Magic fuel cells?

[Carlobrand]

I would be grateful if someone with a lot more chemistry than I have would check me on this:

Per MegaTrav Ref Manual, a 0.1 kl TL15 fuel cell (in a Terran-normal O2/N atmosphere) consumes 0.4 liters of hydrogen per hour to produce 0.27 megawatts of power.

A 0.1 kl TL15 fusion plant consumes 9 liters of hydrogen per hour to produce 1.5 megawatts of power.

So ... my fuel cell is delivering 0.675 MwH per liter, while my little fusion plant is delivering 0.167 MwH per liter.

I'm not criticising the fusion plant. Scale efficiencies and all that, most likely the bulk of the power it produces is being consumed by the machine itself to keep the reaction going, and we're only seeing what it can spare after that. It's the fuel cell that puzzles me: that seems like an awful lot of power for that little bit of fuel. Even the Tech-10 model's delivering better than 200 kilowatt-hours a liter - which I think puts gasoline to shame, no. Or, am I just screwing up the math?

 

[aramis]

mol to g : mol * Atomic Mass

Hydrogen combustion: 286 kJ/mol = 79.444444444 wH/1.007825g = 78.82761833100433 wH/g

Hydrogen, liquid - ~70g/L

1L x 78.8 = 5517.9 wH/L = 5.5179 KwH/L

 

[Carlobrand]

So I'm not crazy: the cell's delivering anywhere from 40 to 120 times the power that nature would otherwise allow.

 

[aramis]

So I'm not crazy: the cell's delivering anywhere from 40 to 120 times the power that nature would otherwise allow.

Yep. And that's before efficiency losses, which are considerable... current ones run around 80% electricity out... so 4.4kWH/L. Theoretically, that could rise to about 5kWH/L

 

[Carlobrand]

Let's say we want to introduce a more plausible fuel cell system in our TU.

Current book rules have TL10 cells ranging from 0.1 L/H for a 10kW (100kW/L) cell to 0.4 for a 90kW (225kW/L). Then that's multiplied by up to 3.5 (up to 787.5 kW/L).

I see two ways to do that. If we decide 5.5 is TL16 magic, then we multiply fuel consumption by about 140, ending with a TL16 cell that consumes 56 L/H to produce 315 kW, or about 5.625kW/L (a wee bit too high, but perhaps accurate enough for game terms). The low tech variants then range from 0.7 to 1.6 kL/H.

Option 2 is to blow off the TL boost completely and multiply fuel consumption by 40. That gives us TL10 cells ranging from 2.5 to 5.625 kL/H. Or we could perhaps multiply by 45 or 50 if we're serious about not violating chemistry.

I don't know enough about modern cells to be able to select a preferred method. Thoughts?

 

[Carlobrand]

Odd idea:

Take the fuel rate in MT Referee's Manual, multiply by 500, apply it as a consumption rate per megawatt generated.