What to do with an unlimited amount of liquid nitrogen.

[Rossum]

Okay, a weird idea I got recently while reading about Maxwell's Demon and Vortex Tubes.

Suppose some company invented a refrigeration system (lets call it a Frost Generator) that basically sucks the heat out of the air, converts it to usable electricity, and spits out cold air as a waste product.

Standard consumer models are cheap and are designed to acheive temperatures low enough to at least freeze water. However, they require energy to operate like any device and they basically act as generators by producing more energy than they use up. To do this, they need to extract the maximum amount of heat from the air (producing colder waste air) and be able to achieve self-sustainability with colder input air. Thus, the cheapest models tend to be used in arid regions where there is plenty of hot air around and expel air that is around -10 C while average ones can work at lower temperatures.

The Industrial models ones can achieve temperatures as low as -200 Centigrade (cold enough to liquefy air) and can basically operate anywhere that isn't a perpetual frozen wasteland. They produce more energy than standard ones (due to extracting more energy from the air) and produce liquefied air as a waste product (which can be seperated into liquid nitrogen and liquid oxygen).

Question is:

1. Assuming that the electricity generated by an Industrial model Frost Generator alone will inevitably pay for its initial cost (which would be incentive enough to get as many of these as possible, which in turn would result in a whole lot of Liquid Nitrogen and Oxygen...) what would people do with all the huge amounts of liquid nitrogen produced as a byproduct of the power generation?

2. What are the possible environmental effects of humans having access to "cheaper than free" refrigeration?

3. Just how much energy could one realistically expect to get by sucking heat from the air? And how utterly absurdly irresponsible would people have to be to cause negative environmental effects with them? How badly before people start complaining?

4. Who would be motivated to spread this tech? Who would try to ban or control it?

[Mayabird]

What would we do if we invented a perpetual motion machine, you mean? Because that's what you're describing.
[line 2]

[The Duchess of Zeon]

What would we do if we invented a perpetual motion machine, you mean? Because that's what you're describing.
[line 2]

Well, perpetual until the atmosphere cools down enough to kill everyone.

[Rossum]

I don't think it would be any more of a perpetual motion machine than a windmill or a solar panel. The hypothetical device cools down air (like a refrigeration system) and converts the extracted heat into usable energy. The technobabbley sci-fi part of it is that there really isn't that much energy in warm nitrogen and oxygen so it would have to suck up a lot of air constantly to get much in the way of energy. It would take energy to suck up the air but if the suction method was efficient enough and one could extract enough usable energy from the air then one could gain more energy than it used up in operation.

Thus, warm air gets sucked in, energy is extracted and converted to electricity (and a good deal of energy would be lost by being converted to sound or by wear and tear on the generators components and such), and cold air is dumped out. It would need a constant supply of warm enough air to get the needed energy (if you put too many of these things in the same room they will just suck up all the heat until they can't get enough energy to be self-sustaining. They would have to wait until the room heated up again before they continued... mainly by using energy from the sun to heat the air.) so its certainly not perpetual motion.

If even possible, the technology would need stuff like superconductors, special coolant, high efficiency motors and engines, and maybe stuff like nano-scale Maxwell's Demon air molecule sorters or a specially designed vortex tube made out of unobtanium or something. Difficult to pull off, but doesn't violate any fundamental laws of thermodynamics I know of.


So yeah, it would suck up air and spit out liquid nitrogen until the air got so cold that it couldn't gain enough energy from it to run... or one of its inner mechanisms wore out... or night came and the temperature dropped... or something breaks because ice crystals form all over it and jam up something.

[Omeganian]

I don't think it would be any more of a perpetual motion machine than a windmill or a solar panel. The hypothetical device cools down air (like a refrigeration system) and converts the extracted heat into usable energy.

It's called a perpetual motion machine of the second kind - the work will eventually be converted into heat, which can be used again, so it works forever. It's impossible to build.

[Zixinus]

This assumes that the magical process that powers the thing breaks even between supplying whatever power and sucking in more air.

Oh, but to actually help: liquid nitrogen can be used to create high-efficiency computers. If designed right, such a computer could archive much higher performance than a room-temperature counterpart (because the room-temperature counterpart has to take heat generation into account).
Of course, I am unsure of that. But that's all I can think of.

[Sarevok]

Oh, but to actually help: liquid nitrogen can be used to create high-efficiency computers. If designed right, such a computer could archive much higher performance than a room-temperature counterpart (because the room-temperature counterpart has to take heat generation into account).

I am pretty sure existing off the shelf cooling systems exist that already do that without breaking physics.

[Ariphaos]

Suppose some company invented a refrigeration system (lets call it a Frost Generator) that basically sucks the heat out of the air, converts it to usable electricity, and spits out cold air as a waste product.

Heat is not in and of itself usable energy. In order to generate energy from heat, you need to take advantage of the transfer of heat from a hotter body to a cooler body.

[Omeganian]

BTW, nitrogen is also used to make ammonia - one of the cornerstones of chemical industry and agriculture.

[Rossum]

Okay, I thought something was wrong with it but I only remembered the 1st law of thermodynamic and not the 2nd one. At least I know where the problem is now. Thanks guys.

Anyway, I'm basically working on a plot for a story and it revolves around a company or organization that deals in sub-zero temperatures and for perfectly rational reasons is producing way too much liquid nitrogen to be even remotely feasible or sane for anyone with that kind of tech. (Think the Frost Legion branch of the Dark Legion from the Sonic the Hedgehog comics... anyone who's foot soldiers use guns that spay Liquid Nitrogen has some seriously crazy tech going on and should be making billions of dollars by selling it and just buy lasers or something instead).

So yeah... the question should probably be "How can I rationalize Liquid Nitrogen becoming so cheap that its getting dumped in peoples backyards because its getting in the way?" or "How can I replace smog and industrial waste with snow and liquid nitrogen and still make sense while not looking like an obvious environmental message?" or "Under what circumstances would it make more sense to spray liquid nitrogen at your enemy instead of shooting bullets?" (I'm thinking the answer to the last one is 'when you can pull Liquid Nitrogen out of thin air but can't do the same for bullets or more useful ammo')

possible ideas:

1. They build super-efficient refrigeration units that can be powered by the solar energy found in particularly arid and hot deserts. There are massive solar arrays (likely with solar-panel factories that use sand as raw materials) set up but no cities to send the power to, so they use it to extract nitrogen from the air and send it through pipelines, this helps condense moisture in the air (possibly) and the nitrogen can be used for industrial or agricultural purposes for local economy. However, years later they make so many of the nitrogen-making plants that problems occur... maybe people say they extract too much nitrogen from the atmosphere or the nitrogen is causing environmental damage from overuse or leaking through the pipelines or something. Its not so much taking heat from the air as having an absurdly huge infrastructure dedicated to the purpose.

2. Liquid Nitrogen could conceivably be pumped through pipes which also have superconducting cables running through them. The Nitrogen keeps the cables cold enough so they act as superconductors and can send electricity for far longer than they could normally. Thus, as long as the energy saved by using superconductors is more than the energy lost by mass-producing the liquid nitrogen then it makes sense. They could have massive networks of pipes with Nitrogen running though them to both distribute Liquid Nitrogen and keep the cables cooled to act as superconductors.

So... they have access to large amounts of renewable energy in out of the way places (maybe in deserts or windy areas or putting geothermal plants around volcanoes or something. They also have highly efficient refrigeration technology capable of mass-producing Liquid Nitrogen using the power gained from the power plants. They then build huge pipelines that pump Liquid Nitrogen through them in order to super-cool the superconducting cables which means they can now distribute the energy they produce in those power plants to the places that use it.

Thus, they have a massive infrastructure in place that requires Liquid Nitrogen to operate. They increase production to ensure they never run out (if their supply of Liquid Nitrogen can't be sent through the pipes then the superconductors stop working and power can't get from the plants to the customers) and makes sure to sell the Liquid Nitrogen for any and all processes that require it (they like making money).

So... since their basic plan is to make way more Liquid Nitrogen then they could possibly use rationally (which is rational since they want to make sure they never run out) then how would the world change, what environmental impacts would take place, and what would the world look like if there was such a thing as 'too much' liquid nitrogen? (I'm guessing you'd by extension have to make too much ammonia or nitrogen rich fertilizer as well to reach that point).


And then, if people like Green Peace or environmentalists found somebody doing stuff like that... basically building totally renwable energy sources in deserts where no animals or plants live and then using super efficient superconductors to send the power to cities, making lots of fertilizers to help third world countries make their agriculture more efficient and avoid having to destroy rain forests to get more farmable land... what could they possibly find fault with them to make them try to 'shut them down before they destroy the environment' (the generators that suck heat out of the air were mostly meant to give people the scare that they might freeze the planet or something even though I'm pretty darn sure that would be physically impossible unless you absolutely covered the entire surface of the planet with those things and somehow froze the oceans which cover 70% of the planet and also started stuffing them into volcanoes or something in a retarded attempt to freeze the earths molten core which is several orders of magnitude more mass than the entire surface of the planet but made out of molten rock).

And... is there any way to have people armed with guns that spray liquid nitrogen (basically a freeze ray that doesn't violate physics) and not have it look incredibly stupid for anyone with a basic knowledge of thermodynamics or weaponry? I mean... with bullets you need armor to protect you and there's really no upper limit to how fast people can shoot bullets into you. Liquid Nitrogen... it only gets so cold and the getting dunked in the stuff is the absolute most it can damage you. Plus, to protect from Liquid Nitrogen you just need a protective suit to keep it from freezing you.

Liquid Nitrogen guns might make sense if you were fighting alien locusts or ooze monsters like the Zerg or Tyranids and you had a virtually unlimited supply of the stuff and not much else.

[Caiaphas]

Alrighty then. Thinky time.

Point one: If your company is building these gigantic solar arrays in the desert, you're definitely going to screw over the local environment. Unless these solar panels are a helluva lot more efficient than today's, much more of the radiation is going to be reflected back into the atmosphere. So two possibilities there: if greenhouse gases at present levels or higher, then some serious heating problems are going to be caused, especially if solar arrays take up significant amounts of the surface. If they are lower than present day, then we should be fine... I think. Not exactly an environmental scientist here. Anyhoo, if your panels are more efficient than modern ones, then you're going to have a heating problem instead. If panels are more efficient, they appear blacker, because they're sucking up more energy, and if you're sucking up more energy, that is going to be put into the local biosphere at some point.

By the way, the above only applies for direct light-to-energy type panels. If you're thinking about the type of solar arrays that act like a huge magnifying glass, then ask someone else.

Point two: The condensation of water out of the air by using the liquid nitrogen in the pipes idea--great, but sadly enough I don't think it's really feasible. If you have a gigantic pipe running through the middle of the Mojave, there's not going to be a lot of water in the air to condense onto the pipe. Also, wouldn't most of the water just freeze directly onto the pipe? What little turns into mist around the pipe is going to be pretty damn hard to collect, because ambient temperatures are still going to be enough to vaporize it rather quickly. Your plan could be workable at night, though. If humidity levels at night are higher, water will still freeze onto the pipe, but I imagine that the mist that forms would linger for a lot longer and be easier to collect, and when the sun rises and some of that ice melts, that would be collectable as well. I don't think the scheme would be economically feasible, though. There's just too little moisture in desert air.

Point three: Liquid nitrogen guns? Pretty cool idea. Only problem is that you'd need a lot to kill a person wearing insulated materials for armor, and you'd lack range--ever try and hit a target 30 meters away with a water gun? Also, the nitrogen would need to be constantly cooled in order to be usable as a weapon, and that would take a lot of energy. I can still understand why you'd want to use it, but modern guns are just better.

Point four: Love the superconductor idea.

Point five: We've already got plenty of problems with artificial fertilizers. Look them up, then imagine them times a hundredfold, with your idea of using the nitrogen plants to pump out fertilizer. Environmental catastrophe.

Point six: I like where you're going with this idea, but I somehow can't imagine how you'd generate electricity by sucking heat out of the air.

[Simon_Jester]

Anyway, I'm basically working on a plot for a story and it revolves around a company or organization that deals in sub-zero temperatures and for perfectly rational reasons is producing way too much liquid nitrogen to be even remotely feasible or sane for anyone with that kind of tech. (Think the Frost Legion branch of the Dark Legion from the Sonic the Hedgehog comics... anyone who's foot soldiers use guns that spay Liquid Nitrogen has some seriously crazy tech going on and should be making billions of dollars by selling it and just buy lasers or something instead).

You're missing something important, Rossum:

Liquid nitrogen is cheap. It's not some exotic alien substance. Scientists and engineers buy it on a regular basis. It's about as expensive, gallon for gallon, as milk.

Nor, when you get right down to it, is it all that great as a weapon. It's really cold, sure but it isn't a magic cold ray: spray it into the air and it vaporizes quite harmlessly. Liquid nitrogen would not make an effective long ranged weapon for this reason: it's cold, extremely so, and it quickly soaks up enough heat from the environment it travels through that it stops being liquid.

So yeah... the question should probably be "How can I rationalize Liquid Nitrogen becoming so cheap that its getting dumped in peoples backyards because its getting in the way?" or "How can I replace smog and industrial waste with snow and liquid nitrogen and still make sense while not looking like an obvious environmental message?"

...Why do you want to do this? Take a step back from your story concept and make sure it makes sense before trying to come up with a way to make it work. If your primary goal is to write a story about "Cold Company with its masses of liquid nitrogen!" then your story is liable to look kind of dumb, because it won't have much else going for it, and Cold Company isn't really all that sweet an idea.

"Under what circumstances would it make more sense to spray liquid nitrogen at your enemy instead of shooting bullets?" (I'm thinking the answer to the last one is 'when you can pull Liquid Nitrogen out of thin air but can't do the same for bullets or more useful ammo')

Bullets are also ridiculously cheap, which is why modern armies can afford to arm every soldier with a machine gun. Seriously, there are factories that turn them out by the millions. It's easy.

1... However, years later they make so many of the nitrogen-making plants that problems occur... maybe people say they extract too much nitrogen from the atmosphere or the nitrogen is causing environmental damage from overuse or leaking through the pipelines or something. Its not so much taking heat from the air as having an absurdly huge infrastructure dedicated to the purpose.

Do you know roughly how much nitrogen there is in the atmosphere? Can you describe mechanisms by which nitrogen, a substance famous for being chemically inert, could cause significant harm?

So... since their basic plan is to make way more Liquid Nitrogen then they could possibly use rationally (which is rational since they want to make sure they never run out)

That makes no sense. I mean, if I need to have X liters of liquid nitrogen a day to replace wastage in my superconducting power lines, why do I need to manufacture more than X liters of liquid nitrogen a day? For that matter, why is the same company running the power lines and the gas liquification plants? I mean, those are not normally related industries. You can totally buy liquid nitrogen on the open market, and it's not that expensive.

Also, liquid nitrogen is not capitalized. Again, we're not talking about some magic exotic substance here.

And then, if people like Green Peace or environmentalists found somebody doing stuff like that... basically building totally renwable energy sources in deserts where no animals or plants live and then using super efficient superconductors to send the power to cities, making lots of fertilizers to help third world countries make their agriculture more efficient and avoid having to destroy rain forests to get more farmable land... what could they possibly find fault with them to make them try to 'shut them down before they destroy the environment'

Why the hell would they even want to?

Greenpeace and the environmental movement are not cartoon villains. They do not automatically oppose everything just because they are evil-minded. If they see someone saving huge amounts of fossil fuels with renewable energy... why are they going to complain?

And what's all this about fertilizer?

Liquid Nitrogen guns might make sense if you were fighting alien locusts or ooze monsters like the Zerg or Tyranids and you had a virtually unlimited supply of the stuff and not much else.

By the same standard, rocks and sticks make sense as weapons if you don't have much else. Obviously, if you have only one option, you use it. That doesn't make it not a retarded option.

[Spectre_nz]

Re: liquid nitrogen as a weapon

Squirting liquid nitrogen at things is going to be a pretty inefficient way of killing things. You’re much better off using the liquid nitrogen to propel a rock or such like, an expanding gas launcher like a potato gun.

Failing that, creating an anoxic atmosphere is probably going to have more kill factor than the cold. You're better off using a flame thrower.

Liquid nitrogen in reality; when I'm filling a dewar of LN2, a jet of the stuff coming out the vent nozzle is my cue the dewar is full. The spray of LN2 doesn't travel far in air at all, and aside from making a sciency looking plume, isn't particularly worrying at a distance of more than a couple of meters. In fact, it's refreshing to stand in it on a hot day; it's mostly all water vapour.
Even at point blank range, I can deflect the jet with a leather glove for quite a while.

Fun fact; you're better off being naked than clothed if you get LN2 dumped on you. You can immerse body parts in LN2 briefly without ill effect, so long as you're quick. It's when LN2 wets cotton clothing that serious burns happen. Given the wetting issue, you're much better off using napalm.
http://www.youtube.com/watch?v=gjsMV1MglA4

Also, yes, as mentioned, LN2 is cheap. It's a byproduct of air separation - oxygen and argon are the desired products. LN2 is a bonus. We pay less than a dollar a liter for it...

[Rossum]

Okay, I think I've got it.

If I stick with the cryogenic theme then I'll have them work with a wider variety of substances like hydrogen for fuel (to have it make sense to freeze it and move it around since it can be used as fuel), or if I absolutely need to have freeze guns or cryo-weapons then either have them use some kind of napalm-like gel so that it doesn't dissipate to a gas instantly and sticks to people (maybe an actual flammable gel thats normally stored at cold temperature and can either be used to freeze stuff or later ignited once it thaws out enough) or they would contain reactive or toxic gasses that are liquefied or to make use of liquid oxygen explosives.

Anyway, my questions are answered.

[Simon_Jester]

Bear in mind that as a weapon, freezing people just isn't that effective. It's got a high weirdness factor, but that doesn't make it superior to conventional weapons. Certainly not to the kind of conventional weapons that can be delivered with the same equipment, such as flamethrowers.

Video game evidence aside, "cold" and "heat" are not balanced. In practice, it is far easier and cheaper to damage something with heat than with cold, and a "freezethrower" isn't going to be worth much compared to a flamethrower.

[Serafina]

Squirting liquid nitrogen at things is going to be a pretty inefficient way of killing things. You’re much better off using the liquid nitrogen to propel a rock or such like, an expanding gas launcher like a potato gun.

Yes it is, since it will pretty much immedeately vaporize upon contact with air, due to the extreme heat differences.

It would work at extremely short ranges or with very large amounts (or in a vacuum) but that's hardly a good weapon.
Really just a stupid version of a flamethrower.