8 or 17 Gallon CNG Tank to Replace the REx Gas Tank

[ultraturtle]

An 8 gallon (30 liter) 3600 psi Compressed Natural Gas (CNG) tank would provide the equivalent energy of 2.7 gallons of gasoline, would make frunk space far more useful than it's current job as EVSE storage (a 10" diameter by 33" cylinder would do the trick), would emit significantly less pollutants than gasoline, and would get our California friends their coveted white sticker.

Better yet, how 'bout a 17 gallon (64 liter) tank, giving the equivalent energy of 5.8 gallons of gasoline with an increase of only 4" in diameter (14" diameter by 33" cylinder length) and the ability to travel at least 174 miles beyond battery depletion (assuming economy greater than or equal to 30mpg gasoline equivalent.)

 

[MikeS]

An 8 gallon (30 liter) 3600 psi Compressed Natural Gas (CNG) tank would provide the equivalent energy of 2.7 gallons of gasoline, would make frunk space far more useful than it's current job as EVSE storage (a 10" diameter by 33" cylinder would do the trick), would emit significantly less pollutants than gasoline, and would get our California friends their coveted white sticker.

Better yet, how 'bout a 17 gallon (64 liter) tank, giving the equivalent energy of 5.8 gallons of gasoline with an increase of only 4" in diameter (14" diameter by 33" cylinder length) and the ability to travel at least 174 miles beyond battery depletion (assuming economy greater than or equal to 30mpg gasoline equivalent.)

Will the 2 stroke engine run on CNG?

 

[Bunter]

Will the 2 stroke engine run on CNG?

Surely it's a 4 stroke engine?

Bill

 

[MikeS]

You are of course correct - my wrong assumption. It would appear that the 647cc petrol engine is based on one of BMW's motorcycle engines which are 4 stroke.

So therefore it would seem that the CNG choice would seem to be a good one, except there are not many places (in UK) where you can top up with CNG.

 

[Lecram]

I do not see any advantages for the CNG powered engine in the i3. It's heavy, consumes a lot of storage space and it's only available at some stations. A CNG filling station at home is too expensive.

The Rex is meant for emergency purposes. I will try to avoid using the rex and drive as much as possible on electric power.

 

[Jazz]

Just to add to the above, the tiny fuel tank is a deliberate move. The i3 is primarily meant to run off the battery power alone, with the REx there just as backup if you need it. Yes that means the range will not be quite as good as some EVs, but BMW aren't too fussed about that. As the new-gen "Mega City Vehicle" the REx will be more than adequate for such environments.

Want a longer range? Just buy an i8

 

[ultraturtle]

I do not see any advantages for the CNG powered engine in the i3. It's heavy

Not necessarily. A 30 liter carbon fiber CNG tank weighs about 37 lbs.

consumes a lot of storage space

The i3 wastes a lot of frunk space that could be put to better use.

The Rex is meant for emergency purposes. I will try to avoid using the rex and drive as much as possible on electric power.

Precisely why a fuel that is inconvenient to procure works so well in this application. It only gets used in an unusual circumstance. Driving the REx this way is smart and would mean very few CNG fill ups per year.

 

[ecoangel]

CNG is a really good idea. Sadly not many outlets in UK but PLENTY in NL and Germany!

http://www.fuelswitch.nl/index.php?mod=map&action=list&type=aardgas

The VW Up CNG version just won the best ECO and cheapest to run small car awards:

http://www.youtube.com/watch?v=tz_gj9Zsark

http://www.autocar.co.uk/car-review/volkswagen/up/first-drives/first-drive-review-volkswagen-eco


Significantly less CO2 and Nox than Petrol cars and CNG could be used on a 660cc 4 stroke engine already in the i3 REX if converted appropriately.


http://www.cngvehicles.co.uk/

 

[shaoyu]

Not really a good idea. The gas range extender can actually enable an odd 300-500 mile trip. Not so for CNG. That would be a significant loss of feature.

 

[ultraturtle]

Not really a good idea. The gas range extender can actually enable an odd 300-500 mile trip. Not so for CNG.

Whether it is a good or bad idea is relative to an individual's situation. It would be a very good idea for anyone who lives in California (and seeks a white sticker, once the green stickers run out), regularly drives less than 60 miles or so between charging opportunities, but needs to make the occasional 150 mile trip. It would also be a more ecologically responsible choice than Tesla Model S (also not realistically capable of an odd 300-500 mile trip) for regular trips of 150 or so. One could fuel up at home overnight, with equipment priced similarly to an EVSE:

http://www.reuters.com/article/2013/10/04/us-naturalgas-home-refueling-insight-idUSBRE9930D120131004

Also, if you did need to make a longer trip, there are vastly more CNG fill stations located in the USA than fast chargers, and it takes only a couple of minutes to fill up on natural gas and be on your way than the 1/2 hour or so it takes to get an 80% charge on a fast charger. Also, filling a CNG tank does not reduce the life of the power source the way that fast charging reduces battery life.

 

[davidrshelton]

Just to add to the above, the tiny fuel tank is a deliberate move.

You are even more right than you may realize. I can't tell if it's a chicken-or-egg (i.e., CARB or BMW) thing, but there was a conscientious decision made by BMW to reduce/match the size of the gas tank to the range afforded by traction battery pack. In California, a new EV classification, "BEVx" was made to distinguish it from the scores of different vehicle emission classes (e.g., ZEV, PZEV, AT-PZEV, EAT-PZEV, EAT-PEZ (okay, I made that last one up)). Ironically, after all of this work to achieve a higher/cleaner level of emission standard, it's unclear whether or not it will make any difference from an HOV sticker (the green sticker shortage issue) perspective. Last year, I'd read that there would be a new sticker color (purple) created for BEVx, but in researching it again, I found no current evidence of it.