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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.
Sure it's not carbon capture, but it is renewable.
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This is not a carbon capture technique
Wait, you can't use it to extract "Fuel" and then pump it back into the ground where the oil used to be?
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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.
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...you know what I could swear this technology sounds like? A motherfucking TREE.
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.
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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.
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Fuel cells are the only way to get thermodynamic efficiency that is remotely competitive with battery electric vehicles. At the moment, fuel cells still have high initial cost, and short service life, relative to the batteries in battery electric vehicles. Sure, they'll ride down the price curve and up the performance curve as the technology matures. But then you get to the hydrogen. All sustainable, carbon-neutral methods of generating hydrogen involve using an energy source for electrolysis of water. Which takes as much energy as the hydrogen itself will release when it is "combusted" with atmospheric oxygen back into water. Adding insult to injury, hydrogen is a gas at standard temperature and pressure. In order to carry a quantity sufficient to provide useful driving range, more energy must be expended to pressurize the hydrogen to thousand's of PSI for storage on-board the vehicle.
Transmissions systems for electricity are way way more efficient than you suggest. In Great Britain transmission and distribution losses run at around 7%, and that is from the power station into the home/business. Expect these losses to fall as we move to HVDC transmission.
The next glaringly obvious mistake is that charging a battery is not 50% efficient either. It is typically around the 85% efficient mark. If you Goggle it you see a Tesla Model S turns 82% of the power at the wall into power in the battery.
With two such glaring mistakes I can only presume that your post is meant to spread deliberate misinformation.
It is a cool dream, but handling liquid hydrocarbons is a lot easier. If you have a good way to produce lots of hydrogen, you can 1) use it to synthesize hydrocarbons, which our existing infrastructure can handle, or 2) compress it to technologically challenging pressures or cryogenic temperatures, and still have lower energy density. You don't need pure hydrogen to run a fuel cell - a variety of fuel cells you can buy today for powering a home or datacenter run on natural gas.
* 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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What matters is overall systemic cost. You should not install massive overcapacity of solar. It would be tremendously expensive, then you'd have to pay even more for inefficient recovery of some of the overcapacity. If we want to make real progress offsetting CO2, we can't waste our money like that.
Actually, you would want significant overcapacity of solar. First, if you're talking about a nationwide system, it evens out the loss of generation in areas that are occluded by things like storms. Second, you can use the excess generation to store energy for overnight usage. Third, is allows for portions of generation capacity to be taken offline for maintenance without reducing capacity below a level where you would need to burn fuels to make up the loss of generation capacity. Fourth, overcapacity would allow you to pull CO2 out of the atmosphere for no other purpose than to remove it from the atmosphere.
Yes, it would be expensive. But, it would be expensive in a "it costs a lot right now, but is almost free (and may be revenue positive) later" kind of way.
I didn't say that you would want to go broke installing massive solar capacity. I said you would want significant overcapacity. I also didn't say that solar was the only option. In fact, I agree that the best energy source is a mix of sources tailored to usage patterns. I am also definitely one of the people that thinks nuclear is a valid power source.
15 times overcapacity is ludicrous. Not that I'm an expert, but you would want probably not more than 2-3X necessary capacity as an upper limit, and probably less. That allows for variations in generation without excessive overcapacity.
Short peaks of overproduction for solar plants tend to run to several hours, which would be fine for a synfuel plant as described in the original article. If generation drops off, electricity can be purchased from other sources in order to run the plant until generation comes back up, or until the plant can be shut down. Also, WRT to solar, as generation falls in one area it tends to rise in other areas. That offsets the loss, which keeps generation levels near a given level.
Those are just a few of the cost issues at hand. The world does not have unlimited funding. I think some folks prefer the dream of "all solar/all wind" over actual CO2 reduction progress.
I never meant to imply that there is unlimited funding, nor that wind/solar is the one and only answer. They are simply parts of an issue that is far too complex to have only one valid answer.
Have you ever looked at trend lines for PV electricity cost? If you want to build a nuke plant with private money they are downright scary and with HVDC distribution isn't much of an issue either. If the US navy manages to cheaply convert electricity to liquids that could be even better for solar than nuclear, if the trend lines hold. As a money man you should have some respect for technical analysis ;) It's mostly bullshit, but in the absence of known physical limits it's as good as any other guess on the bounds of solar electricity cost.
Area is not a problem for the US either, it has plenty of deserts with good sunshine (it is obviously a problem for the EU).
The ideal fuel wouldn't be hydrogen, but something like propane that is relatively easy to store, is not a greenhouse gas if it leaks, and takes a proper oxygen/fuel ratio to ignite as opposed to being set off by virtually anything.
The ideal would be ethanol. It isn't toxic like methanol, has a decent energy per unit volume (not as good as gasoline or diesel, but not horri-bad.) Alcohol is somewhat corrosive, but nothing that can't be engineered around, and in Brazil, this is quite a solved problem.
No, solar overproduction may last 5 or 6 hours in the summer, but it drops to one or two in the winter, and practically none on cloudy days. Fuel process plants take time to heat up just to start processing, which can be on the order of hours depending of facility size, unless you have even more capacity to do rapid heatup. Startup cycle increases means efficiency reduction. You really want to run fuel production as close to 24/7 as you can or you are increasing cost significantly.
From the original article:
An industry that produces a synthetic liquid fuel can preferentially use a peak energy. I think we need to explore this idea more. For example, imagine collecting piles of recycled aluminum at a plant that uses great amounts of electricity to melt it down and turn it into ingots for industrial use. The entire plant could be designed to operate on demand and only now and then, when there happens to be piles of extra electricity in a clean-energy rich energy ecosystem, perhaps because it is sunny and windy and other demands happen to be low. The employment structure of the plant would also be designed to do this, drawing on-call workers off of other activities to run the plant. This would essentially amount to carrying out a high energy demand industrial task with free energy.
It's not the most efficient thing, nor is it an all the time thing. It's not meant to be. It's just something to do with excess energy when you have too much of it. If you don't have the excess energy, then it doesn't get done. So maybe you only make liquid fuels using excess energy in whatever hemisphere summer happens to be in at the moment. Also, the closer to the equator, the less that daylight variability thing is an issue.
I believe that you and I are close to agreement on what can be done. Where we seem to differ is what should be done. You seem to desire an optimally energy and cost efficient system. On the other hand, I believe that a less efficient system with the possibility/probability of excess generation is perfectly adequate, as it provides for a greater flexibility. I don't condone waste, but I am willing to accept 'good enough' as just that, even if there is something potentially better.