@Davemart: High pressure tanks must be manufactured as cylinders or spheres in order to minimize the tensile stress on the tank material. These shapes lead to "dead space" within the body of the car. Lower pressure tanks can be formed into arbitrary shapes that wrap around the other components inside the car, leading to less unused space inside the car body.

The lack of precise information is annoying. They may be hiding something or it may be that such information is misleading, for example the volumetric density as pointed out by Allen.

The 30% less by volume is comparing to the 'standard' 3000psi I presume - didn't bother to check.

The amount stored in a standard tank increases with operating pressure. Same goes for the EnerG2 tanks too, but the pressure-amount relation is not necessarily the same. They've given an example, namely the pressure of their tank that has the same volumetric density as a standard tank at standard pressure.

DavidJ
It appears that:
'For a vehicle to carry enough CNG to travel a reasonable distance, the gas has to be compressed to more than 3000 psi. Even at 3600 psi, compressed natural gas has about one-third as much energy as gasoline, about 44,000 BTU per unit volume;'

http://e85.whipnet.net/yellow/cng.html

So it appears that it should be:
'~30% of the energy by volume of natural gas'
Instead of: '~30% LESS energy by volume.

And that is not including the tank.

What a nonsense article from them.

Allen:
If you have a particular link to demonstrate your point please provide that.
There are umpteen articles, which, after one has re-written the link you provide, are brought up, and a cursory skim of them does not provide enough info to know exactly what they are talking about.
If I were pointing you to information, I would not simply say:
'Look in a library' but would give a precise book and page number.
Google is much the same.

Note that I am not seeking to contest the point you make.
I don't know, and you have not given proper references for me to find out what you are talking about.

@Allen:

On the contrary, if you wish to make an argument, you should do your own legwork and learn how structured debate is conductive, not simply make an assertion and wave your hand towards Google.

There is nothing that you have written and backed up so far to give any indication that you have any idea what you are on about.

I am certainly not going to do extensive research to find out whether there is any grain of truth in it, which seems unlikely in view of your utter incomprehension of how to present your thoughts in a coherent and structured manner.

@SJC:

The sad thing is that Allen probably thinks it is perfectly rational to advance a proposition, which appears to have been on the basis of some snippet he has picked up somewhere, and for others to then have the obligation if they doubt either the facts or his comprehension of them, to keep digging until they realise that he is in fact a genius, who should never have been doubted in the first place!

The educational system has a lot to answer for.
I give you Exhibit A.

Yep. Something has to be done about impurities:

'Although CH4 is the largest component, pipeline-quality natural gas contains many other impurities that can affect the long-term stability and capacity of an adsorbent (Table 3).78 In an ANG vehicle, a guard bed will likely be placed before the storage tank during refueling to minimize exposure to impurities.20 Still, the adsorbent will inevitably be exposed to at least some level of each impurity throughout its lifetime. Additionally, most guard beds are unlikely to remove a significant amount of the C2 and C3 hydrocarbons that are present in natural gas, and it is unclear how this might affect the usable CH4 capacity of an adsorbent. Smaller levels of other impurities, especially sulfur-containing compounds, H2O, O2, and C4 and greater hydrocarbons, may slowly poison CH4 adsorption sites or degrade the framework over an extended time period. Performing cycling studies in the presence of all expected natural gas impurities will be critical to designing metal–organic frameworks with the long lifetimes necessary for use in a natural gas powered vehicle. '

http://pubs.rsc.org/en/content/articlehtml/2014/sc/c3sc52633j

Their ~30% less energy than gasoline seems to refer not to CNG at all, but LNG!

'As a result of the low critical temperature of CH4 (190.6 K, Table 1), natural gas cannot be liquefied by compression alone, and cryogenic cooling is necessary to store liquefied natural gas (LNG). While the volumetric energy density of LNG can reach 20.8 MJ L−1 (64% of gasoline),5 the overall system energy density is reduced due to the insulation required to maintain a low temperature and prevent boil-off.' (ibid)

The EnerG2 website is just as crappy and uninformative as one would expect from this sort of egregious error.

@SJC:
Nice saving on compression costs.

I still haven't found an article which gives a good handle on what the volumetric comparisons are with cylinder storage, or for that matter much else.

How many cycles is the adsorbent good for?
How much of it stays behind when the tank is 'empty?'

It is probably too early to start finding more than hopeful start-ups promotional blurbs, which carefully don't mention the hassles they are having.

Of course there are a range of possible materials too, and the link I gave talked about how the test methodologies are not even standardised as yet.

This sounds like promising technology. We could always use more of this!

John Socrates
Creeklife Supporter
http://www.creeklife.com

The person making the statement should show supporting evidence. I have advocated bio synthetic fuels over the years and have posted links on gasification, bio fuel crops and methods. Some may agree, some may not.

Debate can be a good thing, when it becomes personal it crosses the line. When someone says "you are not qualified to comment here" that is uncalled for. Ideas which promote "sustainable mobility" are always welcome.

EnerG2 has will surely help improving the design and capacity of CNG storage tanks for natural gas vehicles.
American CNG