Slashdot Mirror
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.
The hydrogen economy probably won't be on us for at least about 5 years if it paces itself at a break neck pace. The dream of having a farm with solar panels, converting water to hydrogen to store in tanks in the ground is a cool dream. You can then use that hydrogen to power your car or heat your home. The key is that the tanks haven't hit an economy of scale yet since the commercial hydrogen car just came out by Toyota this year. In the short run Hydrogen is expensive as all get out, but in the long run it can be cheaper than batteries. A battery array likely won't come down in price nearly as much as a pressurized tank will.
Get a farm, a solar array, some underground tanks, and you have unlimited fuel for your car and can heat your home in the winter for free. Gas stations will be something any Joe can make himself by installing a pump in his own personal system. The creation of the hydrogen gas is done on site with electricity and water.
That said, it will be a little while before we can all embrace it because economy of scale need to hit things like pressurized tanks and such. I'm interested in hearing about these other gases being made through solar energy though. I've heard other gases being used at powerplants and such, but I forget which ones.
God spoke to me
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.
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
I think most sane electrolysis projects target methane as the ultimate product because it can be injected into the natural gas distribution network and is much easier to handle than bulk hydrogen.
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).
The thing is, if you're using solar and have no grid use for the generated power at the time of generation, does it really matter how efficient your conversion is? You're using energy that would otherwise go unused. It's free input energy and the output (if you target methane) is a form of storable and transportable energy for which we already have a storage and transportation infrastructure.
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.
I am armed because I am free. I am free because I am armed.
* 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.
Oolite: Elite-like game. For Mac, Linux and Windows