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Enova Hybrid Drive Systems for New Line of Commercial Buses Include Plug-In Option

The Enova hybrid drive systems provided for IC Corporation’s new line of hybrid commercial buses (earlier post) will be available with either a charge-depleting (i.e., plug-in hybrid) or charge-sustaining battery technology. The technologies are expected to improve fuel economy up to 100%.

Enova is offering the same range of battery technology for the new line of hybrid school buses from IC Corporation as well. (Earlier post.)

The Enova 80 kW Post-Transmission System to be used is one in which the electric drive system is integrated behind the transmission and is designed to be installed either as a fully integrated drop-in to an OEM production line or retrofitted in post-vehicle production in a modular, as-needed basis.

The bus market in which IC Corporation plans to compete is approximately 18,000 units annually. The market can be broken into 2 primary segments: public and private. There is an estimated 60/40 split in favor of the public buyers. It is now estimated that 30% of the buses purchased for public transit are some form of hybrid/alternate fuel vehicles and analysts project this number to grow significantly over the next 5 years.



Heres a thought:
Bus stop/terminal/depot rechargers+fast charge batteries+highly efficient auxilary power unit=Near electric bus.


allen: what's the cost of that vs. trolley (of course overhead wires are ugly)

Rafael Seidl

Neil -

overhead power lines for trolley buses aren't just eyesores. They also cast the routes in stone. Recuperation efficiency is actually not all that great, unless you have a special grid topology and a bridge to the national grid.

Besides, there is a large up-front investment in the overhead infrastructure that is amortized (eventually) only if the service is accepted. Unfortunately, many US consumers wouldn't be caught dead in a bus - those are strictly for the poor! Light rail systems, especially subways, do not carry this stigma but they are far more expensive to build.

New technologies, incl. HEV/PHEV and dynamic routing, offer possibilities that did not exist until recently. I would be very surprised if trolley buses made a comeback even in places with very poor air quality. On the contrary, if buses are to become more popular they have to appeal to the well-off in terms of aesthetics, technology/green credentials, convenience and comfort. The Dutch Superbus project, for one, is pursuing exactly those aims.


Given the fact that most city buses run on full-day schedules and cover a good amount of mileage, I wonder how useful plug-in technology really is. What is their business / engineering case for a plug-in bus? How much will a depleting discharge cycle affect battery life? How much all-electric range and diesel fuel replacement do they expect to accomplish with a daily charging routine?

Allen's proposal sounds like it has more potential (depending on the availability of convenient battery depots along bus lines in any particular transit system), and reminds me of an electric delivery van system that the German post office was looking at some years ago.


Buses are unlikely to make a major comeback no matter what. The problem is not just aesthetics, it is schedule. They depend on high volume routes for frequent (therefore convenient) service. The newer rendition of the trolly (sorry for the use of that now twisted word), is in dual mode PRT, which potentially can offer the best of all worlds -- private vehicles, door-to door transport, small battery opperated vehicle, and no limits on scheduling.

RUF is just one version, but it amounts to a trolly configuration (electric feed at the track) with the flexibility of an auto. The capital expenditure and vehicle adoption are still problems. However, the development of EV's may make the concept acceptable.


Buses often park and wait for the next schedueled departure. While they wait, a plugin bus can charge up their quick charge batteries (if fitted). Terminals would be equipped with electrical connections (secure, robust and multiple). 5-15 min (25-50%) charge could be enough to tide them over to the other end of the line (10-20 mi). The diesel engine could tide them over if there is a blackout, or if there is not the time to charge, up due to circumstances.


That approach has some promise, but depends very heavily on the circumstances. There are plenty of routes here in Boston, for instance, which are only 10 miles long or so, but often times buses do not lay over for long periods, and in many other circumstances, they lay over in locations which are unsuitable for installing such a charge station. A switch out pack that would not need to be changed *every* layover, or one which did not need an entire 25 minute layover to effect a "refueling," could be more suited to such circumstances. Or you could contemplate a more systematic change of the transit infrastructure, which would go beyond the obvious expense of installing a number of heavy-duty charge posts.


Here is one point I did not realise at first. Stop and go driving would wear on a battery due to constantly cycling energy in and out, from electric, to chemical and back. Buses often stop at every block due to traffic, or designated stops. Preempted traffic lights would help, but lines often intersect and they sometimes cause conflicts and traffic backups. Is the 150,000 cycle rating good for 10 years?


Another factor is how efficient is the regenrative braking. 25% is lousy, with an average efficiency of 71% per stage in a 4 stage energy flow setup (1-motor gen mode, 2-battery charge, 3-battery output, 4-motor work output; there are other components, but this is a back of the envelope calc). If the average is bumped up to 91%, then it has a ~68% total efficiency rating. With the first (25%), you can cut fuel expenditure by 1/4 in City driving. With the second (68%), fuel mileage triples.


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