times.”

This is a problem — in fact, some governments even classify solar panels as hazardous waste! Other than glass and silicon, they contain many toxic chemicals like lead and cadmium. This makes solar panels extremely harmful when not disposed of correctly.

This can have a few consequences. One major problem is groundwater. with solar panels in landfills, toxic chemicals can easily leach into groundwater and eventually lead their way to humans in the form of water and crops.

So what can be done?

Well, here’s a look at the current recycling process.

A common method of recycling is to remove the aluminium frame and wiring and then shred the panel. This makes it easy to sort the remaining valuable metals like silver, copper and lead after milling the glass out.

Removing the aluminum frame and wiring is very simple — those parts are just simply detached. After this, the process gets a little more complicated.

First, the photovoltaic (PV) modules are shredded into large pieces. Then, into smaller 5mm pieces. The pieces are then placed into a “leaching drum” where the semiconductor films are dissolved and removed.

Solar panels being shredded (Gerard O’Laoi)

After this, the glass and EVA (ethylene vinyl acetate) pieces are separated with a vibrating drum. The glass is then cleaned and can be recycled as regular glass.

The metal compounds are cleaned and then can be reused in semiconductors.

This process recovers 90% of the glass and 95% of the semiconductor materials, says Prof. Marina Lunardi!

The price of recycling a solar panel can be around 10 times (Forbes) more expensive than sending it to a landfill!

Besides the environmental benefits, the benefits of solar panel recycling include economics too. If recycling solar panels can be more efficient and cheaper, the materials in a recycled solar panel can actually turn a profit for solar energy companies! Having solar panels as part of a circular economy would not only help economically but tie back into the environmental benefit of having mass adoption of solar panels.

So why aren’t more solar panels recycled? Well, it simply doesn’t make financial sense. Sending solar panels to landfills is extremely simple since they’re just taken directly to landfills. This is in comparison to the recycling process, which requires specific, proprietary processes like the shredding and vibrating drum. Since these aren’t standard industry processes, The machines, etc. needed are more expensive. After recycling, the materials don’t hold much value either. They‘re common materials.

One way of economically incentivizing solar panel recycling is to find value in the recycled solar panels — after all, one man’s trash is another’s treasure! If we can make recycling solar panels an economically good decision, mass adoption could be very possible.

So where can we find the value in solar panels? Let’s take a closer look at silicon. If we could convert this material into something of more value, the ones recycling these solar panels can sell the raw materials for higher costs. This would make the recycling process cheaper overall.

One Kilogram of silicon nanoparticles, or nanosilicon, can retail for about $36 000 USD. Imagine there was a process to convert silicon from recycled solar panels to nanosilicon!

It turns out there is.

1. The first step is the same as the current recycling process — separating the solar cells from the aluminum frame, wiring, EVA and glass, then shredding the solar cells.

2. A chemical etching process using potassium hydroxide (KOH) chemically removes all parts of the solar cell except for the silicon. The solar cells are essentially soaked in KOH, which melts and dissolves the materials.

3. The silicon is then purified. It is turned into a compound with Hydrogen, Carbon and Iodine called Trichlorosilane. Then, this is distilled to purified silicon. This gets the silicon in used solar panels 80% pure.

4. After, that, the silicon is run through a ball mill, which grinds it down to a powder of <100nm particles. A ball mill is essentially a rotating cylinder with balls inside. When the silicon is fed into it, the impact of the balls will crush it.

A ball mill

Using this process, it would only take the silicon in 6 solar panels to get a kilogram of nanosilicon! This means that with this process, recycling just 6 solar panels can turn immense amounts of money. Imagine we could bring the cost of recycling solar panels to cheaper than the cost of sending them to a landfill. If this was done, many more people would do it!

Even though the bulk of the solar panel is still being sold for very minimal costs, the nanosilicon would retail for $36 000 USD/kg. Of course, this is all just an idea right now, but the potential of this is high.

Let’s recap.

  • Currently, 90% of solar panels are thrown in landfills. This is more than 9 billion solar panels by 2035.
  • Something needs to change.
  • Solar panels aren’t recycled because the recycling cost is 10x more expensive than landfills!
  • This is because the recycling process is proprietary and the raw materials are low value.
  • Converting the silicon in the solar panels to nanosilicon (a smaller version of itself) can make its value skyrocket.
  • Currently, researchers are working on refining this process, which is to take the silicon from the regular recycling process and run it through a ball mill which makes it smaller through impact.
  • This would give the silicon in the solar panels a value of $36 000 USD/kg, or every 6 solar panels. This would increase the adoption of solar panels and stop the looming problem of billions of tons of potentially toxic waste.

With such high value in end-of-life solar panels but also the risk of horrible climate impacts, finding a way to make sure solar energy stays green is the goal.

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