You forgot rubbing the hydrogen lamp, and getting it free, instantly, from the hydrogen genie wherever you need it.
…
Interesting point, though: hydrogen is only about 1/4th as energy-dense as gasoline (IIRC)…so it’s going to take about four times as much liquid hydrogen for anything as it would if you used gasoline. Soooo…you don’t have to distribute as much hydrogen as gasoline, you would have to distribute four times as much hydrogen as gasoline.
…
I’d bet that we’ll see widespread electric vehicles before we’ll see widespread hydrogen-powered vehicles, just for distribution reasons: the existing petroleum infrastructure of the planet cannot be easily converted to accomodate liquid hydrogen, but electrical wires are already strung many places. Using the electricity directly is more efficient also.
~
A very bad assumption. This is the least economical way to make hydrogen. Hydrogen industrially is made by steam reforming of any hydrocarbon, Naphtha, Natural Gas, … even can be made from bio-material.
1. Centralized production of hydrogen at power plants, which is then shipped to hydrogen stations for car refuelling.
Again a very bad idea. Hydrogen is explosive. NASA (Orlando) has enough problems getting its hydrogen from Louisiana. Most fuel cells will need insitu reforming or at the very least a local reformer which will fill up the tanks.
2. Production of hydrogen at hydrogen stations, powered by electricity from the power grid with water from the water system.
Again, not economical or feasible. The only place I know that used to produce industrial hydrogen by electrolysis were old hydroelectric power stations, where power was cheap and there was no technology to make hydrogen from other means. The hydrogen was used to make NH3 (Ammonia) which in turn was used to make fertilizers.
3. Production of hydrogen at each home, powered by the electrical grid and with water from the water system.
Again not feasible. However, there are lot of innovative reformers which may do this job in the future.
**(Would the energy required to transport the hydrogen to various places overcome the production benefits of making it all at a few central locations?) **
Hydrogen is extremely difficult to transport because it cannot be liquefied. So whatever they tell you, you’ll not produce and distribute hydrogen, the way gasoline is. Right now transporting hydrogen bottle in your car will land you in jail for 5 years and a $500,000 fine!
Hope those answers help
Keep in mind that hydrogen is not a primary fuel. It is an “energy carrier,” much like an electro-chemical battery. More energy is expended during the production stages of hydrogen than what you get out of it when its burned. Thus any vehicle “powered” by burning hydrogen is really powered by whatever fuel your power plant uses (e.g. coal, gas, nuclear, hydro, oil), minus the inefficiencies that crop up at every stage.
All fuels are energy carriers. What do mean here ? Coal and Gasoline also require energy to process them before being used.
**More energy is expended during the production stages of hydrogen than what you get out of it when its burned. **
Blatantly False. Any Cites ? Hydrogen has been produced for ages from Methane/Methanol at very high efficiencies.
**Thus any vehicle “powered” by burning hydrogen is really powered by whatever fuel your power plant uses (e.g. coal, gas, nuclear, hydro, oil), minus the inefficiencies that crop up at every stage. **
Again, you assume that hydrogen will be produced by electrolysing water. Its just not true.
Hyrdocarbon fuels may require refining but they are found in a more or less nautual state. There is no natural source of H2.
**
No process is 100% efficient so by definition all processes have more input energy than oputput. You apparently don’t count the fuel value of the methane or methanl being converted to hydrogen.
“In the U.S., 90-95% of hydrogen is produced by steam reforming. Theoretically, the energy that must be supplied to the process is the difference between the heat of combustion of the resulting hydrogen and the heat of combustion of the reformed feedstock. This difference sets the lower limit on the energy required to produce an alternative fuel. In practice the overall efficiency of the process – that is, the energy content of the hydrogen produced divided by the total energy consumed by the reforming process – is approximately 65%.” - M.J. Murphy, H.N. Ketola, P.K. Raj, Summary of Assessment of the Safety, Health, Environmental and System Risks of Alternative Fuels, rep. No. FTA-MA-90-7007-95-1, US Department of Transportation and U.S. Department of Energy, Washington DC. (1995)
“To produce an amount of hydrogen with the energy content of 1 MJ, about 1.6 MJ of energy must be expended. But only 0.167 MJ of energy must be expended to produce a quantity of gasoline with an energy content of 1 MJ.” - M.A. Delucchi, A Revised Model of Emissions of Greenhouse Gases from the Use of Transportation Fuels and Electricity, rep. No. UCD-ITS-RR-97-22, Institute of Transportation Studies, University of California, Davis (1997)
“Hydrogen is not a fuel in the sense that coal or sunlight is. Hydrogen is just an ‘energy vessel.’ It depends on how you make the hydrogen. If you burn coal to generate electricity to electrolyses water, then the only value is in shifting the source of pollution from the urban environment where the hydrogen is used to the location of the power plant.” Dr. Bob Allen, Professor of Chemistry, Arkansas Tech University
“Hydrogen is not a fuel, it is an energy carrier analogous to electricity. It is not a generating technology, it is an enabling technology.” - Dr. H.M. Hubbard, Chair, Committee on Programmatic Review of the U.S. Department of Energy’s Office of Power Technologies, National Research Council, to the Hearing Charter Subcommittee on Energy, Committee On Science, U.S. House Of Representatives, President’s National Energy Policy: Hydrogen and Nuclear Energy R&D Legislation Thursday, June 14, 2001
“It should be borne in mind that hydrogen is not a fuel but an energy carrier.” - Energy at the Crossroads, The Chemical Engineering Contribution to the UK Energy Debate, A response to the PIU Energy Review and the joint departmental energy policy consultation, published in May 2002, Briefing prepared by The Institution of Chemical Engineers for Mr. Brian Wilson MP, Minister of State for Energy & Industry
What good is hydrogen doing if you get it via the steam reforming process? From andy_fl’s post above it appears to me that steam reforming takes a hydrocarbon and produces CO2 and H2. The hydrogen will be later converted to oxygen. Thus the end result is the same as burning the hydrocarbon. I thought the whole point of hydrogen as a fuel was that it did not produce CO2 when used. The only way I see hydrogen power helping is if the hydrogen is produced in a way that lowers the total amount of CO2 produced. Steam reforming will produce more CO2 because of the inefficiencies of making H2 out of hydrocarbons rather than just buring the hydrocarbons.
Liquid hydrogen is a big problem. That’s why no one really talks about it any more. The preferred method now seems to be metal hydride. You get better storage efficiency and much better safety.
The 4th of July would never be the same if we installed an electrolysis device that produces large quanties of Hydrogen and Oxygen in every home in America. I don’t see any way that the technology could be made “safe and sane” enough to serve the untrained consumer. On the up side, we’d get a rash of grim jokes about stupid people who inadvertantly set off Hydrogen bombs in their own basements. :eek:
Squink, I think you’ve still got the Hindenberg disaster planted in your mind. Yes, the hydrogen was very flammable but all the visible flame was from the doped fabric covering the structure. As a general safety rule its a bad idea to use explosive paint when there is fire risk. Hydrogen is not without risk but put the real risk in perspective with the fuels we already use. A good portion of us has compressed explosive gas piped into our homes and nearly all of us have a car with a case of dynamyte underneath.
andy_fl’s original post is inaccurate in two regards.
First (and this is a minor nitpick, but one that actually greatly extends the utility of the steam-refoming process), a hydrocarbon is unnecessary. It was commonly done in the late 19[sup]th[/sup] and early 20[sup]th[/sup] centuries to use coal (essentially, plain carbon), so that the primary reaction was:
C + H[sub]2[/sub]O -> CO + H[sub]2[/sub]
It should be noted that carbon monoxide (CO) itself has considerable value as a fuel gas. There was, naturally, unreacted water vapor in the gas, but most of this was easily removed, and the remnant did not significantly impair its use.
Secondly, the second-stage “shift” reaction:
CO + H[sub]2[/sub]O -> CO[sub]2[/sub] + H[sub]2[/sub]
often does not occur (catalysis helps, but insufficiently). The reason why no one wants to distribute hydrogen contaminated with carbon monoxide is left as an exercise to the Teeming Thousands.
Certainly, but if you want to use an electrolysis system to generate hydrogen, you will also generate one molecule of O[sub]2[/sub] for every two molecules of H[sub]2[/sub]. The mixture is FAR more dangerous than anything involved in the Hindenberg disaster. Safely disposing of the large amounts of pure oxygen generated by the electrolytic production of hydrogen would be more complicated than running a waste pipe up to the roof or into the nearest sewer. If you did the later, your sewer would be liable to explode. Oxygen is a powerful oxidizer, and will kill you if you treat it with impunity, even in the absence of hydrogen.
From here. It takes 50 trucks to haul the more than 300,000 pounds of hydrogen fuel needed for each shuttle launch. Costs of hauling the fuel 600 miles between Louisiana and Florida range in the hundreds of thousands of dollars.
“If you could produce hydrogen on site at Cape Canaveral or right nearby, you could at least cut the cost in half, because the transportation is a huge part of the cost,” said James Burkhart, a senior research engineer at the NASA Glenn Research Center in Cleveland.
From here. Criminal penalties for willful violations of up to $500,000 and five years’ imprisonment (49 U.S.C. § 5124):
Hydrogen is an element while hydrocarbons are a group of compounds. Hydrogen cannot occur in nature due to the high diffusivity of hydrogen. Having said that trace amounts of hydrogen occur in Natural Gas as well as radioactive sources.
**No process is 100% efficient … **
[/QUOTE]
When we look for fuels to do work and not heat, we are more concerned about anergy and less about energy. Explained later.
1> CO2 produced is in one place, hence easier for sequestration. Or put in simple words, instead of letting of CO2 all over the town, you have it in one place where it could be treated.
2> No Nitrogen Oxides. These are far worse than CO2
3> In a typical car only 12% of the energy in the gas reaches the wheel here. So 88% of the energy is used to just heat up the atmosphere. With Fuel Cell Cars the energy reaching your wheels will be more than 90%.
Of course the danger of Hydrogen as an explosive is there. But what many people don’t realize is Oxygen is even more dangerous and has a worse safety record. But thanks Pad.
Thanks for the correction. Coal is not pure carbon and Coal gas/Water Gas was made by passing steam through a bed of burning coal, steam was passed for sometime, then the coal cooled down, hence air was passed to reheat and this was done in a circle. The product gas was of very bad consistency and used for fuel in homes and street lights. CO is a poison : Both for humans and Catalysts in fuel Cells.
Shift reaction does proceed to certain completion. The remaining CO is removed by amine absorption / variety of other processes. It has been done so for the last 50 years or more. If they were not able to remove the CO, the NH3 catalyst would have got poisoned. NH3 is used to make urea, which is responsible for our increased food production over the last 50 years.
Electrolysis does not produce a mixture of H2 and O2, but H2 at O2 at different electrodes. Electrolysis of water had been used before Steam Reforming Technology matured, to make Hydrogen for making Urea/Fertilizers.
So consider the Energy in a gallon of gasoline: Overall efficiency Done if used straight in a conventional Car = 12%
Overall efficiency if first reformed and then used in a fuel cell car = (0.65/(1+0.65)) x 0.9 = 35 %.
So in practice we’ll reduce fuel consumption by 3 times!
Moreover, the energy used in reforming processes can be low grade energy i.e. the steam may be produced by fuel oils (can be even COAL in a CFB boiler) and the like which cannot be used directly to do any work. Moreover, the reformer efficiencies you quote are for Hydrogen for fertilizer/naptha treatment/hydrogening vegetable oils. Mordern reformers are far more efficient and in-situ reformers are even more.
That’s only true if the system is set up and maintained properly. The potential for O[sub]2[/sub] H[sub]2[/sub] mixtures is intrinsic to the electrolytic process. These home units would have to be designed to be absolutely idiot-proof or some yahoo would end up venting O[sub]2[/sub] to the floor of his basement while failing to check for leaks in the hydrogen lines.
Any conceivable use for the O2 you’d make if you electrolized water? Would killing two birds (production of O2 and H2) with one stone (electrolizing water) in any way make up for the inefficency?
If you look at your cite your will see only 62% of the gas engine inefficiency is waste heat. The mechanical inefficiencies will still be there for an electric car. Electric motors are also not without their inefficiencies either. So I will need a cite for the 90% you quote for fuel cells. You have neglected that method to produce hydrogen is only 65% efficient so we will need better accounting for the losses in the system before you can say it is more efficient.
What kind of treatment is there for CO2? I have heard of some talk of pumping into the deep ocean where it will pool at the bottom or maybe storing it back in the same place we got the oil from. Both of these seem pretty expensive to me and I have read that people are worried about the stability of the CO2 pools at the bottom of the ocean.