The Problem with Solar Energy

Over at The Island of Doubt, James Hrynyshyn has a post about solar skepticism on the part of some researchers, who think that claims of increased efficiency are often overhyped.

Of course, efficiency isn’t the only issue. A couple of weks ago, we had a colloquium talk by Peter Persans of RPI, who is working on developing new types of solar cells using amorphous silicon and “quantum dots.” He opened the talk with a fairly sobering description of the energy situation, though, which really puts the challenge of solar energy into perspective.

As best I can reconstruct it, the argument went like this: In order to meet the energy needs of the US entirely with solar power, we would need to cover 0.2% of the land area of the United States with photovoltaic cells, roughly equal to the area of paved roads in the US. And that’s using solar cells with an efficiency of 50%, not too far below the theoretical maximum for a single-layer device.

But efficiency isn’t the only problem: He pointed out that in order to build that sort of solar energy infrastructure, we would need to produce and install 2,000 square kilometers of solar cells a year for twenty years. To put that in perspective, we currently produce about 200 km2 of plastic film a year– plastic wrap, garbage bags, etc.– so we’re talking about producing complicated solar cells at ten times the rate that we make plastic wrap. That’s what they call a “significant technical challenge.”

Of course, it wasn’t entirely downbeat: he did note that great strides have been made in the production of solar cells, and described some intriguing possibilites using “quantum dots” embedded in silicon as a means of increasing the bandwidth of light that produces useful electricity. And there are other ways to use solar energy than direct photovoltaics.

Still, the plastic wrap number is really eye-opening. Research into better solar cells is absolutely critical (and that fact that funding was killed by Reagan in the early 80’s is nearly criminal), but even if some brilliant scientist makes a dramatic breakthrough tomorrow, solar is not an overnight solution to our energy problem.