Thanks to funding from the TIGGER Program, an inexpensive retrofit is helping Palm Tran’s diesel-electric hybrid buses become more reliable and efficient, while also improving the fuel efficiency of conventional diesel buses serving Palm Beach County, the largest in Florida.

The new retrofit addition, a miniHYBRID thermal kit from Engineered Machined Products, is a fully contained system. It replaces the original bus alternator and cooling system with a high output alternator and a cooling package of heat exchangers and eight  electronically controlled electric fans. This upgrade includes temperature sensors for the engine charge air and engine jacket water flow paths in order to optimize cooling of those systems separately

Before this upgrade, some of the newer model dieselelectric hybrid buses were overheating. Palm Tran bought five miniHYBRID systems and tested them in hybrid buses serving the busiest routes with a lot of stop-and-go operation. The overheating problem was eliminated, while fuel usage was cut by 10%. Because of that success, Palm Tran was able to use this TIGGER award to install the thermal motor fan system on 20 of their conventional diesel buses and achieved a documented increase in fuel efficiency of 7.5%. This project achieved its goal of incorporating commercially available technology into Palm Tran’s existing fleet of buses to achieve energy efficiency improvements and greenhouse gas (GHG) emissions reductions.

As demonstrated by this project, the thermal motor fan systems could be used by other transit agencies to retrofit existing transit fleets to achieve fuel savings and reduce greenhouse gas emissions in a cost effective manner.