It makes perfect sense to use plants to harvest solar energy in solar panels or cells, as they're nature's original solar-energy harvesters. I am only surprised this type of research hasn't been going on longer. I think if there can be a way to use this method commercially, it could be a real breakthrough in solar energy cell development and certainly make the cells more environmentally friendly.
Thanks for posting, it's interesting stuff. I was however puzzled at the claim of 100% efficiency in plants (or for photosynthesis, so I googled it and got this from Wikipedia: "which results in an overall photosynthetic efficiency of 3 to 6% of total solar radiation". Sugarcane is the exception achieving up to 8% This is a far cry from the 24% achieved in labs for silicon photocells. Wikipedia talks about the theoretical maximum being ~40% for the wavelengths that plants utilise but a lot of real world stuff gets in the way. This match more closely what I remember.
The efficiency discussed in the Wikipedia article is for the conversion of sunlight into biomass. The starting point, 100%, is for the conversion of the entire bandwidth of sunlight that falls on the leaf into biomass. The calculation of inefficiencies begins with subtracting all bandwidth that is not bioavailable, then all that is reflected from the surface of the leaf, and all photons that strike components other than cloroplasts. Energy used to make sugar, and energy used to keep the plant alive in the dark or to maintian roots are also deducted. This is therefore a measure only of what ends up as new growth, or biomass (while from the "plant's point of view" the goal is survival as a whole, and job well done!)
The scientists in the article are likely referring to the efficiency of the thylakoids, starting with 100% of bioavailable wavelengths that actually strike the cloroplast, and at only the conversion to electrons after splitting the water molecule. In fact, I think they are referring to the efficiency of the thylakoid for conversion of light to electrons.
There is one other inneficiency cited in the Wiki article that may affect the accuracy of the claim by the scientists:
"24% of the absorbed photon energy is lost due to degrading short wavelength photons to the 700 nm energy level"
If this loss is after absorption by the cloroplast but before the conversion by the thylakoids, then the scientists may be referring only to the efficiency of the thylakoids.
If the resulting solor cell technology they create uses the modified thylakoids to directly convert sunlight into electrons then the only loss when measured as other solar cells are measured would be the 47% of non-bioavailable soar bandwidth, leaving at least 50% for conversion. That's quite a good conversion, and double current technology.
Thanks Karl, points well made but I think if you used the measure of how much of the solar radiation is a lattice match for Silicon (very narrow view) we would see higher numbers from silicon too up to 86% (although not as high as just the thylakoids). There's an IEEE article that suggests that quantum efficiencies of solar cells can exceed unity as sometimes two electrons are released for one photon. That's why I see narrowing the field of view to one thing only and not stating that is somewhat misleading. I'm not saying they are deliberately misleading us, more likely is a reporter left all of the stuff out he didn't understand resulting in the article.
Sometimes we can learn a lot from nature, but nature's way of doing things is not always the best way for humans to achieve the same purpose. That is why we have airplanes instead of ornithopters. Flapping wings work well for birds but would be way to complicated for a human-built flying machine. The question will be if this process can improve upon the efficiency of our current solar cells, and I think it will take a lot of research and development to get there.
I came a bit late to these comments so now I'm seeing yours, karl. So it seems that researchesr are not exaggerating and the figure is 100 percent efficiency for converting sunlight into energy? I think we can all agree this research provides an interesting prospect for organic solar cells and has some real potential to benefit their development. Thanks to everyone for bringing up these important points!
Interesting observation, etmax. So it seems like we are catching a researcher in a bit of hyperbole. I think perhaps the greater benefit here is the organic nature of the material--better for the environment. And perhaps with engineering researchers can achieve even greater efficiency.
I agree Elizabeth, the other thing is that if it's a chemical process rather that drawing ingots slicing slivers and etching microscopic structures I'd say that there is an opprotunity perhaps to make them so cheaply that you cover everything. The downside of biodegradable is of course longevity. In a plant the whoile process is continually renewed where as in a man-made panel the lifetime may be only a year or 2. Still if they cost $1 per kW that may not matter. BTW, I think probably it's not so much hyperbole on the part of the researcher but rather the narrow focus of their claim was not obvious to the reporter. I must say without a wonderful resource like Wikipedia I wouldn't have been able to pursue my hunch.
Thanks for that perspective, etmax. I completely understand where you're coming from, and you're right, longevity would be a tricky issue here. I think the truth about efficiency is somehwere in the middle of the researchers' claim and Wikipedia's info, but I suppose it will take testing and use of this technology to get to the truth. I still think it's quite promising, as you point out.
This really is a great discovery because it shows that they have obtained an adequate understanding of the actual mechanism so that they can obtain electrical energy directly.That portion is awsome. Now the challenge will be to enhance the process so that it is scaleable up to useful levels. After that, the remaining concerns would be the process lifetime and moving it to a commercially worthwhile product. Just because something works, even works well, does not mean that it can be a commercially viable thing. It might simply cost to much, but we don't know yet.
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