Ask the EcoGeek: The Power Cost of Solar


Dear Mr. EcoGeek,
I've heard that it takes more energy to produce photovoltaic cells than the cells will ever produce throughout their lifetime. Is there any truth to that, or are those naysayers just saying nay?

David
Spokane, WA

Short Answer:
Those naysayers are just saying nay! But that doesn't mean there's not more to this story.

Long Answer:
This myth was probably perpetuated by studying solar panels created for NASA. If you need something extremely efficient for use in outer-space, yes, then it doesn't matter how much energy you use to create the panel. But for use hear on Earth, it's ridiculous for anyone to say that solar panels consume more energy than they produce.Of course, doing anything in this world takes energy. Whether it's building power lines or shipping oil from Saudi Arabia, it takes energy to make energy usable. In fact, there's a nifty number that puts all of this into perspective. It's called the "energy balance", and it is, in short, the amount of energy you get out divided by the energy you put in.

So, for corn ethanol, for example, we get 1.3 units of energy for every 1 unit we put in, so its energy balance is 1.3. Whereas for Brazilian sugar cane ethanol, we get 8 units of energy for every one we put in. As for gasoline, its energy balance is about 5.

So what does this have to do with solar? It is a bit incorrect to apply energy balance to solar panels, because they don't actually contain the energy, so it's not something that I've ever actually seen done. But I think it makes sense to fudge it a bit in light of your question.

Data from a study(pdf) from Energy Environment and Economics Inc. showed that the average solar panel gets five times more energy out than was originally put in. Roughly the same "energy balance" as gasoline.

Still, no one is satisfied with that number. Thousands of scientists, engineers and business people are working, right now, to increase solar's energy balance, and many have done it substantially. The simplest and most common methods include making sure that the panels are always at a 90 degree angle to the sun, increasing the life of the panels, and decreasing the amount of photovoltaic (PV) material needed in the panels.

As PV material (usually polysilicon) is energy intensive to create, a lot of folks are trying to figure out how to use less of it. One common method is to use mirrors or lenses to concentrate the sunlight on a relatively small amount of polysilicon material. Additionally, a whole other branch of the solar industry is trying to make solar panels from less energy intensive materials, including the much touted copper indium gallium selenide (CIGS) thin-film solar panels.

There may be some economic reason to not be an early adopter of solar, but there is certainly no doubt that they produce a lot more energy than they consume. And soon, they'll be producing even more.

If you've got a question for the EcoGeek, send it to ecogeek@ecogeek.org.

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