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The Car That Makes Its Own Fuel
Spy der Mann writes "A unique system that can produce Hydrogen inside a car using common metals such as Magnesium and Aluminum was recently developed by an Israeli company. The system solves all of the obstacles associated with the manufacturing, transporting and storing of hydrogen to be used in cars. And it's completely emission free."
The superheated water and H2 come from the magnesium metal reacting with water. The metal oxidizes, gives off heat, and releases the hydrogen part of the water. However, there's still the problem of obtaining the metal in the first place.
Spokesbossy for ominous cow herds everywhere.
Yes, you can get hydrogen out of acids by combining them with metals like aluminium or magnesium -- or hell, even sodium with water. But the cost of refining these metals in the first place is very high.
For instance, aluminium is produced by electrolysis: the ore is dissolved in cryolite, and the pure metal produced by passing an electric current through it. (Details)
There's a number of aluminium smelters in Australia (my home country); at least one of these has its own dedicated power plant, burning brown coal to produce its electricity.
So no, it's not "making its own fuel". The fuel is the refined metal and the acids (or water) that are combined with them to make the hydrogen gas. The fact that burning the hydrogen is what generates the useful energy is irrelevant to this point. The pollution is shifted to wherever the power to make the metals is produced.
When it comes to energy, there ain't no such thing as a free lunch.
One thing I've learned over the years: Slashdot editors aren't much interested in science. The publish a lot of pseudo-science articles, or nonsense science articles like this one.
The issue here is that the process works, but it is very expensive in energy, because the metal oxide must be refined.
Anyhow, there is nothing new in the referenced article. The fact that it is possible to produce hydrogen using reactive metals has been known since perhaps 1860, maybe much earlier.
If I remember correctly, there was an explosion in Antoine Laurent Lavoisier's lab caused by hydrogen released by heating with metal. Mr. Lavoisier died in 1794, and not from the explosion.
There is currently not a distribution system for delivery of gaseous fuels direct to consumers at the scale required to power our cars. There are some small-scale delivery systems (propane, for example) but those still require a trained handler and other special steps -- you typically can't pump your own propane, propane needs to be stored outdoors in a ventilated cabinet, etc. And the infrastructure for propane is small: a couple hundred gallons per homeowner per winter up here where it's cold, maybe a few tanks for cooking in the summer, that's it. There aren't nearly enough trucks and tanks required to provide fuel for all vehicles if they were suddenly converted to propane.
Even if the safety issues were handled technologically, neither propane nor natural gas are ready for "the final mile". Most homeowners don't have an existing gas "tap" where they can hook a hose up to their car, so they'd require new plumbing. For that matter, home delivery of natural gas is pretty much restricted to metro areas in northern states: it's not currently available in the far south or in rural areas. To make it available everywhere else would require a huge investment in pipes.
Then there's the problem with the storage of hydrogen or any gaseous fuel. For there to be enough energy to power a vehicle for any useful distance, a fairly large quantity of it needs to be highly compressed. Where do you put a large pressure vessel in a car so that if it's in an accident it has the lowest risk of rupturing? If you've ever seen even a small tank of high pressure gas rupture, you'll realize some of the danger. Now, make that gas highly flammable, and you'll be even more unhappy.
The idea of a magnesium coil as a fuel source is a good one. It could distributed in user-replaceable reusable metal boxes, each containing a humanly-portable 20kg of fuel, and having room for an equal amount of oxidized waste. Assuming a well-designed non-sparking container it would require no special handling, and would be remarkably inert. It would also be quite safe in most accidents, even those involving the fuel containers themselves.
These boxes can be carried by ordinary trucks. They would not require specialized tankers like propane or even gasoline. Any existing trucking firm could safely handle boxes of this product as is. And you could buy and sell them anywhere, not just fuel stations: a grocery store, discounter, convenience store, wherever. They would have no foul or toxic smells or hazardous liquids, and would run the same risk of accidental ignition as any other flammable metal, which is to say: not a lot. If you've ever tried to ignite magnesium or aluminum, you're probably aware of the amount of heat required to get it to sustain flame.
The part of the story that requires the most handwaving is the "mining" of the fuel. Both aluminium and magnesium are naturally found in the oxidized state (much like the spent fuel from the vehicle itself.) The amount of energy required to refine the metal is immense. Keep in mind that you cannot get something for nothing; that means the energy required to refine it must be higher than the amount of energy retrieved from the metal when it is burned. And that means huge amounts of electrical energy will be needed to produce a fuel stream. With an emphasis on reducing costly oil consumption, with today's technology that would basically mean lots of new nuclear reactors will be required.
Think of the magnesium more like a "rechargeable battery", storing electrical energy in the form of unoxidized metal. It's still going to require energy that comes from somewhere else.
John
Actually the link I submitted was a physorg one. IIRC, physorg doesn't publish BS articles.
:-/
Or am I wrong?
a) yes Al takes a lot of energy to make. we would call this a "high energy density" material. This is a good thing, not a bad thing.
It would be a good thing if it were true. The massive ammounts of energy used to reduce bauxite are mostly lost as waste heat. If they were actually stored in the material, this might be an efficient system to transport energy.
Water will add to the weight, yes. I don't know all the physics, but in general I know you can get a LOT of hydrogen out of a little water.
Well, I do know the physics involved. No, you can't get "a LOT" of hydrogen from water. Water is only 2/18 hydrogen by weight. So you only get 111 grams H2 per kg H2O. That's elementary chemistry. The heat of combustion of H2 is about 141 MJ/kg (IIRC), and the heat of combustion of gasoline is about 44 MJ/kg. But if you're only getting 11% H2 from water, then the effective heat of combustion from the products of electrolysis is about 16 MJ/kg of H2O. Therefore, even neglecting the weight of the metal, this is not a very energy dense system as you claim it to be.
There so much wrong with the rest of your post, but I don't feel like addressing it. The FP had it right: this is bullshit.