T-Pain Is On A Boat: Re: [Electric Boats] CNG/Tri-fuel Generators?

Wednesday, July 1, 2009

Re: [Electric Boats] CNG/Tri-fuel Generators?

Chris Witzgall wrote:
> I would think that the biggest challenge would be storage of the CNG,
> depending on your run-time needs. CNG storage is space-inefficient. You can
> store a gallon of gasoline or diesel in the actual space the fuel takes up
> (well, almost). Propane takes more space, and CNG even more.
>
Yes , it's hard to beat the energy density in liquid hydrocarbon fuels.
LPG gives a derate to the engine and has to be stored in a pressure
cylinder. CNG even more so. Liquefied Natural Gas isn't so bad, but the
cryogenic equipment needed to deal with it is some what a problem, so
they tend to only liquefy it for sea transport it appears.

> I have never bought CNG, but have read that it is an expensive alternative,
> where you can find it.
>
Depends. CNG burns clean - hence it's common use in Urban buses. Some
countries subsidise it's use to encourage use of the cleaner fuel.
(Argentina/Brazil ?). If your country has access to large gas fields, it
may even really be cheaper than Oil products at a wholesale level. Would
depend on domestic supply vs imports. Oil is certainly easier to carry
around the planet.

Natural Gas completely replaced 'coal gas' as the gas used domestically
for heating and cooking in Urban Australia and is piped around most
major urban centres. High pressure pipe lines cross the country (1000's
of km of them) to get the gas from the fields to the major urban
centres. The only people using LPG domestically would be people who are
'off grid' and use cylinders of gas to run their appliances.

But unlike some countries, CNG not piped into filling stations for use
in road vehicles. The Sydney buses that use CNG are restricted to
certain depots that have been equiped with suitable filling equipment,
and not all depots can be easily equiped as they are not near a suitable
bulk delivery high pressure gas main. They got to the silly situation in
one area where due to 'political' pressures, they used new CNG powered
buses on a route, but their depot wasn't able to be equiped with gas
fueling facilities (to far from a high pressure main), so the buses
drove to another depot every day to fill up!.

There has been commentary in Australia that we should be encouraging
more use of CNG in transport as we export Natural Gas (in Liquefied
Natural Gas tankers) but have to import oil. If you have to import both,
the higher shipping costs of LNG might rather change the equation.