Hydrogen powered car? better not say "BOMB"!

[rich m]

I'm pretty sure that I won't want to drive a H2 powered automobile. The power-gods in Detroit might surprise me, but, I just don't think the chemistry and the physics will work out for one that I'd enjoy



and you say, "Rich, why the pessimism?"



to which I answer, "Bond reformation energy sorely lacking "



and many of you get the "deer in the headlights" look



Here it is, Hindenburg not withstanding.



Hydrogen's a low-temp fuel. The Hindenburg's conflagration released a buttload of BTU's, but that's because it was a buttload of cubic meters of gas. In the kind of premeasured quantities that you'd use in a controlled combustion situation, like a car engine (notice I didn't type "truck engine" ?), there won't be many BTUs produced... . and you say, "that's OK, it'll run cooler " and I say, "if it'll run at all"





Here's the reasoning. I know the BTU's per gallon of gasoline (approximated) and I know the BTU's per gallon of Diesel (also approximated) I don't know the BTU's per cubic foot of H2, but, if you want specifics the number's gotta be out there in cyberspace, and you could stick it into the math yourself. For now, let's examine some applied physics in the present "real world"



My 7,000+ lb truck gets approximately 17mpg in "urban mix" driving. I happen to know that one gallon of D2 can liberate approximately 14,000 BTU of heat. From this, I can state that I need about 823 BTU per mile to drive my truck.



(14000 BTU/gal divided by 17miles/gal= 823-ish btu/mile)

if all other measurements remained equal, running the same load on the same distances, pushed by gasoline would require the same 823BTU/mile, and so, more volume of gasoline for each mile, cutting the MPG to about 14. 5mpg, due to lack of intrinsic heat in the fuel



Now, for the chemistry.



Both gasoline and Diesel are hydrocarbons. For easy typing, I'll treat them as pure chemicals, rather than the mixtures that, in reality they are.



Gasoline is a saturated Hydrocarbon chain of, like 8Carbons and 18 Hydrogens, commonly schematic'd like this:

H H H H H H H H

H-C-C-C-C-C-C-C-C-H

H H H H H H H H



Diesel is a longer chain molecule, say, for the sake of comparison, 10carbons long, and with 22 hydrogens.



I'm not typing one of those... use yer imagination...



Where does the heat come from?

Oxidative burning (if complete) of the imaginary gasoline fuel molecule releases heat proportional to the breaking, and re--bonding (with O2) of all those bonds, which lead to 11 molecules of water and 8 molecules of CO2





If you do the same to the sample of Diesel, which is a longer, heavier, more oily, molecule will yield more bond-breaking and reforming to make more molecules of H2O and CO2, AND MORE HEAT!!



H2 has NO carbon, and just a single covalent bond to break.

There simply won't be a lot of BTU/ unit of measure available, compared to hydrocarbons...



will need bigger tanks, and lighter vehicles... I don't see them having any power or range... (some of you cyber-pic whiz kids can probably find a pic of Steve Urkel's BMW Isetta, and the Graf Zeppelin, and put them together like the Zeppelin is the Isetta's fuel tank..... get the picture? ) Since its exhaust would be, simply, pure water, call it the Dripmobile!



There might be one neat design, however... . don't go reciprocating piston for an H-motor... Go with a gas turbine for more efficient use of the thermodynamically anemic fuel... at least you'd never need to monitor EGT's



I'm not even going to mention that hydrogen generation requires electricity to produce... . trading wall-plug power for foot-throttle power... .net energy expenditure would be heavier because of that.

 

[illflem]

Rich, point you miss is the "plan" calls for not burning the hydrogen but rather using it to charge batteries to power electric motors. Burning hydrogen is only in the plan during the transition from a hydro-carbon to a hydrogen based economy. It's way too early for us to predict how this will all work, much of the technology hasn't even been invented.



One thing is certain though, petroleum production is expected to peak in the next 10-15 years, after that it's all downhill. Some how, some way something has to change if energy consumption is to remain economic at current levels. We really don't have a choice but to change.



Lots of good reading from the links here http://www.eren.doe.gov/RE/hydrogen.html

 

[Rman]

wow, rich calm down. You paint pictures of doomsday and the end of the natural world with your gross exageration. You are correct that hyrdogen does not contain the same stored energy as other fuels like diesel and gasoline. However, its the readily available energy that made those fuels so promising 100 years ago. Well now we are paying the price for using those fuels, we have become abundantly dependant on them, and now have huge emmissions problems and greenhouse gases created by them.



Hydrogen is being researched to be used in fuel cells to power electric motors like bill said. The technology hasn't developed yet, but it will with time, and some money . Its a simple case of getting enough people to understand its benefits, and understand that it is something that MUST be researched. Even if it leads to realizing maybe their is a better fuel... how do we know if we don't research it? You know people once thought the sound barrier couldn't be broken, that atomic fission was impossible and would destroy the planet in the event of a chain reaction. Relax a little and let science run its course, its worked before ya know.

 

[Dreher]

There's a basic description of hydrogen fuel-cell technology here.



Last year, DaimlerChrysler drove a fuel-cell vehicle across the US, although it took a team of scientists to reach the destination. Last month, Los Angeles took delivery of a fuel-cell Honda FCX as part of a commercial lease program. This appears to be promising technology.



Bob

 

[rich m]

I figured that the goal was "fuelcell" tech....

... so, we'll just pull the heads off all of our beloved CTD's and turn them into 6-hole flower pots?



2H2+O2->2H2O still will yield only a certain amount of power, be it via flame or via electrochemical capture. Admittedly, the electrochemical route will reclaim a bigger percentage of the potential, but to "charge up" the system would still require that H2O be electrolysed to its constituent H and O... . That electricity's gotta come from somewhere, like the electric company, and they get their heat from burning some kind of fuel. They'll use more trying to keep up with our newfangled electrodependant technocars... . Maybe it's just that I'd hate like hell for Algore to think he got something correct... (moderator: I need a "puke" smiley right here)





I'm not sure I want to participate in a future that looks too much like some of the movies I've seen... this just sounds too movie-esque... .



Maybe I'll revert to black-powder firearms, while hydrogen goes into my car, and I stand there on the 34th lap of a grocery run, missing my truck...

 

[illflem]

Rich, you might have to buy a quarter acre out in the desert, install a 100,000 gallon tank and start filling it if you want to continue driving your Cummins. Good news is by then there probably won't be anyone checking for red diesel.

It's just a matter of time...

 

[Peter Campbell]

No one asked where does the hydrogen come from? It is very reactive. It is all tied up in other compounds. To get hydrogen you need to - Crack hydrocarbons to free the hydrogen. or use electricity to dissasociate the water. Where does this energy come from to free this hydrogen? Oil, coal, nuclear, or hydropower. So really it is just a way to fuel cars with a different more dangerous more expensive fuel. If the hydrogen can be used in a fuel cell that turns the bond energy right back to electricity there are very large efficiency increases available. Using hydrogen as a fuel in a heat engine would be plain stupid. Why crack oil (and waste energy) to make hydrogen and carbon, Compress the hydrogen ( use more energy) ship the low density hard to trasport dangerous product to a fueling point ( waste energy ) in very expensive high pressure cylinders to use in a heat engine that has been perfected to only 30% efficiency. The only reason would be a fuel cell at 95 percent efficiency. We are all familiar with anoother easiert to refine and transport, safer fuel product for 30% efficient diesel engines. OBTW at work we use nice pure hydrogen as coolant on the main generator. It takes a 75,000 lb tractor trailer to deliver to us a maximum of 800 LBS of product. How many lbs of diesel fuel are used to move that 75,000 LB container around? Also the product is pure and the price is high. Around 1. 00$ per cubic foot. about 100 times the price natural gas.

 

[tgbol]

BMW has been working on a hydrogen powered engine. Not a fuel cell, but internal combustion burning H2 and air. They have 4 cars in Austrailia and a couple running around the L. A. area. I don't know how you would refuel on the road.