The story of solar PV manufacturing today is one of Chinese dominance and the pressures, and allure, of severely low-cost manufacturing. But we shouldn't lose sight of the bigger picture of why we're all fighting for solar and all renewable energy sources in the first place: a cleaner, more responsible energy future. (That's one of the biggest dichotomies about China: its massive renewable energy push is more than offset by its deep reliance on dirtier energy sources.)

"The fact is, we cannot any longer ignore things like carbon footprinting -- especially in the energy space, where we should be the people most aware of the issue," pointed out Seth Darling, scientist with the U.S. Department of Energy's Argonne National Laboratory, co-author of a new study with Northwestern University seeking to close the gap between bottom-line economics and environmental values. "Today it's essentially being ignored."

In their new study to be published in the July issue of the journal Solar Energy, Darling and peers examines the broader impacts of supplying Chinese solar panels to European end-markets. In a nutshell, they find that mainstream Chinese-made silicon solar panels have more than twice the carbon footprint than panels made in Europe, and take up to 30 percent longer to offset the energy used to make them. And that doesn't include transportation costs to get them to Europe, which would magnify the discrepancy even more.

The key is establishing a lifecycle analysis (LCA) for Chinese PV suppliers, something already established for European and North American supply chains but glaringly underinformed for China where there are different and often less-stringent industrial and environmental rules. The team performed a LCA scenario comparing Chinese and European manufacturing of three kinds of silicon-based solar PV technologies, from mining the raw materials through processing into solar panels, and calculated how long each type of panel takes to offset the energy used to make them. (Monocrystalline was found to have the longest energy payback period despite the best energy output; "ribbon" silicon, stringing out the material from a molten bath, created the least efficient material but did so more efficiently and with faster energy payback.)

Carbon footprints of different types of solar panels made in China (CN) vs. Europe (RER). The colors in the bars
represent carbon-emission contributions from the different stages of making a solar panel. Source: Argonne National Labs

The same basic LCA comparison and result would similarly apply between the U.S. and China since U.S. energy mix and environmental regulations are similar, Darling acknowledged, though only a fraction of solar panels are made in the U.S. They didn't explicitly explore that comparison using U.S. data within the scope of this study, though.

The next step after raising the issue of LCA and carbon footprinting is what to do about it. Ultimately these findings point beyond simply advising whether it makes sense to ship panels from China to Europe -- it's about how to assign value to sustainable solar manufacturing, including where it should come from. And that brings the discussion into the ongoing turmoil of regional solar trade conflicts. "The way it's done now, it's Wild West and unfair," Darling said. Policies need to address how to come at the carbon angle, whether by taxing the emitters or placing tariffs on the final products and those who use them. Each has "their own minefields to navigate," he said. Folding their analysis into calculation for the EU/China tariff negotiations, the Argonne/Northwestern team suggests creating a breakeven carbon tariff model of €103-129/ton of CO₂, close to reported CO₂ capture and sequestration costs, depending on whether and how carbon taxes are finalized by each region. That, the report concludes, "would be a better market- and science-based solution than a solar panel tariff."

Lead image: Global change and Earth climate symbol, via Shutterstock