Hydrogen Powered Cars

June 14, 2007 4:03 PM

Hydrogen Cars. All the talk we hear now of hydrogen powered automobiles involves fuel cells. How about burning hydrogen directly in an internal combustion engine?

I remember seeing a movie set in France during World War II. The vehicles had tubes on the top which someone said contained hydrogen. Thus they were using hydrogen in an internal combustion engine. Was this true? If so, why is there no current investigation into burning hydrogen, rather than using fuel cells?

posted by mbarryf to travel & transportation (19 comments total)

There are several current investigations.

- Wikipedia
- BMW
- Ford
posted by mkb at 4:16 PM on June 14, 2007

BMW has built a fairly conventional internal-combustion engine that runs on hydrogen or gasoline.

I'm not sure what kind of efficiencies they're getting out of this engine in hydrogen mode, but typical ICE drivetrains only get about 35% efficiency. If you could beat that with a fuel-cell+electric motor drivetrain, you should have something that was quieter, mechanically simpler (apart from the fuel cell itself, I guess) and could run on battery power for part of the time (obviously you could add hybrid drive to the BMW, but that would be a whole extra subsystem). The proton-exchange membrane fuel cells do are at least that efficient, AFAICT.
posted by adamrice at 4:22 PM on June 14, 2007

The combustion of Hydrogen produces H20, but water vapor is a greenhouse gas that is a better absorper of black body radiation than CO2. Raising the efficiency of the I.C.E. is a much smarter ideal if we want to reduce environmental impact. There are other reasons as well, many of which involve production. Generally the use of Hydrogen seems to cause more environmental problems than it solves---at least right now.

See Wikipedia's entry on Hydrogen internal combustion for more.

Also try googling for hydrogen combustion.

There are plenty of people investigating hydrogen combustion. You need only look.
posted by bloggboy at 4:25 PM on June 14, 2007

Hyperphysics has a segment detailing hydrogen fuel cell efficiencies. They come up with 83% electrical efficiency, though the motor used to power the car would lose a fair bit of that.

Still much more efficient than just burning it though.
posted by Orange Pamplemousse at 4:32 PM on June 14, 2007

Here's their treatment of a diesel engine. If I recall correctly, diesel engines are more efficient than gasoline ones. The theoretical max is only 56% though.
posted by Orange Pamplemousse at 4:40 PM on June 14, 2007

water vapor is a greenhouse gas that is a better absorper of black body radiation than CO2

This may be true, I don't know. But the nice thing about water vapor is that it easily condenses out of the air. Is anyone actually suggesting that hydrogen powered cars would be a contributer to global warming because of water vapor? Sounds like pro-status-quo FUD to me. Burning regular HYDROcarbons produces water vapor too, though not as much.
posted by DarkForest at 4:55 PM on June 14, 2007

The problem with hydrogen isn't the specific mechanism that's used in a car to convert it to usable energy.

The problem is where the hydrogen comes from, how it's distributed, and how to store an adequate quantity of it in the vehicle.
posted by Steven C. Den Beste at 5:11 PM on June 14, 2007

One of the interesting things about an ICE is that, provided your fuel delivery system (injectors, lines, fuel pump) can handle it, it'll run on anything that'll combust.

In WWII, my grandfather and his buddies once got very drunk on the contents of a barrel marked "fuel" left behind by the Japanese when they fled an airbase in the Pacific. The Japanese had apparently been using ethanol to run their planes, due to petrol shortages.
posted by Netzapper at 5:52 PM on June 14, 2007

To answer the other part of your question: During WWII producer gas (aka wood gas or 'blue' gas), produced by heating wood / coal / tar, was sometimes used to fuel motor vehicles. Basically it's hydrogen, CO, CO2, & some methane.

Wikipedia has a bit on the subject, though doesn't have too much to say about historical automotive uses. Sometimes the producer was mounted on the back of the vehicle with a reservoir on the roof; other times a reservoir was filled from an external producer (e.g. in factories, farms, etc)
posted by Pinback at 5:55 PM on June 14, 2007

There is a pilot project here in Orlando right now testing buses that burn hydrogen directly.
posted by JohnYaYa at 6:00 PM on June 14, 2007

waterpoweredcar.com anyone?

Btw---anyone tried electrolysis like this before? Even to make a welder?
posted by TomMelee at 6:59 PM on June 14, 2007

I worked with engineers who were doing exactly this. They had already used it in aircraft, and they were adapting it to cars for GM.
posted by phrontist at 7:27 PM on June 14, 2007

Running an engine off straight hydrogen is perfectly feasible, as every other poster has been pointing out.

The reason why fuel cells are interesting, the reason why current research is focusing on them, is that hydrogen is very explosive. While it stores a lot of energy per pound, though not as much as petrol, it is much more explosive. In order to have a normal car catch fire you have to set it in a Hollywood movie. In a nasty real-life accident, you have to be unlucky for the car catch fire. Petrol is just not that explosive.

Hydrogen, on the other hand, explodes in a spectacular ball of fire, on a whim, if you just look at it the wrong way.

You would not want to drive a hydrogen car unless the hydrogen was safely stabilized within a fuel cell.
posted by gmarceau at 11:02 PM on June 14, 2007

United Nuclear, fine purveyor of home chemistry things, has had a system in the works for quite a while now.

They use metal hydrides, though, so they're having problems with the CPSC right now.
posted by The Esteemed Doctor Bunsen Honeydew at 12:07 AM on June 15, 2007

Compared to combustion engines, electric engines are gruntier, cheaper to build, cheaper to run, lower maintenance, simpler, more reliable, quieter, vastly greater rpm range with more torque, cooler, more efficient, etc. etc.

Electric engines make combustion engines look like the steam engines that they almost are. If you had a fuel source that could power both combustion and electric engines, you'd have to be crazy to pick the combustion engine.

(slightly related - you might want to look at the world's largest vehicles - mining dumptrucks larger than houses, etc, they use electric engines because combustion engines really aren't up to the job. Instead, diesel combustion is used for the power generation, since a generator only needs to run at a narrower rpm range)

As already stated by others, using hydrogen for combustion is really inefficient compared to electric, and since the energy density of hydrogen is lower than gasoline, efficiency matters in more ways than just cost-per-mile.

(Compounding that, you don't get regenerative braking with a combustion engine, so it's even more inefficient)
posted by -harlequin- at 12:16 AM on June 15, 2007

Burning hydrogen in an ICE also generates some (though not much) oxides of nitrogen (NOx), an ingredient in photochemical smog. This doesn't happen with PEM fuel cells because they don't run anywhere near hot enough.
posted by flabdablet at 12:55 AM on June 15, 2007

The reason why fuel cells are interesting, the reason why current research is focusing on them, is that hydrogen is very explosive. While it stores a lot of energy per pound, though not as much as petrol, it is much more explosive. In order to have a normal car catch fire you have to set it in a Hollywood movie. In a nasty real-life accident, you have to be unlucky for the car catch fire. Petrol is just not that explosive. Hydrogen, on the other hand, explodes in a spectacular ball of fire, on a whim, if you just look at it the wrong way. You would not want to drive a hydrogen car unless the hydrogen was safely stabilized within a fuel cell.

Um, no. Absolutely not. Just about everything gmarceau has said here is incorrect.

Petrol is not explosive as portrayed in the movies, and hydrogen is even less so (in the combustive sense). Hydrogen is even more sensitive than petrol in terms of the precise fuel / air ratio (i.e. how rich or how lean the mixture is) needed for sustained combustion. Plus the fact that hydrogen is the least dense of all gases -- if your storage medium ruptures, the hydrogen will likely float away before it ever ignites.

What I will grant you is that hydrogen gas has to be stored under high pressure, and a ruptured tank could decompress explosively (but 99.99% of the time without combustion). However there are no shortage of tank designs that allow safe, staged decompression in the case of a rupture. Hence the relative abundance propane-powered vehicles.

And don't even mention the Hindenburg -- that myth has been debunked several times over.

The real challenges in conventional hydrogen storage are:

A) Hydrogen gas molecules are so small that they literally squeeze past the space between metal atoms in the tank walls. All high-pressure tanks slowly leak hydrogen right through their walls. Not very practical if you park your car for more than a day and come back to find the tank empty.

B) Hydrogen gas is corrosive -- it gradually embrittles most metals that it comes into contact with. Eventually the tank, the fuel lines and even the engine will rot and crumble.

Hence the attempts to develop chemical storage mediums such as the metal hydrides others have mentioned.

As for why fuel cells are interesting, enough have mentioned that it is their efficiency that is attractive. I won't flog that dead horse again.
posted by randomstriker at 1:07 AM on June 15, 2007 [2 favorites]

Hydrogen gas is corrosive -- it gradually embrittles most metals that it comes into contact with. Eventually the tank, the fuel lines and even the engine will rot and crumble.

Why not use polymers or ceramics?
posted by Snyder at 12:52 PM on June 15, 2007

Using polymers is, in fact, current practice for high pressure hydrogen storage.
posted by flabdablet at 12:13 AM on June 16, 2007