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GM Introducing E-Flex Cadillac Concept with Fuel-Cell Plug-in Hybrid Drive

The Provoq fuel-cell concept. Click to enlarge.

GM CEO Rick Wagoner will use the Consumer Electronics Show in Las Vegas on Wednesday as the platform to introduce the company’s newest E-Flex concept, the Cadillac Provoq crossover. (Earlier post.) The Provoq is a fuel-cell plug-in hybrid that can drive 300 miles (483 km) on a single fill of hydrogen, with 280 miles (450 km) from hydrogen and 20 miles (32 km) from electric energy stored in a lithium-ion battery pack.

The Provoq fuel-cell concept is the fourth example of GM’s E-Flex propulsion system. Like the fuel-cell version of the Volt propulsion system unveiled in Shanghai in 2007 (earlier post), the Provoq powertrain combines GM’s new fifth-generation fuel-cell system with a lithium-ion battery.

Unlike the gasoline-engined range-extending propulsion system for the Volt (due to go into production around 2010) which is battery-dominant, the Shanghai and Provoq systems are fuel-cell centric, and use a blended operating strategy to augment their range and power with a battery pack that is roughly half the size of that in the first Volt.

Compared to the concept system unveiled in Shanghai, the Provoq fuel-cell stack offers 10% more output (88 kW vs 80 kW) and uses a larger lithium-ion battery pack (9 kWh with 60 kW peak output, compared to 8 kWh and 50 kW peak).

A pair of 10,000 psi (700 bar) composite storage tanks beneath the rear cargo floor hold 13.2 pounds (6 kg) of hydrogen to feed the fuel-cell stack, located under the hood. (The fuel-cell variant of the Volt system in Shanghai had a 4 kg hydrogen store.)

The electricity generated by the fuel cell is distributed to a 70 kW co-axial drive system for the front wheels and individual, 40 kW wheel hub motors on the rear wheels, giving the Cadillac Provoq its all-wheel-drive traction and great driving dynamics. (The Shanghai version also featured a 70 kW motor for the front wheels, but 25 kW in-wheel motors on the rear wheels.)

The Provoq’s 0-60 mph (approximately 100 km/h) speed of 8.5 seconds is a more than 30-percent improvement over the previous-generation fuel-cell system. Provoq has a top speed of 100 mph (160 km/h).

The wheels are wrapped in custom Michelin tires incorporating Green-X technology. These low-rolling resistance tires feature a tread pattern that mimics the “H20” notation for water.

Additional vehicle features include:

  • Solar panel integrated in the roof to help power onboard accessories, such as the interior lights, audio system and more.

  • Brake-by-wire technology.

  • Front grille louvers that close at highway speed to enhance aerodynamics, and open at low speed to provide maximum cooling to the fuel-cell stack.

A variety of recycled and recyclable materials are used, as well. Highlights include:

  • The headliner is wrapped in a fully recyclable soy-based material;

  • The carpet is made of recycled polyester and jute;

  • The leather used to cover the seats and instrument panel are free of harmful chemicals;

  • The Xorel material used on the door panels and instrument panel, treated to perform as a carbon-fiber-type material; and

  • The chrome trim is made with less-harmful materials.



This after years of GM spouting that fuel cell vehicles should never have "a completely unneccessary" battery on board.


Nice looker of a vehicle. A fuel cell vehicle could possibly be an easier sell (or lease) as a luxury-mobile. Interesting.

It appears that there would be more room to extend the battery pack towards the back of the vehicle if they wanted to, thus extending the range. Anyone else make that observation? Even at 300 miles range, that's getting pretty good.


This is the 4th E-Flex concept, and we're still a few years away before we even see ONE of those in production (Volt).

Typical GM, smoke and mirrors. They can make all the concepts they want, but it's going to be nothing more than temporary publicity if they don't actually produce these things.

GM has an infamous history of making lots of concepts that are never put into production.


I too can think of a few concepts over the years that never made it to production, some of which would have been some great vehicles. But I can also think of a lot of other concepts from other automakers that met the same fate as well. As far as fuel cell vehicles are concerned, GM and Honda appear to be currently the most serious about getting them on the road. Of course radical changes to the infrastructure have to occur simultaneously with the FCV's being offered to see the hydrogen world forward. But that's a topic for another day.

Roger Pham

Nice concept and layout.

My suggestion would be for GM to stick with the 1.8 kwh battery in current HEV models to reduce cost, and to use adsorptive material for H2 storage in order to reduce the H2 pressurization. The Honda FCX uses adsorptive material in the H2 tank, and is able to store more H2 but at an industrial-standard of 5000 psi, meaning lower cost of all necessary plumbing due to mass production. 10,000 psi would incurr higher cost due to non-standard and low-production H2 plumbing material, and more energy going into compressing the H2.

Since H2 can be a renewable fuel that is petroleum free, there is no need for an FCV to be also a PHEV in order to conserve petroleum, especially when battery is still very expensive, and looming shortages of battery raw materials predicted in the near future.


I remember watching a lot of the GM press releases in the years leading up to their $10 billion loss. Someone should collect and post some of those press releases, it would make for a good credibility study.

George K


Are you saying the Volt is smoke and mirrors? Because most of those Negative Nells have pretty much disappeared from postings.



I agree with using adsorptive material for H2, similar to what is being developed for natural gas as well, although I don't know if some of the carbon structures in those materials might have any catalytic activity with H2.

As for battery size, I say keep the battery capacity, as it will help with regen efficiency (partially depleted battery will allow more room for regen energy, thus using as little friction braking as possible).

Also helps to keep the fuel cell operating at its best operating range (which I believe is generally at lower load).

With regards to cost, if the essential vehicle architecture is built from the ground up around having a large capacity battery, likely future improvements in energy density that are not proportionate to increased costs (e.g. silicon anodes, etc) will mean the architecture won't need to be completely redesigned AGAIN.

Just my $0.02



you ought to know by now that it's ALL smoke n' mirrors.

Sam Plug-in

Yep, I own a 1993 Geo Metro with a three -cylinder engine. 35 mpg and cost about $3,000, used, because it is a convertible. Live and drive in Las Vegas with plenty of pep and easy to park!!

Where do you buy hydrogen??? lol

Plenty of electric golf carts rolling around in lots of towns.

GM is all smoke and mirrors!!

Volt is three years out and will be beat by the Chinese and Japanese!!


The larger battery not only allows the FC to operate at closer to optimal efficiency for power generation, but as you may recall, the PEM will last far longer with less power fluctuations. The other advantages of the larger battery include: 1) If you live within the all-electric range most of the year, then you only need to fill up with H2 for longer trips. 2) You aren't as dependent on H2 infrastructure. 3) You can charge the battery at home without the need for a very expensive home H2 electrolysis machine and pressure pump.
I agree on the H2 storage issue, 10000psi is risky in terms of the pumps that do the pressurization.

George K


I can see why people think it’s smoke and mirrors. But I’ve actually had meetings with some GM insiders, including the head of the Volt design team, Bob Boniface. Early on, I probed for the possibility that this was a publicity thing for GM. He held back a chuckle at the idea (which I am doing now ). His team is currently working on details, which are way past the show car. As an example, he told me some details of the actual tire type, size and tread that will be on the final version (not the same as the show car). There are over 100 engineers working on the project, and that it is the highest priority project in GM. His bigger concern was making some of the internal target dates. But there was absolutely no doubt that the car is coming out.

GM is now coming out with a new hybrid every quarter for the next 2 years! They are a different company than they were a few years ago, when they thought hybrids were just a phase (which Honda is saying about PHEVs by the way).



What comes out of the tailpipe on that 93 Metro when you go to a station with an analyzer? I'd like to know...

Plenty of pep compared to what? My mtn bike has "plenty of pep" when I find a nice downwards sloping hill and I didn't lift weights the day before.


Coaxial motors, big - small batteries for regen braking, no mention of capacitor buffers but sensible coments re destressing the fuel cell and providing greater range between (non existant fueling stations)
Gentlefolk, any concept is plainly just that a platform for great ideas while maintaining fluidity for options which sensibly will be coming thick and fast if technologies emerge at anything like the required pace.
This and similar articles have in my opinion a high value for designers, innovators, thinkers, educators- nearly everone today. The end user well that takes a little longer.
Eventually, the consumer benifits even if a concept becomes shown to be unrealisable, it'll be because the exercise exausted itself and better options present along the way.
As long as these technologies are presented as concept, I think It's really haelthy.
When concepts are presented as 'saviour', the presenter or consumer will do better to see an analyst themself.


The Detroit auto show next week should spark some interest. I can remember one year ago, the Volt was announced. That got people going.


A commenter on one of the business channels said that this could go 300 miles on a fill up of hydrogen. Then he said, "now all you need is....hydrogen". He then smiled and rolled his eyes a bit.


"Smoke & mirrors"

As an engineer with 27 years experience in industry, I know that about 1 in 10 advanced technology developments actually mature into a viable product. Does this mean that 9 out of 10 are just marketing? Not hardly.

"My suggestion would be for GM to stick with the 1.8 kwh battery in current HEV models to reduce cost, and to use adsorptive material for H2 storage in order to reduce the H2 pressurization. The Honda FCX uses adsorptive material in the H2 tank, and is able to store more H2 but at an industrial-standard of 5000 psi, meaning lower cost of all necessary plumbing due to mass production. 10,000 psi would incurr higher cost due to non-standard and low-production H2 plumbing material, and more energy going into compressing the H2. "

Adsorptive materials are a mixed blessing. Most materials today absorb only 7 to 8 percent of hydrogen by weight, so the weight of the material is 12.5 to 14 times the weight of hydrogen. In the case of the FCX, which holds 5 kg of hydrogen this equates to 62.5 to 70 kg of added weight. BTW here is an artical on a new hydrogen adsorptive material that reportadely adsorps 14% by weight .

10,000 psi systems are the latest state of the art and many of the fueling stations either have or are planning on providing 10,000 psi capability. I am encouraged that GM is using the latest technology in their concept cars. You can double the tank capacity by doubling the operating pressure or adding adsorptive material. Doubling the pressure adds less weight to the vehicle.

As for smaller standard size batteries, I note that the reported 9 kW-h capacity is exactly 5 times the 1.8 kW-h battery standard, so they are probably using five 1.8 kW-h batteries. The larger battery bank and a plug-in hybrid electric vehicle (PHEV) is attractive for people with short to moderate commute distance because the cost of electricity from the grid is less than gasoline or hydrogen. Even after you figure in the cycle life of the batteries the electric range is the most economical. OTOH battery replacement cost is the Achilles heel of electric vehicles, so one must carefully trade off energy cost versus battery cost.

Here is link to a map showing the hydrogen refueling stations in California if you live outside of California try this link . BTW there are currently 28 operational hydrogen refueling stations in California and 38 in the rest of the USA. There are currently 39 planned stations in the USA, so by the time you can get a hydrogen powered HEV there will over 100 fueling stations in the USA (and 46 of them in California). Still I wouldn't plan a cross country trip in the near future.

I drive a Compressed Natural Gas Honda Civic GX and I drive it al over California, but it has never left this state.

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