Fuel Power Equivalencies

[Henchman99942]

Has anyone guesstimated the ratio or equivalency between a power tool that requires liquid fuel, and one using power cells?

1 gallon of fuel = ??? Power cell (s)

This is a fuel powered High-Tech tool as a TL9 version.

Air Compressor (TL6). Consumes 1 gallon of gasoline per hour. Halve weight at TL8. $100, 125 lbs. LC4.

I see a TL9 version using Power Cells.

[Fred Brackin]

Originally Posted by Henchman99942

Has anyone guesstimated the ratio or equivalency between a power tool that requires liquid fuel, and one using power cells?

Air Compressor (TL6). Consumes 1 gallon of gasoline per hour. Halve weight at TL8. $100, 125 lbs. LC4.

I see a TL9 version using Power Cells.

I gather that you "want" a TL9 power cell version rather thna you currently see one?

You'd need the rating of the fuel-burning engine for the HT version in KW (or even HP which you'd convert to KW) as well as run time. Then ahving the that information you'd need to get the semi-secret values of UT-style Power Cells in KW seconds. There's one set of possibly correct information in Infinite Worlds.

[malloyd]

Originally Posted by Henchman99942

Has anyone guesstimated the ratio or equivalency between a power tool that requires liquid fuel, and one using power cells? .

GURPS "Power Cells" run anywhere from 2 to a few hundred MJ/kg depending on the TL, application, and edition of the rules you are looking at. Gasoline burned in air (and therefore not counting the weight of the air) runs about 45 MJ/kg thermal, but once you add in conversion efficiencies you aren't likely to get 15 MJ/kg electrical out of it.

You can usually replace the fuel consumption of anything with the something in the vicinity of the same weight of (non-nuclear) power cells and stay somewhere in suspension of disbelief territory. For TL9 cells, which tend to on the physically plausible end, it's probably more like 5 to 10 times the weight of the fuel.

[The Colonel]

Originally Posted by malloyd

GURPS "Power Cells" run anywhere from 2 to a few hundred MJ/kg depending on the TL, application, and edition of the rules you are looking at. Gasoline burned in air (and therefore not counting the weight of the air) runs about 45 MJ/kg thermal, but once you add in conversion efficiencies you aren't likely to get 15 MJ/kg electrical out of it.

You can usually replace the fuel consumption of anything with the something in the vicinity of the same weight of (non-nuclear) power cells and stay somewhere in suspension of disbelief territory. For TL9 cells, which tend to on the physically plausible end, it's probably more like 5 to 10 times the weight of the fuel.

Whilst we're at it, does anyone know what sort of efficiency you can expect from a gasoline fuel cell? I'm guessing somewhere above that of a gasoline powered electro-mechanical generator but well below theoretical...

[malloyd]

Originally Posted by The Colonel

Whilst we're at it, does anyone know what sort of efficiency you can expect from a gasoline fuel cell? I'm guessing somewhere above that of a gasoline powered electro-mechanical generator but well below theoretical...

At the moment, I don't think there is a good idea for the chemistry of a gasoline fuel cell. Most concepts really want hydrogen at the electrode, and cracking hydrogen out of a semi-random mix of 6 to 12 carbon hydrocarbons is going to be challenging.

That said, good fuel cell concepts tend to be something like twice as efficient as internal combustion, and at least a little better than combustion turbines, so 50 or 60% efficient is probably a pretty reasonable guess.

[Anthony]

Originally Posted by malloyd

At the moment, I don't think there is a good idea for the chemistry of a gasoline fuel cell. Most concepts really want hydrogen at the electrode, and cracking hydrogen out of a semi-random mix of 6 to 12 carbon hydrocarbons is going to be challenging.

There's a modest amount of research on diesel fuel cells, though it's basically a two step process where step 1 is to crack some fuel for hydrogen (usually with CO or CO2 as a byproduct) and step 2 is using the hydrogen in a fuel cell.

[Kax]

One thing that's looking rather good for this is purified ammonia and a reformer on a H2 fuel cell. Liquid ammonia has a higher hydrogen density than liquid hydrogen, and the byproduct is N2. The only real problem at the moment is that the reformer is pretty big at the moment, so you won't see a vehicle with a reformer on it.

[Anthony]

Incidentally, fundamentally a battery is equivalent to a power plant with a built-in (normally non-air-breathing) not easily refillable fuel tank, so your best case is generally that the batteries match the weight of the engine plus its fuel tank, not the weight of the fuel tank.