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Author Topic: Fuel Cell vs ICE  (Read 3185 times)

KaiserDunk

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Fuel Cell vs ICE
« on: 09 January 2019, 13:41:29 »
Very simple question since I have not yet been able to get my hands on TacOps; for the purposes of writing fluff for a combat vehicle, how does the operation of a fuel cell powerplant differ from that of a combat vehicle ICE powerplant?

TigerShark

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Re: Fuel Cell vs ICE
« Reply #1 on: 09 January 2019, 13:58:37 »
Fuel cells use a different fuel type. They explode on a critical hit (when mounted in 'Mechs), same as ICE engines. Their weight is much lower and they supply a single heat sink when installed.
These engine types are not widely used due to fuel availability and cost, since fossil fuels are more abundant. They are most commonly found in IndustrialMechs and civilian vehicles. TacOps notes that they can be used on military vehicles "on request," but are not typically offered up-front in a new design.
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AdmiralObvious

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Re: Fuel Cell vs ICE
« Reply #2 on: 09 January 2019, 14:26:54 »
Fuel cells can be used underwater and in space. The common ICE can't, so that's one other difference between the two. The fuel cells usually come with their own oxidizer, usually hydrogen and oxygen, and it basically works like a contained rocket engine, and it spits out water when done.

The ICE uses fuel, of course, and fuel doesn't burn without said oxidizer.

Either way, both will explode when shot at too much.

Sartris

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Re: Fuel Cell vs ICE
« Reply #3 on: 09 January 2019, 14:28:11 »
Range is another one. An ICE engine has fuel for 600km (20,000 hexes at cruising speed). A fuel cell has a lesser range of 450km (15,000 hexes) (TechManual pg. 68)

KaiserDunk

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Re: Fuel Cell vs ICE
« Reply #4 on: 09 January 2019, 14:56:42 »
Thank you.   It sounds like the fuel cells are like what are commonly used on current space craft.   That definitely helps.

Atarlost

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Re: Fuel Cell vs ICE
« Reply #5 on: 09 January 2019, 16:46:53 »
Realistically, ICE should only exist on civilian vehicles on pre-fusion worlds that happen to have oil.  Fuel Cells run on Hydrogen just like fusion reactors and just like fusion reactors if you have a fusion reactor in your force you can make it from water.  ICE runs on liquid hydrocarbons and these are only available on worlds that have had mass extinctions that produced oil beds and that have developed infrastructure to extract and process them, or that have lots of biomass and have developed infrastructure to process that into hydrocarbons, but this is higher tech infrastructure as it requires a power source.  Any world that retains fusion (doesn't have to be mobile) will find it easier to use fuel cells even if it also has accessible oil.  The oil can be used for plastics and a chemical industry for export to those poor benighted worlds that don't have oil.  A world that has never had an extensive biosphere (eg. Trell I) will have no local hydrocarbon source, but any world fit for human habitation has to have water and thus hydrogen and any attacking force has to have a dropship and thus a fusion power plant to crack that water for hydrogen. 

Sabelkatten

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Re: Fuel Cell vs ICE
« Reply #6 on: 09 January 2019, 18:06:27 »
IIRC fuel cells were originally included in "ICEs", just like gas turbines, batteries and advanced steam engines or similar. Btw piston engines, gas turbines and steam engines run fine on Hydrogen (piston engines might require quite a bit of adjusting).

Personally I ignore the name and just call FCEs advanced ICEs!

Daryk

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Re: Fuel Cell vs ICE
« Reply #7 on: 09 January 2019, 19:40:14 »
Just to be clear, Fuel Cells are NOTHING like rocket engines.  They are used on real world spacecraft, but that's about the only commonality I can think of.  [/physics major]

AdmiralObvious

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Re: Fuel Cell vs ICE
« Reply #8 on: 09 January 2019, 21:59:43 »
Just to be clear, Fuel Cells are NOTHING like rocket engines.  They are used on real world spacecraft, but that's about the only commonality I can think of.  [/physics major]
Yeah, I should've made that clear. It works with the same principle... but not at all...

Daryk

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Re: Fuel Cell vs ICE
« Reply #9 on: 09 January 2019, 22:04:33 »
I'm really not sure what principle you're referring to... Fuel Cells chemically convert fuel into electricity while rocket engines generally turn fuel into thrust physically (an argument can be made regarding ion engines, but they convert electricity into thrust)…

boilerman

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Re: Fuel Cell vs ICE
« Reply #10 on: 09 January 2019, 22:32:35 »
And they are not heat engines so their upper limit of efficiency is not limited by Carnot's Law.   :)
The main reason I prefer them in BT over ICE engines; though this has no effect in BT rules.

A little add on for BT fuel cells is you get a 1 free heatsink. I find it annoying you still have to use power amplifiers are for energy weapons with a fuel cell, which generate electricity directly. But I just chalk that up to all the capacitors you need to store enough energy to power a BT energy weapon.
« Last Edit: 09 January 2019, 22:50:19 by boilerman »
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Kovax

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Re: Fuel Cell vs ICE
« Reply #11 on: 10 January 2019, 11:47:15 »
Note that an ICE can be built (or possibly reconfigured) to run on alcohol, oil, hydrogen gas, or almost any other flammable liquid or gas.  They're not limited to worlds with petrochemical deposits or imported gasoline.  Virtually any planet with a breathable atmosphere and able to support even limited agriculture will be able to produce fuel for ICE engines, and many without such amenities will still be able to manufacture it by utilizing local chemical deposits to produce flammable liquids.

My assumption is that many vehicles will have a drivetrain mechanically coupled to the engine (as per the modern day "car"), while others will have an engine which drives a generator, and run off stored electrical power using electric motors (gas-electric hybrids).  The former will be simpler and cheaper to build, but have more restrictions as to fuel type, while the second could have different engines (reciprocating piston, gas turbine, fuel cell, or small fusion reactor) dropped in easily during final assembly, depending on what types of fuels are available at the location where it will be used.  Even if the engine itself is fusion in that individual vehicle, the overall vehicle design and level of performance would still be considered "ICE".

As shown by Tesla, the latter type, with electric motors, can out-perform a mechanically coupled internal combustion engine for brief periods, limited primarily by battery storage capacity.  Having a small or modest-sized "engine" to recharge the batteries would allow far greater duration in the field than a purely battery-powered design which would need frequent breaks for recharging.

Jellico

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Re: Fuel Cell vs ICE
« Reply #12 on: 15 January 2019, 21:20:01 »
Note that an ICE can be built (or possibly reconfigured) to run on alcohol, oil, hydrogen gas, or almost any other flammable liquid or gas.  They're not limited to worlds with petrochemical deposits or imported gasoline.  Virtually any planet with a breathable atmosphere and able to support even limited agriculture will be able to produce fuel for ICE engines, and many without such amenities will still be able to manufacture it by utilizing local chemical deposits to produce flammable liquids.


Fuel Cells run on hydrogen. Literally the most common element in the universe. If you have water (I assume your crew is drinking something) you have hydrogen. The limited factor is conversion which requires large amounts of electricity. If it is an industrial society you have that electricity. Heck. If you flew in by DropShip you have a fusion reactor. If you are Invading a world FC is better than ICE because you don't need to transport fuel.

Really the limiting factor with FC is the tech to build the engine.

More importantly why is any society more advanced than our own using ICEs over FCs?

Atarlost

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Re: Fuel Cell vs ICE
« Reply #13 on: 15 January 2019, 21:28:20 »
Fuel Cells run on hydrogen. Literally the most common element in the universe. If you have water (I assume your crew is drinking something) you have hydrogen. The limited factor is conversion which requires large amounts of electricity. If it is an industrial society you have that electricity. Heck. If you flew in by DropShip you have a fusion reactor. If you are Invading a world FC is better than ICE because you don't need to transport fuel.

Really the limiting factor with FC is the tech to build the engine.

More importantly why is any society more advanced than our own using ICEs over FCs?

If it weren't for the issue with fuel cell engines on supersonic conventional fighters not making sense I'd suggest swapping the fluff, weight, cost, and introduction dates wholesale so that FCEs were the ones everybody used by default and ICE was what you used to squeeze a few extra tons at the expense of needing to worry about special fuel. 

AdmiralObvious

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Re: Fuel Cell vs ICE
« Reply #14 on: 15 January 2019, 21:29:15 »
Fuel Cells run on hydrogen. Literally the most common element in the universe. If you have water (I assume your crew is drinking something) you have hydrogen. The limited factor is conversion which requires large amounts of electricity. If it is an industrial society you have that electricity. Heck. If you flew in by DropShip you have a fusion reactor. If you are Invading a world FC is better than ICE because you don't need to transport fuel.

Really the limiting factor with FC is the tech to build the engine.

More importantly why is any society more advanced than our own using ICEs over FCs?
Because it's relatively cheap to manufacture compared to a FC? Sure, the fuel itself is easy to find and produce. Making something to contain the reaction, or even start it, especially in the outer sphere/pererphiery is pretty hard to do, where in rare cases, you're still using coal fired steam engines to get around.

Terrace

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Re: Fuel Cell vs ICE
« Reply #15 on: 16 January 2019, 00:59:41 »
I was messing around in MegaMekLab and took advantage of Fuel Cell's big advantage over ICE to upgun a Vedette to sport an AC/10 and extra armor.

Because that's the most noticeable advantage of the FC in a one-shot tabletop game: drastically reduced weight means you can stuff bigger/more guns onto the same chassis. Is the fuel restrictions important in a campaign? Sure. But as has been said, if you've got a Fusion Engine hanging around nearby, making more hydrogen mitigates that disadvantage neatly.

Edit: I just realized that the example I gave was basically a Po that shrank in the wash and picked up some extra speed in the process.
« Last Edit: 17 January 2019, 10:00:05 by Terrace »

Col Toda

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Re: Fuel Cell vs ICE
« Reply #16 on: 16 January 2019, 06:49:56 »
Fuel Cell engine have approximately the same motor power on a combat vehicle as a light Fusion engine plus shielding . I have done upgrades to most canon ICE vehicles to Fuel Cell and upgraded the Patton and Romel Fusion tanks because it has only a small laser and the one heat sink handles that .

Jellico

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Re: Fuel Cell vs ICE
« Reply #17 on: 16 January 2019, 07:27:27 »
RS3060 Update was possibly the first major project where this was noticed by the designers after FCs were introduced. You could hear the squeals of glee across the internet.

Elmoth

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Re: Fuel Cell vs ICE
« Reply #18 on: 16 January 2019, 08:28:38 »
I would assume that a fuel cell would NOT be great for vehicles with energy weapons since they would deplete it fast (no idea on rules, just gut feeling), but othewise running on an alkaline tank in the future makes sense, specially if you expect to control the time of the engagement. Refuelling can me complicated otherwise.

The_Caveman

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Re: Fuel Cell vs ICE
« Reply #19 on: 16 January 2019, 09:31:12 »
If a fuel cell breaks down, you basically have to replace the whole thing because it runs off a specially-manufactured chemical catalyst and there is no real way to fix that in the field.

If an ICE breaks down, any shadetree mechanic in the Inner Sphere can fix it with common shop tools.

Maintenance rules don't reflect this, so to get around that I would say fuel cells are built as progressively-larger stacks of universal modules. Plug-and-play. But you still gotta have the modules on hand to do repairs, whereas an ICE just requires having access to a machine shop and steel billets.
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The other half is a first-turn AC/2 shot TAC to your gyro that causes your Atlas to fall and smash its own cockpit... wait, I said fun didn't I?

Sartris

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Re: Fuel Cell vs ICE
« Reply #20 on: 16 January 2019, 12:39:41 »
RS3060 Update was possibly the first major project where this was noticed by the designers after FCs were introduced. You could hear the squeals of glee across the internet.

that was mostly me

I would assume that a fuel cell would NOT be great for vehicles with energy weapons since they would deplete it fast (no idea on rules, just gut feeling), but othewise running on an alkaline tank in the future makes sense, specially if you expect to control the time of the engagement. Refuelling can me complicated otherwise.

they require power amplifiers like ICE vees with energy weapons but there are no special rules that affect fuel consumption


since most of this science is mercifully left out of the rules, the only thing that really matters is that cell engines are super light.

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Re: Fuel Cell vs ICE
« Reply #21 on: 16 January 2019, 17:36:46 »
More importantly why is any society more advanced than our own using ICEs over FCs?

ICE covers things like coal, wood, biodiesel still, aye? Engines that any half-awake tech can figure out and can be rigged to run on whatever's both local and suitably flammable presents a fantastic choice for logistics. The important people have the technology, but let the indigs get by with chichken farm and their fuel-chugging old pickup and you won't have to waste good resources keeping them running. ol' cletus can just fix everything hisself and think he's important for that...
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MoneyLovinOgre4Hire

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Re: Fuel Cell vs ICE
« Reply #22 on: 16 January 2019, 20:21:28 »
If a fuel cell breaks down, you basically have to replace the whole thing because it runs off a specially-manufactured chemical catalyst and there is no real way to fix that in the field.

If an ICE breaks down, any shadetree mechanic in the Inner Sphere can fix it with common shop tools.

Maintenance rules don't reflect this, so to get around that I would say fuel cells are built as progressively-larger stacks of universal modules. Plug-and-play. But you still gotta have the modules on hand to do repairs, whereas an ICE just requires having access to a machine shop and steel billets.

How does repairing a fuel cell compare to repairing a damaged nuclear fusion reactor?
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Kovax

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Re: Fuel Cell vs ICE
« Reply #23 on: 17 January 2019, 11:25:45 »
How does repairing a fuel cell compare to repairing a damaged nuclear fusion reactor?
You don't glow afterwards.

The_Caveman

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Re: Fuel Cell vs ICE
« Reply #24 on: 17 January 2019, 13:02:06 »
Fuel cells are solid-state devices by their very nature. It's a sandwich of metals and polymers. There's nothing really to repair if it gets broken, aside from the fuel lines and electrical cables that connect it to the chassis.

AFAIK fusion engines have always been described as having moving or at least removable parts of some manner (though the writers are understandably cagey about getting too detailed). In high-tech eras, those probably could be fixed at least at depot-level. Deep in the LosTech era, you'd probably have to just yank any mysterious magic components that got damaged and replace them with spares (probably sourced from a different design, while praying to Blake that the whole thing doesn't explode when you turn it on), so not much different from a FC.

In 3025 a fuel cell gives you all the headaches of a fusion engine with none of the "pew pew lazors" goodness that makes fusion engines attractive to begin with. It does let you build a tank that can operate in vacuum, though.
Half the fun of BattleTech is the mental gymnastics required to scientifically rationalize design choices made decades ago entirely based on the Rule of Cool.

The other half is a first-turn AC/2 shot TAC to your gyro that causes your Atlas to fall and smash its own cockpit... wait, I said fun didn't I?

Colt Ward

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Re: Fuel Cell vs ICE
« Reply #25 on: 17 January 2019, 14:42:18 »
To me FCEs were a boon for the 'cheap' ICE/AC line tanks . . . what you can do with a Vedette, Po and Zhukov with a FCE and 3050 weapons gets kind of crazy.  Vedette gets options to make it a real cavalry mech for post 3050- bigger gun, more armor, faster- maybe a supercharger!  Sure it costs more now than the bog standard Vedette but your combat capability goes up more dramatically IMO- and your logistics gets simpler for offensive forces.  Give the Po a Gauss Rifle and X-SPL instead of MG for Anti-Inf, more armor and survivability- AMS, maybe ECM, maybe A-pods.  The Zhukov gets better guns (GR, LBX & large MML rack) with more ammo and more armor- maybe bumped to 4/6.

From a logistics standpoint, ICE vehicles always struck me as placed more in defensive formations.  Offensive formations should have fusion engine vehicles so you do not have to worry about capturing fuel (easier to destroy defender stockpiles than capture) and their range in support of mechs is not limited by fueling needs.  You will also not need to transport the initial fuel requirements of the armor forces though support (ammo trucks, ambulances, mobile kitchens, repair trucks) will still have those needs.
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Maingunnery

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Re: Fuel Cell vs ICE
« Reply #26 on: 17 January 2019, 16:25:50 »

I usually use Fuel Cells when designing environmentally sealed vehicles, these compensate each other quite well.
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Jellico

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Re: Fuel Cell vs ICE
« Reply #27 on: 17 January 2019, 16:55:46 »
Personally when I first started designing with FCs they struck me as Clantech ICEs.

More advanced tech. Lighter. Less range.

Of course they haven't been used that way but I feel that you can make an argument that FCs should replace most of the ICEs in Clan service right down to the very low civilian end. You could say the same for the Star League given what they have been fluffed to have been running in civilian vehicles.

Daryk

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Re: Fuel Cell vs ICE
« Reply #28 on: 17 January 2019, 18:54:58 »
Colt, at the low tonnage end, even support forces are ultimately cheaper with fusion engines.  The 25 rated engine is extremely useful, and not that expensive.

Iceweb

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Re: Fuel Cell vs ICE
« Reply #29 on: 18 January 2019, 02:14:52 »
After I saw this I tried to build a flying Hetzer (with a MRM 40 as the cheep-o big boomstick) in MegaMek Lab with a fuel cell. 
It turns out that conventional aircraft in Lab at least can't be given a fuel cell engine. 

I was wondering if this was in the rules anywhere or just an issue in Lab? 
Is it the range restriction on fuel cells that prevents you from powering a plane with them, even if you allocate extra tonnage for fuel?  Or is there some other catgirl killing reason that a fuel cell wouldn't work.