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The Ultimate Battery?


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Feel free to correct me if I get any of the following wrong.

Due to conservation of energy, the only way to have plenty of energy is to actually have plenty of energy to do the work you want. Especially in ciosed systems that do not extract energy from outside systems.

This manifests itself in rockets by all the propellant required. The only way to reduce the amount of propellant required is to either add more energy to the propulsion or have a propellant source that is more energetic.

In the far future I have no doubt that many of man's technological feats will dwarf what we have now by a large margin. Even so, simple inventions like the wheel and the bath towel more or less won't have much of any reason to be changed much if at all. They are already optimized for what they do.

One future technology that would be nice to have is super batteries. By super batteries I mean batteries that can hold as much potential energy as a fully loaded two stage rocket!


We do not have metallic hydrogen, but if we did, could we not make a battery out of it?

Batteries do not store electricity, rather they create it by chemical reactions when part of a circuit.

So a metallic hydrogen battery I assume could be designed to hold a considerable amount of energy, and compactly at that.

The downside of known batteries is that they loose charge over time, whether or not you charge them. So all batteries have an expiration date, it just takes longer for the most rugged of batteries.

The obvious potential downside of a metallic hydrogen battery is that it could have high enough energy to be a high yield bomb. Even nuclear level probably.

With such high energy levels TWR could increase for electric  quadcopters, and while Ironman won't be a thing, quadcopter man could be!.

So what do you think about metallic hydrogen batteries? Would they work as I think they would or could they be designed to do so?

 

EDIT: Batteries create waste heat like all other energy sources known, so a very high energy discharge would require mass increases due to heatsinks or radiator fins which will lower TWR in space. Unless some physics breakthrough is found there is simply no way around that.

This would also imply that small space vehicles using such technology would be impractical as they would burn themselves up.

Edited by Spacescifi
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Have you heard of people who got injured, when batteries in their smartphones self-combusted? Energy is energy. If you cram a lot of electric charge into small cube, you will basically carry a hand grenade in your pocket. Battery holding the equivalent of two full rocket stages in electric charge, would be indeed an equivalent of a high-yield bomb - you don't need metallic hydrogen for that :)

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OK let’s put all the usual comments to one side and assume, for the sake of argument, that metastable metallic hydrogen (MMH) is a thing. 

I think it would make a lousy battery but you could probably make a decent combined-heat-and-power system out of it.

MMH can indeed store a lot of energy but a good part of that energy is released as heat when hydrogen atoms recombine into hydrogen molecules.  In a rocket engine, for example, that’s not a problem but for a battery it is.  Firstly you end up with a very hot battery and secondly that heat is effectively waste heat unless you have some means of doing useful work with it.

Then, once you’ve converted your MMH back to molecular hydrogen, you need a suitable battery chemistry to use it. 

The only one that I’m aware of is to combine the hydrogen with oxygen in a fuel cell, more specifically a proton exchange membrane (PEM) fuel cell. 

PEM cells are a well established technology (the Apollo missions used them if I recall correctly) but they are nowhere near as rugged and portable as a battery.  I have some knowledge of this, albeit at second hand - I was a patent examiner working on fuel cell and battery applications right around the time that the ‘hydrogen economy’ was the latest and greatest idea. So I got to read a lot about the various problems with making fuel cells and how folks tried to overcome them.

Long story short, I would use MMH in a two stage system, probably in a domestic or municipal setting. Stage 1 - convert MMH to molecular hydrogen and use the released heat to either make hot water for direct use, or steam to drive a generator with, depending on whether hot water or electricity is more useful. Step 2 - use the molecular hydrogen in a fuel cell to generate electricity.  Fixed installation fuel cells can be pretty robust - it’s making them battery sized that would be the problem.

 

 

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Another thought - you could build a thermal generator with MMH. Start with a chunk of MMH, add system to controllably convert it back to molecular hydrogen, wrap the whole thing in thermocouples to generate electricity.

Like a radiothermal generator but without the nuclear material. I have no idea how efficient it would be and you’d be leaking a drizzle of hydrogen gas whilst the generator was on which probably puts a practical limit as to how much MMH you want to decompose at a time, hence how hot your generator gets.

But it’s sort of getting close to an MMH battery.

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4 hours ago, Spacescifi said:

We do not have metallic hydrogen, but if we did, could we not make a battery out of it?

Batteries do not store electricity, rather they create it by chemical reactions when part of a circuit.

So a metallic hydrogen battery I assume could be designed to hold a considerable amount of energy, and compactly at that.

MMH (which is obviously hypothetical) has a high energy density and specific energy because it is monatomic. You cannot extract energy from it without recombination, and that recombination will release hydrogen gas. So even without the heating problem, you will need a place to put hydrogen gas.

Hydrogen fuel cells are extremely well-understood and robust technology, and they convert hydrogen gas (plus atmospheric oxygen) into electricity with minimal waste heat. The only reason they're not in more common use is because hydrogen gas is ridiculously hard to store in any meaningful density. A gallon of gasoline contains more hydrogen than a gallon of liquid hydrogen, let alone a gallon of compressed hydrogen gas at any pressure.

Metastable metallic hydrogen, on the other hand, would have a density ten times greater than liquid hydrogen. So if you could design a form of metastable hydrogen which somehow recycles recombination energy to maintain its stability, it would be great for a hydrogen fuel cell.

"Give me a second, I need to let my phone breathe."

4 hours ago, Spacescifi said:

Batteries create waste heat like all other energy sources known, so a very high energy discharge would require mass increases due to heatsinks or radiator fins which will lower TWR in space.

When we are talking about energy densities on the order of metastable metallic hydrogen, thrust to weight ratio in space is NOT an issue. At all.

TWR in space is rarely an issue anyway. Rule of thumb for science fiction: In the atmosphere you need high TWR; in space you need high specific impulse. 

Besides, if you're using a battery as an energy source for your propellant in space, then you can simply dump the waste heat into the propellant as it exits. No radiator fins needed, and it amps up your specific impulse too!

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A battery in purest concept refers to energy storage. And when storing energy, a lot of things qualify.

Hydroelectric Dam reservoirs are batteries. Their method of storage is gravitational potential energy. If you have a connected pumping system, you can also make them self-recharging.

  • Pros
  • + Enormous energy reserves
  • + Easy to manage for very high power outputs for very long periods of time (weeks-months at a time)
  • + Discharge slowly
  • + Energy storage medium is all natural, non-polluting, quiet, and makes for a great place for boatrides or peaceful hikes
  • + Energy storage medium can also serve as a water supply aquifer in some circumstances
  • Cons
  • - Very large
  • - Difficult to start or stop
  • - Nearly impossible to stop in a runaway discharge - i.e. a dam break
  • - Maintenance involves its own devoted sub-discipline because it is so complicated (dam engineering)
  • - Immobile
  • - Can only be located in certain geographic locations, requiring power transmission and distribution

Flywheels are batteries. Their method of storage is kinetic energy from rotation. They are charged and discharged using electric motor/dynamos attached to their rotors.

  • Pros
  • + Upper limit of storage capacity only constrained by physical size, and tensile strength, of flywheel mass.
  • + Can charge faster than most other forms of energy storage.
  • + Can discharge faster than all other forms of energy release other than exothermic chemical reactions. (GW/sec is achievable using dynamos on magnetically suspended flywheels.)
  • + Energy/mass storage rate is significantly better than any form of electrical batteries, but not as good as chemical fuels.
  • + Proper kinds of suspension (vacuum containment, magnetic bearings) can ensure they hold charge for very long periods (years) and never suffer from degradation from charge/discharge cycles.
  • + Long lasting. There are flywheels which still work that have been in service for over 100 years.
  • + Can cushion abrupt changes in angular momentum in mechanical systems.
  • + Extremely rugged, immune to temperature and radiation changes.
  • + Failsafe modes very stable and harmless.
  • Cons
  • -  Must be carefully configured into system, requring a specific arrangement and relationship to other systems in order to physically fit.
  • - Will suffer friction losses unless flywheel rotation axis is aligned with the axis of rotation of the Earth.
    • This either requires mechanically complicated orienting gyros, or accepting losses due to rotation of Earth.
  • - Heavy and large compared to many other storage solutions
  • - Limited case practicality for mobile systems
  • - Containment failure of flywheel mass can cause violent, high-energy explosion that produces a lot of high-velocity shrapnel.
  • - Rapid charge or discharges can generate large amounts of heat

 

Edited by starcaptain
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2 hours ago, sevenperforce said:

Hydrogen fuel cells are extremely well-understood and robust technology, and they convert hydrogen gas (plus atmospheric oxygen) into electricity with minimal waste heat. The only reason they're not in more common use is because hydrogen gas is ridiculously hard to store in any meaningful density. A gallon of gasoline contains more hydrogen than a gallon of liquid hydrogen, let alone a gallon of compressed hydrogen gas at any pressure.

I'm pretty sure there are a few more issues, like cost of catalysts and the efficiency of cracking methane (water is only cracked for PR purposes).  But you're right in that there would likely be enough work done to make it happen if the really tough issue (hydrogen transportation and storage) went away.

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5 hours ago, sevenperforce said:

MMH (which is obviously hypothetical) has a high energy density and specific energy because it is monatomic. You cannot extract energy from it without recombination, and that recombination will release hydrogen gas. So even without the heating problem, you will need a place to put hydrogen gas.

Hydrogen fuel cells are extremely well-understood and robust technology, and they convert hydrogen gas (plus atmospheric oxygen) into electricity with minimal waste heat. The only reason they're not in more common use is because hydrogen gas is ridiculously hard to store in any meaningful density. A gallon of gasoline contains more hydrogen than a gallon of liquid hydrogen, let alone a gallon of compressed hydrogen gas at any pressure.

Metastable metallic hydrogen, on the other hand, would have a density ten times greater than liquid hydrogen. So if you could design a form of metastable hydrogen which somehow recycles recombination energy to maintain its stability, it would be great for a hydrogen fuel cell.

"Give me a second, I need to let my phone breathe."

When we are talking about energy densities on the order of metastable metallic hydrogen, thrust to weight ratio in space is NOT an issue. At all.

TWR in space is rarely an issue anyway. Rule of thumb for science fiction: In the atmosphere you need high TWR; in space you need high specific impulse. 

Besides, if you're using a battery as an energy source for your propellant in space, then you can simply dump the waste heat into the propellant as it exits. No radiator fins needed, and it amps up your specific impulse too!

 

Hmmm...phone is about to die, so I will brief until I return.

Metallic hydrogen is a rabbit hole of sorts, since we both know the energy required to make it might exceed the energy extracted....unless there is another way, and if we knew that we would be cashing in on it.

 

Perhaps an easier solution that has similar outcomes would be engineering a solid material that can absorb liquid hydrogen and retain it at room tepmperature?

Palladium absorbs water I read, so it would be a stretch to engineer a material that could absorb a lot of LH and retain it, but it is worth a try perhaps.

Going further...perhaps there are other gases that can be metalllicized?

If we cannot squeeze hydrogen into the mold we wish, perhaps there could be some hidden benefits in creating solid materials that absorb other gases, like:

Oxygen: Why not? 

Nitrogen:  Plentiful and why not?

Methane: For Elon...he might think of one or two uses LOL.

 

That's a BIG if. If we can actually make a solid that can absorb liquid gas in large quantities.

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17 hours ago, starcaptain said:

A battery in purest concept refers to energy storage. And when storing energy, a lot of things qualify.

This, really.

 

Though I'd like to draw one more difference :

- A chemical battery (say, Zinc-Carbon dry cell) stores chemical energy, and all you need to do to release them is to short the electrodes, but they only gradually expends energy.

- A tank of diesel or kerosene does store chemical energy, but they're not released because they're not primed to be released - in fact it takes quite a lot of effort to prime them that there isn't a way to make them like normal batteries.

- An electrolytic capacitor does have a chemical component - the electrolyte as cathode, the metals as anode, and the fairly thin oxide layer as dielectric - but if you were to discharge one by shorting the pins, they'd expend all their stored energy at once, and as you can see they're kind of expected to pop as well.

 

So if you want a battery, regardless of the technology employed, you also have to look at how does it discharge power, and what does it take to start it. Hydroelectric storage falls in batteries because all you need to do is open a valve and let the water comes through on it's own, and it'll limit it's own rate; Kinetic energy systems (like flywheel) also counts in because it takes a while to expend the stored energy, albeit it only last shortly so it's often seen more like capacitors - I'd also count it here pressured gas (not fuel) tank, for powering pneumatic stuff. RTG and other nuclear power source are a kind of weird battery, because it continually emits some energy but there's essentially no way to turn it off.

18 hours ago, sevenperforce said:

"Give me a second, I need to let my phone breathe."

Metal-air batteries are a thing.

Edited by YNM
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Antimatter batteries i think are very impractical because their nominal storage requirements are so steep, even if their reaction is so powerful. 

In my opinion, M/AM annihilation will be the next generation's "oh that's too dangerous" by the time when nuclear pulse propulsion has become normalized.

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On 12/24/2020 at 12:31 PM, YNM said:

albeit it only last shortly so it's often seen more like capacitors - I'd also count it here pressured gas (not fuel) tank, for powering pneumatic stuff. RTG and other nuclear power source are a kind of weird battery, because it continually emits some energy but there's essentially no way to turn it off.

Im seeing very little mention of capacitors as a battery here... They don't all have to discharge all of their energy at once, I am pretty sure.

Anyway, nuclear power sources relying on chain reactions obviously control the output, while an rtg doesn't.

A battery as we commonly speak of they is actually a voltaic cell, which were called batteries when you need ed whole arrays or batteries (same sense as an artillery battery) of cells to get sufficient power.

I suspect that what scifi wants is a rechargeable energy storage device that you can just charge by supplying it with electricity.... But then normal non-rechargeable alkaline batteries don't count, so I really don't know what he is asking or how he proposes mmH as a battery (unless conbected to a heat engine generator, and a compressor capable of remaking mmH).

Also, he is wrong about many things about batteries. One example is that a molten electrode battery does not slowly discharge in any significant way, although those are generally single use batteries, as found on missiles.

https://en.m.wikipedia.org/wiki/Molten-salt_battery

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16 hours ago, KerikBalm said:

I'm seeing very little mention of capacitors as a battery here... They don't all have to discharge all of their energy at once, I am pretty sure.

I know supercapacitors exist, but there's clearly a line drawn where it becomes more of a battery instead.

EDIT : Upon further reading, apparently there are supercapacitors that both acts as a capacitor (charges stored as extra electrons / depletion of electrons) and as battery (charging and discharging causes chemical reaction). So I suppose there's some continuum between chemical batteries and electrolytic capacitors...

16 hours ago, KerikBalm said:

nuclear power sources relying on chain reactions obviously control the output, while an rtg doesn't.

I'd say it both does and doesn't. If you store nuclear reactor fuel for a very long time I'm sure there'd be a line when you can't use the fuel anymore because most of it has decayed off, albeit this line would be in billions of years due to U-235 being used rather than Pu-238 which would decay off in under a century. They're both better than most normal batteries that way, though.

Edited by YNM
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7 hours ago, YNM said:

I'd say it both does and doesn't. If you store nuclear reactor fuel for a very long time I'm sure there'd be a line when you can't use the fuel anymore because most of it has decayed off, albeit this line would be in billions of years due to U-235 being used rather than Pu-238 which would decay off in under a century. They're both better than most normal batteries that way, though.

Well, thats in line with any other system having the energy leak out.

Still, a fusion reactor using P-B fuel, or any other aneutronic reaction, has inly stable isotopes: https://en.m.wikipedia.org/wiki/Aneutronic_fusion

Then there is thorium-232, perfectly usable, 14 billion year half life... Just a bit longer than the age of the universe... I wouldn't worry about it.

But yea, RTGs... those are another story (pu-239 though, for use in a reactor, nit an RTG, has a half life of tens of thousands of years)

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17 minutes ago, KerikBalm said:

fusion reactor

Well we haven't managed to do any so I just casually forgets that XD but ok the OP is talking about all sorts of tech as long as it's "within the realm of imagination. (which is why I dare not say much about the proposed tech.)

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1 hour ago, KerikBalm said:

we still have no practical reactors for supplying electricity. :p

Which is ultimately the goal, yeah. Otherwise you can't compare it to a "battery", or I'd start calling a tank of gasoline a "battery", too...

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