With fewer environmental standards for factories and more electricity generated from non-renewable sources, China’s carbon footprint is about twice as large as Europe’s. This makes China’s manufacturing of energy-saving tools, such as solar panels, less sustainable, according to a new study. Researchers from Northwestern University and the U.S. Department of Energy’s Argonne National Laboratory found the manufacture of solar cells in China uses substantially more energy than the same processes in European countries. “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,” said Fengqi You, assistant professor of chemical and biological engineering at Northwestern. This chart shows the number of years that certain types of solar panels must operate in order to generate enough electricity to “pay back” the energy used to make them. Because there are fewer energy regulations in China, panels made there have been found to use more energy. Courtesy of Fengqi You, Northwestern University. Energy and greenhouse gas emissions in the manufacturing processes were compared between Europe and China using a life cycle analysis systematic evaluation. This calculates the total energy used to make a product, including what it takes to mine raw materials, fuel used to transport materials and products, and electricity to power the processing factory. The researchers also compared costs of different types of silicon solar panels. They found that the process of manufacturing this type of panel in China typically takes as much as 30 percent longer, and consumes enough energy to cancel out the energy used to make it. “It takes a lot of energy to extract and process solar-grade silicon, and in China, that energy tends to come from dirtier and less efficient energy sources than it does in Europe,” said Seth Darling, a scientist with Argonne and a lead researcher on the study. He noted, however, that the researchers expect this to improve “as China strengthens environmental regulations.” Single-crystal solar panels demonstrated better efficiency in harvesting energy than other types, but the researchers said the energy renewal process takes much longer because the manufacturing is more energy-intensive. The work was funded by the Institute for Sustainability and Energy at Northwestern University. The research is published in Solar Energy (doi: 10.1016/j.solener.2014.04.008). For more information, visit www.northwestern.edu.