A hybrid bus that cuts fuel consumption in half
Before sitting down to write this story, I asked a professional bus driver about the average fuel consumption for such a vehicle. As it turns out, a standard Agora bus on the roads of any European city burns about 60 liters of fuel per 100 kilometers, which equates to about 4 mpg. So the claim from British company that it can squeeze 10 mpg Imperial (8 mpg US, 29 l/100km) comes as a very welcome surprise.
This bus was created by Revolve Technologies and supplied to Wrightbus, a company that already has 20 hybrid Gemini 2 HEV buses (traditional double-deckers no less!) servicing London. However, the new model goes a step further and uses a 2.4-liter diesel engine sourced from the Ford Transit to work as a generator and make the ensemble a series hybrid. The engine adapts itself to driving conditions – generating more output when the bus needs more electric power – thanks to advanced electronics that predict load and speed changes in advance. Find the full press release after the jump.
[Source: Revolve Technologies]
PRESS RELEASE:
Revolve optimised hybrid bus breaks new ground for fuel economy and CO2 emissions
A hybrid-electric drive system for buses, for which Revolve Technologies' systems engineering team has developed a specially optimised engine management programme, has achieved the best results for fuel consumption and CO2 emissions ever recorded from a double deck vehicle – an unprecedented 10mpg.
Revolve Technologies, the Essex-based leading engine development and engineering services provider, is supporting Northern Ireland-based Wrightbus on a major hybrid drive performance and optimisation programme, which includes the Gemini 2 HEV double decker. Wrightbus is at the forefront of hybrid electric technology in buses in the UK, with around twenty units already in service in the London area alone.
At the heart of the Wrightbus hybrid system is a standard 2.4 litre Diesel engine – as used in the Ford Transit. With the base engine operating as a generator, Revolve engineers have been able to predict load and speed changes in advance, thus allowing greater freedom with injection strategies and EGR (Exhaust Gas Recirculation) rates.
Drawing on its special knowledge of the engine EMS system, Revolve engineers have also been able to utilise some of the existing vehicle based strategies to carry out functions which otherwise would have required significant software changes. This, coupled with a unique CAN interface module, has allowed the full integration of the engine and its controller into the overall hybrid control system – and at a relatively low cost.
Paul Turner, Revolve's Technical Director of Product Development, said, "Having the engine control as a fully integrated part of the hybrid system is a major advantage – and, coupled with a unique calibration, we have been able to achieve exceptional improvements in fuel consumption. The Wrightbus programme involves optimising Series Hybrid Drive systems through a detailed analysis of generator load patterns. As a result of this analysis, we have been able to recalibrate the engine to operate at its peak performance throughout the drive cycle, by using smart charging and load control technology. Overall engine performance is significantly improved when compared with normal applications."
Revolve Technologies' Executive Chairman, Andrew Williams says, "The Wrightbus hybrid programme gives further insight into the depth, scope and capability which we offer this important and growing area of the market. It is also an excellent working in practice example of the formal technical partnership between Revolve Technologies and Ford Component Sales (FCS) and highlights Revolve's rapidly expanding hybrid and alternative fuels activity. The company is currently involved with projects from small capacity, lightweight units through to heavy commercial, marine and industrial applications."
[Source: Revolve]
Reader Comments (Page 1 of 1)
why not the LS2LS7? 11:22PM (5/14/2009)
Impossible. You see, according to some on ABG, putting a Diesel engine that small in there means it can never accelerate any faster than that motor could if it were driving the wheels directly.
Reply
russellgeister 1:07AM (5/15/2009)
they are quite possibally idiots how do they think a deisel electric train works. also i wonder with a slightly larger engine this would work with CNG
Guy 4:41AM (5/15/2009)
Sorry to countradict you "why not", but
1) An electric motor you can easily be stressed to a few times its nominal power for a few seconds.
2) The combustion engine can generate power even as the bus stands still, so the batteries can accumulate more than the generator (at any given moment) can produce so for short bursts, something typical in city traffic, the bus can accelerate for sure faster than when it was directly powered by the CE alone.
GoodCheer 9:40AM (5/15/2009)
"how do they think a diesel electric train works"
Actually diesel locomotives until recently did not have batteries, and so were limited in total tractive power to the output of the diesel generator, less losses in the power electronics. That's why you hear the diesel engine rev up on trains when they take off from a standstill.
Of note, GE recently introduced (or is about to introduce) a diesel locomotive with battery energy storage that WILL conform to your comment, but it's brand new and very much the exception, not the rule.
http://ge.ecomagination.com/site/products/hybr.html
pgrt 4:12AM (5/15/2009)
If you add battery/capacitor to the chain from generator to electric motor, then your electric motor can output more power for a short period of time than the generator and thus it can accelerate faster than the diesel engine from transit. You just keep generating more power when there is not need for the highest output like when you are idle or slowing down or going at a stedy speed.
I think that part of the pros that you get from series hybrid is that you can run the generating motor at a smaller rpm range and get it work better in that range vs a wider range.
BTW. In Finland, awarage city bus uses 46l/100km, not 60litres.
Reply
Geoff 4:15AM (5/15/2009)
@ LS2LS7
Wow man you are so ignorant, but I've seen many of your posts, ad that is just you, so no worries. There is a reserve bank of batteries that recuperates energy while slowing down, and secondly while slowing down and at stop or at low speeds the generator is running above the requirements of the buses movement needs. Thus the battery, and not necessarily a large one, acts as a reserve and buffer for the buses needs and aids in the highly energy intensive acceleration phase.
Seriously I feel LS2LS7 is only on ABG to spread disinformation, i.e. he works for an oil company :P
Reply
atc98092 6:24AM (5/15/2009)
I believe Why Not was being sarcastic. His point (I believe) was to point out that some people on this site believe that this type of power train cannot possibly have adequate performance. I agree with that opinion.
why not the LS2LS7? 11:49AM (5/15/2009)
I was being sarcastic. I said "according to some on here".
http://www.autobloggreen.com/profile/2713785/
russell:
Except for a few switching engines, up until recently diesel-electric locomotives were not hybrids. They just used electricity as a drivetrain instead of a driveshaft and transmission and when slowing down sent the regenerative electricity right into heat. Still, the torque of the electric motors and the ability to easily have 16 drive wheels per locomotive made diesel-electric a better choice than direct-drive.
Woodenbee 9:38AM (5/15/2009)
my guess is that the 2.4 litre diesel is just for the generator, theres no way it actually powers the bus, the regular engine is still in there but it has assist from the generator /battery / electric motor at low speeds probably, and all these comments about how it doesnt work dont make any sense in Europe they don't bother saying something unless its factual, unlike most occasions here
Reply
why not the LS2LS7? 11:51AM (5/15/2009)
Give me a break. Europe is no tower of virtue.
Jeff 11:13AM (5/15/2009)
For anybody still in doubt after some confused posts and some sarcastic posts, this drive train is totally feasible.
With a series hybrid, you size your engine based on AVERAGE power requirements, not the peak power required for acceleration. So if a bus typically spends 10 seconds accelerating using say 400hp, and then spends 10 seconds decelerating, using 0hp, and then 20 seconds stopped, picking up passengers and waiting for a red light to change, using 0hp --- that all works out to an average of 100hp. 400hp for 10 seconds and 0hp for 30 seconds.
You therefore choose a 100hp generator that runs constantly, storing excess power into your accumulator (batteries, capacitors, hydraulic pressure tanks...) when you're decelerating or stopped, and then accessing that stored energy with your electric motors (which are capable of putting out the required instantaneous 400hp) when you're accelerating. The overall efficiency is greatly improved because a small engine running constantly at 100hp is way more efficient than a large engine revving up to 400hp when needed. Electric motors are typically 90% efficient, the generator is probably also about 90% efficient, and charging li-ion batteries is about 99.9% efficient (they stay cool while charging), so the energy conversion losses are small compared to the gains of running a small engine.
On top of all that, if the batteries are large enough, you can introduce plug-in capability, and a coal fire power plant is even more efficient than a little diesel engine.
Reply
DasBoese 12:32PM (5/15/2009)
Yep, serial HEV drivetrains make lots of sense for urban bus transport, after all they're spending a lot of time standing around at bus stops and traffic lights.
One way I can see this improving even further is, since buses drive the same route all day long, to add memory to the control electronics that keeps track of power demands for each route, at different times etc. Maybe they already did that.
Reply