Liquid Natural Gas

[cal40john]

Originally Posted by coopec43

Well I've learned something else today

" LPG pressure is less than 2 MPa whilst CNG - compressed natural gas storage is 20 to 25 MPa. This means high pressure CNG tanks are heavier and more expensive than LPG tanks. ... Both LPG and CNG are much cleaner fuels than petrol or diesel. They both have fuel systems that are sealed.Jun 15, 2019" (Quora)

I have a rough and ready (but nevertheless quite technical) old-timer mate who fills his caravan LPG cylinders at the gas station with CNG because it is much cheaper. He says you have to be very careful to fill them for no more than 15 seconds otherwise they will blow up! (Of course it is illegal)

He spends a lot of time going to the gas station. LPG is a liquid, CNG is a gas (unless cryogenic), so there is a lot more fuel in the same volume with LPG.

LPG is about 25 Mjoules/liter. ( pressurized in its bottle as a liquid, pressure is temperature dependent)
CNG is about 0.0364 Mjoules/liter at atmosphere. You're compressing it 20 times to get to 2 MPa, so 0.728 Mjoules/liter at that pressure.

You have 30 times more energy in the tank with LPG, so he gets about 1/30th of the mileage, or fills up 30 times as often.

https://en.wikipedia.org/wiki/Energy_density

[coopec43]

Originally Posted by cal40john

You have 30 times more energy in the tank with LPG, so he gets about 1/30th of the mileage, or fills up 30 times as often.

https://en.wikipedia.org/wiki/Energy_density

I should have explained he uses the fuel for his cook-top fuel. (The galley is in a converted passenger bus) His bus ran on the same fuel too - CNG or LPG? Obviously from what you say LPG.

[cal40john]

Originally Posted by coopec43

I should have explained he uses the fuel for his cook-top fuel. (The galley is in a converted passenger bus) His bus ran on the same fuel too - CNG or LPG? Obviously from what you say LPG.

There are CNG powered vehicles. You need the appropriate tank to get a reasonable amount of fuel. An LPG tank as you noted above is rated for 2 MPa (300 psi) and a CNG tank is rated for 25 MPa (3600 psi).

At 25 MPa the CNG is up to 9 Mjoules/liter. You would need a tank about 2.5 times the size of an LPG tank to get the same range. The tank is also much thicker and heavier than the LPG tank.

CNG Honda, half the trunk space used for fuel and less mileage range -
https://www.consumerreports.org/cro/...tive/index.htm

Decades ago I ran into a friend in Desolation Sound who's crew was carrying 6 bottles that looked like scuba bottles. Turned out they were CNG for the stove. Places with CNG were hard to find so they had a lot.

[weephee]

Thanks for all the replies. Summary for me is a new LPG stove. T