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Discussion Starter #1
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.
 

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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.
 

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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.
 

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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.
 

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Discussion Starter #6 (Edited)
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.
 

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Discussion Starter #8
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..
 

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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.
 

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Ok lets look at the numbers

Assume perfect compression/expansion
1m3 (1000litres) air tank
Energy to get to 10Bar (150psi)
Take 10m3 and squeeze it into 1m3
Piston (area 1m2) moves 9 meters with a force between zero and 10Bar x 1m2
10 Bar = 10 x 10-power5 N/m2 = 1 Million N - average load = 500KN

500KN x 9 meters = 4.5 MJoules = 1250 Watt hours 1.25Kwhrs

Considering you would only get ~ half of that back - not worth messing with


Lets get up to SCUBA pressures - 200Bar
1m3 (1000litres) air tank
Energy to get to 200Bar (3,000psi)
Take 200m3 and squeeze it into 1m3
Piston (area 1m2) moves 199 meters with a force between zero and 200Bar x 1m2
200 Bar = 200 x 10-power5 N/m2 = 20 Million N - average load = 10 Million N

10MN x 199 meters = 1990 MJoules = 552 Kwhrs (about half "available")

So a 25Kwhrs "pack" - would be a tenth of that - 100 litres of Scuba cylinders - steel or aluminium would be 100Kg+

Carbon fiber tanks would be a lot lighter ~ 10 off 2 Kg tanks

Compared to batteries
Need very high pressures to be comparable
Three stage air compressor much much more expensive than battery chargers
Need carbon fiber tanks - Steel Scuba tanks are ~ $400 for a 10 liter tank? - 10 tanks - $4,000

Not as bad as I thought
 

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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
 

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Buy some extra batteries and just fill those for your extra distance. Cheaper, lighter, and you go sooooo much further. Just think of all the electricity wasted to fill those tanks only to make a tiny bit more by running a generator with the compressed air to recharge the batteries. Makes ZERO sense. Just use the electricity and don't bother with conversions.

Be sure you use lithium batteries and not lead acid for all your batteries.
There is a single failure mode that drives all of these discussions Pete: what do you do when you run out of energy? There's nothing about "Buy some extra batteries." that solves that issue because no matter how many cells you have in your pack, when they are empty, you are stuck.

That is the sole reason there are so many discussions on compressed air, liquid nitrogen, diesel/gas generators, solar, hydrogen, methanol, and the like. Because like it or not, with a gas car, when the tank is on E, it's easy to refill and get going again. With an electric vehicle, when the battery is on E, precious few options with a short refill timeframe exists.

In short, I can hop in my truck right this minute and drive the 2100+ miles from Atlanta to the Pacific Ocean without stopping for more than 15 minutes at a time. Even with an unlimited supply of cells, which I cannot afford anyway, there is no way to do this with a pure EV like the Leaf (at least that I know of).

Then there is the issue of amortized cost. With a gas car, even if the 10 gallon tank is situated for 300 mile range, and the common usage of the car is within that range, there's no issue if an emergency trip doubles or triples that range. Just buy an extra tank of gas.

Batteries are the proverbial "gas tank". So buying extra has a large cost associated with it, where it's not clear that the return on it is valid. Doubling the range of an EV with lithium can cost thousands of dollars. Where is the ROI if the doubling of the battery size only gets used in 1 out of 100 trips?

All of this is to say that hybrids are going to need to be a vital phase of the transistion from gas only vehicles. The problem with current hybrids is that they are E-assist vehicles, not E-vehicles. All except for the Leaf, the Volt (costs way too much), and custom/DIY setups gas is the primary motivator of the vehicle. So it isn't much progress.

LN2 isn't perfect by any stretch. It's inefficient. It adds weight to the system. There are dangers with carrying around supercooled liquids. But it can be made with electricity, and the source is plentiful: just pull it out of the air. Finally it can be refueled quickly, which is the marked disadvantage of batteries, even with fast charging.

ga2500ev
 

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{From an owner of 3 EV's (plug in's, not those hybrids everyone sez r electric}

"When your gasoline/diesel tank is empty, it is empty too...."

If you are an idiot, and can not plan ahead, no matter what you drive, you are going to run out..PERIOD.

Take command of your life. You ran your car out- not the battery.

(Flame away-I have thick skin)

Miz
 

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{From an owner of 3 EV's (plug in's, not those hybrids everyone sez r electric}

"When your gasoline/diesel tank is empty, it is empty too...."
You missed the point. It's not the fact that the gas tank is empty. It's the fact that it will take a minimal amount of time to refill, with over 100,000 stations in the US to do so. In fact, gas tanks do not typically go empty precisely because the infrastructure is in place. Gas has already set an expectation of 5-10 minutes tops to refuel. Anything outside of that window is a non starter for most drivers. Current EVs simply do not have that infrastructure in place.

If you are an idiot, and can not plan ahead, no matter what you drive, you are going to run out..PERIOD.

Take command of your life. You ran your car out- not the battery.

(Flame away-I have thick skin)

Miz
No need to flame. It's an infrastructure issue, not a planning issue. We need discussions like these because we need the ability to transition from where we are now to something electric based.

From an infrastructure standpoint, driving an EV is analogous to having a 3 gallon gas tank and no gas stations except for at home. You can plan until the cows come home. But the first time you have to take an emergency side trip that's outside of your range, you are stuck. The solution isn't to call for a 4 gallon tank. The solution is to figure out how to put up stations that you can refuel in short order, so that even if you have a 3-4 gallon tank, you can drive 100 miles, stop in and refuel in 5-10 minutes, and be on your way.

It would also be extremely helpful if that fuel was some form of electricity, instead of reverting back to gas, which defeats the purpose.

No matter how hard you try, there is no way to explain away the deficiency this situation creates for pure plug-in EVs to the general populace. Be it flow batteries, compressed air, LN2, electrified roads, or even battery swapping, there has to be some fast fuel electric based infrastructure in place in order for EVs to make it in to the mainstream. The only mainstream hybrids right now are all gas based. They are the only commercial EV type vehicles (with the exception of the Leaf, which of course is range limited) that the vast majority of drivers will consider. There needs to be a discussion about alternatives to range limited pure EVs and gas based hybrids. Note that all of these should be hybrid technologies coupled with pure plug in EVs, not a replacement for batteries and plug in charging.

So while no flame is required, let's not kill this thread based on the argument that "If you allow yourself to get out of range, then you must be an idiot."

ga2500ev
 

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And you, sir, miss my entire point.

We on this forum, are visionaries. We look beyond temporary conveniences, inventions and conventions. We advocate the entire replacement of the existing petro fuel society with something cleaner and sustainable.

I seriously doubt you will make any converts to support the same old party rhetoric. We have heard it all.

So, our system is not perfect. Yours ain't neither....and we are still perfecting ours.

To most of us, a "hybrid" is just another polluter.

Miz
 

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And you, sir, miss my entire point.

We on this forum, are visionaries. We look beyond temporary conveniences, inventions and conventions. We advocate the entire replacement of the existing petro fuel society with something cleaner and sustainable.
I most certainly did not miss your point. If I did, I would have been calling for what already exists: a gas ICE hybrid.

Unfortunately, you cannot replace an existing infrastructure without addressing the conventions of the existing one. No matter how much cleaner or sustainable the goal that you envision, if it isn't perceived as better than the current incarnation, it'll never get any traction.

And being able to reliably move an electric vehicle outside of a carefully planned route isn't simply a temporary inconvenience. The ability to fast refuel is a crucial one. I just want to clarify that I do not mean refuel in the petrol only sense. I mean energy replenishment in EV terms. Honestly, if you can give me a 100 mile charge in a 10 minute window, I'll declare victory and keep moving. But I haven't seen it yet.


I seriously doubt you will make any converts to support the same old party rhetoric. We have heard it all.

So, our system is not perfect. Yours ain't neither....and we are still perfecting ours.

To most of us, a "hybrid" is just another polluter.

Miz
OK. Now that you've gotten your rhetoric out, please come back and address the technical issues of my proposal. LN2 only requires electricity and air. It's neutral to the environment. Nitrogen exists all over the planet. The electricity can be generated from sustainable resources such as solar or wind.

Here's an example of using Liquid Air for energy storage.

It's not visionary to try to shut down new ideas. Nor is it visionary to want a sea change without addressing the infrastructure required to pull it off. Note that I didn't just shut down compressed air or extra batteries. I gave reasoned arguments of why they are not sustainable ideas.

All I ask is that you do the same with mine instead of simply dismissing it out of hand.

ga2500ev
 

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When we are driving 500 kwh packs (2000 miles) and charging at 250 kwh (150 mile per 10 minutes) these sort of discussions become fairly moot. (possibly sooner than you think!)

In the end we'll be back to large SUV's and trading reverse air con for resistive heaters and using DC motors over AC.

As efficiency will be traded for cost and convience.

To reach utopia we just need to stick to the path and have faith.

:)
 

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It is not perfect or good or practical in ANY stretch.Terrible inefficient and expensive. Quickly refueled? Hardly. Your not going to pull it out of the air in a few minutes.
Station Pete. Stations. Pull up somewhere that already has it available, pour it in the tank, and drive away. The station keeps the high powered compression equipment and has the power to keep their tanks topped off. The EV doesn't need to generate any LN2. Also users can generate and store their own at home and can top off their tanks at home while they are recharging.

The station can even be dual mode, facilitating some direct plug in charging of the batteries at the same time.

The key point is that stations can be erected in short order, and that refillability goes down into the same 5-10 minute range that fueling gas cars now.

I acknowledge that the setup is crappy. But when the alternative is carrying $50K of batteries and hoping that charging stations directly connected to power plants (250 Kw, seriously?) come online without breaking our backs costwise, there are some limitations we may need to accept.

Why go to the extreme of converting the electricity to an inert gas then using that to push your vehicle. Damn you really need to see the reality of that.
Fast refillability and cost effective. No one is going to build or support a cost unsustainable infrastructure, especially when in relative terms that the cost of gas is so cheap that any alternative that's not in the ballpark isn't going to fly.

LN2 is already a widescale liquid that's an afterthough of other industrial gas processing. You can buy it off the shelf for less than 50 cents a gallon.

And to reiterate for the third time, this is not a replacement. It's the second component of a hybrid infrastructure for a plug in EV.

If you need a vehicle with 100 mile range at freeway speeds then be sure you build or buy one that does that for you. If you need 300 miles then use a clean turbo diesel vehicle. It is truly the next best way to go a long distance for less. I guarantee our nitrogen system will leave you stranded far sooner than the battery vehicle or diesel vehicle.
As an enthusiast, cost is of no object to you. You cannot propose an infrastructure without doing a comparative cost analysis. Diesel is out because we're only having a discussion of all electric infrastructure. If diesel is in, then the problem is solved using current tech to put a plug in diesel/EV hybrid on the road and call it a day.

Here are the parameters:

1. 250+ mile range.
2. Refilling from empty to full in 15 minutes or less (I'll throw in an extra 5 minutes)
3. Per mile cost competive with gas/diesel at $2.50/gallon over a 5 year period. I'll allow for amortization of equipment over that time.
4. All electric with no petro in the loop.

It just cannot be all batteries. Not cost sustainable and no current tech will accept the nearly 100 kW of charge in that time period at anywhere near the price point. Diesel is out.
This is a think out of the box thread. Time to get to it.

I will go further with the electricity used to convert nitrogen to a usage form than you will go after you do the cost factor for the conversion and then buying the nitrogen then driving how ever long you can go.
Did I not start with it's inefficient? This is a supplemental thread. The only reason for the discussion is fast refillability at a cost effective price point. The most efficient, and primary mechanism, is charging of batteries. But batteries cannot currently meet points 1,2 and 3 above all at the same time. So you have to supplement with something else that's cheap, even if it's inefficient.

Go electric. Go direct. Use solar to a very large bank of batteries then use that bank to do fast charging. No other conversions needed. During the time no one is charging the charge from the solar will be banked in a huge battery to be utilized later and it will still be far more efficient. Building a Solar Electric Fast Charge Station like your typical Station is a very doable thing and even existing stations can ADD that to an existing system that caters to gassers that will still remain for a long time to come.
Price it out for me. Time it out for me. Do we have batteries that will accept that type of charge in the 10-15 minute timeframe that's cost effective? What's the cycle life going to be? Most LiFePo4 cells accept charge at 5C or less. That's why it takes hours to charge. How are you going to get that down to 15 minutes and keep the cost competitive?

I have no disagreement with you about augmenting existing stations. Side by side is how it'll get done. But like most consumers, I'm going to look at the sign with the price on it to decide if I'm going to buy. If gas cost me $50 to go 400 miles, and electricity cost me $16 to go 100 miles... If filling with gas takes 10 minutes, and filling with electricity takes an hour, then I'm not convinced as it costs more and is less convenient.
I have been driving my Leaf since Last June on a daily basis to work and back and a few side trips too. I would not have purchased the car if it did not fit the needs. My Leaf is used literally for 99% of MY driving and when I do NEED to go further I DO take the ICE. Not an issue. It also only costs me $1.50 to go 45 miles. Guaranteed you won't be doing that in your nitrogen vehicle.
You are an enthusiast. I'm arguing this from the perspective of an average ordinary user. So unfortunately, I'm going to have to pick apart your analysis:

1. The only discussion we are having is the 1% that the Leaf does not cover. While I wish that we could convince the populace that 99% is good enough, it's not. The only argument you will get from them is that if their mother calls and says come now, and she lives 150 miles away, the car won't get it done. It's a perception problem, and most of us are way to invested to see it. No ordinary person is going to drive home, and pick up the ICE. No ordinary person is going to call a cab. An ordinary person will hop in their car, even if the gas light is on, and start driving toward their mother. They will stop, get gas in 5 minutes, and keep moving. This situation and how people feel about it is the only reason we continue to have range extension discussions. Ordinary people already have a set expectation of their vehicle, and any challenger that isn't better and cheaper in virtually every area isn't going to get traction.

2. Does the $1.50 include the price of the charging station? From Nissan's site that $2K in cost. How do you amortize that? Also how much is the battery replacement? How do you amortize that too?

3. Charging at 120V takes 20 hours, 7 hours at 240V. This entire discussion is what happens when the car is on E due to unforseen circumstances.

4. The 480V quick charge is a step in the right direction. However, it's still 30 minutes, it only gets you an 80% charge, and it's unclear how much such a charge will cost, or where you can get it.

People switch because something is better or cheaper, not out of a sense of nobility. I'm wondering what will happen with the Leaf once the enthusiast market gets its fill.
I feel the same about any type of fuel cell too. They work but using electricity to convert is poorly used when that power could be banked in a battery for direct charging to a battery is the best way. The fuel cell vehicle can't really go any further than a good well built electric vehicle anyway and its way cheaper and available NOW.
Fuel cells use petro, so it's off my list.

I know that I'm being stubborn, but we are really discussing infrastructure sea change here. While limitations and high overall costs work in an enthusiast market, it will not fly with regular consumers. Just believing isn't going to be enough to get a large number of people to convert. People want a tangible return for switching.

Say for the sake of argument you have the Leaf, and you outfit it with an LN2 dewar, radiator, and air turbine and the LN2 filling infrastructure exists. In the emergency with the proverbial mother, one would hop in the car and start driving on the remaining electricity and using the LN2 that's in the tank. Before both run out, stop in a station, take as much of a fast charge as you can get in 5 minutes along with a full tank of LN2, and keep it moving.

It closes that 1% gap and does it in a cost effective way. Which is the objective.

ga2500ev
 

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When we are driving 500 kwh packs (2000 miles) and charging at 250 kwh (150 mile per 10 minutes) these sort of discussions become fairly moot. (possibly sooner than you think!)

In the end we'll be back to large SUV's and trading reverse air con for resistive heaters and using DC motors over AC.

As efficiency will be traded for cost and convience.

To reach utopia we just need to stick to the path and have faith.

:)
How much will it cost? At $4 with a 25 MPG car, the base fuel cost is $0.16 USD a mile. How much will this 500 kwh pack cost? How much to replace? How much for the infrastructure?

Saying that the point is moot is like saying that soon commericial flights into space will soon be moot. You can do it. But it'll cost you $200K USD for the privilege.

ga2500ev
 
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