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EnerG2 develops new carbon adsorbent material for on-board natural gas storage

18 December 2013

EnerG2, a manufacturer of advanced carbon materials for next-generation energy storage (generally for batteries and ultracapacitors), has leveraged its polymer chemistry technologies to develop materials for adsorbed natural gas (ANG) applications. The ultra-high surface area carbon adsorbent material, which packs at optimal density and has been produced at scale, is compatible with any and all tank geometries and systems, the company says.

Currently, natural gas vehicles are fitted with on-board fuel tanks that are too large, cumbersome, and expensive to properly facilitate the widespread adoption of natural gas vehicles in the US and globally. Additionally, the low volumetric density of natural gas (~30% less energy by volume than gasoline) limits range, and makes cost-effective storage solutions a significant challenge. One possible solution is adsorbed storage; the interest is so keen, that ARPA-E awarded a combined $10.875 million in 2012 to four different projects (led by Ford, GTI, Texas A&M and SRI) to develop new sorbent materials for on-board natural gas storage. (Earlier post.)

Among the issues that need to be addressed for adsorbent materials are (1) sorbent lifetimes, (2) deactivation rates/processes, and (3) plans to deal with compaction, ARPA-E noted in its funding notice.

In terms of raw storage capability, EnerG2 says that its material allows similar volumes of gas to be stored at lower pressure levels of 500-800 psi (34-55 bar), as opposed to the more standard pressure levels of 3,000-3,600 psi (207-248 bar). The new adsorbent material for natural gas tanks on vehicles has a number of advantages:

  • Design efficiency and no wasted space, because a tank at 500-800 psi can store as much natural gas as a tank at 3,000-3,600 psi, but its flexible form factor will allow it to fit in a space on board a vehicle that’s about half the size.

  • Lower pressure tanks also mean a much simpler and cheaper transition to home refueling. This would help alleviate another key obstacle to natural gas vehicle adoption: availability of refueling infrastructure. Low-pressure compressors are a fraction of the cost of high compression systems.

  • Lower-pressure tanks are also safer, and they hold more fuel longer if there’s a puncture. In addition, they require less energy to compress the gas.

  • The lower pressure tanks also lower the cost of compression, as well as the capital investment required for a compressor itself.

This material represents a real breakthrough because we’re ready to go at scale with a material that totally changes the dynamics of natural gas tanks on board a wide variety of vehicles.

—Dr. Aaron Feaver, Co-Founder and CTO at EnerG2

What EnerG2 is doing can radically change the availability of natural gas vehicles in our country and around the world.

—Garret Alpers, Founder and CEO of World CNG, a converter of light- to medium-duty vehicles

There are approximately 135,000 natural gas vehicles on US roads today, and more than 15.2 million operating worldwide, according to Natural Gas Vehicles for America. About one-fifth of all transit buses were run by compressed natural gas or liquid natural gas in 2012; almost 50% of the trash trucks purchased in 2012 are powered by natural gas; and more than 35 airports in the US have natural gas vehicles in their own fleets or encourage natural gas use by private fleets operating on their premises.

EnerG2 materials would enhance performance for these fleets and infrastructure already in place using high pressure storage. Using their polymer chemistry approach to materials engineering, EnerG2 can tune the adsorbent’s nanostructure to improve the storage capacity of high-pressure storage systems by up to 30%.

Regardless of the ultimate outcome, EnerG2 said it is committed to enabling natural gas as a transportation fuel.

Natural gas has huge benefits. It’s still a fossil fuel, but now it’s far cheaper than gasoline, it’s domestically produced, and it generates lower emissions than gasoline. That’s one of the key reasons why we’re actively seeking natural gas system development partners for our new material.

—Rick Luebbe, Co-Founder and CEO of EnerG2

December 18, 2013 in Materials, Natural Gas | Permalink | Comments (22) | TrackBack (0)


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Additionally, the low volumetric density of natural gas (~30% less energy by volume than gasoline) limits range,'

?? Only 30% less by volume?
That makes no sense to me, especially as the pressure is not given.
By weight, maybe.

'Design efficiency and no wasted space, because a tank at 500-800 psi can store as much natural gas as a tank at 3,000-3,600 psi,'

This makes no sense to me either, as presumably it would store way less.
Presumably they are taking into account the volume and mass of the storage cylinder, but the author's make no attempt to clarify what on earth they are in fact on about.

@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.

> Lower-pressure tanks are also safer, and they hold more fuel longer if there’s a puncture.

I'm not so sure about this. A tank filled with gas plus carbon has a lot more flammable material that stays closer to the passengers for a longer period of time.

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.

I am aware of that, perhaps I was not specific enough when I mentioned the volume and mass of the cylinder.

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;'

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.

Adsorption allows the same mass of gas to be stored at a lower pressure within the same volume tank

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.

@Davemart: If you're interested in learning more, you'll have to do the leg work yourself.


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.

That would be a bit like a debate team member waving their hand towards the library and saying the answers are there somewhere.


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.

"Lower pressure tanks also mean a much simpler and cheaper transition to home refueling."

I would say that is a major point, the compressors are less expensive and could fill more quickly. A big factor has been adsorbant weight, a lower pressure tank can be lighter but the adsorbant adds weight.

Another issue is purity, adsorbants work with pure methane, the natural gas that comes out of the pipes in the U.S. is not pure methane. That would require some cleanup before compression and tank filling.

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. '

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.

"Over 20 percent of the cost of CNG is related to compression; high-performance ANG can significantly reduce this expense."

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.

@Davemart, Allen gave you a perfectly reasonable explanation. As you've done in the past, you requested a spoon-fed answer. You really could put out a little more effort amigo.

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

John Socrates
Creeklife Supporter

electric whatever:

If you think asking someone to find out information to support an argument he has put forward, and presumably it is all your fault if you don't find anything to support his case so that you should try harder until you do, is reasonable, you are as shot away as he is.

But I don't expect you to understand that, as clearly you are unable to reason in any way.

Don't waste your time on the internet.
You have a lot of studying to do to catch up with all the time you have missed at school.

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.

I am always up for debate.

What is being presented here is not argument, but a wholly irrational refusal to engage in it, which if accepted would make productive discussion impossible.

My view is that if someone puts forward such an incredible dumb notion they should be called on it, not treated as though it were a reasonable thing to say.

The original argument put forward was bad enough, but when someone else comes on to say how reasonable that was, then I am afraid my patience wears thin.

Clearly to the extent that this forum is about rational debate, they are not qualified or capable of participating, as they don't understand what it is.

If instead it is some random assemblage of tweets, they are eminently qualified.

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

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