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Scientists Recycle CO2 with Sunlight to Make Fuel
An anonymous reader brings us this article from Wired about a new method to produce fuel with the help of concentrated sunlight and carbon dioxide. The process "reverses" combustion, breaking down the CO2 into carbon monoxide, which is then used as a building block for hydrocarbons. Quoting:
"The Sandia team envisions a day when CR5s are installed in large numbers at coal-fired power plants. Each of them could reclaim 45 pounds of carbon dioxide from the air daily and produce enough carbon monoxide to make 2.5 gallons of fuel. Coupling the CR5 with CO2 reclamation and sequestration technology, which several scientists already are pursuing, could make liquid hydrocarbons a renewable fuel."
My grandfather used to be an employee in a biotechnology venture in the 30's. It was a two stage process. The first was a corn - or sometimes a potato - plant. The second was a still. ( He was a tinsmith. ) The input was CO2 and sunlight, the output was ethanol.
Here is a link for more technical information on how this works http://www.greencarcongress.com/2007/12/sandia-applying.html
It doesn't make sense to me: first you burn coal, which basically creates energy by oxidizing carbon and creating CO2; then you use solar energy to undo that and turn the CO2 back into CO. Wouldn't it make more sense to make electricity directly from the solar energy and not involve the coal at all? Besides which, if the CO is later used as fuel as they say, then eventually you're going to oxidize that anyway and create the same CO2 you would have in the first place. It seems like a very roundabout way to add solar energy into the mix.
2.5 gallons of fuel produced per plant, per day, per installed Counter-Rotating Ring Receiver Reactor Recuperator (CR5).
So long as any of the carbon in the cycle is coming from sources currently in the ground or oceans (e.g. coal, oil, natural gas, or methane clathrates). I.e. we are harvesting energy by oxidizing previously reduced carbon -- it is NOT RENEWABLE or SUSTAINABLE!
The only cycles which potentially work over the long term are: (a) solar; (b) fusion reactors; (c) breeder reactors; (d) thorium fuel cycle reactors. That is probably in decreasing order of length of time we could sustain our civilization off of those sources (your opinions may differ).
The coal power plant output conversion of CO2 to liquid fuels simply shifts the problem from an CO2 source one can easily sequester (coal plant smokestacks) to one which is much less easy to sequester (automobile exhausts). You have a fundamental problem here which is when are we going to incorporate the cost of "full sustainability" into our energy costs? That means any carbon you put into the atmosphere you pay to take back out of the atmosphere. Ideally you do more than that to reduce atomospheric CO2 levels back to pre-industrial levels [1], i.e. you are taking more CO2 out of the atmosphere than you are putting into it. We are currently very far from being able to do that.
So long as we continue to live off of the reduced carbon sources (stored solar energy harvested by plants hundreds of millions of years ago) and don't fully pay for them we have a real problem.
Robert
1. Or humanity makes a decision to allow the glaciers and icecaps to melt, the sea levels rise a bit, some islands and low lying areas get flooded, weather patterns to change a bit *and* spends the money necessary to mitigate the negative effects of these processes.
Warning, cape does not enable user to fly
Seems to be a couple years old though, this page (second story down) which includes the same photo is dated feb 2006, and includes a much better description of how it works, including how they use alternate direction rotation rings for heat conservation within the drum, although it looks like they've more recently been trying it with CO2 instead of H20. This page contains more info and diagram of the counter rotating drum. Very interesting stuff though.
The revolution will not be televised... but it will have a page on Wikipedia
It's nice that it might scrub pollutants but it seems the solar energy could be more profitably used to directly produce electricity.
Great idea in the equatorial region, but solar really doesn't count as an option in the polar two-thirds of the planet (at least not until we have near-100% efficient PV panels that cost a pittance).
I would also point out that very few companies seem to want to build solar power plants, even in ideal places such as the vast tracts of desert wasteland in the US SouthWest. I presume this results because the long term costs might look great, but the books would take a big hit up front, and most companies (or at least, their current boards) couldn't care less beyond next quarter.
Given those two facts, we can either talk endlessly about why we don't use cool-tech-X, or we can deal with the reality we have now: We use a LOT of cheap and dirty coal power plants. And it costs considerably less to retrofit them with spiffy scrubbers such as TFA mentions than it does to rebuild new clean plants.
Also, who says only power plants can use this? Why couln't I (and everyone else who might care enough to give something like this a try) buy one (probably a scaled-down version to make it affordable) and toss it in my backyard? Five or ten tons a year, times a few hundred thousand people who want a free gallon or two of gasoline per day, could really make a difference.
No one renewable energy source will solve all our problems. Between them all, however, perhaps we can at least keep the planet habitable for a few more generations of humans.
http://www.snopes.com/business/genius/spacepen.asp
Claim: NASA spent millions of dollars developing an "astronaut pen" which would work in outer space while the Soviets solved the same problem by simply using pencils.
Status: False.
Property is theft.
I am working on a similar process that synthesizes hydrocarbon fuels from carbon dioxide, water, and non-fossil energy (could be solar) and should eventually have some publications out about this. There are several ways to go about this. But first, let me comment on some of the comments:
... all this thing does right now is produce carbon monoxide." comment, reducing CO2 to CO is the hardest part of the process. Once you have concentrated CO, you can follow the coal-to-liquids processes and water-gas shift (CO + H2O => CO2 + H2) to get hydrogen and run the syngas (CO + H2 mixture) into Fischer-Tropsch reactors. They've been doing this for 50 years in South Africa to produce synthetic diesel.
Regarding the "They're leaving the production of actual liquid fuel to other people
Regarding the "Renewable not!" comment and using power-plant flue gas CO2 as the input to this process, this would indeed not be sustainable. However, if industrial capture of CO2 from the air is available, one can fully close the loop and have a sustainable hydrocarbon fuel cycle. Flue gas CO2 could be a good option in the short term, however. For instance, if solar and other nearly-carbon-free energy sources begin to rapidly take over, coal plants will not immediately be shut down. Other CO2-emitting industrial plants such as aluminum smelters, etc, will also have CO2 emissions to deal with, and this form of using it to store non-fossil energy by recycling it once as a liquid fuel would be worthwhile. One comment discussed this transition well.
Related, other comments say "why not just use the solar energy to produce electricity". These intermittent resources need storage, and liquid fuel storage is not a bad method (and very versatile). Others responded about storage.
So, processes like this are a way to store non-fossil energy as a convenient energy-dense fuel which can be used in our existing petroleum fuel infrastructure and vehicles (as opposed to hydrogen and batteries). Biofuels can do the same, and there are many comments above ("I saw something like this... it's called a tree") mentioning biofuels and how this process replicates it with much more complexity; indeed you could call this whole process including the Fischer-Tropsch fuel synthesis "artificial photosynthesis". However, this process cuts out the middle-man of the plant in biofuels processes, which has much lower sunlight-to-fuel efficiency than industrial solar collectors (PV or thermal) and requires a lot of fertilizers and pesticides to boost growth rate. Such land- and resource-intensive agriculture is not sustainable in its current form and may not ever be on the scale we will need it.
TFA discusses a solar-heat-driven thermochemical process that has potential. A somewhat similar solar-heat thermolytic process splits CO2 directly at higher temperatures. There are many other methods of accomplishing this that are at different levels of development and being researched, including electrochemical (pdf link1, pdf link2), photoelectrochemical, photo(bio)chemical...