General Motors fifth-generation fuel cell stack
Filed under: Hydrogen, GM, AutoblogGreen Exclusive
A plastic mock-up of the GM Gen5 fuel cell stack
General Motors built the first fuel cell-powered vehicle back in the 1960s when they created ElectroVan, a concept that was only tested briefly before being shelved. Over the past decade however, the company has worked aggressively to develop fuel cell technology. Last spring when they showed off the fuel cell variant of the Chevy Volt at the Shanghai Motor Show, they also announced their fifth-generation fuel cell stack.
At the time, VP of R&D Larry Burns discussed the new stack but didn't give much detail. The focus of the new design was on dramatically reducing the cost while improving the power density. One of the improvements that was mentioned was catalyst thrifting. This involves improved methods of applying the catalyst materials to ensure thinner, more uniform surfaces. This reduces the total amount of catalyst material that's required while allowing it to be more effective.
Update: At General Motors request two photos were removed from the gallery.
Continue reading about the Gen5 stack after the jump.
The Gen5 stack on the left with a bipolar plate, the Equinox Gen4 on the right
The Gen4 stack that was used in the Chevy Sequel concept and also in the new Equinox fuel cell was designed as an experimental prototype system. That means most of the parts are individually produced with the case itself being assembled from many machined components. In the early decades of the auto industry, engines were produced in much the same way with individually machined cylinders being mated to crankcases, water jackets and cylinder heads.
Eventually they developed casting methods that allowed cylinder blocks to be cast as a single unit that could then be finish machined. This drastically reduced the cost of manufacturing engines. This type of manufacturing technology is now being applied to the Gen5 fuel cell. The new cast case includes integrated passages for fuel and coolant. The Gen4 stack had most of its cooling and fuel system plumbing hand built on the outside of the stack. Most of that duct-work is now inside resulting in a major decrease in assembly time. This internal ducting can be seen in the colored parts of the Gen5 mock-up that was on display.
Another major change is in the design of the stack itself. A fuel cell stack is made up of a series of bipolar plates that are stacked up with membranes in between. The more plates you stack, the more power you get, in addition to more size. The Gen4 stack plates had the anodes and cathodes combined with a layer of graphite as the separator. The graphite was expensive and brittle. The new plates have a metallic separator that is much thinner as seen in the photo of the two plates side by side. The result is that a stack with similar power output is now half the size and less expensive to build.All of these design changes result in near doubling of power density to 3kW/L and 2kW/kg. By comparison the latest Honda vertical flow stack in the FCX concept only achieves 2kW/L and 1.5kW/kg. An 80kW Gen5 stack is about half the size of a similar power stack in the Equinox or Sequel. The changes to the catalyst application also nearly double the efficiency of the stack allowing a vehicle like the Sequel which took over 7kg of hydrogen to go 300 miles to now cover that distance on 4kg.
All these advances are part of GM's effort to get the cost of the fuel cell system down to $50/kW for volume production within the next two years. GM has prototypes of the Gen5 stack running and Volt prototypes using the new system will probably hit the track some time next year after the flex-fuel range extender is running.
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Reader Comments (Page 1 of 1)
8-27-2007 @ 12:30PM
kert said...
Ok, when did you see the magnificient third and fourth generation fuel cells by GM the last time ? On sale ?
Considering how uberadvanced this fifth generation is, third must be pretty good to and fairly cheap by now ? no ? i wonder why ..
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8-27-2007 @ 2:01PM
Ron Fischer said...
All that lovely fuel cell technology coming together... but still no practical way to store hydrogen aboard the vehicle.
Largely this media event looks to position GM as "ahead of Honda". Although, if one compares, GM is showing mockups and giving estimates of performance, while Honda's FCX is already being driven around by journalists.
Keep going GM. I'm looking forward to the media event where someone opens the hood of a working vehicle to reveal the Gen 5 stack, rather than plastic mockups.
Given this, its somewhat reassuring to see GM's hybrids finally coming to market. I still wonder if anyone will pay $10,000 for a dual-mode transmission to "green" their full-size SUV?
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8-27-2007 @ 9:26PM
A.Brien said...
I dream of buying a fuelcell car in my life, the sooner the better. There is no reason to wait, it's mainly done. The main stop remain hydrogen station on the road. I hope it begin in 2008 for the cars and fueling station. Someone has to invent a practical method of making hydrogen at the fuel station instead of transporting it. There is electrolysis of water and some other methods too like the one with ammonia, so on. The fuelcell cars are running with electric motors so the smootness must be way better and traction and stability control are easier to implement and that whole system need less maintenance and all and all it's a car that is less complicated. It just that it's not mainstreem but im sure it's a lot better and cheaper(simpler) than ice( internal combustion engine ) + petrol. Viva 21's century.
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8-27-2007 @ 9:31PM
Dave said...
"All these advances are part of GM's effort to get the cost of the fuel cell system down to $50/kW for volume production within the next two years."
The whole article focuses on improvements in size and efficiency, but never really gives us a serious indication of how close GM is to this goal.
What is the cost of the raw materials? How expensive are the catalysts in this fuel stack?
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8-28-2007 @ 7:55AM
dean said...
Dave, I think your quote clues you in on you own question. "Ready to manufacture within 2 years", which may only mean manufacture a small test fleet, but still.
I really don't see fuel cell vehicles available to the public for quite a number of years. There is still a lot of R&D to be done, and definitely an infrastructure to be put in place. The cost of this system, even at Gen 5, is still probably more than a comparable electric vehicle. At least GM is going to produce a multitude of alternative vehicles (all electric, hybrids, fuel-cell, ethanol, even a new light duty truck diesel V8). Its expensive, but it should pay off in the end for them.
Fisher, those FCX vehicles are just marketing fluff. GM could have stuffed a primitive fuel-cell in a Vue and done the same thing (5 car fleet, each car worth 1 million bucks), but they chose not to. Doesn't mean they are behind. They look to be on par or maybe even ahead of Honda. Honda is claimed a while back to have a fuel-cell vehicle on the roads for general public in 2008, but either thats a lie or it will be a lease only for $500+ per month deal (like GM's electric vehicle).
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8-28-2007 @ 12:18PM
Dave said...
The way I figure it -
The fuel cell is just a generator. If it were installed in a series hybrid (such as the Volt, but with a much smaller battery pack / capacitor pack) it would only need to produce a bout 25 kw (30hp) running constantly.
25kw multiplied by $50/kw is only $1250.
I can see where $50/kw is a reasonable goal. But they aren't telling us if they are anywhere near that goal.
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8-31-2007 @ 11:44PM
AirZurk said...
I am an Autoblog reader and don't frequent AutoblogGreen often. After reading your comments here, I am appalled at how misinformed you all are. I would think that those who visit this site would be at least somewhat interested in the "green" side of the auto world and therefore somewhat informed. And if not informed would refrain from commenting.
kert, the third and fourth gen cells could be found in the Hy-Wire and Sequel concepts. And I feel it would be very irresponsible for a company to market its first iterations of a developing technology to the public don't ya think?
Fischer, GM's carbon composite tanks are perfectly capable of safely storing hydrogen at 10000 psi. And lets compare... True, Honda's handful of FCX's are skating around their little test track entertaining reporters. But, two of GM's fuel cell powered Equinoxes just completed a 300 mile trip in real world conditions, during rush hour, on a single tank of hydrogen. And have you ever heard of something called "Project Driveway"? You can look it up but I'll give you the gist. GM is leasing 100 fuel cell powered Equinoxes to the general public for two years. Honda, by contrast, has leased just two (PopSci had a small but good article this month). So, soon you won't have to worry about going to a media event to find that gen 5 cell, cuz it might be in your neighbors driveway.
Ok, now I'm calm.
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