GM’s Opel used the 60^th International Show for Commercial Vehicles in Hanover, Germany (overlapping the Paris Motor Show) for the world premier of a natural-gas-powered production version of its Combo commercial van—Combo 1.6 CNG.

Opel currently is the CNG marketleader in Germany, and Opel Special Vehicles (OSV)—the offshoot of Opel that builds the CNG vehicles—the largest CNG manufacturer in Europe. The two CNG versions of the Astra station wagon and the Zafira (which is also the foundation for GM’s prototype HydroGen3 H₂ fuel cell vehicle) currently have a share of around 80% of the CNG market in Germany—currently at 21,000 vehicles, but which Opel thinks has tremendous upside potential.

The BGW (Bundesverbandes der deutschen Gas- und Wasserwirtschaft—the federal association of gas and water management agencies) estimates growth in the German CNG market to 95,000 vehicles by 2007, and 500,000 by 2011. Italy already has a CNG fleet of some 381,250. Worldwide there are currently some 3.1 million CNG vehicles, with Argentina and Brazil in the lead.

One reason for the upside optimism: new EU regulations for commercial fleet operators in 2005 forcing emissions standards.

Natural gas vehicles tend to come in two versions: bivalent or monovalent. Bivalent vehicles are designed to drive both with natural gas and with gasoline. If the natural gas supply is exhausted, the engine switches automatically while driving to gasoline drive. (This is the approach BMW is using with its hydrogen 7-Series vehicle.) Monovalent vehicles, on the other hand, operate only with natural gas, or with a small emergency tank for gasoline. The bivalent design produces longer driving ranges at the cost of a higher level of emissions and fuel consumption. The monovalent focus on natural gas allows for better fuel consumption and lower emissions, but a shorter driving range.

Opel’s CNG vehicles are monovalent; or monovalent^plus to use Opel’s marketing term. These engines feature dual injection banks for gas and gasoline operation, with sequential injections. Special pistons support high compression, and special valve, valve guides and valve seats support natural gas combustion.

The Combo 1.6-liter engine produces 97 hp, optimized for CNG. A 14-liter emergency gasoline tank provides the fuel for gasoline mode. CNG tanks are stored under the floor of the van (see diagram above). OSV has built a nicely performing engine. In the comparison below you can see some of the tradeoffs mentioned above between monovalent and bivalent design.

OSV has ambitious plans for further development of its CNG vehicles, all based on production models of Opel cars and vans. These plans fall into two areas. First is extending the driving range of the vehicles through developing improved storage tanks for the gas, and by incorporating turbocharging in the engine. OSV estimates that turbocharging could reduce fuel consumption by some 7%. The second is to further improve the emissions profile by supporting Biogas: gas derived from biomass to power the engine.