03.09.2021

Electronic “zero waste”? AGH researchers are developing innovative methods of recycling photovoltaic panels


Professor Barbara Tora and the head of the research group Krzysztof Broda, DSc, from the Faculty of Civil Engineering and Resource Management during works on recycling techniques for PV panels /photo by 2loop Tech S.A.

Electronic waste as a rich source of valuable raw materials? It is possible! The research group under the guidance of Krzysztof Brody, DSc, from the Faculty of Civil Engineering and Resource Management creates innovative methods of recovering precious metals and other valuable elements from old electronic equipment. As part of the scientific and implementation consortium established by AGH in cooperation with 2loop Tech, the research group is preparing a technology for recycling renewable energy systems. The international group of researchers concentrates on the possibility of full recovery of photovoltaic panels containing elements such as silicon or silver.

The idea of ​​"zero waste" means, among other things, a strive for building a circular economy. Recycling is one of the ways to achieve it, that is, recovering raw materials from waste materials to deliver new products. In order to do it, each and every waste item should be treated as a potential source of resources. In this way, it is possible not only to protect the environment from pollution, but also to obtain valuable elements, the Earth’s deposits thereof, in light of the strong global economic growth, may soon be depleted. A good example of the "zero waste" philosophy was given by the organisers of the XXXII Summer Olympics, by making all medals out of electronic waste. The Tokyo Medal Project initiative gives the opportunity to every inhabitant of Japan of getting involved in the games by handing over waste equipment that contains some gold, silver or copper. This action perfectly illustrates the country's sustainable development strategy.

Separation processes

The question is whether everyone can arrange their own electronic Eldorado at home? Better not to do it, because waste equipment may contain poisonous substances. But some separation techniques are simple and known to everyone from chemistry classes. For example, the gravitational method which is based on different densities of materials. Others methods are more complex and require a laboratory as in the example of separation with thermal or chemical treatment. One of the most popular and effective methods of separating electronic waste components is the method that employs different magnetic properties of specific substances.

When recovering electronic materials, the electromagnetic method is very often applied. In low-field magnetic separators, iron can be separated, and in high-field ones, for example, copper and aluminium, which have weak magnetic properties - professor Barbara Tora says, who studies separation techniques at the Faculty of Civil Engineering and Resource Management.

Challenges for ecotechnology

Today, one of the challenges the researchers who deal with the separation methods of electronic waste face is the problem of recycling of so-called ecotechnologies. From year to year, more and more households decide to install renewable energy systems, such as, solar collectors, biomass boilers and heat pumps. It is not such a burning issue yet, but in a decade or two we will have to cope with the task of recycling waste household appliances. AGH scientists already think about the future and create new techniques for separating the components of the green power systems.

Scientific and Implementation Consortium

Once again proving its profound importance for the Polish economy, AGH established a scientific and implementation consortium with 2loop Tech - technology and research company. The agreement on cooperation on behalf of the university was signed by the dean of the Faculty of Civil Engineering and Resource Management, professor Marek Cała. The consortium aims at developing a technology for recycling PV module waste, which will allow for the recovery of almost 100% of the elements needed for production of this type of devices. Dynamically growing market of photovoltaic panels with 20 to 30 year service life will bring around 2050 in Poland the problem of recycling hundreds of thousands of tons of modules used for converting solar energy into electricity. This is the challenge the research group led by Krzysztof Brody, DSc, now faces. The group develops new techniques for recovering valuable materials from panels, which will be later implemented at 2loop Tech, where a recycling line for solar cells made of, for example, silicon will be built.

Photovoltaic panels separation methods

What exactly does the process of separating the PV components from each other look like? At present, thermal treatment and grinding of waste equipment are often carried out first. Due to costs and ecology, separation by means of furnaces is being gradually withdrawn, and the crushing method, which uses machines breaking panels or vibrating mills is only taken into consideration. The obtained product is then separated on a conveyor belt using optical separators or the granulometric (sieve) method. Mechanically separated glass can either be used to deliver new panels or transported to the plant for the production of bottles. Copper and aluminum, which are part of the conductors, can also be easily separated and melted. Silicon from solar cells, on the other hand, could be successfully recovered using a very interesting technique, developed in Poland over 100 years ago.

There is so-called the Czochralski method, a Polish chemist who devised how to make cells from silicon. It can be said that these cells are cultivated. Probably everyone at their science classes at primary school learned the method of crystallization, which consists in putting into a glass with dissolved salt a string on which crystals are formed. In this case it is exactly the same, the salt, however, dissolves in water at ambient temperature, silicon, in turn, needs a solvent that will be heated up to the temperature of 1414 degrees of Celsius - professor Barbara Tora explains, who is also a member of the scientific and implementation consortium.

Can a medal be made from solar cells?

The fact is that one gold ring can be recovered out of 10 mobile phones. Can you also make jewellery from photovoltaic panels? It appears that one of the important elements of older generation solar modules is silver, a good conductor of electricity, which can be recycled and jewellery can be made out of it. It is estimated that one standard photovoltaic panel, consisting of, for example, 60 cells, contains up to 8 grams of silver. Medals made of this metal, awarded during the Olympic Games, weigh 550 grams, which means that almost 70 photovoltaic panels would have to be fully recycled to make one such trophy. What is more, many of these pieces of equipment contain also copper, which is the main component of the alloy known as bronze. The materials from waste systems could, therefore, be used to produce up to two out of three Olympic medals.

It is definitely not worth throwing away the electronic waste!