Paying Back Over a Lifetime

This post isn’t so much about erosion—the closest I can come is to claim it’s vaguely about sand—but I think there’s an interesting question here nevertheless. An article  published last month in the Economist, commenting on research recently conducted in the Netherlands, discusses the “greenness” of solar panels. Solar energy, it acknowledges, is certainly clean energy; no carbon dioxide is produced as solar panels generate electricity.

What researchers at Utrecht University wanted to know, though, is whether the process of creating the solar panels takes more energy—such as electricity that comes from burning fossil fuels—than they save. “Melting and purifying the silicon that these panels employ to capture and transduce sunlight needs a lot of heat,” the article notes. “Silicon’s melting point, 1,414°C, is only 124°C less than that of iron.” Each solar panel therefore begins its working life with a “carbon debt.”

So the question is whether, over its lifetime, the panel can repay that debt by producing more energy than went into its creation.

The study, published in Nature Communications, calculated how much energy was needed to produce all of the solar panels installed worldwide for the last 40 years. Unlike some earlier studies that looked at the same thing, though, this one took into account the fact that the process of manufacturing the panels has steadily become more efficient. But it depends on where the panel was made—in a country that relies heavily on fossil fuels to generate the electricity to power the furnace that melts the silicon, or in one that uses cleaner energy? The researchers concluded that a panel made in China starts with a carbon debt nearly double that of one made in Europe, but also that a panel installed in China provides a greater overall benefit because the electricity it generates replaces energy generated by burning coal.

The researchers then calculated the carbon savings from those panels—how much clean energy have they produced that would otherwise have come from gas or coal? Again, it’s not as simple as it might seem. “Depending on the numbers fed into the model,” the article says, “global breakeven could have come as early as 1997, or might still not have arrived . . . Under even the most pessimistic assumptions possible it will do so in 2018.”

And there are still other variables to consider. As this item from Energy Storage Solutions notes, the mineral perovskite is showing promise as a material for solar panels, with a greater efficiency than silicon.