So, what are teh advantages and disadvantages of Fuel Cell engines?

[SCC]

I went to check this out, and couldn't find any reference to what kind of fuel cell we're talking about. Your post implies hydrogen, and honestly that's my hope, but the rules actually don't say what the fuel cell is burning. If it's a hydrocarbon fuel cell, then it's got the same logistical train issues as an ICE.

I've got a rules question posted on this one.

It's hydrogen, or at least that's the default usage.

[wellspring]

It's hydrogen, or at least that's the default usage.

That's what I thought, but I can't find a cite supporting it, and I can find several that seem intentionally ambiguous about it. My question is posted in Strat Ops Rules questions if you want what I've found.

By all means enlighten me if I missed something.

[Acolyte]

That's what I thought, but I can't find a cite supporting it, and I can find several that seem intentionally ambiguous about it. My question is posted in Strat Ops Rules questions if you want what I've found.

By all means enlighten me if I missed something.

It's in AToW pg.325. The fuel table has a "notes" section that mentions which engines each fuel goes into.

   - Shane

[wellspring]

It's in AToW pg.325. The fuel table has a "notes" section that mentions which engines each fuel goes into.

   - Shane

Excellent! Many thanks; that's a book I don't have.

[False Son]

Well, in my universe they do. I look at the vehicle guides as simply representative of what's out there, not the entirety. These are also the most common vehicles and the most common variants of said vehicles. An army that might be fighting on an industrialised, advanced planet one day may be fighting on a water poor periphery lostech planet the next. It makes sense for them to use the most widely fixable and fuelable. Also, using ICE allows manufacture just about anywhere. This makes ICE the most common vehicles out there.

Except that there are plenty of fusion powered tanks in 3025.  Heck, the Patton/Rommel series was good exactly because they had fusion engines to free up weight.  Considering the scarcity of fusion engines in the later SWs, rare enough to be canibalized for mechs during the 3rd SW, the use of rare or complicated engines in combat vehicles didn't stop anyone from using fusion.  Let's face it, fuel cells were retconned into the setting with a hand wave reason as to why they had not shown up before.  I think it is silly to pretend the tech level or comparitive complexity of the fuel cell engine to the ICE is the reason why it wasn't used.  If battlemechs and fusion engines were becoming more and more rare, combat vehicles with additional free tonnage via FCEs would be more desireable as opposed to less.  Especially if there's no in-universe reason to suggest that the ability to manufacture FCEs was diminished by the widescale destruction of the SWs in the same way fusion plants were.

[Acolyte]

The Rommel/Patton tanks were an experiment precisely because of the engine. Besides, who wants to re write all the TRO's when they can be producing new ones?

   - Shane

[glitterboy2098]

as for the "handwave reason' thy aren't used.. keep this in mind. Gas Turbine engines offer major power to weight improvements over Diesel engines, but diesel engines are still the primary engine of choice for military vehicles.

so either military designers are just too stupid to see through the silly handwave excuse preventing the superior turbine engine from being adopted, or logistical and training concerns really are important.  ::)

[False Son]

as for the "handwave reason' thy aren't used.. keep this in mind. Gas Turbine engines offer major power to weight improvements over Diesel engines, but diesel engines are still the primary engine of choice for military vehicles.

The fuel consumption differences between an ICE and FCE are not the same as a diesel vs a gas turbine.  Turbines are still used in limited applications, like the Abrams, which is likely the same space occupied by fusion engines, in that they are expensive, high performance power sources used to achieve certain aims not otherwise reached by ICE.

so either military designers are just too stupid to see through the silly handwave excuse preventing the superior turbine engine from being adopted, or logistical and training concerns really are important.  ::)

Or it was retconned into a poorly conceived setting in the first place.  If training and logistics were valid concerns the FCE wouldn't be popping up in modern designs where fusions are more plentiful.  Unlike the Binary Laser, which really wasn't viable when it was invented, the FCE was viable and had even more importance to be adopted in the SWs because of diminished fusion plant numbers.  But, no.  It just wasn't practical.  But, now it is practical.  Nevermind that Hydrogen has been able to be condensed for decades in the real world.  It's magically outside the capacity of BT worlds.

[Wolf72]

hold on a sec ... The tech manual (and errata) doesn't say that ICE can't have Environmental Sealing, you can have a sealed 45 ton car and drive around in a toxic area.  Just don't plan on going underwater. 

Just to be clear, this should not affect naval submarine units, right? (although a 300 ton sub with FCE can carry lots more stuff!)

[wundergoat]

ICE - C/A-A-A  Dirt cheap, able to be built on most worlds, and widely available.  As noted in the TechManual, they use many of the same parts as industrial ICE systems, so successfully sourcing spare parts from local industry is likely very effective.  Also, given how ubiquitous ICE is, finding fuels should not be much of an issue.  I would imagine that modern ICE systems would be extremely flexible with the types of fuels used.  Improvements in material sciences should also yield lower maintenance needs when compared to real world combustion engines.  Final verdict: they make complete sense for militia, budget forces, and tech-strapped SW-era armies.


FCE - D/C-D-D  Twice as expensive in raw C-Bills when compared to ICE, but half as much as a fusion engine. Now, there are some real advantages, but there are logistical considerations that make ICE more attractive.  First, FCEs are more complicated and MUCH less common that ICEs.  Good luck foraging for parts.  Second, 'exotic' fuel usage.  Yes, hydrogen is "free" if you have a fusion engine and water.  However, we have no idea how fast a fusion plant can make hydrogen.  We do know that the existing logistics for ICE is better and that water is not necessarily abundant. 

There are other issues with trying to keep a primarily FCE force topped off with fusion units.  For one, losing your fusion engines becomes much worse, as their loss can strand many more units.  Second, at the very least the fusion units will have to stop to make fuel.  They don't have large storage tanks for water and hydrogen, right?  Therefore, you lose your operational tempo when compared to pure fusion forces.  FCEs might even lose out to ICEs if there is enough local fuel (i.e. gas stations & truck depots)

Final verdict:  FCEs are great when you can support them, but that means new infrastructure.  Post-Jihad, it seems that most factions are operating defensively and cottage military industry has sprung up all over the place, so FCEs work.  I wouldn't want to try to run a 4thSW-style blitz using FCEs though.

[wellspring]

Second, 'exotic' fuel usage.  Yes, hydrogen is "free" if you have a fusion engine and water.  However, we have no idea how fast a fusion plant can make hydrogen.  We do know that the existing logistics for ICE is better and that water is not necessarily abundant. 

There are other issues with trying to keep a primarily FCE force topped off with fusion units.  For one, losing your fusion engines becomes much worse, as their loss can strand many more units.  Second, at the very least the fusion units will have to stop to make fuel.  They don't have large storage tanks for water and hydrogen, right?  Therefore, you lose your operational tempo when compared to pure fusion forces.  FCEs might even lose out to ICEs if there is enough local fuel (i.e. gas stations & truck depots)

Strat Ops, p179 if I recall, gives the rules you're looking for. Bottom line: it's not a big deal.

Far less of a big deal than fossil fuel tanks, especially if you're raiding a planet that's lacking in dead trilobytes.

[False Son]

Final verdict:  FCEs are great when you can support them, but that means new infrastructure.  Post-Jihad, it seems that most factions are operating defensively and cottage military industry has sprung up all over the place, so FCEs work.  I wouldn't want to try to run a 4thSW-style blitz using FCEs though.

That's really the point.  Nothing makes sense in the Succession Wars and never will.  A military is exactly the kind of place where a FCE would have a place, because they would have a supply infrastructure able to procure Hydrogen in huge amounts and train techs to service FCEs, and transport all the men and materials needed to keep a force dependent on these technologies.  BUT, this is Succession Warfare, where the house militaries more resemble the militaries of old, foraging off the land and not even going into battle with enough techs to make repairs on their own.  The greater rate of fuel consumption is even a distraction.  With the weight savings, isn't it possible to use your magical Battletech tons to make a bigger fuel tank?

The fact that FCEs are found in the civilian sector, in a complete flip flop of the real world, is even more annoying. 

That being said, it is nice to see a viable alternative to fusions and ICEs.  Fission offers weight savings over ICEs but otherwise is pretty bad.

[Wolf72]

Strat Ops, p179 if I recall, gives the rules you're looking for. Bottom line: it's not a big deal.

Far less of a big deal than fossil fuel tanks, especially if you're raiding a planet that's lacking in dead trilobytes.

I'm guessing the creation or manufacture of alternate petrol products or use of alcohol based products is even less of a big deal.  hmph ... BattleTech ICE engines are the ultimate in Flex Fuel Engines.

[False Son]

Prolly retconned in as well. #P  Were the writers of BT in 80s any more aware of biofuels than they were of FCEs being a product of the 19th century?

But, yes.  There are a variety of fuels that an ICE could run on, provided it was built to the specifications of running on petrochemicals one day, switchgrass another day and ethinol the next.  Meanwhile Hydrogen can be collected by electrolosys by anyone with a middle school education scientific understanding.  Granted, this is BT and drinkable water is a valuable resource, but yeah, Hydrogen is everywhere and can be manufactured by simple means without fusion reactors.

Meanwhile, for RL FCEs there are very few moving parts.  I wonder if BT FCEs have lots of spinning flywheels and Tesla coils and such to justify their higher tech rating.

[TigerShark]

That's really the point.  Nothing makes sense in the Succession Wars and never will.  A military is exactly the kind of place where a FCE would have a place, because they would have a supply infrastructure able to procure Hydrogen in huge amounts and train techs to service FCEs, and transport all the men and materials needed to keep a force dependent on these technologies.  BUT, this is Succession Warfare, where the house militaries more resemble the militaries of old, foraging off the land and not even going into battle with enough techs to make repairs on their own.  The greater rate of fuel consumption is even a distraction.  With the weight savings, isn't it possible to use your magical Battletech tons to make a bigger fuel tank?

You described the 3rd Succession War, not "the Succession Wars," plural. The first and second Succession War were not marked by equipment or technician shortages. In fact, only a tiny, miniscule fraction of BT history has the "Mad Max" universe equivalent and even then it wasn't on every planet in the galaxy.

I do know that we're limited by our technical know-how of 2013 at the moment. Hydrogen is the most abundant element in the universe. Our only problem is finding H2 sources on Earth, making the production of hydrogen fuel far too costly to be efficient at this time. This doesn't mean that pure sources don't exist elsewhere in the universe and I've even seen some hypotheses for vessels which could harvest hydrogen gas as they traveled in space. (How viable that is would be highly debatable until someone actually succeeds/fails at trying it.)

On the other hand, fossil fuels and ethanol are made from organic sources. You're not going to find oil stores in an asteroid; it needs to be on a planet which once held abundant vegetation millions of years in its past. Same goes for alcohol, since it's a byproduct of organic life. These things are abundant to us, but who knows how much of it would be anyplace else in the universe. We've recently found huge stores of methane on Titan, but it would be extremely difficult to convert it to any useable fuel source without expending more energy to produce/ship it than was procured from the substance itself.

[SCC]

Meanwhile Hydrogen can be collected by electrolosys by anyone with a middle school education scientific understanding.  Granted, this is BT and drinkable water is a valuable resource, but yeah, Hydrogen is everywhere and can be manufactured by simple means without fusion reactors.

Meanwhile, for RL FCEs there are very few moving parts.  I wonder if BT FCEs have lots of spinning flywheels and Tesla coils and such to justify their higher tech rating.

Doesn't need to be drinking water, there's a passage in one of the core books about MechWarrior's refueling their 'Mechs with urine

[Liam's Ghost]

Meanwhile, for RL FCEs there are very few moving parts.  I wonder if BT FCEs have lots of spinning flywheels and Tesla coils and such to justify their higher tech rating.

Complexity and technology are so not the same thing. For that matter, neither are "working fuel cells" and "practical fuel cells".

I would assume the higher technology rating is a result of the advanced materials that go into making the fuel cells practical.

[False Son]

I do know that we're limited by our technical know-how of 2013 at the moment. Hydrogen is the most abundant element in the universe. Our only problem is finding H2 sources on Earth, making the production of hydrogen fuel far too costly to be efficient at this time. This doesn't mean that pure sources don't exist elsewhere in the universe and I've even seen some hypotheses for vessels which could harvest hydrogen gas as they traveled in space. (How viable that is would be highly debatable until someone actually succeeds/fails at trying it.)

The trouble with Hydrogen infrastructure in real life is that it would require one energy source swapped out for another.  Instead of gas stations you have Hydrogen refilling stations.  The expense of building a Hydrogen station to replace every gas station in the world is impractical.  However, in military applications, where you are only servicing a limited number of vehicles, the infrastructure needed is much smaller.  What drives me nuts in BT is that civilian use of FCEs is present, but where it makes sense, in military application it was passed over.

And the problem of developing a new Hydrogen supply infrastructure is less of a problem when FCE tech exists today and offers clear advantages over ICEs.  Any planet settled would be better off with a Hydrogen based energy supply over a petrol or even biofuel economy from day 1.

On the other hand, fossil fuels and ethanol are made from organic sources. You're not going to find oil stores in an asteroid; it needs to be on a planet which once held abundant vegetation millions of years in its past. Same goes for alcohol, since it's a byproduct of organic life. These things are abundant to us, but who knows how much of it would be anyplace else in the universe. We've recently found huge stores of methane on Titan, but it would be extremely difficult to convert it to any useable fuel source without expending more energy to produce/ship it than was procured from the substance itself.

To be fair, there are bacterias which produce condensable vapors that could in a few years be developed into a viable source fuel grown in augers.  Though most ICEs prolly don't run off of something that exotic.

[wellspring]

Meanwhile, for RL FCEs there are very few moving parts.  I wonder if BT FCEs have lots of spinning flywheels and Tesla coils and such to justify their higher tech rating.

IIRC, really good FCE's use highly advanced materials science. High price, low maintenance if I were writing it (I suppose we need Cray for a better opinion than my half-informed recollections).

Doesn't need to be drinking water, there's a passage in one of the core books about MechWarrior's refueling their 'Mechs with urine

With a high enough BAC, they could run an ICE that way too.

[glitterboy2098]

Prolly retconned in as well. #P  Were the writers of BT in 80s any more aware of biofuels than they were of FCEs being a product of the 19th century?

victor Milan in the 90's had the Kurita's using an entirely ethanol based fuel infrastructure for ICE's. apparently it had additives that left Formaldehyde as a by product too. (mentioned specifically in several scenes as a way to set the atmospheric elements of a scene)



and regarding FCE tech levels.. while fuel cells are very simple in gross design (basically a membrane through which the H2 and O2 combine, the membrane stripping electrons to provide power), the actual construction of an efficient Fuel cell is rather complicated. the membrane has to be made of specific materials engineered in specific microstructures for best effect. ones with high efficiencies need knowledge of and ability to produce certain types of metamaterials. high output fuel cells also require very careful monitoring of the H2 to O2 ratios.. too much of either one will cause drastic reductions in output. this needs complex computer support. storage of the fuel as well requires cryrogenic storage systems for best results, hydrogen being a very low density material in all its forms. and fuel cell systems use a lot of fuel especially at high electrical outputs. so you need lots of fuel to be stored.

whereas ICE's can be built fairly easily with little more knowledge required than basic industrial and chemical processes, their fuel can be stored fairly easily at typical environmental temps.

[evilauthor]

On the other hand, fossil fuels and ethanol are made from organic sources. You're not going to find oil stores in an asteroid; it needs to be on a planet which once held abundant vegetation millions of years in its past.

Which SHOULD describe the vast majority of worlds settled by humanity in the BT universe, because otherwise they'd have been inhospitable worlds that wouldn't have been colonized to begin with. The few worlds it doesn't describe would need a high tech infrastructure to remain habitable.

[TigerShark]

Which SHOULD describe the vast majority of worlds settled by humanity in the BT universe, because otherwise they'd have been inhospitable worlds that wouldn't have been colonized to begin with. The few worlds it doesn't describe would need a high tech infrastructure to remain habitable.

"Life" doesn't mean the planet underwent a carboniferous period, like we did. Oil came from a very strange period in our planet's history where plant life was teeming. We could assume that every planet underwent a period like that, but I don't know if the BT authors would go that far.

[Diablo48]

"Life" doesn't mean the planet underwent a carboniferous period, like we did. Oil came from a very strange period in our planet's history where plant life was teeming. We could assume that every planet underwent a period like that, but I don't know if the BT authors would go that far.

Or you could just brew alcohol or some other biofuel with bacterial cultures.  It is really not very hard to do, and there are probably ways to shortcut at least some of it with industrial chemical production to bypass agricultural bottlenecks.

[TigerShark]

Or you could just brew alcohol or some other biofuel with bacterial cultures.  It is really not very hard to do, and there are probably ways to shortcut at least some of it with industrial chemical production to bypass agricultural bottlenecks.

Still probably more difficult to find than hydrogen. :-\ And I'm not convinced the maintenance is "cheaper" anyhow, since ICEs have a lot more moving parts which generate heat and require lubrication.

[evilauthor]

Or you could just brew alcohol or some other biofuel with bacterial cultures.  It is really not very hard to do, and there are probably ways to shortcut at least some of it with industrial chemical production to bypass agricultural bottlenecks.

One idea I had for a fanfic is that the Star League (or one of its precursor nations) created genetically engineered crops for the express purpose of making bio-fuels, and that these crops are pretty much spread all over the Inner Sphere. No one "drills" for oil (god knows they don't dig very deep for mineral ores either); they all GROW their ICE fuel.

[SCC]

Still probably more difficult to find than hydrogen. :-\ And I'm not convinced the maintenance is "cheaper" anyhow, since ICEs have a lot more moving parts which generate heat and require lubrication.

This, Fuel Cells come pretty close to being batteries, they aren't going to need much in maintenance compared to something with 100+ moving parts

[Marwynn]

There's bureaucratic inertia to factor in here. They're not going to like change, even if it's somehow 'more efficient' as they're used to hearing. You're talking about a whole new set of training courses, regulations, tools and equipment, and so on. Even with BT's standardization, that still has to be daunting, even for a planetary militia.

In-game, even the need to use Power Amps isn't much of a hindrance. That is, at most, one ton for most weapons. The heatsinks will of course be a burden, but that just means that energy weapons are no longer no-brainer choices.

The shortened range and relative scarcity of the parts (compared to ICE) will be a big roadblock in adoption. But on the tabletop, they're excellent. 

[glitterboy2098]

This, Fuel Cells come pretty close to being batteries, they aren't going to need much in maintenance compared to something with 100+ moving parts

no you are just moving all your complex maintence heavy parts to the fuel system. An ICE can get by with a tank and a simple fluid pump.
Fuel cell engines need cryogenic or pressurized storage, complex pumps to handle moving hydrogen vapor around, and complex computers to manage all of it.

All of which are substantially more maintenance intensive than with an ICE.

[TigerShark]

no you are just moving all your complex maintence heavy parts to the fuel system. An ICE can get by with a tank and a simple fluid pump.
Fuel cell engines need cryogenic or pressurized storage, complex pumps to handle moving hydrogen vapor around, and complex computers to manage all of it.

All of which are substantially more maintenance intensive than with an ICE.

Hoses and computers are easier to swap out than blown rods, bearings, water pumps, valves, etc. Every estimate you see of Fuel Cell Engine costs in consumer automobiles estimates a lower maintenance cost due to these factors.

[False Son]

I also think we're underselling the complexity of an ICE expected to function in a variety of non-Terran environs on a wide array of fuels in different gravities.  Modern ICEs have computer systems for managing the cumbustion of fuel and automatic transmissions.  Heck, some of them may even be rotary engines requiring their own training.

I also don't get this idea that it would be so impossible to train people to service the engines, either.  Maybe i'm just having trouble with the idea that in 1000 years we're still using ICEs in military vehicles meant not to fight one another or conventional infantry, but fusion powered battlemechs and battle armor when reasonable non-fusion alternatives have apparently existed this entire time.

Look at the Ontos, for example.  If this is going to be the backbone of your armored forces, why settle on something that is so clearly poorly designed?  Even with all the heat sinks and the power amps, the Ontos would be massively better off by having a FCE and some liquid storage for fuel.  Then cover it in a blanket of more Simple Plate and there you go.  But, at this point, i'm digging at BT economics and the intentionally poor designs of early BT tanks.