After putting on his blue lab gloves, Martijn Ronchetti builds a solar panel layer by layer. First a back made of polyolefin, a fire and weather resistant polymer. Then a layer of copper, to lead the solar energy away later.
A sheet with adhesive foil, with the special property that it can also be detached again in the future and the composition of which is still a secret. Then the solar cells themselves, which are made of silicon and silver and look like a dark blue sky with constellations drawn in at close range. That adhesive film again. And finally, a sheet of glass that must be strong enough to withstand hail, rain, heat and frost for thirty years.
Moments later, all parts have been fused into one whole: a brand new solar panel. The special thing about this ‘module’, as the researchers in this TNO lab call the solar panels, is that all parts can also be taken apart. That makes it easy to recycle, if it ever reaches the end of its life.
It is a big difference with the solar panels that are currently appearing on roofs and in meadows. The layers are glued so firmly that it is almost impossible to take all the materials apart again. The result is that solar panels that now give up disappear in the shredder and then often find a destination as a soil hardener under roads. Harmful substances such as lead and pfas (poly- and perfluoroalkyl substances) also end up in the environment.
‘That will certainly be a problem’, says TNO researcher Martin Späth. After all, the waste mountain from solar panels will grow rapidly. To give you an idea: in 2020 solar panels made approximately one third of all electrical and electronic equipment that came on the market in the Netherlands.
Späth picks up a list of numbers. In 2020, 124 tons of solar panels were discarded in the Netherlands, 50 thousand tons are expected in 2030, and no less than 400 thousand tons in 2050. By then, the whole world will have a waste mountain of 10 billion solar panels, with a total weight of 60 million tons – ten times the pyramid of Giza.
It begs the question: are solar panels really that sustainable? What should we do with all that waste? And if we do look at the life cycle of a solar panel: how sustainable is the production? Is the energy it takes to make a solar panel in proportion to the yield?
Silicon
Atse Louwen, a Dutch scientist who specializes in the life cycle of solar panels, starts at the beginning. He describes how to make a solar cell – one with silicon, the type that is by far the most sold.
First, pure silicon has to be extracted from quartz sand, then it is crystallized: processes that require a lot of heat energy and electrical energy respectively. Then the silicon is cut into thin slices, and it goes to the factory where a positive and a negative pole are applied. Silicon has the property that an electron is released when a photon (particle of light) lands on it. The intention is that those electrons are all sent in the same direction, so that an electric current is created.
It is a production process that requires quite a lot of energy. And yet all solar panels together have produced much more energy than the production cost, Louwen calculated. ‘In 2011, the industry as a whole has already a tipping point achieved, both for energy and greenhouse gases’, says the researcher.
The balance sheet also looks favorable for the Netherlands. Louwen points to a recent study from a colleague, who calculated that a solar panel generates net energy here within 1.5 years. ‘And in Southern Europe that period is even one year. If you consider that a solar panel lasts about thirty years, each panel therefore produces fifteen to thirty times as much energy as it costs.’
So that’s not the problem. At the end of the life cycle. ‘Solar panels are made in such a way that they can withstand all kinds of weather influences for as long as possible,’ says Louwen. Everything is glued together very firmly. That makes it difficult to take them apart again.’
They also know this at the Open Foundation, which is responsible for the collection and processing of discarded solar panels on behalf of the suppliers in the Netherlands. ‘They are now processed in a very basic way,’ says Jan Vlak, director of the Open Foundation. ‘First the cable is cut off so that the copper can be reused. The inverter and connector come off. A machine presses the panel out of the aluminum frame, which is also recycled. The rest then goes into the shredder. It is ground into very small particles, a kind of fine gravel.’
The solar panel grit is then used for various purposes: it first serves as an abrasive in metal melting furnaces, after which the slag that remains in road construction is used as a soil hardener. ‘Until now, we’ve lost everything in this way,’ says Vlak. ‘I immediately acknowledge: these are low-value applications.’
Isn’t he concerned that lead and pfas end up in the environment in this way? ‘No, it is new to me that there is supposed to be lead in it,’ says Vlak. “And the slag is tested for leaching from materials before they are used as road surfacing.”
A useful application as a road pavement? TNO researcher Martin Späth sees it differently. ‘The waste from solar panels is simply dumped’, he says. And certainly, there is lead in today’s solar panels – while other electrical appliances in the EU are subject to a strict maximum amount, solar panels are subject to that directive. excepted† Späth: ‘Many of the current solar panels are soldered with lead. As long as they are shredded, it ends up in the environment.’
Atse Louwen, the researcher of the life cycle of solar panels, puts this into perspective. ‘Unfortunately, no technology is completely green. Burning coal produces even more heavy metals,’ he says. “They go straight into the atmosphere.”
However, it is clear that things will have to change in the future – everyone involved agrees on this. ‘In the long run, this will no longer be the case,’ says Späth. ‘If the amount of waste increases, it is no longer justifiable that these harmful substances end up in the environment. We still have to process a huge amount of panels that contain lead.’
So two things have to happen: it is necessary to devise better ways to process the current solar panels, and there must be more recyclable panels on the market.
Heavy metals
Also according to the Open Foundation it is ‘essential‘ to recover raw materials from solar panels, not least to make the Netherlands and Europe less dependent on the rest of the world. The foundation commissioned Martin Späth to list what is possible to recover glass, silicon, silver, aluminum and lead.
The first step is to separate the glass, the most important component by weight, from the solar cells themselves. ‘This can be done by means of pyrolysis, a combustion process without oxygen,’ says Späth. ‘In this way the adhesive film of ethylene vinyl acetate (EVA), which otherwise sticks to everything, disappears.’
Then the trick is to separate the silicon from the metals. Späth: ‘It is becoming increasingly attractive to do so. The EU wants to pass on energy costs in the import price, and it takes a lot of energy to make pure silicon. This means that it is becoming increasingly profitable to recycle silicon.’
Späth himself is working on a technique in which silver and silicon are separated. “It is becoming more difficult to mine silver and there is a huge demand for silver,” he says. ‘So there will come a time when we really won’t throw away silver anymore.’ Recycling will also become more economical as the volume of discarded solar panels increases.
The conclusion of Späth is therefore: the problem is solvable. ‘It is purely a question of costs, because all these technologies are of course much more expensive than the shredder.’
Significantly, the ‘disposal fee’ paid by suppliers is only 13 cents per panel. In the House of Representatives, CDA, D66 and GreenLeft questions about this. ‘The financing of high-quality processing of discarded solar panels in the future is not in order,’ admitted State Secretary Heijnen (Infrastructure, CDA) in response. She made no move to solve this, but put the responsibility on the Open Foundation.
In the meantime, Martin Späth and his colleagues at TNO are working hard on the solar panel of the future, which is already circular in its design – with raw materials that can be reused over and over again.
‘I think it ends up being the parts of a solar panel being replaced one by one’, Späth considers. “Not a revolutionary change, but an evolutionary one.”
For example, a small part of the solar panels no longer uses solder with lead, but electrically conductive glue. For the rear, an alternative is available without pfas, made from, among other things, polyolefin. Currently it is used in one in five new solar panels†
The different layers can be glued together with the ‘releasable’ adhesive film that is already being used in the TNO lab. It will only come on the market in four or five years, Späth expects. By this time, the glass plate can be effortlessly lifted from the panel to use it in a new round, as well as the solar cells.
Before that happens, all kinds of certificates have to be earned: for fire safety and lifespan. TNO carries out the corresponding tests. In special rooms, the solar panels of the future are exposed to climate extremes. The panel is dragged back and forth from a temperature of 40 degrees below to 85 degrees above zero, or spent thousands of hours in an environment of 85 degrees and 85 percent humidity.
‘The new adhesive film also withstands these kinds of weather extremes well,’ says operator Martijn Ronchetti, showing a panel without cracks. ‘The yield is not decreasing.’
Spath sighs. ‘A sustainable solar panel: it’s possible and it doesn’t even have to be more expensive. The industry is just very conservative. The manufacturers in China are not inclined to take risks: they now have materials that are proven to last thirty years. It is very difficult to compete with a tradition. But if China were convinced or compelled, it would go very quickly.’