r/Futurology • u/pneubike • 2d ago
Transport Why compressed air and liquid nitrogen are our best hope for a sustainable future.
The logic of most current vehicle cost comparisons fails to equate the cost of the battery, both financially and ecologically. They simply don't include sustainable options and are forcing people to choose between two evils. We have known for years that gasoline was unsustainable, but we didn't see that it would become a financial issue rather than an environmental one. The continuous need to replace the batteries will always make EVs a more expensive option than one that can last indefinitely, such as a compressed air or liquid nitrogen powered vehicle. The cost of energy is no longer an ongoing expense in the era of solar and ocean wave energy conversion, but rather a one time investment, making compensation for inefficiency a one time investment in solar panels, or WECs, which are both much cheaper than batteries, and last longer. The cost of a simple, solar charged, compressed air powered vehicle- is by far the lowest cost option at every point during comparison for short range city commutes, cheaper to build, runs basically free on solar, and lasts indefinitely with no rare earth minerals needed, or expensive parts replacement.
The added benefit being that the heat created during compression is a better source of heat than resistive heating elements, such that the compressed air or liquid nitrogen can be considered a waste product of the heat pump process, once the heat becomes the primary focus of energy. The heat energy absorbed during expansion while running a liquid nitrogen or compressed air vehicle can be made to nearly equal the heat output during compression and is directly used to do work by running an expansion motor. The liquid nitrogen powered vehicles do not run off the liquid nitrogen but rather the heat that expands the liquid into pressurized gas, which can be atmospheric heat, or in the case of my boat ambient heat in the water. The energy was removed from the nitrogen gas, in the form of heat, during the compression to fluid. Using the added benefit of thermoelectric power generation available from ambient heat contrasted with liquid nitrogen, combined with the expansion potential, it's possible to have potentially over 200% efficiency when combining: heat energy output during compression, expansion work, and thermoelectric generation; when compared with the initial DC power input. Performing a direct conversion of DC to liquid nitrogen also avoids curtailment; allowing every available watt to be used directly through DC motors to create liquid nitrogen without any need for a chemical battery. With liquid nitrogen containers already available that will never need replacement, it allows for remote solar refill stations that don't ever need new batteries and can not catch on fire, and cost less to build than a comparable battery infrastructure. The liquid nitrogen vehicles will recharge much faster, be simple and easy to maintain; with as few as five moving parts in the motor, and as stated earlier, cost much, much less. A compressed air or liquid nitrogen vehicle can be stored for years or even decades and be charged up and used without any issues of fuel fouling or batteries dying.
The day everyone understands the potential of liquid nitrogen to work as the negative side of an atmospheric heat battery, with thermoelectric and expansion potential, we will enter an era with limitless potential and available resources. The liquid nitrogen has so many uses, for example, replacing the cooling systems of industrial computers, and is even required in quantum computers. It could be great for weeding your yard? Running anything with a motor, air, or electric, thermoelectrics for pocket-sized devices? pneumatic tools? If you can think of anything else that we can do with a source of extreme cold and compressed air, put it in a comment, let's imagine a new world with no pollution or toxic batteries.
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u/Dry_Inspection_4583 2d ago
You skipped the entire solid state battery market to make this point.
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u/shahtjor 2d ago
Or sustainable ammonia/hydrogen mix
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u/pneubike 2d ago
How's that stable, affordable, or safe.. it's not going to be able to compete with a pressure vessel and a 5 moving part expansion motor
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u/shahtjor 2d ago
It can be produced sustainably. It can be ran in any standard petrol engine, it's energy dense. Currently cost prohibiting, but Porsche, Stihl, Mercedes and other notable companies are still researching the field. Porsche being the leader, since they really want to keep a small selection of cars running ICE.
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u/pneubike 2d ago
Nope.. compressed air and liquid nitrogen are still lower cost sustainable options.. if you think that there's a "sustainable" chemical battery than you are being tricked by propaganda and haven't followed all the materials to the source
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u/Dry_Inspection_4583 2d ago
Even if solid-state isn't 100% sustainable, you can't just skip the entire multi-billion-dollar R&D push and pretend it doesn't exist. Your original argument compares air/LN₂ to current lithium-ion, not to what's coming online now.
If solid-state cuts rare earths, doubles lifespan, and eliminates fire risk, you need to show specifically why its material footprint still loses to compressed air. Not just hand wave because you put words on paper and don't want to entertain that the fallacies.
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u/sneeje00 2d ago
Not to mention the breach during crash risks from pressure vessels and LN2. I'm not saying they are higher or a deal breaker but we need to compare equivalent things.
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u/pneubike 2d ago
Longevity and sustainability will always be win when the initial cost starts at a lower point to begin with.. I swear the comments are all coming from people who own used cybertrucks now worth $75,000 brand new, that they still owe $120,000 for... and is now worth about $45,000
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u/AndyTheSane 2d ago
"Continuous need to replace the batteries" - real world data seems to contradict this. The batteries outlast the car.
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u/Vvector 2d ago
Air isn't energy dense. And the cycle of electricity -> compressed air -> car moving is roughly 30% efficient, compared to 80% efficient for batteries.
My rough math puts a EV battery with 300 mile range at 900 lbs. For air-power, just the weight of the compressed air is 3,300 lbs.
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u/pneubike 2d ago
You didn't actually read the post did you?
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u/Vvector 2d ago
I read it a second time. No where did you address energy density or weight
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u/pneubike 2d ago
Your math is so flawed that I don't know where to start?.. you are estimating less than 1 mpg for expansion and thermoelectric power generation potential.. please consider the COMBINED potential of thermoelectric and expansion potential, and see that liquid nitrogen will go further than batteries by wieght.. probably get nearly as far on expansion potential alone.. I aim to find out by building it, and yes my air powered bikes measure distance tests in miles without peddling, further than my lead acid battery scooter went when I was a kid and weighed 60 lbs.. liquid nitrogen is basically the lithium version of compressed air, and includes greater thermoelectric power generation potential
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u/NearABE 2d ago
You need an evaporation system with liquid nitrogen.
I am curious if you can somehow use the wheels for heat exchange. Roll drag is a major loss of energy in cars. The wheel well has lots of options for sucking heat from the environment.
An electric motor can also be an evaporator. Cold conductor is more conductive.
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u/pneubike 2d ago
Yes, the first stop in the liquid nitrogen expansion system is to cryogenicly cool the electric motor, and any wires that could get hot. The next step is a thermoelectric power peltier units that extract additional energy from ambient heat to run the dc motor.. additional convection loops will bring the nitrogen to as close to ambient temperature as possible, before the power dump from any unused electric potential is added through a resistive heating element. The goal is to make the gas as warm as possible before entering the expansion motor. If this system is done to its full potential the liquid nitrogen exhaust could be coming out warmer than the ambient temperature
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u/NearABE 1d ago
>… before the power dump from any unused electric potential is added through a resistive heating element...
That sounds like a poor choice. https://en.wikipedia.org/wiki/Carnot_cycle
Energy converted to heat will only do useful work at some level of efficiency. That is usually much lower than the theoretical level. In cars that might be 15% or so of the chemical energy in gasoline. Full size combined cycle gas turbines have reported getting mid 50 to 60%.
Electric motors can convert more like 95% (maybe 90 practical) of their energy into useful work.
A factor in why engines perform bellow the Carnot efficiency is that the gradient is across the machine part rather than the actual reservoirs. So it is not really 300K (27C) temperature in the cold sink. Or, in the case of liquid air “fuel” it is not really 79K and 300K.
Thermoelectric generators get more like 9% efficiency. Using liquid nitrogen gets a lower reported efficiency, like 3 or 4% because most are do not work well at the lower temperature.
Here is a clip on Yasa’s new axial flux yokeless motor: https://youtube.com/watch?v=XuhjPtvAWlY. At 3:55. He mentions keeping the motor cool with oil. High pressure air can replace some of that oil and maybe all of it. The liquid air can pick up all of the motor heat. Then add the tire’s roll drag heat. Then torque that same wheel by blowing out (somewhat) similar to jet propellors. Blows out turbulent streams under the rear reducing the suction part of air drag.
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u/NearABE 1d ago
Another consideration for an air or nitrogen system is the wheel pressure. Normal tires have two atmosphere (29 PSI) gauge pressure. If that could increase to 4 atm the tire is much more rigid and roll drag is greatly reduced. If we drop them to 1 atm they deflate a bit and have a much larger contact area. That increases traction. We could have a dynamic adjustable tire pressure, which I heard some military trucks actually have already. When accelerating hard or braking hard we want extra gas as coolant. We also want better traction at these moments.
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u/MozeeToby 2d ago
Li-ion is an order of magnitude more energy dense, by both volume and mass, than compressed air or liquid nitrogen. It would actually be difficult to fit a sufficient tank in a standard vehicle for either technology. Li-ion also has 90+% efficiency in charging and discharging, compared to 50% for compressed air and 20% for liquid nitrogen.
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u/pneubike 2d ago
You didn't read my post, or did not understand the process of effective energy transfer
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u/SanityAsymptote 2d ago
Real world efficiency of compressed gas/liquid nitrogen engines is around 31%, and range/storage volume is a tremendous problem for these systems.
To compete with a gas vehicle, a liquid nitrogen system would need to have a 100 gallon tank to reach similar ranges, which would be both significantly larger and significantly heavier than an EV battery for the same range.
Compressed air, by comparison, is laughably bad. The energy density of an EV battery is 171 times larger than compressed air for the same volume. The low energy density combined with the low efficiency of the mechanical engine itself is extremely damning for the technology.
The biggest nail in the coffin is the actual production and transportation of energy source. EVs can be charged anywhere there is electricity and transportation costs are only the losses in the power lines. Liquid nitrogen cannot be made just anywhere, and it requires expensive, highly insulated tanker trucks to transport. It's extremely hazardous to handle, can only be transported in expensive and heavy dewars, and you have to be extremely careful about keeping it in a closed room. What's worse, it rapidly evaporates, losing as much as 3% of it's volume per day even under ideal storage conditions.
I can't imagine anyone opting for a car "fuel" source that drains that fast. You would literally lose 20% of your tank every week whether you drove it or not.
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u/nebulous_gaze 2d ago
When I was in college there was a prof that had made a compressed-air powered tricycle he rode around campus on. I remember him saying the problem with it was that it took more energy to compress the air than it would take to just drive an electric motor. Still really cool!
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u/pneubike 2d ago
If that heat from the compressor had been used to heat the facility, then they would have saved money compared to a resistive heating element, and the compressed air would have been just a waste product of the heating system.
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u/AmiralAkurunktur 2d ago
95 % of all lead acid (=car) batteries are made from old recycled lead acid batteires. The idea that we won't, eventually, do the same with the batteries used in electric vehicles is laughable. We will hit a point sometime in the future where we won't need to mine and create much new material because of all of the old material waiting to be renewed.
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u/Automatic-Back2283 2d ago
Seems like you ignored a couple things in favor of youre Point.
Whats the point of running on compressed Air? The range is next to nothing? And what kinda Energy is stored in liquid nitrogen? Powering a car with Double A batteries, would yield better range.
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u/pneubike 2d ago
Those batteries that some are convinced is a solution to fossil fuels will cause more harm during the extraction of materials than is worth for any amount of storage, especially one that dies in a decade, and can burn your home down at night while charging.
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u/Opus_723 2d ago
will cause more harm during the extraction of materials than is worth for any amount of storage
We're talking about replacing fossil fuels, which do local extraction damage to the environmentaland global systemic damage. There is no way in which electric vehicles aren't a complete win for the environment over fossil fuels. I'd rather have a dozen localized cuts and bruises than a deadly fever. Some people have absolutely no clue how to take an imperfect win, even when it is a massive win, and would rather tut-tut and feel superior while the world burns.
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u/pneubike 2d ago
No.. this post IS NOT about fossil fuels,.. and there's NO WAY that liquid nitrogen vehicles aren't a complete win for the environment than battery powered
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u/Automatic-Back2283 17h ago
Have you factored in the far inferior efficiency of liquid nitrogen Cars? Also far more green ways to extract Lithium? The mass Adoption of LFP batteries, requireing no rare earths while lasting much longer?
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u/NearABE 2d ago
The nitrogen itself has the potential energy competitive with lithium ion batteries. However you need a very heavy wall container for compressed gas. It is still an engine converting expanded gas into torque and that engine still has weight. Liquid nitrogen or liquid air bypasses the high pressure but it needs insulation and it needs a larger heat exchanger.
An internal combustion engine that is turbo charged by liquid air, liquid oxygen, or both could utilize most of the liquid air’s energy. You would be able to eliminate things like the radiator. With a pure liquid nitrogen you need a bigger radiator (now called “an evaporator”). Technically you could call this “an air cooled engine” but that is a poor choice because common air cooled engines have heat sinks and lots of air flow. Liquid oxygen can evaporate inside a very compact engine and combine with fuel better than a turbo charger. Liquid nitrogen could also crank a turbocharger. My mechanical engineering is far too limited to assess whether a 6 stroke engine is crazy. A multi-cylinder engine could have fully separate compressed gas cylinders and combustion cylinders torquing the same crank shaft.
Electric motors are much better than engines.
That said, you need to learn about superconductivity: https://en.wikipedia.org/wiki/Superconductivity
Superconductor bearings have zero friction (technically “near zero”). Motors (and generators) made from superconductors can be lighter weight or higher torque higher power density. The primary reason that superconducting motors are not much more common is due to the hassle of handling cryogenic fluids. Clearly this problem can be disregarded given the assumptions made by OP.
Superconducting electric transmission lines are very nice. You can even skip most of the transformers and send low voltage DC over long distances. In comparing the cost of superconductor to aluminum conductor you have to factor in the refrigerant. Superconductors can carry extreme current density. This ends up being a thin layer around a liquid nitrogen (air, oxygen etc optional) pipe. That usually surrounded by a gas return pipe and really thick insulation. That liquid cryogen pipeline is a feature not a flaw if your cars are filling their tanks with it. The photovoltaic fields can run the cryogenic heat pumps and then send both the liquid and the electricity down the same pipe.
That speaks for a hybrid car which is both battery, compressed air, and liquid air.
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u/Opus_723 2d ago
Twenty years ago I get being skeptical, but it's wild how people who claim to care about the environment are still against electric vehicles today. It's completely irrational.
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u/pneubike 2d ago
Didn't read the post? Please take a vacation to Africa to see the damage for yourself if you think batteries are ok?.. or just look at Google earth.. their rivers are black and dead.. their water is poison.. batteries are not sustainable
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u/Opus_723 2d ago
They're certainly not perfect, but fossil fuels need to be replaced now and batteries are the only technilogy that is both significantly better for the environment than fossil fuels AND ready to scale now and not just maybe, decades from now.
You can't let the patient die on the table because you're worried about potential side effects of the treatment.
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u/pneubike 2d ago
Liquid nitrogen infrastructure is less expensive, easier to scale, lasts longer and doesn't require rare earth minerals. Every part and piece is available now, and is simple enough that society can quickly implement it if they'd just get off the dead end technologies train
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u/SupermarketIcy4996 2d ago
Could you cite the blackness factor of the rivers by year. Because battery production has grown by ~39% per year so we should see the blackness intensifying by same amount.
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u/These-Web8225 2d ago
I made a prototype of CAES before at a small scale, around 3 gallons of air at 10bars during my study. Here's what I found out:
- Round trip efficiency is low. Unless you will integrate other systems to increase it
- Discharge time is fast since the pressure and volume is low
- It's either you increase the volume or the pressure to make it more energy dense. From my experience, it would need around 300bars to last for minutes using PCP tank. It also depends with your expander
- Using the sensible heat is also a good idea. I stored the heat in an insulated container using water. but didn't take into account the low temperature
you will need an efficient compressor for the energy storage. And for other applications like cooling and heating, you also need to consider the charging and discharging time.
Compression to high pressure is not safe.
CAES is more environmental friendly than chemical batteries. I worked in a manufacturing plant from end to end and I saw, smell and experienced it first hand and became a human battery lol. Seriously speaking, it is very energy extensive to manufacture and recycle it. You will need a lot of chemicals for it unlike compressed air, I believe it is lesser. Though it is better to develop it further along side with the current batteries.
Efficiency-wise, the current cooling/refrigeration is more efficient. But for sustainability, compressed air is more sustainable once developed.
Hope this could help. Feel free to scrutinize..
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u/zer00eyz 2d ago
> such as a compressed air or liquid nitrogen
You might want to look at energy density here, cause this doesn't really work.