VW Highlights Three Fuel-Cell Vehicle Prototypes at LA Auto Show
19 November 2008
|The Tiguan HyMotion fuel cell concept uses a VW-developed high-temperature fuel cell stack. Click to enlarge.|
Volkswagen came to the Los Angeles Auto Show to tout the efficiency and performance of its diesel powertrains and the recent market success of the Jetta Clean Diesels in the US, as well as to introduce the new Touareg V6 TDI.
However, the company said it was also casting an eye to the future with its presentation of three fuel cell prototypes: the Tiguan, a compact SUV; the Touran, a compact minivan; and the Passat Lingyu, a sedan customized for use in China (earlier post). In Germany, the Tiguan and Touran are the most successful cars in their class. The same is true of the Passat Lingyu in China. All three zero emissions vehicles were available for test drives at the show.
|Under the hood of the Tiguan HyMotion. Click to enlarge.|
Tiguan HyMotion. The Tiguan HyMotion fuel cell prototype is VW’s first fuel cell-powered SUV. Compared to earlier prototypes, VW has delivered further performance gains in the fuel cell drive, and its efficiency has been optimized.
The fuel cell stack in the Tiguan Hymotion is a VW-developed high-temperature fuel cell (HTFC) stack. (Earlier post.) Low-temperature, conventional PEM fuel cells (LTFC) operate at a membrane temperature of about 80° C. If the temperature rises significantly above this value, fuel cell performance collapses, and the cell experiences irreparable damage. Therefore, prototypes with LT fuel cells have an complicated and expensive cooling system. The radiator surface alone is about three times as large as that for diesel engines, according to VW.
In addition, in a LT system the supply of hydrogen and air gases must be constantly humidified; otherwise energy production breaks down and the fuel cell is permanently damaged. This humidification causes water molecules to be embedded in the membrane, which also introduces undesirable added weight, and the process wastes space and money.
By contrast, the high-temperature membrane developed by Volkswagen, together with a new electrode design, can be continually driven without power loss at temperatures of 120° C without humidification.
In the HTFC, proton conduction occurs via phosphoric acid. This acid has electrolytic properties that are as good as those of water, but it exhibits a higher boiling point. Therefore, the HTFC can operate with a considerably less complicated cooling system and water management, thereby reducing weight and costs. The space requirement of the fuel cell system is also reduced by more than 30%.
HTFCs historically have had an issue with product water formation—the water permeates the membrane and leaches out the phosphoric acid, in turn interrupting the flow of electric current. To prevent this problem, VW modified the electrodes to prevent product water from penetrating the membranes. Using a screen printing machine like the ones used in the semiconductor industry, VW researchers coated carbon fleece elements with a new type of paste.
The 80 kW fuel cell system is integrated in the engine compartment of the Tiguan, along with the 100 kW electric motor. The fuel cell outputs its generated power to the electric motor via a converter and a downstream inverter. Top speed of the Tiguan HyMotion is 87 mph (140 kph); the 1,870 kilogram prototype accelerates from 0 to 100 kph in about 14 seconds.
A 22 kW lithium-ion battery with a charge capacity of 6.8 Ah is recharged via regenerative braking. The battery system is installed in the car’s cargo area under the dual cargo floor that is available on the production Tiguan.
A new 700-bar hydrogen tank is integrated in the space under the rear bench seat and the cargo area. It can hold 3.2 kg of hydrogen—sufficient for a driving range of 125 miles (about 200 km).
Touran fuel cell prototype. The Touran fuel cell prototype also uses the VW-developed stack, but with an 80 kW electric motor. The protoytpe uses a 1.9 kWh NiMH battery instead of a Li-ion battery, because it was conceptualized a generation earlier than the Tiguan, VW said. The battery is recharged by the fuel cell stack or by recovered braking energy.
Both Tiguan and Touran fuel cell vehicles are currently being tested in a durability study conducted as part of the California Fuel Cell Partnership. In parallel, other prototypes are running in Germany. For test purposes, an infrastructure of hydrogen filling stations is being built between Berlin and Hamburg.
|Passat Lingyu with fuel cell system. Click to enlarge.|
Passat Lingyu fuel cell prototype. The prototype was developed in China by Shanghai Volkswagen together with scientists at the Tongji University, where the low-temperature fuel cell stack was developed. This is the fourth generation of a line of fuel cells so far developed at the university.
The 55 kW fuel cell stack is located in the car floor of the Passat Lingyu, which is driven by an electric motor with 88 kW of power and 210 Nm of torque. An 8 Ah, 376 V (approx. 3 kWh) Li-ion battery provides energy storage, and is recharged by regenerative braking and the fuel cell. Hydrogen gas is stored at 350 bar in a carbon fiber reinforced pressure tank.
Shanghai Volkswagen provided 20 Passat Lingyu fuel cell vehicles for use at the Beijing Olympics.
Oops. MORE FCs. I guess Obama can do nothing to stop this colosal waste of energy.
Posted by: | 19 November 2008 at 06:42 PM
I want to hear more about that v6 diesel...
Posted by: Joe | 19 November 2008 at 06:53 PM
Fuel cells waste as much energy as ICEs. Don't they? The hydrogen will most likely come from fossil fuels since that's the cheapest way to get it. So what's the point of a hydrogen economy? And what's the point of a fuel cell anyway, since an ICE can also run on hydrogen? Does anybody understand why they are spending so much money and research effort on FC technology?
Posted by: creativforce | 20 November 2008 at 07:00 AM
To keep the jobs for researchers..and they also like money from goverments...
Posted by: | 20 November 2008 at 07:55 AM
I made a bundle on fuel cell stocks years back. I bought the best stories, then I did a lot of research (yeah, backwards I know) and got out. Turns out just in time.
Actually the hydrogen fuel cells themselves are extremely efficient in turning hydrogen to electricity. It is the most efficient way to turn hydrogen into electricity (since fusion isn’t manageable yet). The problem has always been the fuel. Hydrogen is the least energy dense fuel. But in this efficiency lies the promise of the fuel cells.
These demos will never see the showroom. But the knowledge is important.
In this case they're experimenting with ways to use a higher temperature at the membrane. This will be important because the only way they'll pull off fuel cells in a passenger vehicle is with cells that can handle a higher density and lower impact carrier(eth/methanol or cng). In these kinds of cells, in order to keep the efficiency up, the carbon must either be prevented from reaching the membrane or must be flushed away. One way to use a high-density fuel is to use the process of reformation. This is breaking down the fuel into its constituent parts. The one we want is hydrogen in this case. Most industrial hydrogen is created this way by using high pressure and steam combined with natural gas. So we’re sending this hot electrolyte to the membrane, either you’ve got to cool it down or the membrane needs to be able to handle the temps.
This is, by far, the toughest application of a fuel cell out there. Ballard had PEM (proton exchange membrane) hydrogen fuel cell vehicle working a long time ago that could use, I believe, methanol. They had an on-board reformer to create the electrolyte. But they had to include a lot of special cooling and controls. This in addition to the ‘normal’ humidification plumbing. We’re talking an engineering marvel here. Cost millions. What’s interesting about it though is that even after all that extra crap they were looking at a 60% efficiency vehicle compared to a 20% (probably 22% now days) ICE. How about that? A never-ending battery that can use the existing fueling infrastructure that blows away an engine that been continuously improved for like a hundred years. One small team working on it for what, 5 years (at the time)?
You’ll be seeing lots of fuel cells in the world. You’ll see them as electrical backup for business or as combination heat/electric generators in apartment buildings. These are mostly SOFC (solid oxide). They run hot and run on direct natural gas. If you take advantage of the heat they are in the extreme range of efficiency.
You’ll begin seeing them in the small emergency electricity generation space too. They’ll be the replacement for your Honda generator.
Where you’ll see the most however, are the DMFC (direct methanol). These babies will be running your laptop and camera.
Posted by: Paul | 20 November 2008 at 12:50 PM
@Joe, I'm told the diesel is the same one they put into the Cayenne for the Paris/Dakar race.
Posted by: ai_vin | 20 November 2008 at 02:08 PM
Heh. Its not that complex or convoluted.
The push that is driving h2 is from outside the car markets. They arnt driving it they are simply taking advantage of it.
As such it doesnt matter what happens car wise h2 will still improve and progress until at some point it just happens.
All the gov money is realy about is trying to push that time forward and likely bushes big h2 push did indeed push the timeframe of real h2 cars forward a good 50 years.
But your car isnt the point of h2 there are a hell of alot of other things that will need h2 and fuel cells.
Posted by: wintermane | 20 November 2008 at 11:52 PM
To Paul, The fuel cell that VW has is not that efficient...125miles/3.2kg = 39mpg... diesel can achieve that or even greater when diesel hybrid comes in...
also HCCI engine is as efficient as fuel cell
Posted by: | 20 November 2008 at 11:56 PM
22% ICE is old story... most ICE now has over 30% and looking for 40% or more when HCCI technology is perfected...and with some hybrid, overall system will reach well over 50%
Posted by: | 21 November 2008 at 12:01 AM
Wait a moment. 3.2 kg H2 for 200 km means 53 kWh for 100 km, or the equivalent of 6 liters of gasoline. How come can this be considered as an energy-efficient fuel cell? If you add the energy waste for producing hydrogen it's miserable.
Posted by: François | 21 November 2008 at 11:30 AM
As they say its a 4000 lb suv and its getting the equive of almost 40 mpk. Its also not likely to be all that great of a fuel cell stack as europe is far behind the us in fc tech.
Posted by: wintermane | 21 November 2008 at 08:17 PM