Has anyone analyzed the viability of a compressed-air energy distribution system? It could be simpler and safer than electricity distribution.
* Electrical transmission lines are lighter and smaller per watt than compressed air transmission lines.
* Electrical transmission has lower inductance than compressed air has equivalent momentum.
* Compressed air vessels can fail explosively; electrical stuff just heats up.
* One has to contend with adiabatic heating/cooling when exchanging air pressure for flow rate, while there's no analogous concerns when using transformers to exchange voltage for amps.
* Electrical equipment tends to be much quieter than air equipment.
Much of Amtrak's Northeast Corridor, and SEPTA's rail network in the Philadelphia area, still use 25 Hz for traction power, provided from converters or from a few hydroelectric plants that have 25 Hz generators.
[0] https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4412948
Large-scale systems were built in the 19th century, especially in ports, where large intermittent loads were required, especially for lifting and operating canal locks.
Disadvantages include size, limited range (up to several kilometres, but generally far less) leaks, limited capacity (high applied force but limited energy storage), controls, etc.
Electric power distribution is the diect analogue of such systems, and is in virtually all regards superior, more flexible, cheaper, and more readily and precisely controlled, though hydraulic power distribution existed in London, England, as late as 1977.
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.51...
https://www.lowtechmagazine.com/2018/05/history-and-future-o...
I think the most promising application of distributed compressed air is in refrigeration, especially if the power source is not an adiabatic process.
We have thousands of kilometers of high-voltage transmission lines, imagine that's now carrying compressed air. Firstly, these lines can carry multiple Gigawatts of power, i do not think it's even possible to have a pipe of compressed air that could transport that amount of power. The most powerful air compressor in the world appears to be 28 mW in power consumption! - not output.
Secondly, how are you going to look for leaks in that thing?
Also any rupture in the line will release the equivalent energy of many kilograms of TNT.
How do I power my TV with compressed air, do I have to have a generator in my house? If so, you've just lost a ton of efficiency.
Losses in a compressed air energy distribution pipeline would primarily come from friction between the moving air and the walls of the pipeline. Fortunately, we can increase the pipe size to reduce losses from friction. This is because friction increases linearly with pipe diameter, while flow increases quadratically [1].
Electrical power transmission requires large amounts of land. The towers and lines are hazards to aircraft. They are fragile infrastructure sitting out in the open. They start wildfires. Compressed air using buried pipelines has none of these problems.
Air streams out of a broken pipe. It emerges from the pipe at high pressure (100 ATM?) and then expands until reaching local pressure (1 ATM). Its flow rate is limited by friction with the pipe wall and cannot be instantaneous. An entire section of pipe will take several seconds or minutes to empty. By comparison, a TNT explosion produces a small amount of 1-billion-ATM gas which expands instantly in one big burst. A broken pipeline is more like a rocket engine than a TNT explosion.
How to detect and find leaks? Listen for the sound? Fortunately, compressed air leaks pose no danger of explosion or asphyxiation.
Refrigerators can run on compressed air directly and very efficiently.
A TV would need a small electricity generator powered by compressed air. The generator could be noisy, so it would probably be in another room or outside the home. The generator could cool your home in summer. To be efficient in winter, it could use some buried pipes to draw heat from the ground.
Coal-powered and natural-gas power plants are essentially electricity generators powered by compressed air (actually steam). They are adiabatic engines and have the same efficiency problems as a small generator in your home.
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[0] https://www.eia.gov/tools/faqs/faq.php?id=105&t=3
[1] https://www.fluidmechanics.co.uk/hydraulic-calculations/pipe...
To substantiate your claim you pick some links with formulas for pneumatic systems, but leave the actual calculation as the exercise to the reader. Why would you do that?
If you have the skills to do the calculations yourself, you should do them and demonstrate that for some set of realistic parameters, greater efficiency is possible. If you either can't do them, can't find parameters to support your claim, or you can't be bothered to, then it's not fair to leave it to the reader.
I have done what I can, but it's not my speciality, so there could be mistakes.
Firstly, what does it look like to have a pneumatic system transfer 4 GW of power? I have used this PDF on sizing cylinders, and made the assumption that the pipe and the cylinder would be of the same size. http://www.gearseds.com/files/chp2-5_diff_work_energy_pneuma...
With the help of a calculator at: https://www.sensorsone.com/pressure-and-area-to-force-calcul... I have arrived at a pipe with the inner diameter of 2 meters (!), pressure of 100 atm, and the speed of air at half the speed of sound (125 m/a). How Thick is the wall of the pipe? Using the calculator at: https://www.engineersedge.com/calculators/pipe_bust_calc.htm... details here: https://whatispiping.com/pipe-thickness-calculation-per-asme...) It comes out at 3 inches thick, for steel, with 50% safety margin.
How much is this pipe going to weigh? Here is a pipe weight calculator: https://wcalcul.com/pipe-weight-calculator - It comes out to 4.1 tons per meter. This pipe is quite similar to those used for gas transportation, but it's about twice the width. Certainly doable, but this is >10X times the material needed for high-voltage cables.
To calculate pressure drop, i have used a calculator at: https://www.engineeringtoolbox.com/pressure-drop-compressed-... - I end up with 0.3% for 100 KM, which is is roughly in line with HDVC: "Depending on voltage level and construction details, HVDC transmission losses are quoted as less than 3% per 1,000 km"
So I am surprised that it's even theoretically possible. There are obviously many unaccounted losses - valves, turns, distribution to smaller pipes, etc. Casual glance at compressed air storage, which has none of the distribution issues, shows that their efficiency maxes out around 70%.
Electrical transmissions lines can be and sometimes are placed underground, especially the DC variety - earthworks are very expensive and that why it's not usually done.
Now, safety - have you seen tyre explosions on a truck? They regularly kill people, and they are 10- times lower pressure than this pipe would be.
You point out fragility of powerlines, compared to what? Do oil and gas pipelines need repairs any less often that powerlines do? How many fires were started by high voltage powerlines? Substantiate your claims.
Everything indicates need for a lot more equipment than is required for dealing with electricity, I think the pneumatic system would be much more expensive and dangerous.