My Technology's Better Than Yours: GM's 'Extended-Range' vs. Toyota's Plug-in
By Bill Visnic, Senior Editor
So here's what it comes down to: two global automotive giants jousting over who has the better technology for future hybrids.
In this corner, if somewhat reluctantly, it's Toyota Motor Corp. and the "plug-in" hybrid-electric vehicle
(PHEV), an extension of its renowned Hybrid Synergy Drive system popularized the world over by the standard-setting Prius.
And in that corner, simultaneously playing underdog and catch-up, is General Motors Corp. and its heavy-duty green hype-machine, the Chevrolet Volt - a vehicle that, just as with Toyota's plug-in Prius, doesn't yet exist in retail form.
The Volt, still being tested and prototyped, is the high-fashion showcase for GM's potentially game-changing but unproven "extend-range" electric vehicle (E-REV) technology.
GM says that a Volt vs. plug-in Prius match-up isn't really an apples-to-apples comparison because the Volt isn't really a hybrid.
The company insists that it is an electric vehicle - albeit one fitted with a "range-extender" combustion engine that can recharge its lithium-ion batteries in the event the vehicle needs to be driven beyond the planned 40 miles of electric-only propulsion.
Truth is, the Volt is an EV, but it also fits the classic definition of a series hybrid, in which one powerplant produces electricity to feed the electric motor that propels the vehicle.
The Prius, plug-in or otherwise, is a hybrid of another stripe; a parallel hybrid, so called because its two power plants (gas and electric) can work separately or be harnessed together- operating in parallel - to provide propulsion.
The two systems are going to end up head-to-head in the race to win the hearts and minds of an expanding population of environmentally concerned buyers and head-to-head in the struggle to determine whether one design prevails in a high-efficiency future nobody can yet fully forecast.
Oh, and one final bit of fun and intrigue: neither company has been immune to a little trash-talking about the other's technology.
Let's Get it Straight: The Differences Under the Hood
The Volt's E-REV system is the cornerstone of what GM calls the E-Flex architecture: electrically propelled vehicles that can get the juice from various sources.
For the near term, E-Flex is focused on grid-recharged lithium-ion batteries bolstered with power generated on-board by a gasoline engine. But E-Flex also is designed to accommodate a diesel generator and ultimately fuel cell-derived electricity.
As presented, the Volt concept car's E-REV design uses a battery pack that's sized to store enough power for a 40-mile driving range - a capacity GM's battery guru Denise Gray recently claimed is about 16 kilowatt-hours.
For longer trips, a small 4-cylinder engine kicks in when the battery charge is exhausted. The gas engine is not connected to the drive wheels, though - it functions strictly as a generator to recharge the batteries.
GM says this series-hybrid layout is good for more than 300 miles of driving range.
More important, however, the automaker has claimed the 40 miles of all-electric propulsion from the initial grid charge would serve the needs of a majority of daily commuters. In that event, the Volt's combustion engine would never fire up. No fuel burnt - and no emissions.
For its part, Toyota, in cooperation with the University of California at Berkeley, is testing several Priuses
converted to plug-in status with a double-size, 13-ampere-hour nickel-metal hydride battery pack that enables an approximate 7-mile electric-only range at speeds in excess of 60 mph.
A stock Prius without plug-in recharging can operate in all-electric mode, but only for a few miles at speeds below 30 mph.
Toyota and other carmakers also are known to be developing PHEV systems that will leverage the energy density advantage of lithium-ion versus today's nickel-metal hydride batteries.
Until now, Toyota has been circumspect about its lithium-ion development path - and essentially was discussing its PHEV potential in terms of what's possible with sized-up nickel-metal hydride batteries, saying any Toyota plug-in using lithium-ion batteries wouldn't be in showrooms until sometime after a 2010 test of the vehicles in commercial and government fleets.
GM, however, has said it will launch a retail-ready Volt by late 2010, possibly putting it in the lead in the race to get to dealers' showrooms.
But GM's continual promotion of the Volt appears to have affected Toyota's posture. The company recent said it is accelerating the date for fleet testing of lithium-battery Prius PHEVs to late 2009.
Toyota spokesman Irv Miller was careful to note on the company's Open Road blog, though, that there still is no firm timeframe for when a Prius PHEV will be available in showrooms. And Toyota remains nebulous about what kind of electric-only driving range a production Prius PHEV with lithium-ion batteries will have.
It comes down to Toyota's likely lesser-range, plug-in parallel hybrid argument versus GM's E-REV series-hybrid layout.
On the face of it, who could object to a 40-mile battery range? But Toyota and others insist it's far from that simple.
The Arguments
The sniping began a year ago
as buzz continued building about the Volt concept that GM had unveiled in January, 2007, at the Detroit auto show.
In September, Miller, Toyota's vice president of corporate communications and an occasionally acerbic contributor to the company's blog, said in his "Irv's Sheet" column that people at Toyota were "actually quite surprised at the apparent enthusiasm for series hybrids."
That's because, he said, "at this point in time, there are no automotive series hybrids in mass production that actually work. They simply don't exist."
There was "a high-profile showing of a series-hybrid prototype called the Chevrolet Volt at the Detroit auto show last January," Miller continued.
But keep in mind that the advanced lithium-ion batteries that the Volt would use, batteries suitable for the long-term rigors of every-day automotive use, don't exist, he wrote.
"Indeed, several firms are working hard on perfecting them for automotive use. But for now, the 40 miles between charges that the Volt's engineers talk about, and that have so many people fired up, are purely theoretical.
"So the choice seems clear," Miller concluded. "If you want a product that's easy on the environment, gets great fuel economy and has good performance, the only reasonable choice is [Toyota's] Hybrid Synergy Drive. You can buy a vehicle powered by the system right now, today. But if you want a series hybrid, well - you can cross your fingers and wait for a few years until some difficult engineering and production problems are solved."
Following that shot across the bow, some tittering could be heard from both sides at various enviro-conferences and auto-industry confabs.
GM's response to Miller's "it-ain't-even-invented-yet" pooh-poohing of the Volt came in an early-2008 Society of Automotive Engineers paper (SAE2008-01-0458) detailing the results of a company-conducted study that pitted E-REV against PHEV.
And guess what? GM's study said Toyota's PHEV strategy was vastly inferior.
The study took real-world driving models and superimposed projected PHEV and E-REV performance.
GM reasoned that to be "urban-capable" with battery capacity designed only to complete an urban drive cycle - essentially the performance "envelope" expected of a nickel-metal battery Prius PHEV - a vehicle "may not satisfy the vast majority of drivers' needs."
The bottom line: GM's study said a PHEV that is merely urban-capable will complete a typical Southern Californian's driving day fully under electric power only six percent of the time.
The worst part of that, according to the study, are the cold-start emissions when the PHEV's engine must be fired up to augment the electric motors.
GM's study contained plenty of other figures to demonstrate the folly of the kind of urban-capable PHEV Toyota currently is testing as compared with the GM E-REV system - which, as Toyota's Miller reminded, exists only in pre-production test form and relies on battery performance that has not been proven in real-world use.
The GM comparison may prove outmoded, however, if Toyota effectively bypasses nickel-metal hydride-battery technology and employs lithium-ion batteries for the first plug-in Prius.
Even if this is the case, Toyota's parallel-hybrid PHEV is likely to offer markedly less electric-only range than GM's series-hybrid E-REV layout for the Volt.
Okay, So Who's Right?
Well, just about everybody, it seems.
"There are so many possible (hybrid) configurations," said Ron Gremban, technology lead for CalCars, a California-based group pushing for development of plug-in hybrids. The main question, he asks is "What are you trying to accomplish?"
Gremban told Green Car Advisor that both technologies are, for the most part, about "fuel displacement" - getting vehicles away from burning oil-based liquid fuel.
If that's the goal - and GM, for one, has repeatedly stressed fuel displacement as the crux of its wide-ranging alternative-vehicle development programs - then Gremban says both the Toyota and GM strategies can be successful.
The differences are small enough, he said, that either could be surpassed by a rival with superior engineering.
Pet Savagian, GM's engineering director for hybrid and electric powertrain systems - and one of the authors of the PHEV vs. E-REV Society of Automotive Engineers paper - admitted that the Volt's E-REV leapfrog approach is "riskier," but said it ultimately does more for the environment.
He said E-REV technology is the bridge between what the GM's landmark 1996 EV1 electric vehicle (left)
"could have been" and the improved technology of today.
The much-greater electric-drive capability of the E-REV design will provide "real and substantial benefits" for a greater population of drivers, Savagian said.
Equally important, it helps the industry take "progressively stronger steps in vehicle electrification" that eventually lead to zero-emission solutions such as fuel-cell vehicles, he argued.
Meanwhile, Paul Boskovitch, chief engineer for advanced hybrid systems at engineering specialist Ricardo North America, says both technologies are likely to serve roles in the market, as everyone determines what's required - and what buyers want - from a new generation of more environmentally friendly vehicles.
"I think they're both right," said Boskovitch, a man who's spent the better part of his career around hybrids and EVs. "I think it's going in the right direction."
He said PHEVs might be better for driving situations where "you think you're going to be doing a lot of (battery) depleting." Short-range, intra-city commutes, for example.
GM's E-REV arrangement could be better suited for those who envision driving longer distances and want a vehicle with a lot of electric range and don't mind paying more for that capability.
Boskovich thinks the E-REV design ultimately is more reaching.
"It's more of a natural progression to (pure) EVs," he said, adding that Toyota's PHEV approach is "a safer play."
Equal Parts Engineering and Perception
For Bill Reinert, Toyota Motor Sales USA's national manager-advanced technology group, the sustained hype and promise of the Volt is a bit too overheated, particularly for Toyota's historically measured approach to developing and launching innovations.
He characterized Toyota' s approach as "a little bit more cautious in what we say."
Reinert said that one concern with either technology is that electricity for PHEVs and extended-range or full-electric vehicles has to come from somewhere.
Emissions from powerplants "may increase, not decrease," he warned, unless the nation develops more environmentally friendly fuels for generating plants - wind- and hydro- power, for instance.
By relying much less on grid-supplied electricity - which parallel-hybrid PHEVs such as Toyota's do - Reinert thinks the auto industry keeps more of the carbon debate in its own camp. And under its own control.
He said it's possible the future is full of low-carbon liquid fuels that are better for the environment than what's being used to make electricity.
With Toyota's measured (some critics say "incremental") PHEV approach, Reinert said, there's a proven technology, an infrastructure of readily available liquid fuels - and a price that looks to be more palatable than that the $35,000-$45,000 range discussed for GM's Volt.
"I don't think we're going to work on a series hybrid," he said. "I'm not absolutely convinced that's where society is going to end up."
How the consumer understands and perceives the models that result from these technologies will be as important as the actual benefits. Regulators, too, will matter.
CalCars' Gremban said that the way emissions and "fuel-economy" are measured may play in the consumer-regulator equation.
He said if it can be proven that an E-REV can eliminate a high proportion of cold-starts, the vehicle's emissions profile can be small, because cold-starts are "the place where criteria (measured) emissions mostly happen." This, in fact, was a major talking point in the SAE paper from GM.
But, he countered, if the goal is to introduce as many low-emitting vehicles as possible, Toyota's approach may be superior because it allows the use of mostly existing mass-production components.
To help consumers sort it out, Gremban said, the SAE has a study group working on a test regime for various types of vehicles using various degrees of electric propulsion.
One of the group's goals is to use the test to create a window sticker to detail the vehicle's driving range on electric power, similar to today's ubiquitous Monroney Sticker that lists city and highway fuel economy,.
For now, Toyota's PHEV is more than a year away from introduction, through fleet-only sales, in a test program, and GM's E-REV Volt isn't slated to be in anybody's hands for nearly two years. By that time, most everybody agreed, customers are likely to welcome any and all approaches.
Just the same, we wanted a definitive answer about who wins. We got it - sort of.
Where They Stand
"GM's approach is higher-cost, higher-risk - and higher potential advantage," said Gremban.
"We're not going to wait for the 'ultimate solution,'" said Toyota's Reinert, adding that if the target really is a car that can handle commuting duties solely on electric power, a series hybrid probably isn't the best answer.
It should be noted that Reinert and all the sources commenting here spoke with Green Car Advisor some time before Toyota's late August announcement that the company is accelerating lithium-ion-battery PHEV fleet testing.
"Why don't we just make a small electric car?" he asked, adding that it's too important a time to insist any single direction currently is the best.
"The next 10 years will define the automobile for the next 100 years. Eventually, I think we'll need a secret decoder ring," Reinert laughed.
GM's Pete Savagian: "We think there are considerable benefits (for the E-REV technology) beyond a plug-in hybrid."
Paul Boskovitch from Ricardo sees a place for both technologies, along with a buying populace that understands each may better serve a certain kind of driving regime.
"I don't think it's going to play out bad for the consumer in any sense," he said of GM and Toyota's gently aggressive technology competition.
Visnic is a senior editor for Edmunds
Auto Observer
- Posted by
- John O'Dell September 2, 2008, 1:00 AM
- Permalink
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- Chevrolet, Fuels & Technologies, General Motors, Green Vehicles, Hybrid, Plug-ins and Electric, Toyota
- Technorati Tags:
- Chevrolet Volt, General Motors, GM, Plug In Prius, Toyota Motor
I think it's funny that GM said the Volt is not a hybrid. It is the very definition of a hybrid. Draw a box around the car. Energy goes into the box, work comes out. With the Volt, the energy going in can either come from an electrical power station of from liquid gasoline. Two energy sources, thus a hybrid. In contrast, vehicles such as the current Prius are not hybrids. The only energy going into the box is from the liquid gasoline. The car is capturing and re-using energy that would otherwise be wasted (braking) in the same way that my turbo captures and re-uses exhaust energy. I do not call my turbodiesel a hybrid. 'Plug-in' hybrids are true hybrids.
The most promising hybrid technology is neither described in this article. It is series hydraulic hybrid, being persued by the EPA and others (see Valentin X-car). One of the main advantages is that 600hp worth of hydraulic motors weighs less than 100 pounds, can easily be integrated into the car, and can absorb >70% of all braking energy, unlike the 70% fuel consumption improvement. EPA showed 80+ mpg from a 3800 pound mule. Valentin's 130 mpg calculations for his 2200 pound sedan (real mpg, running only off the chemical fuel, not the 'fake' numbers you hear for plug-in hybrids that aren't accounting for the energy coming from the electric company) is not unrealistic, if he can keep that weight down.
My laptop touch-pad strikes again. Missing text shown below:
One of the main advantages is that 600hp worth of hydraulic motors weighs less than 100 pounds, can easily be integrated into the car, and can absorb >70% of all braking energy, unlike the <25% for electric motor hybrids. Real world testing has shown 70% fuel consumption improvement.