Hydrogen-Powered cars with Zero-Carbon-Emission?

Roland Piquepaille writes "Researchers from the Georgia Institute of Technology have a bright idea — at least at first sight. They want to create a sustainable transportation system by using hydrogen-powered cars. They would like to create an infrastructure where people could use a liquid fuel for driving while the carbon emission in their vehicles is trapped for later processing at a fueling station. 'The carbon would then be shuttled back to a processing plant where it could be transformed into liquid fuel.' Where will all this liquid carbon be stored? The researchers don't know. They suggest that it could be stored in geological formations or under the oceans."

Comments

What, nobody's thought of the obvious?

[KublaiKhan]

The carbon-fibre industry's been taking off like a rocket, and we keep studying those nanotubes. The manufacturers are going to need carbon to make 'em. Why waste time and money burying it under the ocean or in the middle of a mountain?

Waste not, want not.

Re:What, nobody's thought of the obvious?

[Zymergy]

Combustion Carbon will be in the form of Carbon Monoxide (CO) and/or Carbon Dioxide (CO2). We do not have technology to create solid forms of carbon (quickly enough) to be useful on a passenger vehicle. (but that would be cool)
Both of these waste carbon gases (CO2 and CO) require significant refrigeration with high compression to store them in any significant quantity and that, my friends, *Requires tremendous Energy*. The work of "sequestering" the Carbon and storing it will eat away any profits in the manufacturing of and efficiency of the vehicle and it will add complexity to an already complex piece of machinery. Not to mention there will have to be one or more pressurized vessels (think explosion, frostbite, and suffocation hazards potentials too).
Carbon Sequestering is a pipe dream (thermodynamically) but it is great for getting venture capital from those investors who have not studied and understood the principles of thermodynamics and basic organic chemistry and who also want to claim that they are investing in "green" technology. (And there may just be tax breaks for such obvious non-competitive investments like 'Sequestering' to the 'Fossil Fuels Industries'??)
"Carbon Sequestering" is really only handy (though still very efficient) if you happen to be talking about a sessile terrestrial power installation over a suitable subterranean geological Carbon gas receiving reservoir. Like this one: http://science.slashdot.org/article.pl?sid=08/02/03/1845204&from=rss (A budget increase from 1.0 Billion to 1.8 Billion proves its inefficiency alone, and that's before you consider how much more fuel is required to capture all of the HOT exhaust and cool it down to the point it could be compressed and injected into exhausted/abandoned Oil or gas 'injection' wells.

The "Oceans" basically make CaCO3 (Calcium Carbonate) out of CO2 and CO (with the help of Trillions of organisms) and it falls to the ocean floor and becomes rock eventually. This is the PRIMARY carbon "sink" on the planet. I would put more research into helping that process (oceanic Carbon capturing) and focus on Electric Cars powered by Hydrogen cells and NOT Hydrocarbons and not Hydrogen combustion engines... they are too inefficient. Carbon is simply not needed in the fuel cycle. (Unless you want fuel cells that run off of Natural Gas (Methane/Ethane AKA CH4/C2H5) or some form of Alcohol (Methanol/Ethanol AKA CH3OH/C2H5OH)).
Ultimately, using electricity to power the car's electric motor is the only truly efficient way to go (as of today)... It is only a matter of whether it is powered from a battery that is charged with electricity from the grid (preferably Nuclear and/or Hydroelectric), from an internal generator burning fuel (like modern diesel/electric Trains), and/or capacitors, solar cells, or small nuclear reactors... Burning Carbon-containing fuels (from whatever source...but note: they *WILL be from Fossil Fuels* as long as they are cheaper) is just more of the same since the invention of the combustion heat engine. It is business as usual.. Using Corn to make alcohol is a pretend market that will utterly fail without the heavy government subsidies it is seeing. (Research ADM and its lobbying efforts.)

Carbon Sequestering is really interesting, but it requires TOO MUCH energy to do.. Last time I checked, you use about 2 Watts of power to remove about 1 Watt of heat from your home/office using efficient air conditioning. What will it require in energy to remove the heat and to compress (compression releases MORE heat BYW) the exhaust of a car buring some Carbon-containing fuel? Exactly. Electric is the ONLY way to!

Re:What, nobody's thought of the obvious?

[Rei]

and focus on Electric Cars powered by Hydrogen cells and NOT Hydrocarbons and not Hydrogen combustion engines... they are too inefficient.

You talk about efficiency and advocate hydrogen fuel cells in the same sentence? You do realize that hydrogen fuel cell vehicles are extremely inefficient, right? At low loads, fuel cell vehicles are typically 46% efficient at turning hydrogen in the tank into wheel torque and 36% in the NEDC driving cycle. On top of that, you have generation losses (modern power plants are 40-50%, older ~30%, and possibly up to 60% in the future), transmission losses (7.2% average in the US), electrolysis losses (80-85% efficiency if done in the most efficient manner possible, regeneratively on hot steam). Which makes hydrogen worse than gasoline in terms of a carbon footprint. You can also make it from methane reforming, but that's no better. You can grow it from bacteria, but that costs an utter fortune. There are direct sunlight to hydrogen cells, but they are expensive, very inefficient, and break down quickly.

The hydrogen economy is simply unrealistic. On the other hand, there is an awful lot of promise in electric vehicles.

Re:What, nobody's thought of the obvious?

[Zymergy]

You make a very good point, Thank You. I do not disagree, I should have re-read the post before submitting
Hydrogen Fuel Cells are not as efficient as what I would consider to be "Efficient" either. BUT, they are more efficient than the burning any Carbon-containing fuel in order to spin a generator or to spin a drive shaft. I was thinking of Hydrogen fuel cells as being more efficient than the mechanical "heat engines", but you are absolutely right. (plus fuel cells have to have ultra-purified fuel stock and the membranes breakdown and become even less efficient, etc...

I am hopeful that the new Lithium-Silicon-Nanowire Batteries as discussed here recently will make the rechargeable storage-battery to electric motor-powered passenger vehicles efficient and practical: http://hardware.slashdot.org/article.pl?sid=08/01/16/027236
A Toyota Prius with one of these new batteries (about the same size/weight as the existing Toyota Lithium Ion battery module) would have a range of over 300 miles per recharge (about the range of a standard fuel tank's worth of gasoline and farther still if one pulled out the gas engine and added more battery capacity under the hood too).

Re:What, nobody's thought of the obvious?

[Rei]

Do realize that those batteries don't provide a 10x increase in energy density. After the first charge, the capacity drops to only 8x. Furthermore, it's only an anode advancement, so it would only provide a 2-3x increase in battery density. Of course, in pure electric vehicles, that's good enough to put them on range-parity with gasoline. Other techs that have the potential to do the same are lithium vanadium oxide and barium titaniate ultracapacitors.

Also, two neat things happen as you increase the energy density. Unless they cost a lot more to manufacture, you lower the cost per stored watt at the same time. Also, you reduce the number of charge/discharge cycles they need to be able to tolerate, since a single charge/discharge cycle takes you further. Then factor in mass production on top of that all...

Yeah, the future for EVs looks pretty good right now.

Re:What, nobody's thought of the obvious?

[mlts]

Another thing that the hydrogen/fuel cell "economy" is missing is the fact that there are virtually zero hydrogen fueling stops. The cost to put in hundreds of thousands of H2 pumps and the infrastructure to haul the liquid H2 to the corner gas station will be enormous.

Electric cars? Got a 120VAC or a 240VAC outlet? Its not that simple because 120VAC won't charge a car's batteries quickly (though its viable for overnight use.) However, adding circuits and having people standardize on a charging mechanism for cars when parked in parking lots is a lot simpler than the tanks, transportation, and specialized fuel dispensing systems needed for hydrogen. The technology for bringing electricity to every car in a parking lot does exist -- Many Alaskan shops and businesses have plugs for customers to plug in their engine heaters because at -20 (F) and below, the oil starts solidifying in the car.

I look forward to electric cars. In a lot of cities, 100% of power comes from wind and solar, so its not shifting the carbon to another source. Slow charging can be done at home, fast charging (especially with supercap batteries that can charge very quickly) can be done at the normal filling stations, so the existing gas stations won't be losing market anytime soon.

I don't look forward to a hydrogen economy, and the bugs and hassles a vastly new fuel infrastructure will bring with it. Not to mention the fact that someone has to pay the cost of sinking the H2 tanks underground in tens of thousands of gasoline stations... and that will end up being the customer.

Re:What, nobody's thought of the obvious?

[Rei]

Eh, while electric engines are somewhat more efficient than internal combustion or hydrogen fuel cell

Huh? What planet are you from?

* ICE: 30-35% efficiency for the engine, but due to internal losses, only about 20% efficient to the wheel well
* Fuel cell: 40-60% efficient *before* the power goes to the electric motor.
* Electric motor: 85-90% efficient in typical driving conditions (in optimal conditions, with an optimal engine, you can near 95% efficiency).

They have the same power generation inefficiency and higher transmission losses than hydrogen.

Huh? In the US, there's only an average 7.2% efficiency loss in electricity transmission. That doesn't even compare to the energy costs of making and pressurizing/pumping hydrogen.

[quote]Then toss in the considerably lower energy density of electricity storage[/quote]

Once again, huh? Hydrogen not in a storage medium will get you 250 miles, perhaps 300 at best. Li-ion present-day typically gets 200-250, but there are three different techs being worked on which each individually can 2x-3x that range (lithium vanadium oxide, silicon nanowires, and barium titanate caps). To get the range on hydrogen up, you need to either increase the pressure (which nobody wants to do), use liquid hydrogen (whole host of major, major problems that nobody wants to deal with), or use a storage medium. With a storage medium, you can get up to 300-350x (the reported range of the upcoming all-electric ZAP-X is 350mi, might I add -- and 300-350x is still way below the upcoming battery techs), but you lose even more efficiency in the process. The more hydrogen dense a storage medium, in general, the more inefficient it becomes. So, you take something that's already less efficient than an ICE, and you're making it *even worse*.

and even though you might get more wheel torque from the original source, the vehicle is going to be heavier than a fuel cell driven vehicle (even though the latter will probably have some sort of electricity storage as well).

Since when are fuel cell vehicles any lighter than electrics? The FCX weighs in at almost two tons. The Tesla Roadster's not even 1 1/2 tons.

Hydrogen? Carbon?

[_merlin]

First you say the cars are hydrogen-powered, then you say the carbon emissions will be trapped and disposed of when refuelling. Hydrogen doesn't contain carbon. Where do carbon emissions come from? This has to be the most contradictory Slashdot summary in a long time.

Re:Hydrogen? Carbon?

[moderatorrater]

That's one of the worse summaries I've seen on Slashdot, and as we all know, that's saying something. Basically, there are three parts to the plan. Instead of using an internal combustion engine, you use a reactor that changes the hydrocarbon chains into hydrogen and carbon. The hydrogen is used to power the car using the already developed fuel cells while the carbon is stored. You fuel at a station, but instead of just filling up with hydrocarbon (like we do now), you also give back the carbon that your car's been storing.

In the short term, this carbon would be taken and sequestered in a variety of methods that scientists have been studying for years, either under the ocean, in old oil wells, other underground locations, or in solid carbonate form. In the long term, the carbon would go back and be remade into hydrocarbon chains to be distributed back out. As someone else pointed out, you could also use the carbon for nanotubes.

Re:Hydrogen? Carbon?

[RingDev]

Step 1: Generate pure hydrogen in highly efficient processing plant
Step 2: Merge with carbon to create less stable and lower density hydrocarbon based fuel
Step 3: Using a vehicle based unit, crack the hydrocarbons back into hydrogen and carbon
Step 4: oxidize hydrogen to power fuel cell.
Step 5: return carbon to processing plant.

This would work amazingly if there were a shortage of carbon and an excess of easily accessible hydrogen. Unfortunately, our problem is the other way around. I can walk to any local gas station in the middle of summer and pick up a 20lbs bag of carbon for a few bucks. Getting my hands on 20lbs of hydrogen is a bit more challenging and expensive.

Not to mention there is no way they are going to get a vehicle based cracking unit to be more efficient than the factory unit. Not to mention that energy density is already an issue in pure hydrogen storage, turning it into hydro carbons isn't going to help on that issue if they are only using the hydrogen for energy generation.

The whole concept seems to fall on it's face as yet another attempt at a perpetual motion device.

-Rick

Re:Hydrogen? Carbon?

[Rostin]

You were doing more or less ok until you got to the energy density part.

According to Wikipedia, liquid hydrogen has a density of 70.8 kg/m^3. That sets a generous upper bound on the density we could hope to achieve in pure hydrogen storage.

Let's assume a density of 700 kg/m^3 for our liquid hydrocarbon. According to Wikipedia (again), gasoline is around 737 kg/m^3. Let's further assume that hydrogen makes up about 15.8% of the weight of our fuel. I arrived at that number by doing a straight average of the percentages for C5 to C12 linear alkanes. That means the part of the density we can attribute to usable hydrogen is around 111 kg/m^3.

So, in terms of effective hydrogen density, liquid hydrocarbons beat the pants off of even pure liquid hydrogen.

Re:Hydrogen? Carbon?

[sectionboy]

I might be one of "global warming idiots" - for not knowing too much about it, but I failed to see how water is as bad as CO2 in this issue. Earth, as we know, has 3/4 of its surface covered by water, thus the atmosphere is basically saturated for water vapour, i.e., no matter how much water (liquid, vapour, ice, all forms combined) exists on this planet, the amount of water vapour in atmosphere as a whole system is almost constant as long as the climate (temperature, pressure) doesn't change dramtically.

Re:I thought

[ciggieposeur]

There were already some pretty good ways of storing hydrogen for cars and the issue was just creating the hydrogen in the first place.

Not really. The Department of Energy has estimated that one would need at least a device capable of storing up to 0.6 kg of hydrogen per kg (e.g. a 100kg storage tank has 6kg of raw hydrogen in it) before hydrogen is just barely usable as a transportation fuel source. Ideally, 12% wt/wt storage is necessary to achieve the 300 miles per tank that most cars get today on gasoline. The best storage systems (circa 2004 when the report came out) topped out around 8% for liquified hydrogen tanks, but those are very difficult to use in practice because the hydrogen leaks out quickly. All other systems topped out around 4% and required either high temperature (metal hybrides) or very high pressures (700bar, approximately 10000 psi), again making them not yet ready for widespread use.

Hydrogen production is still an issue too though. Most of what we get now is a byproduct from natural gas processing, so it's still not carbon-neutral.

(Disclaimer: This topic is actually part of my master's thesis.)

Can we make this any more inefficient?

[Radon360]

1. Fill up with regular gasoline
2. Instead of burning it outright, let's strip the hydrogen off the hydrocarbons and just burn that.
3. Somehow sequester the leftover carbon from the breakdown (this is the ???? step)
4. Return the carbon (somehow stored in liquid form) for recycling >>> Profit!

First, let's ignore how much energy we're throwing away in step 2 by not utilizing the full energy potential stored in the hydrocarbon molecules. Second, somehow we'll expend more energy to liberate the hydrogen and capture the carbon, both without oxidizing them. Third, we're going to tote around another 75 - 100 pounds of weight with the stored (and somehow liquefied) carbon that will be returned. Less energy potential that ever reaches the engine/fuel cell, and even more expended to refine something fairly energy dense into something that's a fair amount less energy dense.

The problem with this idea is there's too much fixation on sequestering every last bit of carbon, rather than focusing on a bigger, more important concept called energy efficiency. Work on improving that and the carbon emission reductions usually follow.

Re:Already is a way, and it's in development

[blair1q]

And where do they get the electricity to reprocess the Mg02?

From an oil- or coal-burning power plant, of course.

Or a nuke plant.

These ideas of using renewable chemical fuels is all pretty silly, because they all use electricity to renew the fuel. But electric vehicles are efficient, viable, can be made attractive and fast, and they cut out the middle-man by allowing you to plug into a supply of electricity you already access. No infrastructure cost = lowest economic barrier to entry. And it's infrastructure that we have 150+ years of experience maintaining and improving.

Eventually all of our energy will be delivered from electrical utilities, generated from coal (the oil will run out soon but we have several hundred years' worth of coal left), nuclear processes (about a thousand years' worth), and the sun (several billion years, but it's terribly inefficient so far).