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Making Liquid Fuels From Sun and Air
GregLaden writes: There is promising research on converting atmospheric CO2 and water, using sunlight as a source of energy, into burnable liquid fuels. This is not a carbon capture technique because the CO2 ultimately returns to the atmosphere after burning the fuel, but it could allow the production of enough liquid fuel to allow the rest of the motorized economy to switch to mainly electric. There are key uses for liquid fuels, even if most 'engines' become electric motors. The science of how this works is fairly interesting, and a recent writeup in Science gives some of the details.
Wait, you can't use it to extract "Fuel" and then pump it back into the ground where the oil used to be?
You could do that ... but that would be dumb. Once you extract the CO2 from the atmosphere, you can just pump it directly into the ground, rather than expending a huge amount of energy to convert it to a hydrocarbon first. Any geologic formation that held methane, should have no problem holding CO2, so any depleted shale bed should work fine.
Another option would be to use the CO2 to enhance oil or gas recovery. Pump the CO2 down, and it can mobilize and displace the hydrocarbons, and make them easier to pump out. There are a few projects where this is actually being done.
...you know what I could swear this technology sounds like? A motherfucking TREE.
A tree is less than 1% efficient. A solar panel is about 20% efficient. Trees need a lot of water, solar panels do not. Solar panels can put placed in a desert, on roof tops, or over parking lots. Growing trees for fuel displaces agriculture or wilderness.
1% Efficient at what? Converting sunlight to electricity? Please explain what you mean.
Trees are part of the wilderness - they don't 'displace' it.
Deserts are pretty much harsh environments because they are lacking trees.
Trees need a lot of water? Its stops if from running off, keeping the eco-system moist around them. They regulate moisture so that if rain is not falling, everything else around them doesn't die (including other smaller plants which also absorb C02).
Ever seen what happens to a river when you cut the trees around it? It shrinks. How would that happen if the trees were 'stealing' the water away from the river?
If there was salmon, it dies because of the rise in water temperature. What do you think the 'efficiency' of solar panels for that?
Here in Iceland they're even doing CO2 injection at the Hellisheiði geothermal power plant. It does indeed seem to work - although it doesn't come free, of course
Fuel from CO2 and renewable energy is a great example of why it's irrelevant whether liquid fuels are produced in an "energy positive" manner like the "peak oil" crowd obsesses over. Liquid fuels don't need to be energy positive, just human society as a whole. Liquid fuels are actually a very expensive form of energy per joule compared to most other widespread forms of energy that we use. It can make perfect economic sense to produce them in an energy-negative manner using other, cheaper forms of energy as the source; all that matters is that when all forms of energy combined are considered, that the energy outputs outweigh the energy inputs to produce that energy (preferably by a large margin).
Of course, it's probably going to be a while before fuel from CO2 is the cheapest way to get it. You can make liquid fuels from syngas (CO + H2), which can be made by the incomplete combustion of almost any organic matter, from coal to trash. I'd think it'd be hard for these CO2/sunlight fuels to compete with that.
"This administration is so incompetent that they cover their tracks with bigger tracks." - Seth Meyers
Since E=Mc^2 the whole earth gets 1.9 kg/s of sun's mass in the form of ultra-violet, and visible photons. But the earth recycles these photons to longer wavelengths and radiates slightly more mass/s in the form of infrared photons (the excess comes from the heat generated by radioactivity in rocks).
In addition the sun sends matter to Earth in the form of solar wind, mostly protons and electrons and a few helium nuclei send by the solar atmosphere. The average direct mass flux for the whole earth amounts to about 0.75 kg/s.
One could also think about the sun neutrino flux but most of these particles traverse the earth without stopping.
A tree is less than 1% efficient. A solar panel is about 20% efficient.
How is it "only" 1% efficient? I can't find the exact reference at the moment but I think I heard that photosynthesis is ~99% efficient (Take that with a grain of salt since that is relying on my memory).
Apparently it appears some complicated quantum effects take place in the photosynthesis process. Some info is presented on (possible) quantum behaviour in biology by Prof Jim Al-Khalili in in this Royal Institution Lecture
The hydrogen economy is, and always has been, a stupid idea. The cycle throws away two thirds of the energy for no good reason. And the fuel to store is detonation prone (not just deflagration), very low density, metal-embrittling, ignites with trivially weak static sparks (which common household devices are not rated to prevent), destroys ozone when it leaks, leaks trivially easily, and has a bunch of other nasty properties like pooling under overhangs, entering pipes from the outside, flowing to their destination, and then pooling there. People should read NASA's guidelines for safe handling of hydrogen - it includes things like for any building that handles more than a dozen or so kilograms at a time, the roof should be designed to be blown off in an explosion, among other gems. But all that pales in comparison to the main issue: the hydrogen cycle is just way, way inefficient.
Just stick with electricity. It's what you start with, it's what you want to end with... it's stupid to convert forms. (Okay, technically, storing in a battery is conversion to chemical energy, but it's extremely efficient in doing so - at least with modern forms like li-ion).
And no, hydrogen fuel cells are NOT "cheaper than batteries", they're absurdly expensive systems (and with, I should add, shorter lifespans than batteries to boot). A FCV with the performance of Honda Civic will run you several hundred thousand USD. And one should note that they still have to have a battery pack (hybrid-sized) to average out the demand fluctuations. And yes, batteries are coming down significantly in price (way more than fuel cells), and are predicted to drop even faster in the coming years due to developments like the gigafactory coming online.
"This administration is so incompetent that they cover their tracks with bigger tracks." - Seth Meyers
asked then answered: it's a commercially viable option already: http://cleantechnica.com/2014/...
Political debates have me rolling my eyes so much I think I got optical whiplash. I should sue. - Foamy The Squirrel
Making fuels from sun and air sounds like a tree huggers dream but as long as we can find something cheaper it will be useless.
We've all heard the phrase that time equals money, and there is a lot of truth in that. Time is money, energy is money, a lot of things are money. To make fuel from "free" things like sun and air will take time, labor, energy, and other things that require money to buy. This is going to be very expensive.
What I see as more promising is some research done by the US Navy where they want to make jet fuel using sea water. The US Navy found that it is much easier to get CO2 from water than from the air, meaning it takes less time, energy, and therefore less money. As a byproduct of the CO2 extraction they get hydrogen gas, which is fortunate since with the CO2 and the hydrogen they have the raw materials needed to make jet fuel. The energy required would come from nuclear power, something that the US Navy is very good at managing.
I believe that if we are going to see a leap forward in energy technology that it won't come from the tree huggers. I believe it will come from military research.
Also, in the linked article (yes, I did read it) there was a comment about shutting down an aluminum plant when there was not enough energy, one does not shut down an aluminum plant on a whim. Once everything in a smelter gets hot it is so much easier and cheaper to keep it hot. If allowed to cool then it takes a lot of time and energy, which means money, to heat it back up again. There is also the issue of continued heating and cooling stressing the equipment, that means repairs and more money.
I've seen a lot of people that think we can shift the load to match the supply but that does not work well in a real world. We can shift some loads to off peak times but at some point we are simply going to have to build more supply so that people can do their work on schedule. If production shuts down for lack of sun then that means time lost, and money lost. Solar powered anything is going to have to be so ridiculously cheap or people will go elsewhere, and I've never seen cheap solar power.
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See https://en.wikipedia.org/wiki/Photosynthetic_efficiency (and its references).
According to that, plants are typically 0.1%-2% in sunlight-to-biomass efficiency, with sugar cane reaching at most 8%.
Simply the "47% lost due to photons outside the 400–700 nm active range" makes it not 99% efficient.
* Power transmission is not anywhere near as inefficient as you suggest. The UK National Grid for instance suffers losses of only 7% power station to consumer.
* Electric motors are not anywhere near as inefficient as you suggest. A decent brushless motor will do better than 90%
* Batteries are not anywhere near as inefficient as you suggest. A good Li-Ion type battery has an efficiency of over 90%
So, a petrol engine is not demonstrably more efficient. Overall, electric vehicles significantly beat petrol (gasoline) engines for thermodynamic efficiency even including power generation losses (a large generator tends to be more thermodynamically efficient than millions of tiny ones). Then add to that an electric car can effectively be nuclear powered or wind powered or solar powered or combinations of those if they are the local generating plants.
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"Converting water into Oxygen and Hydrogen SPENDS the water, not renew it."
True, but burning said hydrogen CREATES water.
english isn't too bad for consonant clusters, polish and slovic languages are far worse.