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Discussion Starter · #1 ·
As I've been getting deeper into the EV learning curve I've been wondering if there's a way to build a longer range, lighter EV without having to resort to expensive lithium.

I've been doing some research on compressed air starting with the blog page here:

http://www.diyelectriccar.com/forums/showthread.php/green-cars-part-4-compressed-air-11068.html

and I realize that it isn't ideal by itself. However, it seems that by combining compressed air in a hybrid config you can gain some significant advantages.
So I wanted to bounce some ideas and get some feedback.

Start with the traditional Electric motor/battery pack EV. For the sake of argument let's say we're rolling with 96V. But instead of the traditional 6V battery we use a 12V 125Ah lead acid set. With 8 batteries and 70 lbs each, you have a pack with 96V, 12KWr (9.6 KWh usable to 80% DOD), that weighs in at 560 lbs.

Now of course the problem is that you are range limited. At 300 Wh/Mile that pack will get you 32 miles or so depending on Peukert.

Now couple that system in series with compressed air. You have a compressed air genset that produces 115V to charge the pack. Now the amount of power you can extract from a CA system depends on a lot of things:

1) Amount of air you are carrying
2) Temperature of the stored air.
3) Heating the air before decompression

I'll come back with details on these later. But let me outline the advantages of the compressed air genset:

1) Fast recharge. Air tanks can be refilled in only a few minutes from a standing tank of compressed air.

2) Free AC. Compressed air cools as it decompresses. So a system that captures that cooling effect and passes it into the cabin gets you auto AC for little additional cost.

3) Regen braking. If braking is done by running an air compressor to refill the tanks and be capturing the heat of braking/air compression, then a lot of the energy that would usually be lost by braking can be reused to propel the vehicle.

The primary advantages of using a traditional electric/battery system are:

1) Plug in recharge.
2) Good instant power on the low end.
3) No power expended at stops. Typically an air engine needs to idle in order to be prepared to go when the light turns green.

I don't have it all fleshed out, but these are some of the thoughts that I'm having about such a hybrid.

All that would be required are the air tanks and an air motor to power the electric genset.

What do you think?

ga2500ev
 

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That would be great if you can get it to work. I looked into the air motors a while back and it seems to me the air needed to be compressed to several thousand psi and I'm not sure what the cost is to do that for a usable quantity. I imagine normal air grinders aren't very efficient but my 3 hp 12 amp 220 volt compressor won't keep up with a 4" cut off tool or any of my orbital sanders once the tank is depleted in about 20 seconds hence the need for very high pressure. I also looked into the vortex tubes they use for chilling air to use for a/c but again it takes lots of cfm. I'm not saying it can't work though. Norm
 

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That would be great if you can get it to work. I looked into the air motors a while back and it seems to me the air needed to be compressed to several thousand psi and I'm not sure what the cost is to do that for a usable quantity.
SCUBA and paintball actually have both created an infrastructure for this. There are a variety of pumps that can pump up to 300 bar (4320 PSI)

I imagine normal air grinders aren't very efficient but my 3 hp 12 amp 220 volt compressor won't keep up with a 4" cut off tool or any of my orbital sanders once the tank is depleted in about 20 seconds hence the need for very high pressure.
Absolutely. The air cars out there are compressing 340 liters of air to 300 bar then dropping the pressure to 30 bar at the motor.

I also looked into the vortex tubes they use for chilling air to use for a/c but again it takes lots of cfm. I'm not saying it can't work though. Norm
You'll already get the effect simply by running the air motor. The interesting thing about the vortex tube is that you can also get hot air out of it too.

ga2500ev
 
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