Energy in 1 liter of biogas @ 1 bar
I've been looking for how much energy is in 1 liter of bio- (or natural) gas, so I can work out how far 1 can drive with a 3 gallon (=11,35 l) tank (natural or biogas compressed herein to 250 bar).
These sources have some useful info: deepresource ct.gov Anyway, here are some of my calculations, let me know if they're correct (I'm not sure, since the difference with hydrogen is HUGE. In comparison, hydrogen has 0,003 kwh/l whereas natural or biogas has 5,42 kwh per liter, so 1806x more) 1 cu foot of natural gas = 0,012 gallons natural gas @14,73 psi (=1,0155 bar) = 0,045424941 liter natural gas @14,73 psi (=1,0155 bar) 1 cubic metre of natural gas = 8,8 kwh 0,0283168 cubic metre = 1 cubic foot 1 cubic metre = 35,31472 cubic foot 8,8 kwh / 35,1472 = 0,25037 kwh per cubic foot 1 cu foot of natural gas = 0,012 gallons natural gas @14,73 psi, so 0,25037 kwh is in 0,012 gallons natural gas @14,73 psi or 0,25037 kwh is in 0,045424941 liter natural gas @14,73 psi 0,25037 kwh X 22,0143 = 5,51 kwh is in 1 liter of natural gas @1,0155 bar 5,42 kwh is in 1 liter of natural gas @ 1 bar 135,64 kwh is in 11,35 liter of natural gas @250 bar |
Thats a lot of extra math...and I can say right off the bat that 1 litre is not equal to 2/3rds of a cubic meter, as your 5.5kwh/litre vs 8.8kwh/cubic meter suggests. 1 cubic meter is 1000 litres, so it would be 0.0088 kwh/litre.
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250 bar is pretty close to the 3600 psi mentioned (3625), at which it takes 3.82 gallons of CNG to equal the 33.40 kwh. You have "only" 3 gallons, so 3.82/3 = 0.78534 multiply that by 33.40 kwh and you have 26.23 kwh in your tank. (~2.3kwh/litre @ 250 bar - or 9.2 watt-hours per litre at 1 bar vs the 8.8 watt-hours per litre of our original math. The 0.4 difference is either from using a different value per litre, or from rounding too much in the math) Now you see why CNG vehicles have such big tanks... |
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26,23 kWh = 11,35 litre x 2,3 kWh/litre @ 250 bar 26,23 kWh = 11,35 litre x 0,0092 kWh/litre (@1 bar) x 250 bar 26,23 kWh = 26,105 kWh so doesn't match, but it's close Calculating it another way: 1 GGE = 3,587 m³ @ "standard conditions" (=250 bar ?) 33,4 kWh = 3,587 m³ @ 250 bar 33,4 kWh = 3587 liter @ 250 bar 33,4 kWh = 11,35 liter @ 250 bar x 316,0352 33,4 kWh/316,0352 = 11,35 liter @ 250 bar 0,1056 kWh = 11,35 liter @ 250 bar 11,35 liter x 0,0093 kWh/l @ 250 bar That last calculation seems wrong (perhaps because standard conditions doesn't mean 250 bar ?) but I got a number of 0,0093 kWh which seems to be close to the 0,0092 kWh I got from the above calculation, so that may be the right number (it also almost matches the 9,2 watt you also calculated). Recalculating: 11,35 litre x 0,0093 kWh/litre (@1 bar) x 250 bar = 26,388 kWh So that's even worse than with 0,0092 kWh; with 0,00925 it gives: 11,35 litre x 0,00925 kWh/litre (@1 bar) x 250 bar = 26,246 kWh That seems to be about the right figure ? It would mean that natural/bio gas is about 3,083x more energy rich than hydrogen. |
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And multiply by 250 to get the energy density @250 bar. |
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Any bad math came from me. ;) |
Depends on how much CO2 is contaminating your bio gas.
Probably should get a diesel and run bio gas intake fumigation. That way when your roughly 2/3 of a gallon equivalent worth of bio gas runs out you're not stuck on the side of the road with no fuel. |
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That's pretty close to the 26,23 kWh Stubby79 calculated out. 8,8/1000= 0,0088 kwh per liter natural gas. We got a figure of 0,0092 - 0,0093 so pretty close to that too. I doubt any of us is really wrong, rather some differences can be explained by the fact that natural gas varies in its make-up (gases) so energy ratings can fluctuate a bit. Let's round it off and say its 0,009 kwh per liter ;) |
So what kind of vehicle is going to be cursed with less than 1 gallon worth of liquid fuel range?
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I have the equivalent of 2 gallons in the ranger
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