| Photovoltaics 100X More Efficient than Biofuel |
| Written by Hank Green | ||
| Wednesday, 27 June 2007 | ||
 A reader over at AutoblogGreen (one of my all-time favorite blogs) sent in a short essay comparing the efficiency of photovoltaics to the efficiency of biofuels. and ABG rightly saw fit to publish it. I'm not tremendously surprised that photovoltaics won...I'm just surprised by how big the difference is. Now biofuels are kinda like solar power. Plants capture the the sun's light and convert it to energy. We then convert the plants into fuel, and then turn the fuel into useful power. Photovoltaics skip a few of those steps, converting sunlight directly to power without any pesky nature getting in the way. It turns out that creating biofuel with an acre of land produces about 100 times less power than covering that same land with solar panels. While it's fascinating to discover, the sad fact is, it doesn't really matter. We can hope that someday our global footprint will shrink. But right now, it doesn't matter how much space we take up, it only matters how much money we spend. What we really need to see is a per-unit-of-power analysis of the cost of biofuels vs. photovoltaics. It's my guess that that analysis will make it quite obvious why no one's replacing corn fields with solar panels. Via AutoblogGreen
Comments
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written by Nick , June 28, 2007
What I'd like to see is, before they consider the costs, factor in the effects that weather might have on energy capture... I imagine these numbers would be region dependent, and while sunnier areas might have a larger benefit from solar power, if it is possible to grow plants that can produce ethanol in very rainy, cloudy areas (I imagine it would be, but I don't know) then ethanol might even gain an advantage over solar power.. just a thought
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written by Jim , June 28, 2007
You don't measure photo cell area in hectares.
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written by mind , June 28, 2007
wow! and keep in mind that the ethanol has to be burnt and go through a thermodynamic cycle, whereas the electricity "merely" needs to be transmitted and stored. (although of course producing batteries is a lot more complex than producing an engine)
i look forward to some developments in possibly less efficient, but really cheap and durable solar cells. imagine the economics being such that you'd be foolish to -not- put them all over roofs of new construction. the thing about ethanol that i'm sure makes it appeal to more people, is that the biomass is grown somewhere else, and the end result is some magical liquid that they can continue to put in their cars just like they're used to. given the tendency of government to screw up whatever it touches, it's no wonder they're pushing ethanol :p
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written by Rob , June 28, 2007
you're comparing apples to oranges here. as mind has stated the step down efficiency of the ethanol with it mechanized and chemical process are of course going to make it drastically inefficient. besides ethanol has one of the worst energy content of the biofuels sector. i would have liked to see other fuels included in the comparison.
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written by Nathan , June 28, 2007
I think the efficiency of land use is very important especially as our fuel supply increasingly effects our food supply, but there are a few important omissions in the analysis that was given on Autoblog.com. First, this doesn't take into account the energy produced from the lignin. In most scenarios that I have read lignin is used to power the entire operation of the ethanol refinery. It is predicted that enough energy can be produced by lignin that the company can sell electricity to the grid. Secondly, I don't know if this analysis looks at only cellulose to ethanol or also takes into account hemicellulose to ethanol. Thirdly, half of the sugar molecules turn into ethanol and half are converted to CO2, if we can capture the CO2, say in Algae, and harvest the oils then we can increase the efficiency of the process tremendously.
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