Do you have any idea how proud I am to be a Hydrogen advocate while the majority here have no idea what is going on with the tech?

These threads will be fun to look at a few years from now. I guarantee it.

Meanwhile, what has the US done for energy independence lately?

NOT A GOD DAMN THING

The Democratic Nominee has just chosen Salazar to head the "transition" team. ROFL

energy in electric vehicles then using electricity to create hydrogen via electrolysis of water. After the hydrogen is produced it must be compressed in storage tanks requiring more electrical energy.

Battery powered.electric vehicles are 3 to 6 time more efficent at using electrical power in this usage.

Hydrigen is not a fuel it is an energy carrier. It takes energy to create it. Either via electrolysis of water or by reforming fossil fuels like natural gas to convert it to hydrogen and carbon by products
Niether process is efficient or provide a cost advantage over electric vehicle or efficient fossil fuels powered vehicle such as hybrids.

All of these experimental hydrogen fueling stations in states like California are subsidized. The cost of the hydrogen is not the real cost. It is being sold at a loss or given away in these pilot programs.

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If it was, no one would buy any car that gets less than the current max MPG, would they.

But people buy cars every day that get less mileage than the max. Because they trade efficiency for something else.

If someone's time is worth $300 or $400 dollars per hour do you think they would like to refuel their electric car in 3-5 minutes or wait around at a supercharger for 45 minutes?

Hydrogen makes it possible for those whose time is valuable to drive electric without the constant time drain of recharging. Also those who can't put a fast charger in their garage.

Half way right.

You can't compare gaseous hydrogen with a liquid fuel by volume. It has to be by weight.

Here's a hydogen advocate's takeo nit:

http://www.solarhighway.org/HydrogenFacts.html

h2-- 60,000 btu per pound
gasoline 18,000 btu per pound

And here's a more neutral chart that claims the same:

http://cta.ornl.gov/bedb/appendix_a/Lower_and_Higher_Heating_Values_of_Gas_Liquid_and_Solid_Fuels.pdf

Now, will a real chemist or physicist kindly explain why such a flimsy thing as hydrogen has such a high BTU level? Do all those carbon atoms in hydrocarbons mean little?

And, yes, I'm aware of the trade-off in the energy used to compress the hydrogen-- the point made by the first guy is that you can reduce compression costs.

Last edited Thu Aug 18, 2016, 09:52 AM - Edit history (2)

Breaking bonds takes energy, making bonds releases energy. If the bonds you make release more energy than the bonds you break, the overall reaction produces energy.

Here’s a comparison of hydrogen and methane. Starting with two hydrogen molecules and one oxygen molecule, producing two molecules of water, two H-H bonds and one O=O bond are broken and then four O-H bonds are created:

https://www.wou.edu/las/physci/GS361/Energy_From_Fossil_Fuels.htm

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The correct unit for comparison is the mole because they would contain the same number of molecules. When comparing the btu per pound you actually have far more molecules of hydrogen than you do of gasoline (octane) because the molecular weight of diatomic hydrogan is 2.0 grams/mole while the molecular weight for octane is 114 grams/mole.

you want to bring moles into it? I haven't taken a chemistry course since High School.

Here's the thing-- if I got a tank of liquid hydrogen and a tank of gasoline, which will do more work? Since it's a lot of energy to liquify hydrogen, what density of the gas is the most efficient pressure to get the most work done? And how does that compare with, say, methane?

I have no argument with hydrogen, and have even played around with it a little (electrolysis is easy), but any discussion of it has to end up with practical uses and comparisons.

One mole of methane (at “standard temperature and pressure”) has roughly the same volume (22.4 liters) as one mole of hydrogen.

http://www.science.uwaterloo.ca/~cchieh/cact/c120/idealgas.html

On the other hand, one mole of methane weighs sixteen times as much as one mole of hydrogen.

http://www.convertunits.com/molarmass/Methane : Molar mass of CH4 = 16.04246 g/mol
http://www.convertunits.com/molarmass/Hydrogen : Molar mass of H = 1.00794 g/mol

Last edited Thu Aug 18, 2016, 12:04 PM - Edit history (1)

The Saturn V used kerosene “RP-1” in its first stage, and (liquid) hydrogen “LH₂” in its upper stages.

Why? Well, different priorities:


http://history.nasa.gov/SP-4206/ch6.htm

Well, a UK tablespoon comes close… (assuming the hydrogen is brought to “standard temperature and pressure.”)

However, the question is, “So what?” To produce that mole of hydrogen requires a great deal of energy; somewhat more than you will get back if you recombine it with 11 liters of oxygen to produce the original mole of water.

I believe hydrogen has great potential as a way to store energy, but I don’t see where this particular bit of trivia is meaningful.