Many secrets lurk beneath the surface of a solar panel (image: sxc.hu)
Solar panels are a double-edged sword. On one hand, they’re a great way to get clean electricity. Unlike fossil fuels, sun power isn’t radically altering our climate, and we won’t be staring down the barrel of a “peak sun” problem for at least another 5 billion years. On the other hand, they are relatively expensive (per watt) compared to other energy sources, and the materials used to make them tend to be rare, toxic, or both. For example:
Gallium Arsenide – A semiconductor compound used to build the solar cell; it’s made out of gallium (rarer than gold) and arsenic (a deadly toxin)
Cadmium – Used in energy-absorbing alloys (so toxic there’s a whole kind of poisoning named after it)
Silicon – A more efficient semiconductor than cadmium alloys (very expensive due to widespread demand)
Toxic Sludge – The solar power industry produces millions of pounds of this waste per year (carcinogenic and poisonous)
All of which makes this bit of news from Science Daily that much more of a game-changer: Stanford researches have created solar power cells made entirely from carbon. Carbon, of course, is abundant, cheap, and non-toxic* (and the materials used here are not adding to the atmospheric carbon that causes climate change). The downside, at the moment, is that the cells aren’t very efficient compared to normal photovoltaics. But the technology is very new, and in the future we could very well see a whole industry of carbon solar panels.
Now that’s clean energy. For more, see the abstract at ACS Nano.
*Correction: Carbon’s toxicity is actually highly variable, depending on its form (see the comment below). The Stanford team used nanotubes and sheets of graphene, the former of which may be carcinogenic at some level. The latter’s health effects are disputed. I should have made the weaker assertion that these are nevertheless significantly less toxic than cadmium and arsenic – not non-toxic.
(Sorry if today’s post was a little shorter than usual [and apparently under-researched!], but I’ve been working under deadline for the Urban Times on a piece about suburban sustainability. It’s submitted, and I’ll be excited to share it with you soon – but more importantly, I can turn my attention back to Cosmic Revolutions!)
Cosmic Revolutions 
This is a very important and awesome advance. However…
As an important point, carbon is not “non-toxic”. First my head swam trying to figure out how to explain the inaccuracies of that statement, (which is a fairly common sentiment might I add), and I think an analogy serves here.
Saying carbon is “non-toxic” is like saying the sun is made of iron.
Yes, technically the sun has some small amount of iron in it, but that’s hardly the whole story. Carbon does in fact have a large number of toxic forms (we’ll stick to “pure carbon” forms here, not compounds). Notably many forms are carcinogenic (ask a coal miner). Most carbon nano structures are toxic as well. So too, there are some relatively benign, harmless forms. The difference as a material (vs. gallium, cadmium, etc.) is that we can often convert one carbon form into another, and so might detoxify or recycle the carbon that way. Many metals like cadmium are toxic any way you find them.
It’s also not different than the carbon in the air.Carbon dioxide is constantly being converted to sugars, and those sugars converted back to CO2 through metabolism and decay. Further, all pure carbon forms (including diamond) are combustible, and that’s likely a “detoxification” route that would/will be sought by the solar power industry.
Several important questions arise from this advance. Is the carbon form being used toxic? Is it easier to recycle/dispose of than the heavy metal materials used now? My bet would be that toxicity issues, if not inherently negligible, can be mitigated, and that recycling of carbon nano materials can be done cheaply. These are very large challenges, however, and should not be taken either easy or certain.
This is a valid point. Carbon can be toxic in some forms. I should have first specified the exact forms of carbon used, and secondly asserted only that they were significantly LESS toxic than cadmium and arsenic, not non-toxic – I’ve actually made this correction in the text.
The specific materials used by the Stanford team were simple nanotubes and graphene sheets. The former might potentially be carcinogenic. The health effects of the latter are disputed, but I don’t think anyone would say they’re anywhere close to, for example, the problems associated with cadmium compounds.
As for the difference with atmospheric carbon, I just wanted to emphasize that the mere use of carbon-based materials does not have the same effect as burning carbon fuels. Of course a carbon compound is a carbon compound regardless of where it is; but carbon that is locked into a solid material will not contribute to global climate change (unless you burn it, I guess – please don’t start burning solar panels!).
I continue to wonder where our optimum energy sources will come from. Nothing appear simple or clearly superior when all factors are taken into account. Major conservation efforts seems essential, no matter where are our energy comes from. Whatever we use, use less.
This is a really good point. The cleanest energy of all is the energy you don’t use! Improved efficiency and smarter systems can help with this, without even affecting our quality of life.