"It's an incremental solution," See said. "Automakers don't have to design a whole new vehicle. They don't have to overhaul the entire drivetrain. They just use the battery to squeeze out extra bits of fuel efficiency."
Start-stop will evolve over the next few years, and some of those technical evolutions could add to the cost of the vehicle. Some systems may add new capabilities, such as stopping during coasting. And some start-stop vehicles will employ so-called mild hybrid technology, which employs a belt-driven motor-generator, a lithium-ion battery, and a higher-voltage electrical architecture. (See predicts that mild hybrid vehicle sales will hit about 350,000 by 2017.)
But the move to start-stop is unlikely to be thwarted. Automakers need to boost fuel efficiency to 54.5mpg by 2025, and consumers can add this feature for only a few hundred dollars more.
"This is a substantially lower-cost approach than putting a giant battery in the back of the car," See said. "It's the cheapest way to save fuel and the easiest path forward for OEMs looking to reduce emissions."
For a close-up at GM's Chevy Volt, go to the Drive for Innovation site and follow the cross-country journey of EE Life editorial director Brian Fuller. In the trip, sponsored by Avnet Express, Fuller is taking the fire-engine-red Volt to innovation hubs across America, interviewing engineers, entrepreneurs, innovators, and students as he blogs his way across the country.
These adoption numbers are definitely compelling, Chuck. What are some of the Start-Stop micro hybrids now available on the market? Does the Prius fall into that category (I know it has some sort of similar technology onboard)?
One thing that strikes me about what you've been writing about lately is the variety and depth of efforts underway to address the fuel efficiency and environmental challenge. Given than no one technology can be expected to be the savings grace, it's good to see a lot of different irons in the fire, both as short-term and long-term solutions.
Beth, in answer to your question, yes, the Prius uses start-stop technology. It's considered a full hybrid, however, not a micro-hybrid, because it uses a motor-generator to propel itself and to gather regenerative energy from the brakes. Simple micro-hybrids can't do either of those things.
And, yes, you're right about this being a short-term solution. Interestingly, though, it could have a more profound effect than pure EVs for quite a while, because there will be so many of these vehicles on our streets, all boosting their fuel efficiency by 3-10%.
Might a redesign of the starter system (instead of beefing up the existing) be in order? Maybe something that keeps the starter engaged all the time, instead of using a solenoid to pull it in and out on startup?
TJ is right they need a redesign. And again they know what to do but won't.
Solution is simple, lower cost, weight. First go to a 36/42vdc system and replace alt, starter, belts, pulleys, gears, etc.
Then build a motor/alternator in the flywheel. This saves at least 40lbs copper/car and another 30lbs in alum and steel plus labor. All it is is some magnets on the flywheel and some coils next to them. The coils can be made to service easily.
Plus this lead to major performance gains in Air conditioning, power steering, e cams, e oil pumps, etc all can then be electric and smaller, more eff and flexable packaging advantages. Taking al these parasitic drags off the engine and onto the electrical system if 4x's as eff about. It's things like these and lightweight chassis/bodies along with better aero that will easily get big auto to well above the 54.5mpg goal. Done right ligter, more eff is cheaper especially in the future when materials become more expensive as more people want them.
Re TJ's comments, I'm pretty sure Chuck has previously reported that many of the start-stop systems are implemented so that you're not repeatedly engaging a solenoid during restart. That would lead to early failures, cause it'd be like using five years worth of your current starter in a month. The point about voltage is also important. Cars went from 6V to 12V in the, what?, late 1950s? Now there are plans go to various high(er) voltage systems, which will help support new technologies. Mostly these will help on the advanced drivetrain side, including the starter issue, as mentioned in the comments, as well as in the increased use of in-auto electronics systems.
It's an automatic shut down, Rob. The car would use wheel speed sensors and brake pedal sensors to determine if it is at a stop. Then, as you point out, it would have to come back to life quickly, or acceptance of this technology wouldn't be high. To do that, suppliers want to keep the restart -- from the time you move your foot from the brake pedal to the accelerator to actual motion -- to between half a second and a second. To do that, engineers want to use a crankshaft sensor to help "know" which cylinder needs to have fuel injected into it.
Current ones in Europe are auto shut down and restart, you don't have to alter your driving at all. I've driven a 3 Series BMW with start stop and it's very good once you get over the feeling that the engine has stalled every time you are waiting at the lights. I think on some manual cars they may be linked to the clutch pedal so that the engine fires up when you press the clutch to engage 1st gear.
This is a good example of an incremental improvement that is enabled by more sophisticated control technology.I know individuals who do this manually.Whenever they know they are stopping for more than a few seconds, they turn the car off.Most people leave the car running.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.
One other area I have seen this, by the way, is in gasoline powered golf carts.My relatives on the farm use these to get around off road (with riser kits for the wheels).If you take your foot off the gas the engine stops.It starts up quite quickly when you step on the gas and the starter motor also recharges the battery (you use much more of that, of course).For automotive use the system was probably not acceptable (there would be some perceptible delay), but for this use it was fine.The reason they liked these, by the way, in contrast to the off road ATV (which they all had), was that they could go a couple of weeks on a tank of gas.It wasn't as powerful or fast, but it fit the bill.
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.
Charles, in this and another post about the Chevy Volt, the main issue seems to be cost versus fuel savings. In your many dealings with the car companies, did you ever hear about any of them using a Stirling engine instead of a standard ICE to do the same job as the ICE in the Volt? I know Ford looked into a Stirling engine at one point, but not in the hybrid mode. The Stirling is much more efficient, and if you could run it at its most efficient speed then you could simply use electric for the motility. You would only need a 5-10 kw battery, or even just a bank of supercapacitors (although the cost is still high on these). The Stirling's only drawback is that it takes time to warm up to produce power. The battery/capacitor removes that drawback, but does add cost. Overall though, the total package should be very simple. Any thoughts?
Davidmac, I'm not aware of any Stirling-hybrid projects at any of the big automakers right now. You're right that a hybrid would seem to be a good application for the Stirling, especially since its reputation as a "slow starter" wouldn't matter as much there. Ford recently installed Stirling engines at its Michigan Truck Plant, but only to generate electricity. Most of the major automakers looked seriously at Stirling engines in the '70s, but little came of it. AMC did put a Stirling engine in an experimental AMC Spirit and GM put the technology in a concept car in 1969. A couple of years ago, former Design News Engineer of the Year Dean Kamen created a Stirling hybrid using a Think City electric vehicle, but I haven't heard much about it since. Some of the automotive engineers I've spoken with over the years have alluded to packaging issues with the Stirling. But in these efficiency-obsessed times, when we seem to be considering every imaginable possibility, it seems like we should be hearing a little more about a Stirling hybrid.
Charles, thanks for the tip about Dean Kamen. I'll see if I can find more info about the car. BTW, my wife and I looked at a so-called hybrid in 2009. It was the Saturn Aura. The test drive proved to be a dud, as the battery that was supposed to keep the car going while it was stopped had to charge up, so it didn't actually work until we arrived back at the dealership. We went with a different Aura. The price difference was too great for us to justify such a small increase in gas efficiency.
Thought about this article as I drove around this weekend. I didn't realize how much time I spend idling. Not just traffic lights, but waiting in line at drive up ATMs and drive through food for the kids. I agree this technology would save a lot of energy.
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.
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.
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 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 am amused by the way that today's marketeers try to force an 'in word' [hybrid] onto any idea that they can. IMO, stopping the motor is just that - stopping the motor. Oh well...
Continuous incremental improvement is proven to be a successful avenue in many cases. An interesting thought that I had while reading the article - we all know that modern cars have been [and continue to be] invaded by microcomputers, but I haven't given thought to the large number of motors and solenoids that keep appearing each year. Start/stop will probably add an additional motor to spin the AC compressor and who knows what else.
I think the next thing to go will be engine speed/road speed corelation. The throttle will control torque/power to the rear wheels via an improved transmission and the engine will operate within a few preset speeds/conditions that will be optimized for efficiency. The base engine will only operate within 80% [??] of the expected conditions - possibly calling on the electric supercharger for that occaisional burst of power. Solenoid control valves will allow for almost infinite 'camshaft timing' without the mechanical heartaches. When vehicles are smart enough to kill the engines when we hit the brakes and transparently restart the engine if we didn't stop, we will have electric assisted brakes. It is all basically here now. Wow!! That is a lot of electricity for an ICE vehicle - we will definitely need batteries with more uummp!
I agree with you, mellowfellow. The use of the term "microhybrid" is a stretch at best. There is no hybrid powertrain propelling the wheels. And, yes, we will need more batteries with more oomph, as well as electric pumps and cooling storage evaporators, if we want the cabin to stay cool in summer and warm in winter.
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.
"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.
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.
The talk of shutting off the engine in coast phase in addition to while stationary brigs to mind a car built over forty years ago that I owned, a 1970 VW Squareback or 361, w/ Bosch electronic fuil injectin. When coasting w/ engine RPM over ~1500 the injection system stopped injecting fuel, though the breaker point and coil ignition system still sparked. One never felt or was in any way aware of this, but it did reduce HC (and CO?) emissions. I can't believe that modern injection systems aren't/can't go to zero fuel mode in coating conditions where the engine is being overdriven by by the drive train.
Re: A/C heatup, assuming a electricly driven compressor this would not be an issue, otherwise the ECM would have to modulate/cut the blower following shutdown and restart to avoid blowinghot air.
Lasy, this might be the final straw to push autos over to 42V vs 14V electrical systems.
A well-known automotive consultant who did an extensive teardown of BMW’s i3 all-electric car said its design is groundbreaking in multiple ways. “We’ve torn down about 450 cars, and we’ve never analyzed anything like this before.”
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