[veoeluz]

I was just thinking about different ways you could utilize an outside (or rather, inside) power source to generate energy as you go. This is not a free energy post.

I saw a concept car they were making in Thailand that was basically a pneumatic car. The point here is that they were using two rather large (as a percentage of the car's volume) carbon fiber air tanks. What if you rigged up some sort of pneumatic electric generator that you flip on to use when/as you need it as a sort of backup. Not only could you potentially raise the range, but you could also refill those tanks at any gas station (as long as they have an air pump.)

What do you guys think? Too much extra weight? I was thinking a small light truck with the extra bed space for larger tanks. I know carbon fiber tanks are expensive, but I was just looking at it from a practicality standpoint.

[Ziggythewiz]

Go compare the cost/kwh of those tanks to batteries and you'll have your answer.

[veoeluz]

Originally Posted by Ziggythewiz

Go compare the cost/kwh of those tanks to batteries and you'll have your answer.

But wouldn't the tanks be much lighter than just running extra batteries? I know the question still lies in how much potential you can stuff into those tanks, but I figured that half the benefit would be quick and convenient fillups on the road of a renewable source of energy.

[TigerNut]

Originally Posted by veoeluz

I was just thinking about different ways you could utilize an outside (or rather, inside) power source to generate energy as you go. This is not a free energy post.

I saw a concept car they were making in Thailand that was basically a pneumatic car. The point here is that they were using two rather large (as a percentage of the car's volume) carbon fiber air tanks. What if you rigged up some sort of pneumatic electric generator that you flip on to use when/as you need it as a sort of backup. Not only could you potentially raise the range, but you could also refill those tanks at any gas station (as long as they have an air pump.)

What do you guys think? Too much extra weight? I was thinking a small light truck with the extra bed space for larger tanks. I know carbon fiber tanks are expensive, but I was just looking at it from a practicality standpoint.

I don't have the Formulas for energy stored in a compressed gas handy, but think of it this way, just to get a rough estimate of the volume required: If you have a 2 HP compressor with a 20 gallon tank, it will take it about 10 minutes of continuous running to get that tank to the cutoff pressure - usually about 120 PSI. If you had perfect energy recovery (and for compressed-gas motors that is distinctly not true, due to adiabatic effects), your 20 gallon tank would give you a maximum of 2 HP advantage for at most 10 minutes, and then it's toast. A larger tank or higher pressure will give you proportionally more energy storage, but will require a proportionally longer time to refill as well - even commercial tire shops don't usually use more than about a 5 to 10HP compressor, and most gas stations have nothing like that. If you can't get high pressure from the gas station, then you get no significant energy storage.

Seriously high pressures (such as for scuba tanks) require multistage compressors with intercooling and moisture scavenging, and I'd be really scared of a large tank at high pressure. Filling would not be quick or convenient at least partially due to safety concerns.

[Ziggythewiz]

If the compressor is running at 2 HP, you're likely to get ~1/2 a HP of stored air, and after converting that to electric you'd be lucky to get half of that. The air starts out light, but it can get heavy depending on the compression, plus you have the added weight of he tank and the generator.

You're probably better off with supercapacitors or flying geese or something.

An air powered car can work great, but trying to add that to electric doesn't make much sense.

[veoeluz]

Originally Posted by TigerNut

I don't have the formulas for energy stored in a compressed gas handy, but think of it this way, just to get a rough estimate of the volume required: If you have a 2 HP compressor with a 20 gallon tank, it will take it about 10 minutes of continuous running to get that tank to the cutoff pressure - usually about 120 PSI. If you had perfect energy recovery (and for compressed-gas motors that is distinctly not true, due to adiabatic effects), your 20 gallon tank would give you a maximum of 2 HP advantage for at most 10 minutes, and then it's toast. A larger tank or higher pressure will give you proportionally more energy storage, but will require a proportionally longer time to refill as well - even commercial tire shops don't usually use more than about a 5 to 10HP compressor, and most gas stations have nothing like that. If you can't get high pressure from the gas station, then you get no significant energy storage.

Seriously high pressures (such as for scuba tanks) require multistage compressors with intercooling and moisture scavenging, and I'd be really scared of a large tank at high pressure. Filling would not be quick or convenient at least partially due to safety concerns.

Well, the tanks that were used on those pneumatic cars each (there were two per vehicle) were around 25 gallons and were filled to around 250psi.

To clarify, I wasn't proposing you use the air to propel the car or anything, but to generate electricity through some sort of method.

So with 50 gallons at 250psi, I was just thinking this energy could be used to generate electricity in a similar fashion that I've seen people use gasoline hybrids to generate electricity.

With respect to the safety of the tank - that's why they used carbon fiber. It's stong, but won't cause an "explosion" if ruptured. Though I'm sure it'd still be a sight to see.

[TEV]

Hi,
Filling those air tanks require a special compressor, so you wouldn't be able to use the compressor from the gas station.

[veoeluz]

Originally Posted by TEV

Hi,
Filling those air tanks require a special compressor, so you wouldn't be able to use the compressor from the gas station.

I can see where that would be a problem. But if it's just used to extend your daily commute range? I guess it just kinda depends on what you have to work with.. How much the pneumatic generator would put out and how much room you'd have for tanks.

Anywho.. it was just a thought I had. I've not even been able to find a place that makes large capacity carbon fiber tanks. They might've been custom made for that company that made those pneumatic cars..

[Ziggythewiz]

Once again, there's no point in speculating much without numbers. Look em up, run the numbers and see what the result is. If compressed air is somehow far cheaper/lighter than LiFePo4 then it's a great idea that we'll all want to incorporate.

When it comes to physics, most issues are just a couple simple math problems.

[ga2500ev]

Originally Posted by veoeluz

I was just thinking about different ways you could utilize an outside (or rather, inside) power source to generate energy as you go. This is not a free energy post.

Smart of you to point that out.

I saw a concept car they were making in Thailand that was basically a pneumatic car. The point here is that they were using two rather large (as a percentage of the car's volume) carbon fiber air tanks. What if you rigged up some sort of pneumatic electric generator that you flip on to use when/as you need it as a sort of backup. Not only could you potentially raise the range, but you could also refill those tanks at any gas station (as long as they have an air pump.)

I've spent quite a bit of time looking at alternatives to petrochecmicals as a hybrid substitute. Something that is quickly refillable and does not require massive infrastructure to pull off. Compressed air was one of my first tacks. It doesn't work. The power density is way too low to be of any usefulness.

Better would be liquid nitrogen. Fundamentally the same concept except that liquid has a much better energy density than air due to the energy of the phase change. LN2 expands to 700 times its volume when changed to air, and the LN2 can be kept at near atmospheric pressure, not at 6000 PSI like compressed air. The source material is everywhere, pretty much anyone can make it. Since it's liquid it can be transferred between containers quickly. The University of Washington and the University of North Texas did some experements in LN2 vehicles about 10 years ago. Look up "Cool Car".

What do you guys think? Too much extra weight? I was thinking a small light truck with the extra bed space for larger tanks. I know carbon fiber tanks are expensive, but I was just looking at it from a practicality standpoint.

It simply won't get you far. Put it this way, it won't get you any farther than if you simply had put in that weight in batteries.

You're on the right track. I just think that compressed air is the wrong tool to get you there.

ga2500ev