"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.
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.
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.
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.
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.
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.
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?
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!
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