The beauty is in the numbers, Rob. In five years, we could be seeing eight million new vehicles a year incorporating this technology, and that's in the U.S. alone. That's a lot of gasoline saved.
JLJarvis, Great points about how this idea dependsthe importance of cycle time and driving patterns. That definitely complicates quantifying the benefits.
Sounds pretty good, Chuck. I'd love to see how that feels in real life. I guess until you experience, the notion of the car going dead during a red light seems odd. Good idea, though, on saving energy.
These "start-stop micro hybrids" are really simply using the existing most inexpensive aspects of hybrid vehicles to get a good fraction of the benefits at a small fraction of the added cost. The potential problems identified by many posters here have already been solved.
Existing hybrids already stop the engine when possible when the car stops, and automatically start it up again when engine power is needed. Restarting does not use a solenoid-engaged starter motor. It is incredibly smooth, and for someone used to a traditional starter motor, unnervingly quiet. I have seen no reports of additional engine wear from the increased frequency of engine starts.
All present-day hybrids that I am aware of will automatically restart the engine when auxiliary loads require it. If I am at a long light, my hybrid may start the engine after 20-30 seconds if I am using a lot of auxiliary power. Once again, this is a solved problem.
Over twenty years ago, I was working with the research labs of a major automaker on the prototype of such a system. It was a ring motor that went where the flywheel usually goes that served as starter, alternator, supercharger, and flywheel substitute, modulating the torque dynamically between spark firings. So these ideas have been around and under development for a very long time.
"In general, for general wear, it is better to avoid starting and stopping.Of course, this is a leftover from much older carburation technology.With older cars there was a lot of wasted fuel each time you started up.This has not been the case for a long time, but people still believe it."
Not really. It's a result of the lack of oil pressure at startup, which causes the majority of the engine wear. A reliable micro hybrid system would need to be capable of supplying oil pressure before each engine start, or else we'll be faced with a fleet of cars with engines that fail at 50000 miles or less. Just slapping on a larger starter, and changing the ECU programming is not enough.
I'm with Jim, Having lived in Phx. AZ for 40 yrs., in the summer ( which is from about May 1 to November 30) when the compressor stops it takes about 8 seconds for the air comming out of the vents to go from a comfortable 44 deg to 100+ deg not at all something that would be tolerated by most of the local (Texas, New Mexico, Airizona and Southern California) residents.
The underlying assumption is that the vehicle is stopped and idling an appreciable percentage of the time. There are large areas of the country where that is not true.
Then there is the question of maintenance impact generated by 10 times more startup cycles on the engine. Engine lube quality will play a greater role.
And finally, we come to the fact that a gasoline engine tooled for efficiency, running at its optimal speed, is far more efficient that our current variable speed engines.
In toto, I suspect we will find that a full life-cycle costing of start-stop would fairly quickly get someone looking at a Prius style hybrid. If we get battery life and efficiencies up, as market penetration grows, the hybrid argument will be more economically compelling.
The idea of inserting an electric motor/generator in place of the flywheel is good, but the confinement and heat problems in that location may present problems, whereas a front-mounted motor would have more space to work. Consider the same idea, but front mounted with a belt or direct drive. If you electrify all of your accesories, you would not need a serpentine belt.
The motor-generator could perform starting, accesory power, acceleration assist, and regenerative braking all in the same package. A small lead-acid or lithium battery or capacitor at a higher voltage would keep the power density up, energy density is less of a concern. We don't need to drive the car with it, just enough torque to start the engine quickly is plenty and cooling could be sized for a duty cycle for start-stop duty. Thermal monitoring of the motor and battery could reduce the effectiveness of the regen/acceleration cycle if the temperature got too high in rigorous use. If we don't ask the system to perform at max efficiency in all situations, we can save alot of cost.
I'm not sure where any dramatic savings would come from. Electrical power will still be needed during a light interval for climate control, etc. I think it would add 1 or 2 mpg to a city number depending on the number of stops that had to be made. By the way this isn't new. The Mobil economy run proved it helped somewhat during the 60's. I was thinking someone was talking about something like small assist motors and re-generators to reclaim the energy expended stopping and starting say in a large bank of super capacitors backed up with a smaller battery pack. That in my opinion would do more to improve efficiency. Sitting at a red light in Texas in 110 degree heat will not be tolerated if the ac compressor cuts out with the engine going off, as some lights take several minutes to cycle and the car will heat up fast during that interval.
It is encouraging to see that there is some support for this concept. The Buick powere assist system that utilizes the alternator as the additional drive device is a very good start. That same device could serve as the starter motor once the engine has warmed up to operating temperature.
BUt the savings could easily be more than doubled, compared to just shutting down at lights.
An option to allow the driver to initiate an" engine shutdown and coast" mode would allow the more skilled drivers to cut engine running time a whole lot more than just having a shutoff at traffic lights. The two additions needed would be to have power steering and brakes that did not require engine power, and a transmission that could free-wheel. The only other requirement would be a durable engine on-off switch for driver control of the engine. (NOT that stupid "Big Red Button" found on some cars today).
The added unintended consequence would be increased safety, brought about by the increased driver attention to driving.
The big challenge would be in measuring the amount of fuel economy improvement, since it would depend on the drivers skill level much more than on the hardware sophistication. So proving the benefit to the EPA might be a challenge.
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