Manufacturing solar panels can be a dirty business, from the mining of raw materials to the chemical-laced process of purifying silicon to the assembly of silicon wafers.

 

Solar energy is a renewable source, of course, but it’s essential to examine the full supply chain to gauge its total environmental impact. One potential concern is the use, containment, and disposal of toxic chemicals. Another is the energy-efficiency of the manufacturing process and the source of the energy used.

 

Researchers at Northwestern University and the U.S. Department of Energy’s Argonne National Laboratory recently examined the solar panel production process in different locations and published their findings in the July issue of the journal Solar Energy. “We estimated that a solar panel’s carbon footprint is about twice as high when made in China and used in Europe, compared to those locally made and used in Europe,” says Fengqi You, a co-author of the paper and an assistant professor of chemical and biological engineering at Northwestern. “While it might be an economically attractive option to move solar panel manufacturing from Europe to China, it is actually less sustainable from the life cycle energy and environmental perspective.”

 

The primary differences, the researchers found, are the less stringent enforcement of environmental regulations in China coupled with the country’s more coal-dependent power sector. “It takes a lot of energy to extract and process solar-grade silicon,” says co-author Seth Darling. “And in China, that energy tends to come from dirtier and less efficient energy sources than it does in Europe.”