One of the great debates when it comes to solar panels is what happens at the end of their life cycle. While many solar panels will last over 20 years, there are still considerations to be made for what happens to them when they are no longer viable. Building up renewable energy resources is absolutely necessary to combat climate change, but we also have to be wary of counteracting that good with excessive e-waste.
Let’s start at the beginning of a solar panel’s life. Solar panels are made primarily of glass, a metal frame, silicon cells, and wiring made of silver and copper. The silicon cells can be arrayed in monocrystalline or polycrystalline formats. Monocrystalline silicon is more efficient, as molecules are arranged in a single unified mesh. This results in an even, dark color. Polycrystalline silicon is cheaper since it’s amalgamating several crystals. These panels typically appear blue. The downside here is that polycrystalline solar panels are less efficient. Monocrystalline panels are 15% to 20% efficient, while polycrystalline panels are 13% to 16% efficient. This article digs into the chemical and component breakdown of solar panels.
If we’re on a quest to minimize e-waste, we need to know the environmental cost of leaving these materials in landfills, and the cost of producing them from virgin materials.
Silicon production is based on silica, which is derived from quartz sand. It’s typically heated with coal at a high temperature. Needless to say, using coal to combine carbon with silica is less than ideal. Silica mining isn’t great for the environment either. The vast majority of silica mining is happening in China, and most of it is for low-quality sand with a high carbon footprint. Even with improved silica mining, it’s a double-edged sword. Fracking used in oil and gas exploration requires silica sand. It’s safe to expect silica producers to sell equally to oil interests and solar panel manufacturers.
The latest methods of silicon production have reduced carbon footprints 12-fold, though these processes still have to propagate through the industry. From 2000 to 2019, the average carbon footprint of energy used in silicon production went up 43%.
At the tail end of a solar panel’s life cycle, research shows that cadmium, lead, indium, molybdenum, and tellurium are prone to leaching into the soil from discarded solar panels, but generally at low enough levels to by a minimal risk.
Most solar panels can last 20 years or so. Many manufacturers provide 25-year warranties, with expected efficiency losses between 5% and 10%.
Solar panels can absolutely be recycled and turned into new polycrystalline panels. Most metals are able to maintain purity when melted down and reconstituted. Silicon is a metalloid, which means it has some aspects of metals — and also a lower melting point than pure metals. This means it requires less energy overall to recycle solar panels.
Europe has mandated that manufacturers provide recycling options for their solar panels at the end of their life. Unfortunately, the U.S. hasn’t enjoyed similar life cycle support, making domestic recycling partners hard to find — 76% of producers currently do not recycle or reuse their panels.
Methods for recycling solar panels are still being actively researched and tested. One project with Fraunhofer Institute for Solar Energy Systems was actually able to increase the efficiency of a solar panel after going through their recycling process, though it still fell shy of the top-of-the-line solar panels available.
Recyclers first face the challenge of finding individual modules that are still usable. Then there’s extracting individual components, such as the silver weaving through the silicon cells. Then there’s extracting raw materials, like grinding up the glass cover or melting down the aluminum frame. Every process adds costs, and with the volatility of component prices and the race to the bottom for panel prices, it can be very tricky for recyclers to make it all worthwhile.
Despite these barriers, there are a handful of partners in the U.S. who can provide solar panel recycling.
In the end, recycling solar panels is hard. Even with promising new technologies for making the most out of old panels, economic incentives need to be there for recyclers to implement those techniques at scale. If the market doesn’t provide those incentives, we’ll be relying on governments to legislate that manufacturers foot the bill. That’s a tall order.