With natural gas production soaring and prices dropping, it makes it an attractive fuel for many applications. One that’s been a hard sell for years is automotive. Although it’s not a new concept, in light of the US shale boom, people are looking at it in a new way. That includes GM, and they are going at it with guns blazing… literally!
Compressed natural gas (CNG) is better for engine components than gasoline and better for the environment as it burns cleaner with less particulate. There are drawbacks, however, such
GM is looking to ease minds with its 2015 Bi-fuel Chevrolet Impala. Like other hybrids, this one will run on a cleaner source (CNG) until that runs out, and then it seamlessly switches to tried-and-true gasoline. The bi-fuel approach can ease concerns over fewer fueling stations and lower mpg ratings with CNG, but what about safety?
GM has been putting its CNG set up under fire. 800 degree fire to be exact. After being pressurized to 3,600 psi the tank is subjected to the industry-standard Bonfire Test where it is placed 4 inches above the fire to test pressure release valves and rupture resistance. To take it further, engineers tested the tank in a variety of configurations to ensure it would hold up no matter where the heat was coming from.
The tank must also be resistant to puncture. During the Penetration Test, the tank is filled to its service pressure and then shot with a 7.62 mm armor piercing bullet (how do I get that job?). The bullet should enter one side without piercing the other. The hole should maintain structural integrity without rupturing. Over-pressurizing and cyclic pressure testing were also performed to ensure reliability.
Finally, the somewhat more likely scenario of a collision was tested. The testing included front, side and rear-impact collisions. As described in a press release, “A large piece of cast aluminum helps
protect the tank valve and connection from certain side impacts. Sheet metal plates on either side of the
The Bi-Fuel Impala is a 2015 "Green Car of the Year®" finalist and available for order now. The all-steel, 7.8 gal tank will power the car for about 150 miles before the car switches to gasoline. While the present offering will help ease concerns associated with CNG, I’m sure there will still be some skepticism. The prevalence of natural gas may be the factor needed to push this technology into popularity, though low gasoline prices (for now) are lessening that appeal.
The video below shows rear-end collision testing of the car.