A new process makes regenerating hydrogen fuel more efficient.
One challenge in using hydrogen as a transportation fuel--besides finding a clean, cheap source of the fuel itself--is how to safely and reversibly store it without taking up too much space. Hydrogen has a low density, so it's necessary to confine it either under pressure, which presents a safety hazard, or chemically or in an absorptive material.
In chemical storage, hydrogen is bonded to the molecules in a solid material such as ammonia borane. The advantage of chemical storage is that these materials are inert solids, and the hydrogen can be readily removed for reaction in a fuel cell. But the materials under development for chemically storing hydrogen have a major limitation: refueling them once they're spent takes a large amount of energy. Now researchers have developed a series of reactions for refueling the high-density hydrogen-storage material ammonia borane at lower temperatures through a process that consumes much less energy.
The U.S. Department of Energy (DOE) has set a goal of a hydrogen fuel-cell car that can travel 300 miles on a single fuel tank using chemical hydrogen storage. The cars would be taken to a center to exchange the spent tanks for fresh ones, with the spent tanks regenerated at a plant.
The capacity of a material to chemically store hydrogen is measured as the percentage of its weight taken up by the element; in order to meet its goals, the DOE benchmark for hydrogen-storage materials is 6 percent by weight by 2010 and 9 percent by 2015. "The good news about ammonia borane is it can hit or surpass the volume and weight targets" set by the DOE, says Jamie Holladay, a senior research engineer at the Pacific Northwest National Laboratory. Ammonia borane contains 19.6 percent hydrogen by weight. "The challenge is regeneration of the spent fuel," he says.
"Once you get the hydrogen out of the ammonia borane, you can't just pressurize it with more hydrogen to regenerate the fuel," because this is too energy-intensive, says John Gordon, a research chemist at Los Alamos National Laboratory in New Mexico. In order to find out which reactions were likely to work best without having to test hundreds on the bench, chemists at Los Alamos collaborated with David Dixon, a professor of chemistry at the University of Alabama, who developed algorithms to predict the energetics of the reactions. The group then tested the most promising chemistries and found that using a tin catalyst and regenerating the material in several steps required much less energy than driving the reaction directly.
Of course, a major problem remains before hydrogen fuel-cell cars become practical: developing improved methods for making hydrogen fuel in the first place, a challenge other researchers are working on.
Proton OnSite's lack of progress toward its proposed "hydrogen highway" demonstrates the low priority America gives this alternative fuel.
Using nickel as a catalyst rather than platinum could also mean less-expensive fuels cells.
Despite doubts about its feasability, hydrogen is finding its way into niche applications.
Is it still an energy sink if the energy is renewable? Recent success in photochemical production of hydrogen has proven to be very interesting.
http://www.technologyreview.com/energy/21155/
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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durs
44 Comments
Like putting Lip-stick on a Pig
It does make the Pig look better, but it's still a Pig.
Unless you can drill a well that gushes hydrogen, hydrogen will alway be a net energy sink.
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erbium
340 Comments
Yea, but is a handy pollution free form to store energy
hydrogen gusher:
at room temp aluminum and water react to form aluminum oxide plus hydrogen (very quickly), when a small amount of surfactant (e.g. gallium element) is added.
http://www.fuelcellsworks.com/Supppage7355.html
http://www.physorg.com/news98556080.html
same reaction occurs with other metals at temperatures similar to internal combustion engines, magnesium is example.
http://www.techbriefs.com/component/content/article/3498
so we can produce hydrogen on demand as the car drives without storing more than a small amount for startup, by investing the energy in recycling the spent oxides in cars to turn back into the metal, which is of course the energy that powers the vehicle using this arrangement.
It lends itself to similar energy densities as fossil fuels, no storage degradation like batteries have, losing energy over time.
it has the convenience of filling stations that would be very easy to implement to dispense metal pellets and water. Much easier than recycling whole gas tanks or battery packs, waiting 8 hours for your car to charge (what if is an emergency?) or other strange ideas people are grasping at.
is safer than storing hydrogen gas, which by the way is safer than storing gasoline in cars as it quickly evaporates UPWARD in a crash, not pooling along the freeway underneath your burning engine as gasoline does.
infrastructure is already in place to refine aluminum, it's called ALCOA and other large aluminum companies, tho presumably if used in cars, the locations would be moved around to optimize.
the fueling stations could, probably less efficiently, than trucking it in like gasoline in tankers, or maybe the stations would have a thermal solar modular dish or two and could produce some themselves.
additional benefits:
a car using fuel cells can run on the metal produced by any electric source including renewable so we can transition transparently for the driver to less polluting energy sources.
a car using fuel cell plus electric motors is simpler mechanically so would likely cost less to maintain
electric cars like this could be designed with the powertrain flat like a sandal and arbitrary body on top, limited only by wheel spacing. (this idea was elaborated in the futurecar episode last year on disovery channels)
fuel cells are twice as efficient converting energy to motion so the would cost less than half per mile for equivalent fuel inputs.
we need some kind of chemical powered locomotion. batteries, despite advances are wimpy and wear out much quicker than an internal combustion engine. if we can get fuel cells to the same lifetimes we should be in good shape. This should be theoretically easy as they are just a mix of molecular membranes and chemicals.
A similar material, reverse osmosis membranes were very expensive and now are churned out by the mile in petrochemical plants.
of course the water is available, covering 70% of our planet. even put thru a reverse osmosis filter, which cleans it better than triple distilled water, is twenty five cents a gallon in front of every grocery store and drugstore in the US.
Aluminum is the seventh most abundant element in the earth's crust.
there you go, the pig has lipstick, and it FLYs!
(presuming that flying car guy ever gets into production)
Reply
GaryB
119 Comments
Re: Like putting Lip-stick on a Pig
The hydrogen is an energy storage medium, so I don't quite get what you mean by "sink". All storage takes energy to maintain. You can say it's not an efficient storage medium and then we could argue. I'd like to see what the total efficiency would be for solar or nuclear energy used to split water for hydrogen and then the energy to combine the hydrogen into and out of the chemical store. I suspect it's not great right now and swapping whole takes is kind of stupid -- people will run out of fuel trying to milk the whole tank. I like the idea of metal pellets much better.
Reply
fkearney
6 Comments
Re: Like putting Lip-stick on a Pig
You're right to question the TOTAL energy balance around the system. Why do so many ignore the energy that goes into making the hydrogen in the first place? [I think that is durs' point.] Similarly, the metal pellet idea fails to consider the electricity that goes into turning bauxite into aluminum. ALCOA is a huge consumer of electricity.
Yeah I know, once we have totally renewable electricity sources like solar, it will be "free." Yada, yada, yada.
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erbium
340 Comments
Alcoa is a huge consumer of electricity
of course,
that is why the aluminum spontaneously releases so much energy in the form of hydrogen when it reacts with water to produce hydrogen.
not your wimpy a**d electric batteries,
aluminum (or other unreduced metals as mentioned) store energy in the general ballpark with hydrocarbon fuels (gasoline, diesel)
That's the main benefit of it.
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