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New material should give a boost to the hydrogen economy

Many believe that hydrogen is the eventual replacement for gasoline and that future vehicles will be fuel cell-based plug-in hybrids.  However, in order to transition to such a hydrogen-based economy, many key challenges remain.  The biggest challenges are devising and implementing means to make, store, and ship hydrogen to distribution centers.

One of the key challenges in making hydrogen is the need for purification.  Many chemical reactions that produce hydrogen also produce a mixture of hydrocarbon gases and water vapor.  In the past separating these substances has been a tricky and inefficient process.

Now chemists at Northwestern University have developed a class of porous materials that may solve this problem by letting hydrogen gas through selectively, while impeding other gases.  According to the researchers, the materials exhibit the best known selectivity towards hydrogen over methane and carbon dioxide of any known material.

Mercouri G. Kanatzidis, a professor of chemistry at the university and co-developer of the material, states, "A more selective process means fewer cycles to produce pure hydrogen, increasing efficiency.  Our materials could be used very effectively as membranes for gas separation. We have demonstrated their superior performance."

While current separation techniques rely on separating molecules by size, the new porous membrane material separates them by polarizability.  The new membrane, composed of germanium, lead and tellurium, lets hydrogen through faster, as it is a hard, small molecule which interacts little with the charged walls.  The membrane is a hexagonal nanoporous structure, with parallel tubes about two to three nanometers wide.  The gas molecules are at least half a nanometer wide.  The membrane selects hydrogen at a rate approximately four times higher than the current best methods.

Professor Kanatzidis describes the material stating, "We are taking advantage of what we call 'soft' atoms, which form the membrane's walls.  These soft-wall atoms like to interact with other soft molecules passing by, slowing them down as they pass through the membrane. Hydrogen, the smallest element, is a 'hard' molecule. It zips right through while softer molecules, like carbon dioxide and methane take more time."

The membrane operates within a "convenient temperature range" of zero degrees Celsius and room temperature.

Professor Kanatzidis worked closely with postdoctoral research associate Gerasimos S. Armatas on developing and testing the material.  The pair has published a paper entitled "Mesoporous Germanium-Rich Chalcogenido Frameworks with Highly Polarizable Surfaces and Relevance to Gas Separation".  It is published online at the journal Nature Materials.



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stupid question...
By jaybuffet on 2/17/2009 9:27:45 AM , Rating: 2
Why can't we have a hydrogen tank in our cars and simply fill up at home using electrolysis?




RE: stupid question...
By freeagle on 2/17/2009 9:43:26 AM , Rating: 3
1) Because storing hydrogen in a liquid form is not an efficient storage. Gasoline contains more hydrogen than the same volume of pure liquid hydrogen. The distance you could drive with full tank would decrease significantly.

2) It's much more expensive to have several thousands/millions of small devices for producing hydrogen through electrolysis than to have a few factories specialized on it.


RE: stupid question...
By jaybuffet on 2/17/2009 9:56:03 AM , Rating: 1
I was talking about splitting water into hydrogen at home using electrolysis. How much hydrogen gas would one need to travel 80 miles? Wouldn't hydrogen gas also make your car weigh less making it a little more efficient? You could come home, connect your car to a machine which simply splits water into H2 and O. When you wake up, your car is filled. I'm sure someone has thought of this, and it's probably been proven as not feasible, but i am wondering why?


RE: stupid question...
By freeagle on 2/17/2009 10:08:44 AM , Rating: 3
quote:
I was talking about splitting water into hydrogen at home using electrolysis


I don't see in what way was I talking about something else.

quote:
Wouldn't hydrogen gas also make your car weigh less making it a little more efficient?


The weight of a full tank is only a minor fraction of the weight of whole vehicle. Even if liquid hydrogen weighted nothing, the gained efficiency would not be very noticeable.

quote:
probably been proven as not feasible


As far as I know, current methods of hydrogen production are not very efficient. You'd lost a lot of energy producing the hydrogen, which rather could be stored in a battery and used directly.


RE: stupid question...
By jaybuffet on 2/17/2009 10:32:29 AM , Rating: 2
Ok so I stopped being lazy and did a few quick calcs.. if I wanted to travel 90 miles a day in a car which gets 30 mpg.. to get the equivalent energy, i would need about 388ft^3 of H2... thats a lot of H2 in gas form.. (~5ftx2ftx2ft) but couldnt a car be designed around that? plus h2 is lighter than air so yes it would be lighter than gas, and wouldnt it also lift the car slightly reducing the weight even more. (here are the numbers i used: Gas weighs about 3kg/gal, energy - 46.9 MJ/kg. Hydrogen energy - 143 MJ/kg, density - .0899 kg/m3)


RE: stupid question...
By jaybuffet on 2/17/2009 10:38:45 AM , Rating: 2
ok maybe 388ft^3 is more like 4ft x 5ft x 2ft.. i've been out of school for too long.. but still..


RE: stupid question...
By freeagle on 2/17/2009 10:54:18 AM , Rating: 2
or maybe something like 10ft x 10ft x 3.88ft.

quote:
and wouldnt it also lift the car slightly reducing the weight even more


If you put that big balloon of hydrogen above it, then it would get a bit of lift (don't have time to calculate how much), but the weight would not be reduced. The lighter hydrogen would be pulled upwards in the heavier atmosphere, which would make it look like it weights less. You'd also loose a lot of grip due to this, so your efficiency would decrease drastically, because the tires and their contact with the road transforms the rotational energy produced by motor into a force pushing your car forward. The car would also be a lot less maneuverable.


RE: stupid question...
By jaybuffet on 2/17/2009 10:59:20 AM , Rating: 2
A quick search on google turned up a 0.158 kw hours per cubic foot number for generating hydrogen from water using electrolysis. If this is true, then I would need 61.3 kwh to fill 388ft^3. My coned bill says a kwh costs me $.12. So that would equate to $7.36 to go 90 miles (if this was gas, and i'm getting 30mpg, thats equivalent to $2.45/gal)


RE: stupid question...
By freeagle on 2/17/2009 11:06:08 AM , Rating: 2
But that only calculates the cost of produced hydrogen. You need additional energy to squeeze the 388ft^3 of hydrogen into a conventionally sized tank. My guess it won't be very cheap.


RE: stupid question...
By jaybuffet on 2/17/2009 11:16:59 AM , Rating: 2
who says we need a conventional tank :-) lets throw a tank on the roof.. there enough space up there for a tank 5ft wide, 4ft long, 2ft tall.... might look goofy in the beginning.. but what doesnt..


RE: stupid question...
By freeagle on 2/17/2009 11:22:01 AM , Rating: 2
Since you've been talking about reducing weight.... do you realize that 5x4x2 ft tank for storing pressurized hydrogen would add significant amount of weight to the car?


RE: stupid question...
By jaybuffet on 2/17/2009 11:32:34 AM , Rating: 2
not pressurized... but the weight reduction seem moot (another site said 1 ft^3 at STP lifts 0.07lbs, so 388ft^3 would only lift 27lbs, probably less than the container)

this sounds too feasible.. i must have messed up a calc somewhere


RE: stupid question...
By freeagle on 2/17/2009 11:38:55 AM , Rating: 2
quote:
not pressurized


5x4x2 ft can store only 5x5x2ft^3 of unpressurized H2. If you wan to put 388ft^3 of into that space, it has to be under pressure


RE: stupid question...
By jaybuffet on 2/17/2009 11:48:51 AM , Rating: 2
i'm dumb +1. So anyways, i wonder how much energy that would take to compress the hydrogen. I guess thats what this whole issue is about... hydrogen storage.. that took a long time for me to get it


RE: stupid question...
By freeagle on 2/17/2009 11:55:51 AM , Rating: 2
The whole issue is about efficient production and storage. We need to store much more hydrogen than those 388ft^3 you calculated, because 90 miles driving distance is not much compared to what you get with full tank of gasoline. We also need to figure out a way to cheaply produce a lot of hydrogen. For now, storing the energy in batteries is more effective.


RE: stupid question...
By jaybuffet on 2/17/2009 12:03:27 PM , Rating: 2
i would think 90 miles would be more than enough for peoples daily driver. i mean, my calculation came to the equivalent of $2.45 per gal of gas.. which isn't too bad.. add on the cost of compressing it.. not sure what is involved there cost wise.. i wouldn't think it would be substantial since we're not talking a huge compression (10:1), though i could be wrong. at least we would reduce our dependency on foreign oil.. efficiencies can only go up.. (gov't wouldn't get its taxes though, so they would probably make the production of hydrogen illegal much like marijuana)


RE: stupid question...
By codeThug on 2/17/2009 4:31:10 PM , Rating: 2
stop. stop.

I can't take anymore...


RE: stupid question...
By monomer on 2/17/2009 12:25:57 PM , Rating: 2
Even if the hydrogen under pressure was lighter than air, you're neglecting the fact that the hydrogen sill has mass, which takes energy to accelerate.

All the reduction in weight would do is reduce friction between the car and the road, which is good while rolling, but bad while accelerating.


RE: stupid question...
By DaveLessnau on 2/17/2009 10:00:40 AM , Rating: 2
Thanks for that information. I had assumed that the energy content of hydrogen was higher than gasoline's regardless of the form. Here's a link that gives numbers to support your statement:

http://www-formal.stanford.edu/jmc/progress/hydrog...


RE: stupid question...
By nafhan on 2/17/2009 10:05:13 AM , Rating: 3
You can do that now with our current tech.
The problem is that you wouldn't want to. Electrolysis and hydrogen storage are, respectively, expensive and bulky compared to just using electricity and batteries.
A lot of people forget that hydrogen cannot be found lying around under the ground like gasoline can. When burning gasoline, you can actually get back more energy than it took to extract it from the ground, because the energy from decaying plant matter, etc. has been stored in the crude oil. When burning hydrogen this will never happen because we have to create the hydrogen in energy intensive processes such as electrolysis, which thanks to the laws of thermodynamics we know will never make back more energy than we put into it.


RE: stupid question...
By ironargonaut on 2/18/2009 1:43:39 AM , Rating: 2
What would that solve? Energy is neither created nor destroyed. I believe it is a law. The energy you can get from combining H+H+O->H20 can never be more then the energy it takes to reverse the process H2O->H+H+O. Otherwise you could make a perpetual motion machine by cycling the process. Therefore, without doing any math one can see that taking into account efficiency of electrolysis and efficiency of power line transmissions. It takes more energy to create the hydrogen gas than it can be gained from it. Assuming 100% efficent engine. The extra energy to create the electricity will come from the burning of fossil fuels since green energy can not supply current demand. This is ignoring storage and other issues.
Tne net result is if all vehicles could switch tomorrow to hydrogen more fossil fuels would be needed to keep them running or more nuclear reactors.
Perhaps someday someone will create a plankton that uses the suns energy to create hydrogen from H20. But, would it be more or less efficent than solar cells?
My question is if CO2 is so bad how come we don't cap the coal mine fires that spew as much CO2 as all the cars in the US?


Please pull this through
By Regs on 2/17/2009 8:34:38 AM , Rating: 4
I would hate the industry to be dependent on lithium batteries for hybrids. It would be worse than our oil dependency.




RE: Please pull this through
By freeagle on 2/17/2009 8:49:10 AM , Rating: 1
So instead of lithium, we will be increasingly dependent on germanium, lead and tellurium, among other materials used in the hydrogen making-storing-transporting-using chain. You will always depend on something. And every dependency brings it's own set of problems.


RE: Please pull this through
By Jansen (blog) on 2/17/2009 8:49:27 AM , Rating: 2
Lithium ion is not the only battery type, there are alternatives to that as well.


RE: Please pull this through
By Noya on 2/17/2009 9:04:01 AM , Rating: 2
That have equal or greater performance....?


RE: Please pull this through
By Radnor on 2/17/2009 9:25:51 AM , Rating: 2
That is the cool thing about batteries, with enough research, materials can be changed and new types can be formed.

The combustion engine hasn't changed almost nothing from the invention of the turbo and Electronic injection concepts. Look at he history of batteries on the same period of time, you will be amazed.

The rest were, minor changes.


RE: Please pull this through
By Innocent Hawk on 2/17/2009 9:19:02 AM , Rating: 2
But do any of them work well enough to balance out a possible higher cost that may come with it?

Lithium Ion batteries are widespread, well developed, and cheaper that many of the other alternatives out there at this current point in time.


RE: Please pull this through
By randomly on 2/17/2009 2:23:07 PM , Rating: 2
Unlike oil though the Lithium isn't consumed and it can be recycled out of the old batteries which almost certainly will happen because of the high dollar value of the resources in a used electric car battery.
Also a rule of thumb for mined resources is that doubling the market price increases the extractable reserves by a factor of 10 as less concentrated mining sources become economically viable.

Hydrogen as an energy carrier has so many unresolved problems that it's implementation as the 'fuel of the future' seems unlikely at this point.

1) Storable density is low.
There is less hydrogen in a gallon of liquid hydrogen than in a gallon of gas. However it would be workable except for the very high energy cost of liquefying the hydrogen. It takes 30% of the available energy in the hydrogen to liquefy it at 20 degrees above absolute zero. You also have the problem of significant fuel boil-off from heat soaking into the Dewar. The best solution so far available is compressed gas, or chilled compressed gas cylinders. They only have a 12-15% energy cost but the fuel density is much lower, the tanks are heavy, and at 5000-10,000 PSI they are a real safety concern in case of tank failure. Also unlike a liquid fuel working with gaseous Hydrogen you incur significant pumping energy costs every time you transfer fuel from a hydrogen production facility to a tanker truck, tanker truck to refueling station, station to vehicle tanks.

Using materials that can adsorb a few percent by weight of hydrogen, such as paladium, is interesting science but all those materials require considerable energy input to get the hydrogen back out of the material since these materials all glom onto the hydrogen pretty hard and the energy efficiency is again so dismal as to make them unworkable. That's even before you get into the longevity, excessive weight and terrible economics of such approaches.

The gallium-aluminum fuel approach also just doesn't work because of the terrible energy efficiency of the cycle.

Fuel transport costs are high. Because the density is so low it takes considerable energy even to pump the hydrogen around in pipelines. For a gas station that can be supplied by one tanker truck of gasoline a day, to deliver the same fuel energy with hydrogen it would take 20 tanker trucks a day.

2) Hydrogen production is inefficient.
Electrolysis is only about 50% efficient. That coupled with the fuel cell efficiency of about 50% means it takes 4 KwH of electricity from the power station to deliver 1 KwH of electricity at the vehicle motor. 25% round trip efficiency for an energy storage system isn't too good. Lithium batteries with a round trip charge/discharge efficiency in excess of 90% will give you 4 times the mileage of a Hydrogen system. In fact generating hydrogen from electricity is almost always an economically poor idea since there are almost always better places to use that electricity directly. Using solar cells to make hydrogen is just a PR stunt since it makes no economic sense whatsoever compared to putting that electricity into the grid and displacing some fossil fuel generated power.
The only efficient way to produce hydrogen is by reforming natural gas, at 80%+ efficiency. However this does nothing to get you off fossil fuels, or minimize carbon footprint since as pointed out in an MIT study that even by 2020 hydrogen fuel cell vehicles will still be less efficient well to wheels than a simple cheap Diesel hybrid vehicle.

The one economically realistic future option for non-fossil fuel derived hydrogen is by using Very High Temperature nuclear reactors and a sulfur-iodine cycle. However developing the reactors and hydrogen technology to the point of commercial deployment will take 20-30 years.

3) Fuel cells are bulky, heavy, expensive, delicate, and don't last long enough. The catalysts are expensive. They are also easily poisoned by carbon monoxide and sulfur compounds so the hydrogen and oxygen (derived from air) have to be purified and monitored. The water management has to be controlled so the cell neither floods or dries out (which ruins it). You can't let it freeze, or it destroys the cell. The membranes just don't last long enough, you'll have to replace them multiple times during the life of a vehicle. All these points are probably solvable to some degree given enough research and development but fuel cells won't be economically deployable for vehicles for many years to come.

4) There is no hydrogen infrastructure. There are no hydrogen production facilities( other than natural gas ones). There are no distribution systems either trucks or pipelines. Existing pipelines can't be used because of hydrogen embrittlement of the metal, you have to lay all new lines. There are no hydrogen fuel stations, no hydrogen distribution tankers. You can't even use local electrolysis supplied by the electrical grid to generate hydrogen locally to any significant degree because the grid is incapable of those levels of power transfer.

The general population are almost totally unaware of all these issues. Car manufacturers and energy companies tend to use the technology only for green washing, gaining eco-friendly PR points with demonstration vehicles and fueling stations that in reality will never be deployed in useful numbers because they are too expensive and too inefficient. Researchers also trumpet this stuff regularly in order to get funding, as do companies looking for investors.

Is it possible that a number of unimagined huge breakthroughs will make hydrogen fuel viable? It's possible, but at this point it seems an uphill climb and not the way to bet. Advancing battery technology and ultracapacitors have many fewer hurdles to overcome and seem a more likely solution for passenger cars and vehicles that do not require a great deal of energy density. Fossil fuels will probably reign supreme for trucks, ships and planes for a long time to come, even if it comes to synthesizing the fuel instead of pumping it out of the ground. It's very hard to beat the energy density, portability, and ease of handling of petroleum fuels. Long haul trucks and trains may trend toward electric on special roads and tracks that can supply an electrical connection, with fossil fuel supplement when the vehicle leaves that grid.

I'm certainly in favor of continued research, but you also have to be realistic, look at the overall picture, and not get emotionally attached to a single approach. Sometimes things just don't work out, no matter how cool they seemed at first.


RE: Please pull this through
By freeagle on 2/17/2009 2:41:54 PM , Rating: 2
Too bad many will skip this post for its length. They'll miss a lot


RE: Please pull this through
By Regs on 2/18/2009 1:12:27 PM , Rating: 2
No, many of us read it. Though it would take a reply twice as long to argue.


Efficient Hydrogen
By owyheewine on 2/17/2009 9:47:45 AM , Rating: 2
Now if it were only posible to create a process to generate hydrogen that is thermodynamically efficient, we'ld be in business.




RE: Efficient Hydrogen
By SpaceJumper on 2/17/2009 12:14:42 PM , Rating: 2
Hydrogen fuel cell vehicle is actually less efficient than the gasoline vehicle.


RE: Efficient Hydrogen
By freeagle on 2/17/2009 12:23:03 PM , Rating: 2
Because with gasoline you get lot of energy for "free" by just pumping to oil from ground. But this wont go on forever, oil deposits are limited. If you'd like to stay with gasoline forever, you'd have to, at some point, start to create it from basic components - hydrogen and carbon. The gasoline vehicles would become extremely inefficient compared to pure hydrogen ones.


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