Solar Cells Without Heavy Metals

Many solar cells contain heavy metals. That could be a problem if there’s a fire. But actually, there are alternatives.

In the discussions about pollutants in solar modules, the focus is primarily on lead and cadmium. Lead is contained in solder. Cadmium is processed as cadmium telluride in specific thin-film solar cells. Both heavy metals can have toxic effects on the environment and the demand will have to be more closely aligned with supply just as in the case of Bitcoin Dust in the future or create sustainable ways to use the same.

Are there harmful substances in all solar cells?

Most manufacturers still use lead in the solder, says Jürgen Werner, head of the Institute for Photovoltaics (IPV). The German Solar Industry Association put the market share for Germany of all thin-film technologies, not all of which contain cadmium telluride, at around 1%.

Could photovoltaic systems be built from pollution-free solar cells?

Werner says unequivocally: Yes. Reasons, given earlier, such as cheaper production, no longer played a role due to technical progress. Like the Federal Ministry of Economics, he referred to manufacturers who already produce without lead and cadmium.

An exception applies to solar cells.

As per the government regulation, the value for lead is 0.1% of the total weight. And for cadmium, which is even more toxic, at 0.01%. However, photovoltaic systems are exempt from the directive. Despite heavy criticism, the EU Parliament approved a new version of the directive in 2010 with a large majority.

Do politicians want to change something about the exemption for solar cells?

A spokeswoman for the Federal Environment Ministry explained that photovoltaic modules are excluded from the scope of EU Directive 2011/65/EU, meaning that they “make an important contribution to achieving both national and European climate protection goals.” Unfortunately, inclusion did not seem necessary from a waste policy point of view. Therefore, no findings would lead to a reassessment of the situation.

Germany is also lagging when it comes to WEEE.

Accordingly, the manufacturers and importers have the legal obligation to ensure their old modules are taken back. Germany has not yet passed a national WEEE law. According to a spokeswoman, this is expected this year.

What do the researchers know about possible heavy metal emissions?

The Stuttgart researchers from the Institutes for Photovoltaic (IPV) and Sanitary Engineering, Water Quality, and Waste Management (ISWA) have shown in a study that pollutants can be released from defective modules through acidic solutions.

However, the solar cells were ground up until they resembled a powder. Michael Koch from the ISWA emphasizes that this was a “worst-case scenario,” i.e., an assumption of the worst case.

“There is no danger from intact photovoltaic modules that use these substances,” emphasizes the Federal Ministry of Economics spokeswoman. Koch emphasizes that holes caused by hail, for example, are probably not enough to cause damage. “We don’t want to say that the technology could be dangerous. As long as the module is fine, everything is fine,” he says.

Heavy metals in solar cells – the consequences of fire are unclear

According to the Baden-Württemberg Ministry of the Environment, landfilling of the photovoltaic modules is generally not permitted. If they end up in a landfill after a fire in exceptional cases, this could increase the risk of leaching. However, the exceptional dumps for fire debris are specially sealed.

Why are the researchers interested in heavy metals in solar cells at all?

According to the University of Stuttgart, more than 17 million tons of modules are installed worldwide. The service life is currently estimated at 20 to 25 years. There are also recycling processes on the part of the manufacturers. However, the scientists see the danger that defective or less productive modules could be disposed of improperly, for example, after further use in developing countries. As a result, they could end up on wild dumps, warns IPV director Jürgen Werner.

Therefore, researchers at Stuttgart want to investigate how these heavy metals can escape from photovoltaic modules. The aim is to understand the processes and identify the weak points so that future leakage can be slowed down or even prevented.

The Federal Ministry of Economics funds the Institutes for Photovoltaics (IPV) project and Sanitary Engineering, Water Quality and Waste Management (ISWA) with more than 800,000 euros.