USA, San Diego

San Diego’s Metropolitan Transit System (MTS) has launched what's believed to be the first commercial bus with a CNG and electric hybrid drive system. The new technology was made possible by grants from the South Coast Air Quality Management District (SCAQMD), San Diego Air Pollution Control District (APCD), and the California Air Resources Board (CARB).  ISE Corporation conducted the R&D on the new drive system, which was installed within a standard size MTS bus. The hybrid drive system is composed of a Cummins ISB Gas Plus engine, a Siemens 165kW electrical generator, two Siemens duo inverters, two Siemens 85kW drive motors and Cobasys-developed NiMH batteries. MTS provided the New Flyer bus and New Flyer assisted ISE in the modification of the chassis and integration support. 

The $1 million prototype will cut significant emissions from the already clean-burning CNG buses in the MTS fleet, providing more power and a quieter ride.  “This new technology is important to California transit agencies that have invested heavily in CNG infrastructure and are seeking even more efficient power drives,” said San Diego County Supervisor Ron Roberts, who also represents San Diego on the boards of directors of MTS, APCD and CARB.  “The CNG-electric hybrid technology represents the next step forward in our commitment to a healthier environment.”

The CNG-Hybrid is expected to provide the following environmental benefits:

• Significantly greater fuel economy
• Reduced NOx emission
• Reduced CO2 emissions
• Reduced brake wear and brake maintenance
• Quieter operations

“MTS is committed to providing clean, safe, reliable and environmentally friendly transportation,” said Paul Jablonski, CEO of MTS.  “We have been in the process of retiring our old diesel buses and replacing them with cleaner and more efficient technologies since 1997. We have already replaced almost 75 percent of our fleet with CNG buses and will complete the conversion over the next five to six years.”     

San Diego MTS