The CNG train has left the station. With the plethora of alternative fuels and powers that have emerged in the last 20 years, none has gained as much steam in manufacturing, sales, infrastructure and legislative willpower as quickly as compressed natural gas.
Nonetheless, engineering, technology and logistics challenges remain to propel CNG implementation even further. (We’ll leave the challenge of extracting the fuel from shale reserves for other bloggers.)
But what are those challenges? I asked Jon Coleman, Ford’s fleet sustainability and technology manager, for insight.
Are we moving closer to dedicated CNG vehicles?
“Right now the dominant solution is bi-fuel, without a doubt,” Coleman says. This is for the same reason — range anxiety — that plug-in electrics are outperforming pure electric vehicles. Similar to electrics, it’s both a fueling infrastructure and vehicle technology issue.
A dedicated system does work for vehicles running predictable routes that can be centrally fueled. And dedicated fuel systems are being propelled legislatively in states such as California that offer tax incentives for pure CNG systems as well as HOV lane access. But outside those parameters, the range of a dedicated CNG vehicle combined with the lack of fueling infrastructure makes bi-fuel the preferred choice, at least for now.
But wouldn’t a dedicated system be more efficient from an engineering standpoint?
Producing two types of fueling systems may seem like over engineering, however, a dedicated system usually requires the removal of an already produced gasoline tank, which is replaced with CNG tanks. With bi-fuel, you’re not left with a scrapped fuel tank.
Some manufacturers, such as Freightliner, are beginning to offer a dedicated system manufactured for CNG from the get-go. But that entails a massive assembly plant restructuring, which doesn’t make sense before the CNG fueling infrastructure is built out. For now, automakers need to build trucks with regular gas tanks and fuel them to transport vehicles before they get shipped off to a CNG-conversion company.
And CNG tanks can’t simply replace gasoline tanks and offer the same range, Coleman says. While a gas tank can take any form, a CNG tank must take that familiar missile shape to be safely pressurized to the necessary 3,600 psi. Taking out a 26-gallon gasoline tank from a pickup will only yield space for about a nine-gallon cylindrical CNG tank.
Then what technology would improve range?
Engineers are using materials science to build CNG tanks with high-strength materials and geometry to break free from the cylindrical shape into a more box-like traditional fuel tank, or “whatever shape you can imagine,” Coleman says.
Coming at it from a different angle, engineers are also working on lowering the fill pressure in the CNG tank using “adsorbent technology,” in which a compound is used that has an affinity to natural gas. If the same amount of fuel can be added to a tank at one-third of the pressure, this too allows for tank conformability.
A formfitting CNG tank opens up exciting possibilities, such as wider implementation in passenger cars — where the CNG tank wouldn’t have to take up 75% of the trunk.
Tanks are the most expensive part of a CNG system and implementing these new technologies right now would double the tank price, Coleman cautions, though prices are coming down rapidly.
Are there technologies being developed to reduce the costs of CNG?
Being able to fill a tank at a lower pressure would also drop the cost of the fueling infrastructure exponentially, Coleman says.
The highest cost of a CNG filling station is the compressor, because compressing to 3,600 psi takes a tremendous amount of energy. By reducing that compression to 1,000 psi, or even further to the “Holy Grail” of 500 psi, “this is game-changing technology because it enables home refueling,” Coleman says. “And you have 53 million potential fill points at every residence in the country that has natural gas running into it.”
Are there developments in the manufacturing process?
In the case of Ford, which works closely with its QVMs (Qualified Vehicle Modifiers) to convert vehicles to CNG, logistical issues are being met using an existing supply chain — with certified technicians doing the conversions at large upfit companies.
While order-to-delivery times have come down significantly for smaller orders, challenges remain to handle large orders of, say, 1,000 units. Nonetheless, the process develops as orders come in.
“I would be hard pressed in any six-month period in the past three years where there has been any stability in the production process,” Coleman says. “It’s a constant evolution driven by customer demand and getting the product to the customer at the lowest possible price without compromising quality.”
Are there any other developments to watch out for?
Coleman warns fleets to consider in the initial implementation plan how their CNG vehicles will be serviced.
By regulation, dealerships are engineered to protect against the ignition of fuel that pools on the floor. Therefore, heating systems in dealerships are traditionally on the ceiling. But natural gas, which is lighter than air, could collect next to an open-flame heating system in the ceiling and create a hazard.
Building new CNG-friendly service facilities isn’t more costly — but retrofitting existing facilities can be prohibitively expensive, Coleman says.
On the legislative front, Coleman says CNG is really taking off in states in which favorable governments are facilitating infrastructure build out. This is happening especially where natural gas is being extracted, such as Oklahoma, the Texas triangle and West Virginia.
The economics of CNG make sense without government help, and that’s one of the reasons CNG is taking off. But the states that further facilitate CNG through friendlier regulation and with some tax money, that’s a bonus. “It lets everyone know there is a level of certainty of support,” Coleman says.