Electric Buses: Hybrid Buses May Need to Step Aside
In the late 1990’s and early 2000’s, hybrid bus systems were being developed at a feverish pace, based on low emission and higher fuel efficiency requirements from many major cities in the U.S. Market. However, as transportation technologies march forward, it appears that hybrid bus systems may experience serious competition from pure electric bus systems. Many countries external of the U.S. are venturing into the zero emission vehicle (ZEV) market to improve air quality (i.e., China, Singapore, etc.) this is driving the need for bus fleets with ZEV systems. Companies such as BYD and Proterra have quickly caught the eye of several U.S. cities that are shifting from traditional diesel powered buses directly to ZEV bus systems, eliminating the “in between step” of using hybrid technology.
The reason that ZEV buses can be utilized is that Lithium battery technology has superior specific energy and energy density that reduces the size and mass (weight) of the battery pack system. Therefore, enormous battery systems are not necessary for a bus system due to the advantages of Lithium technology. This alters the need for large battery packs which may no longer be necessary for bus systems. If high power wireless charging technology is placed on bus routes and in depot sub-stations to permit fast charging of the battery pack, large battery packs will no longer be necessary. Also, logistics would be significantly easier because, requiring the bus to return to the main depot for charging would not be necessary. While this is occurring on a global scale, keep in mind there are and will continue to be other technologies that will be considered for charging batteries along a bus route. Overhead wire systems located only at bus stops or sub-depot locations can also be used to rapidly charge the batteries. This would eliminate the need for modifying streets or roads when installing wireless charging pads.
Innovating Vehicle Electrification Technology: Hybrid Electric, Fuel Cell, and beyond.