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Old 07-18-2008, 01:34 PM   #41
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150 thousand / 250 million is .0006

I agree, air is inflammable, ...
Actually air isn't inflamable in most circumstances.

inflammable - Definition from the Merriam-Webster Online Dictionary
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Old 07-18-2008, 02:18 PM   #42
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Non Flammable?
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Old 07-18-2008, 02:25 PM   #43
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I think all this discussion about the safety of the compressed air is somewhat of a non-issue...if you personally don't feel it's safe, don't buy one. But, if a car company can produce a vehicle like this that is reliable, meets the US safety standards, gets 106 mpg and retails for anything under $20k, there will be a 5 year waiting list to get one. It will instantly become THE green vehicle to own....leaving the Prius in the dust. The big question for me is whether they will ever come to market here in the US in large enough quantities to actually make a difference.
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Old 07-18-2008, 02:40 PM   #44
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I'm pretty sure we were all just fooling around about the safety component, but thats not readily apparent to some.

I'm pretty doubtful about the cheapness, and I'd like to see it in action. I'm having a hard time resolving a natural gas fired electric plant (pretty much the standard here in CA where we've got the most cars) sending electricity over a distribution network to my house where an electric compressor turns it into highly compressed air thats pumped into a car which then uses the air to turn a motor ending up being more efficient than a simple small high efficiency 3 or 4 cylinder gas or diesel engine. Plus there ya are burning natural gas instead of gasoline.

Now you change that over to nukes at a brazillion dollars to build 40-50 new plants in the state, and then its probably a pretty good deal.

You throw a trillion into solar panel development to get something thats about 8x12 and generates all the electricity a home needs and its also good.

I'm still just missing the free lunch.

I've also got some experience with compressors and have never seen one that I'd like to have running in my garage for four hours a day. I'd imagine a super high efficiency model with a lot of noise dampening isnt going to run for $500 over at sears
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Old 07-18-2008, 03:23 PM   #45
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I'm pretty doubtful about the cheapness, and I'd like to see it in action. I'm having a hard time resolving a natural gas fired electric plant (pretty much the standard here in CA where we've got the most cars) sending electricity over a distribution network to my house where an electric compressor turns it into highly compressed air thats pumped into a car which then uses the air to turn a motor ending up being more efficient than a simple small high efficiency 3 or 4 cylinder gas or diesel engine. Plus there ya are burning natural gas instead of gasoline.
I agree, it doesn't appear to make sense from a thermodynamic efficiency standpoint. Still, if they are giving honest numbers, from a $$/mile standpoint, it appears to be more efficient. Maybe we're missing the costs of trucking all that liquid fuel around, and the price markups every time it changes hands. The turbines that turn that NG into electricity at the central plant are very efficient. OTOH, for those living in a place with cheap NG, it would be simple to power an air compressor at home with NG directly (no inefficient electric conversion).

Heck, if the same compressor could be used to safely fill an NG tank onboard the vehicle to 3000 PSI, you'd never have to stop at the gas pump.

All just in time for Mr Pickens's plan to be implemented, doubling NG prices nationwide.
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Old 07-18-2008, 03:52 PM   #46
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Heck, if the same compressor could be used to safely fill an NG tank onboard the vehicle to 3000 PSI, you'd never have to stop at the gas pump.

As long as you never venture more than a half-tank away from home.
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Old 07-18-2008, 05:48 PM   #47
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More back-of-the-envelope calcs:
Natural gas delivered to your home: If it costs 13 dollars per thousand cubic feet (close to national average) and there are 1031 BTU per cubic foot, then your cost is .00126 cents per BTU.
Gasoline at the pump: If it costs $4.00 per gallon and there are 124,000 BTU per gallon, your cost is .0032 cents per BTU

So, that natural gas being piped into your house in volume might quite be quite a bargain. Maybe that liquid fuel infrastructure we now have in place has a lot of costs built in that we've just gotten used to.

Electricity: If you pay the national average rate (10.2 cents kwh), and there are 3413 BTUs per kwh, then this form of energy costs you .003 cents per BTU. That's nearly identical to the cost per BTU that we pay for gasoline. Which brings up another question--why will plug-in electric cars be so much cheaper to run? I'm guessing that it's because the conversion from gasoline to mechanical energy is less efficient (in small motors) than the conversion from electricity--> chemical PE (battery)-> electricity --> mechanical energy. Plus some gains from regenerative braking (in city driving).

Tentative conclusion: The cheapest energy available to most of us (dollars/BTU) is natural gas. Maybe, for those who have access to it, the cheapest way to drive is with a vehicle powered by a NG internal combustion engine, with compressed NG provided by your own in-home compressor--powered by natural gas. About a year ago I read about a company that was preparing to market NG compressor stations for home use. I don't know if that has taken off or not.
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Old 07-18-2008, 06:00 PM   #48
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From what I saw in the You Tube video, this thing is made to be light. When you get the US safety standards built in, it is going to gain a lot of weight!

An interesting idea. However, unless you just need second car, spending $15,000+ to get good gas mileage does not make since. I don't see this as a primary car.
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Old 07-18-2008, 06:01 PM   #49
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If you pay the national average rate (10.2 cents kwh), and there are 3413 BTUs per kwh, then this form of energy costs you .003 cents per BTU. That's nearly identical to the cost per BTU that we pay for gasoline. Which brings up another question--why will plug-in electric cars be so much cheaper to run?
I think thats the dirty little secret written in the laws of unintended consequences...in a lot of areas they wont be cheaper to run.

PG&E's current electric rates are ~11c a kwh for your baseline use, pops to 13c for 100-130% baseline, 130-200 is 22c, 200-300 is 30c and 300+ is 35c.

I've got a house full of CFL's and run around turning things off and we're still getting a few kwh in the 300+ bucket. So if I were plugging my car in overnight I'd be seeing 30-35c/kwh costs.

Plus in CA we dont have a lot of excess electrical capacity in the summer time. Nighttime use is lower, but thats when they take a lot of screaming, smoking stuff offline to do maintenance. Lots of NIMBY problems with new power plants.

I'm not sure what the natural gas production/distribution issue is like...havent heard of any shortages or problems with it. But it doesnt get any prettier cost wise at $19 per 1000 cubic feet for baseline use and $21.44 past that.
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Old 07-18-2008, 06:35 PM   #50
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From what I saw in the You Tube video, this thing is made to be light. When you get the US safety standards built in, it is going to gain a lot of weight!

An interesting idea. However, unless you just need second car, spending $15,000+ to get good gas mileage does not make since. I don't see this as a primary car.
I actually see just the opposite happening....people will buy this type of car as their main "commuting to work" car since most people drive alone, and then their current car would be their second car. I guess it just depends on which car you drive the most. I have a car that gets 28-30 mpg and if I had another one that got 100+ mpg, I'd drive the 100+ mpg car almost all of the time, therefore it would be my primary car. I'm sort of assuming that you're actually in the market for a new car. Obviously if you have another car that you just bought, it wouldn't make much sense to have a 2nd car.
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Old 07-18-2008, 09:20 PM   #51
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More back-of-the-envelope calcs:
Which brings up another question--why will plug-in electric cars be so much cheaper to run? I'm guessing that it's because the conversion from gasoline to mechanical energy is less efficient (in small motors) than the conversion from electricity--> chemical PE (battery)-> electricity --> mechanical energy. Plus some gains from regenerative braking (in city driving).
That's it.

Internal combustion engine - Wikipedia, the free encyclopedia
Quote:
Most steel engines have a thermodynamic limit of 37%. Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency of about 20%.[7][8]
Batteries and motors are pretty efficient. Charging a battery can be > 90%, maybe less on discharge, brushless electric motors > 85%.

Pretty big delta from 20% ICE

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Old 07-18-2008, 09:26 PM   #52
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Another thing not mentioned. How does this thing do in traffic? i.e. What happens to the AC when stuck on a Houston freeway going 0 mph?

We live in a golf community. Most folks have a second vechile.... a golf cart!

DallasGuy... when I did go to work, it seemed I saw a lot of Beamers and such on both sides of me. While I don't deny that some folks are going to go for this, I don't think it will be enough to make a big dent. Americans tend to like their creature comforts. Also, in Texas, at least Houston, Everybody is for mass transit..... so the other guy will use it and get off my freeway!
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Old 07-18-2008, 10:03 PM   #53
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To follow up on this:
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This would be a very good application for solar power. The big problems with solar today are the intermittent nature of sunlight and the high cost of making electricity from the sun (the cost is coming down, but the dollars/watt still makes sense only in very expensive electric markets and with government subsidies).

BUT, converting sunlight into mechanical energy skips the expensive PV step. A collector/tracker and a heat engine capable of utilizing low-grade heat (e.g a Stirling cycle motor) could directly compress air at your home while the sun was out. When you get home, you've got a tank of compressed air ready to "refuel" your car. And, the intermittent nature of sunlight is no problem--if the day was cloudy, just plug in the electric compressor instead.
More rough estimates:

A Stirling cycle motor converts heat to mechanical energy with an efficiency of 15-30% (Stirling engine - Wikipedia, the free encyclopedia )

We already found out that it takes approx 20,240 kwh of energy to fill the compressed air tank. Sunlight gives 1000 watts/sq meter on a cloudless day. So, if we had a practical size tracking dish (say about 2 meters diameter= 3.1 sq meters) it would receive 3100 watts when the sun is out. If the Stirling Cycle unit converts it to mechanical energy at 22% efficiency, we are getting 680 watts worth of "compression work." At this rate, it will take 30 hours of sunlight per day to recharge our car's air tank if it is entirely empty.

So--If the sun has been shining and you've got a collector this size, you'd be able to refill 1/3rd of the compressed air in your car (10 hours of sun). That's approx 250 miles of driving IF you've also been burning gasoline in the car (getting 100+ MPG). If you need to refill more than 1/3rd of the air or it has been cloudy, you'll need to plug the car in at home to refill the air tank.
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Old 07-19-2008, 07:28 AM   #54
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As I understand it, the material for the air tanks (there are 3) was chosen because its failure mode is to rip more or less gradually without throwing shrapnel all over the place.
The question that isn't answered anywhere is if those tanks are good for the life of the car or if they have to be replaced at some point because of fatigue.
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