It ain't easy

Ever wonder why even knowledgeable folks disagree? Or at least appear to disagree? Here's a good example.

In the May/June 2005 issue of Resurgence, in an interesting article on biomimicry, you will find the following: "...for every hundred particles of light that strike the leaf, ninety-three are turned into sugars." (p. 21.) It would be easy to conclude that photosynthesis is 93% efficient at turning sunlight into stored energy. In fact the author, Janine Benyus, suggests just that: "A leaf has tens of thousands of tiny photosynthetic reaction centres. They're like molecular-scale solar batteries operating at ninety-three per cent quantum effficiency..." (p. 21). Wow! Let's duplicate that process, post haste!

Now fast forward a few months to the Jan/Feb 2006 issue of Solar Today. In another interesting article, on possible near-future breakthroughs in solar technologies, we find the following: "...even the fastest growing crops...on average convert only 0.3 percent of the incident solar energy into stored chemical fuel energy." (p. 18.) Whoa! Let's not duplicate that process! Silicon does better than that, by a whole lot!

Are these compatible claims? Sure. One refers to the relative number of photons that get converted; the other refers to the amount of energy that gets converted. But how many readers are going to make the effort to really understand what is being said in these statements? In fact, unless one happened to read both articles (or some other pair of conflicting statements), there would be little inclination to seek out the true--as opposed to the apparent--meaning of what is being said. As long as the author writes coherent prose, we just nod right through to the end, chalking up another entry in the "knowledge gained" column.

And I would have been one of those folks just nodding through. I would love to believe that the leaf is the most efficient solar cell ever discovered. Why? Because I find biomimicry to be a very appealing strategy generally, so I'm inclined to try to make it work in all cases. It was by sheer accident that I happened to read both articles within a period of a week. Moral: I need to work harder at seeking out conflicting--or apparently conflicting--positions on my most cherished views. Otherwise, I won't be careful about uncovering the true meaning of what I read.

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Note: After I wrote the above piece, I did some further research on photosynthetic efficiencies. One of the often-stated values for the efficiency of photosynthesis is 5%. In fact, if you leave out the "losses" that occur as the plant works to keep itself alive (respiration), efficiency values as high as 13% have been calculated. The fact is, we are interested in the net value, and that requires that we subtract the losses incurred by the plant in keeping itself alive. So we can't use the 13% figure. It turns out that different plants have different efficiencies, so values from 0.1% to 8% (claimed by some for sugarcane) can be found in the scientific literature. The point remains, the energy conversion efficiency for photosynthesis is no where near 93%, while solar cell energy conversion rates, in many cases, now exceed even the most generous numbers offered by scientists for photosynthesis.

As Louisiana goes, so goes the nation

I have recently completed reading two remarkable books. Mike Tidwell is the author of both. The first, Bayou Farewell, has dual themes. On the one hand, it is a beautiful portrait of life in the Louisiana bayou country, with an especially detailed account of Cajun life and culture. On the other hand, it is a detailed description and analysis of the ongoing destruction of the vast Louisiana wetlands. This was written before Katrina and is a remarkably clear account of why Katrina ended up being as devastating as it was. The second, The Raging Tide, was written post-Katrina, and is the hands-down best account I've read of one of the likely consequences of global warming, namely, the rise in ocean level. New Orleans (and Louisiana in general) emerges as the model for understanding the consequences of ocean level rise.

If you read only one of these, make it The Raging Tide. If you are inclined to read both, then I suggest you read them in chronological order, with Bayou Farewell first. (I read them in reverse order, which certainly works, but it is not as dramatic.)