Can someone give the specifications of the BMW new Hydrogen 7 hydrogen tank?

It holds 8 kg liquid hydrogen in 74 l volume. How much does the tank itself weigh?

How much would a bigger hydrogen tank weigh, if you had volume in your car, van, bus, truck etc. for it?

Now I though about this, I have to say, what a totally pointless car this is (and I am driving my 5th BMW).

Who ever thought about this needs to go and have this done to himself http://www.simviation.com/cgi-bin/yabb/YaBB.cgi?board=gen;action=display;num=116...

You take a 6L V12 and put in the capability to run on Hydrogen to the tune of 125 mile and then give it a further 300 miles of a carbon based fuel 
It is so obvious that BMW and the other major car companies are in the pocket of the oil producers other wise we would see that technology in a nice 1.8 or 2.0 litre car doing 500 miles and getting a very good equivalent MPG.


Matt

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Hmm, that surprises me, my earlier ( e38 ) 7 Series has an 85 Litre tank!

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Except that BMW Hydrogen 7 does not have a fuel cell. It has an Otto engine, no heavier (except for the second injection system) than a benzine burning Otto engine.

Presumably, hydrogen could also be burnt in a gas turbine?

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I was actually refering to all possibilities, not just the BMW. Sorry for the confusion.
Now for a little more about hydrogen as a fuel:

Direct injected diesel engines coupled with hybrid energy accumulation systems will have efficiencies exceeding 55% (source US DOE).
The problem with hydrogen is that it is an energy carrier, and must be produced from other primary energy sources.  The most economical method to produce hydrogen is by steam methane reforming (SMR) technology.  This technology recovers approximately 75% of the energy in the methane used to produce the hydrogen.  Compressing hydrogen requires electric power.  Compression requires approximately 10% of the energy content of the hydrogen in the form of electricity.  Power generation from natural gas is at best 50% efficient so that the equivalent of 20% of the energy in the hydrogen is used up in the natural gas used in generating the power to compress the hydrogen.  Liquefying hydrogen is even more energy intensive requiring 50% of the energy content in the form of electricity or 100% of the energy content in the form of natural gas to generate the electricity for compression.
  The overall efficiency of producing, compressing, and using the hydrogen in a fuel cell is 46.9%.  This is not much greater than the 40% efficiency of the Prius hybrid and well below the efficiency of a diesel hybrid.

Hydrogen has more energy per unit mass than other fuels (61,100 BTUs per pound versus 20,900 BTUs per pound of gasoline).  The problem with hydrogen is that it is much less dense (pounds per gallon) than other fuels.  A gallon of gasoline has a mass of 6.0 pounds, the same gallon of liquid hydrogen only has a mass of 0.567 pounds or only 9.45% of the mass of gasoline.  Therefore one gallon of gasoline yields 125,400 BTUs of energy while a gallon of liquid hydrogen yields only 34,643 BTUs or 27.6% of the energy in a gallon of gasoline. Compressed gaseous hydrogen is even less dense than liquid hydrogen.  At 5,000 psi of pressure gaseous hydrogen only has a density of 0.25 pounds per gallon or one twenty fourth the density of gasoline.  Gasoline and diesel are far superior fuels to hydrogen in this regard.

Burning hydrogen does not create any carbon dioxide emissions.  However, producing hydrogen typically does create carbon dioxide emissions. Only electrolysis using renewable sources of energy such as wind, solar, hydroelectric or geothermal have no carbon dioxide emissions associated with hydrogen production via electrolysis.  As more than 55% of the electricity produced in the USA is based on coal as the fuel, there are significant quantities of carbon dioxide emissions even when the hydrogen is produced via electrolysis.  Steam Methane Reforming (SMR) is the most common method of hydrogen production and each pound of hydrogen produced emits 9.42 pounds of carbon dioxide

masmith wrote on Jan 1^st, 2007 at 1:43pm:



Do you mean "Standard Liters Per Minute" or something else??

Matt

Now I understand. The BMW Hydrogen 7 does not have a fuel cell, so SLPM I would think cannot be measured. The car uses a standard petrol engine and used hydrogen in a similar fashion to a LPG converted car. The hydrogen is in liquid form under pressure in a gas tank and then via BMW black magic into gas and then as LPG-ish process injected and burnt.

Matt

masmith wrote on Jan 2^nd, 2007 at 6:45pm:



The tank hold 74 litres and can travel 125 miles (200 km). If the car travels at a constant speed, say the standard 56 mph (100 kph) at say 4000 rpm you should be able to get a basic figure, however bearing in mind it is 04:45 in the last hours of my nightshift, I am not the person to work it out. I would say that I think it is going to be a very low figure. A bit more than if it was petrol.

Matt