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How much hydrogen is needed for an average fuel cell car, to run for say a week?
How much hydrogen is needed for an average fuel cell car, to run for say a week?
I understand that the Enthalpy of Hydrogen is about three times that of petrol. You would need about one third of the mass of Hydrogen, compared with the equivalent mass of petrol. That only offsets, by a tiny amount, the overhead involved with storing hydrogen in a stable form. The best that has been achieved has been about 6% by mass. That means you would still need to carry around about four times the extra mass of the (very expensive) storage medium. This compares badly with the mass of a petrol tank. The medium can be easily contaminated by an impure hydrogen supply. Also, I should imagine that re-charging would take a lot longer than just pouring 40litres of petrol into your tank. We have some way to go, yet but, when it can be made to work, it will be very clean - but not a free energy resource.
In energy storage applications, the energy density relates the mass of an energy store to its stored energy. The higher the energy density, the more energy may be stored or transported for the same amount of mass. In the context of fuel selection, that energy density of a fuel is also called the specific energy of that fuel, though in general an engine using that fuel will yield less energy due to inefficiencies and thermodynamic considerations—hence the specific fuel consumption of an engine will be greater than the reciprocal of the specific energy of the fuel. And in general, specific energy and energy density are at odds due to charge screening.Gravimetric and volumetric energy density of some fuels and storage technologies (modified from the Gasoline article):(Notes: Some values may not be precise because of isomers or other irregularities. See Heating value for a comprehensive table of specific energies of important fuels. The symbol ** indicates the item is an energy carrier, not an energy source.) storage type energydensity recoveryefficiency by mass by volume peak practical MJ/kg MJ/L % %**mass-energy equivalence89,876,000,000**binding energy of helium nucleus675,000,0008.57x1024nuclear fusion of hydrogen (energy from the sun)300,000,000423,000,000nuclear fission (of U-235) (Used in Nuclear Power Plants)77,000,0001,500,000,00030% 50%**liquid hydrogen14310.1**compressed gaseous hydrogen at 700 bar1434.7**gaseous hydrogen at room temperature1430.01079beryllium (toxic) (burned in air)67.6125.1lithium borohydride (burned in air)65.243.4boron (burned in air)58.9137.8compressed natural gas at 200 bar53.610gasoline46.934.6diesel fuel/residential heating oil45.838.7polyethylene plastic46.342.6polypropylene plastic46.341.7gasohol (10% ethanol 90% gasoline)43.5428.06lithium (burned in air)43.123.0Jet A aviation fuel42.833biodiesel oil (vegetable oil)42.2030.53DMF (2,5-dimethylfuran)4237.8crude oil (according to the definition of ton of oil equivalent)41.8737polystyrene plastic41.443.5body fat metabolism383522-26%butanol36.629.2LPG34.3922.16**specific orbital energy of Low Earth orbit33 (approx.)graphite (burned in air)32.772.9anthracite coal32.572.436%silicon (burned in air)32.275.1aluminum (burned in air)31.083.8ethanol3024polyester plastic26.035.6magnesium (burned in air)24.743.0bituminous coal2420PET pop bottle plastic?23.5 impure?methanol19.715.6**hydrazine (toxic) combusted to N2+H2O19.519.3**liquid ammonia (combusted to N2+H2O)18.611.5PVC plastic (improper combustion toxic)18.025.2sugars, carbohydrates & proteins metabolism1726.2(dextrose)22-26%Cl2O7 + CH4 - computed17.4lignite coal14-19calcium (burned in air)15.924.6dry cowdung and cameldung15.5wood6–171.8–3.2**liquid hydrogen + oxygen (as oxidizer) (1:8 (w/w), 14.1:7.0 (v/v))13.3335.7sodium (burned to wet sodium hydroxide)13.312.8Cl2O7 decomposition - computed12.2nitromethane11.312.9household waste8-11sodium (burned to dry sodium oxide)9.18.8iron (burned to iron(III) oxide)7.457.9Octanitrocubane explosive - computed7.4ammonal (Al+NH4NO3 oxidizer)6.912.7Tetranitromethane + hydrazine explosive - computed6.6Hexanitrobenzene explosive - computed6.5zinc (burned in air)5.338.0Teflon plastic (combustion toxic, but flame retardant)5.111.2iron (burned to iron(II) oxide)4.938.2**TNT4.1846.92Copper Thermite (Al + CuO as oxidizer)4.1320.9Thermite (powder Al + Fe2O3 as oxidizer)4.0018.4**compressed air at 300 bar40.14?ANFO3.88hydrogen peroxide decomposition (as monopropellant)2.73.8Lithium Thionyl Chloride Battery2.5Regenerative Fuel Cell1.62**hydrazine(toxic) decomposition (as monopropellant)1.61.6**ammonium nitrate decomposition (as monopropellant)1.42.5Molecular spring~1**sodium-sulfur battery?1.23?85%**liquid nitrogen0.77 0.62**lithium ion battery0.54–0.720.9–1.995%**lithium sulphur battery0.54-1.44?kinetic energy penetrator1.9-3.430-545.56 × 45 mm NATO bullet0.4-0.83.2-6.4**Zn-air batteries0.40 to 0.72???**flywheel0.5??81-94%melting ice0.3350.335**zinc-bromine flow battery0.27–0.306**compressed air at 20 bar0.27?64%**NiMH Battery0.220.36?60% **NiCd Battery0.14-0.22??80% **lead acid battery0.09–0.110.14–0.17?75-85%**commercial lead acid battery pack0.072-0.079???**vanadium redox battery.09.1188?70-75%**vanadium bromide redox battery.18.252?81%**ultracapacitor0.0206???**ultracapacitor by EEStor (claimed capacity)1.0???**supercapacitor0.01?98.5%90%**capacitor0.002???water at 100 m dam height0.0010.001?85-90%**spring power (clock spring), torsion spring0.00030.0006?zero point energy00
There has been a new fuel cell technology developed. It uses a hydrogen compound that is liquid at room temperature and doesn't require the expensive platinum catalyst. I don't recall the details.
With a hydrogen fuel cell, the chemicals are hydrogen and oxygen, and they are continually fed to the fuel cell, so they do not run out (or, if your tanks run dry, you just fill up with more hydrogen, but you don't need to throw away the fuel cell).
So oxygen is used as well?
It's a hydrogen oxygen liquid fuel mix?
Could you not also used liquid helium, or nitrogen? With transfer of electons, surely any Gas atom could be used.
Is this the silly season for nakedscientist forums?Doesn't anyone read books before starting to post here?
Quote from: JOLLY on 08/12/2007 15:08:39So oxygen is used as well?Yes, it is crucial, but oxygen is readily available from the air, so you don't need to tank up on it.Quote from: JOLLY on 08/12/2007 15:08:39It's a hydrogen oxygen liquid fuel mix?The hydrogen and oxygen are stored separately. To premix them would have a dangerously explosive mix, and would anyway have to be separated when entering the fuel cell. In any case, as I said, for most applications, you don't need to carry your own oxygen (it is normally available from the air around you - unless you are looking for applications in space, or submarine applications).As for whether the hydrogen is liquid - cryogenically stored liquid hydrogen is one choice, so is high pressure gas storage, and so is gas absorption in some solid matrix. Each solution has its own problems.Quote from: JOLLY on 08/12/2007 15:08:39Could you not also used liquid helium, or nitrogen? With transfer of electons, surely any Gas atom could be used.No, it depends on the structure of the electrons around an atom. All atoms are naturally electrically neutral (i.e. the number of positively charged protons in an atom normally balances the number of negatively charged electrons), so there is good reason not to give away or accept another electron, since that would make them no longer electrically neutral. On the other hand, atoms also like to have certain specific configurations of electrons around them in preference to other configurations, and if they have too few or too many electrons for their ideal configuration, then they may give up or accept another electron in order to obtain an ideal configuration. When you get an atom that has too many electrons for its ideal configuration, and one that has too few electrons for its ideal configuration, then the one that has too many electrons will give away its electron, and the one that has too few will accept an electron, and between them you will get a stable chemical compound (that, in a nutshell, is the basis of all chemistry).The first rule is that electrons like to go around in pairs. Normal helium has exactly two electrons, and so for it, that is an ideal number of electrons, and so it will have great difficulty either accepting another electron or giving up an electron.
For oxygen, it naturally has 8 electrons, but the ideal number of electrons for an atom of about oxygen's size is 10 electrons. Neon is slightly heavier than oxygen, and has 10 electrons, and so, like helium, neon is very difficult to make chemical compounds with.Hydrogen would really like to have 2 electrons (like helium, its heavier cousin), but it will just as readily give up its one electron, so it has no electrons.If you then have two hydrogen atoms, each willing to give up one electron, and one oxygen desperately seeking to get two more electrons, you can see they are in a strong position to make a swap - and between them make a chemical compound of two hydrogen atoms and one oxygen atom - this compound is water.
Could you not give helium an extra electron? Or is that what helium 3 is?
So the trick really is to make a electron full store of hydrogen to put in your car. Could you not, return the hydrogen to the fuel cell after use, by running it through a coil where it could pick up more electrons?
As you say, both of these feedstocks contain carbon, and so will produce carbon dioxide, but since both can (and often are) created from plant matter, thus the carbon dioxide created is from carbon dioxide taken from the atmosphere (true, the same can be argued for mineral oil combustion, but in the case of mineral oil, the counter argument is that it was taken from the atmosphere millions of years ago, whereas boifuel sources of methenol or methane could be take from the atmosphere with the preceding 12 months).
The arguments about efficiency are far more complex that that stated.
I don't really get the it takes energy to produce it arguement, it takes a huge amount of energy to produce petrol surely.
And helium as a fuel, could be, or would be, highly volitile?
Hydrazine hydratea compound of nitrogen, hydrogen, and wateris liquid, which makes it easier to store and deliver than gas. And it contains no carbon, so cars using it would still be environment-friendly. But perhaps the main advantage of the new fuel cell is simply that it's cheaper.
Quote from: JOLLY on 12/12/2007 13:59:26I don't really get the it takes energy to produce it arguement, it takes a huge amount of energy to produce petrol surely. As SJoeberg has mentioned, it is all about how much you spend for how much you get.Think of energy as money (very much, energy is the currency of science).If you spend £1 million, and get £2 millions back, you are in profit, and it is a good deal. If you spend £1 millions pounds, and get only £1 million back, you have achieved nothing, and by the time you have paid your brokers commission (because all real life processes have inefficiencies that lose energy beyond the theoretical ideal), you will actually have made a small loss - certainly not the kind of deal you want to make.Yes, it does take a huge amount of energy you have to put in when processing petrol; but in that particular case, the amount you get back exceeds what you put in, so you are in profit.
Hi all, been reading this forum for a while. Decided to register and post.I have been reading a lot about hydrogen electrolysis and maybe some people here could provide some additional input. I have plans to build a gas-saving device for my car.This device supposedly injects hydrogen into the vehicle's intake manifold in order to allow for a decrease of gasoline consumption on some level or another. It does this by allowing the engine to burn hydrogen in the combustion chamber along with the existing gasoline and oxygen mixture. Supposedly, doing so will allow an engine to run at a max of 30:1 air/fuel ratio (hydrogen being included in the air part of the ratio). That's pretty lean. Supposedly it can double gas mileage. It's just an electrolysis device that creates hydrogen ions from water. I'm not exactly sure how much hydrogen must be electrolyzed, how existing fuel management must be modified, or how much energy it would take to do so, so have not been able to figure out if the task would be worthwhile. There are claims that it does work, such as this: http://waterpoweredcar.com/hydrobooster.htmlWhat do you think?
You don't need to worry about trying to store hydrogen in gas form, using pellets made of an alloy of aluminium and gallium, you can just store a tank of water in your car, and add the water to these pellets which reacts and turns the aluminium into aluminium oxide, and produces hydrogen. This way you get hydrogen on demand, without storing anything at high pressure. Then once you've exhausted your aluminium you get some more, and recycle the aluminium oxide. The gallium is not used, it is just a catalyst, normally aluminium will not react with water because an oxide layer forms over the surface of the aluminium protecting the rest of it from oxidising, but this does not happen when alloyed with gallium.read about it here http://www.physorg.com/news98556080.html
"Most people don't realize how energy intensive aluminum is," Woodall said. "For every pound of aluminum you get more than two kilowatt hours of energy in the form of hydrogen combustion and more than two kilowatt hours of heat from the reaction of aluminum with water. A midsize car with a full tank of aluminum-gallium pellets, which amounts to about 350 pounds of aluminum, could take a 350-mile trip and it would cost $60, assuming the alumina is converted back to aluminum on-site at a nuclear power plant."How does this compare with conventional technology? Well, if I put gasoline in a tank, I get six kilowatt hours per pound, or about two and a half times the energy than I get for a pound of aluminum. So I need about two and a half times the weight of aluminum to get the same energy output, but I eliminate gasoline entirely, and I am using a resource that is cheap and abundant in the United States. If only the energy of the generated hydrogen is used, then the aluminum-gallium alloy would require about the same space as a tank of gasoline, so no extra room would be needed, and the added weight would be the equivalent of an extra passenger, albeit a pretty large extra passenger."
Drastic times call for drastic measures man. We've done a hell of a lot to mess up the atmosphere, it makes sense we're going to have to put a hell of alot of energy into fixing it.
Burns hydrogen instead of oil. So you can fill your car up with water, and only oxygen comes out the back. Actually, I saw a commercial for this on TV, they said water vapor comes out which I find hard to beileve cause I thought we were years away from these things.