Driving Toward the Future
GM fuel cell endurance run shows progress on road to commercial viability.
The auto industry’s race to create commercially viable hydrogen fuel cell vehicles should be considered as a marathon not a sprint, argues Larry Burns, General Motors’ research and development chief. That being the case, then GM recently sped up the pace with the successful completion of a trans-Europe endurance run for its HydroGen3 fuel cell prototype.
Based on the Opel Zafira compact minivan, HydroGen3 is powered by GM’s own 94 Kw (125 hp) fuel cell stack and uses a 12-gallon liquid hydrogen tank. In May, the vehicle set off from Norway on a 6,200-mile odyssey to Portugal to prove its durability over a record distance and through a wide variety of road and climatic conditions.
Approximately halfway through the trip, I took over the wheel for the leg from London to Paris. By the point we reached Paris, HydroGen3 had covered some 3,000 miles without any serious problems, and shortly afterward it established a new fuel cell vehicle endurance record of 3,400 miles. The previous record was set in May 2002 by DaimlerChrysler, whose NeCar5 fuel cell development vehicle covered 3,200 miles on a U.S. coast-to-coast run.
While DaimlerChrysler’s proving run was an internal event, GM was sufficiently confident in the HydroGen3 to invite automotive journalists to drive various segments of the journey across Europe.
In my hands, the driving experience was remarkable mostly for being so similar to a conventional vehicle. There are no special tricks to starting HydroGen3. You twist a standard “ignition” key and after a few seconds the fuel cell stack announces in a dashboard digital display that it’s ready to deliver energy to the electric motor under the hood.
|Linde portable liquid hydrogen fueling station met the Zafira every 125 miles thanks in part to a bunch of lead-footed journalists.|
The 'ignition' sequence involves the 'startup' DC-DC converter switching the 12-volt battery feed to 300 volts. This activates the cathode air compressor to blow air into the stack. Simultaneously, the injection valves feed hydrogen to the anode side of the stack. Then the main DC-DC converter is turned on and within five seconds, the stack is generating enough power for full operation.
For the driver, the next step is to push a forward arrow button on the center console and to get moving it’s simply a matter of pressing the throttle pedal (although with a fuel cell stack absent of any moving parts, the word throttle no longer applies).
From this point the special Zafira’s driving characteristics are much like those of a conventional electric vehicle. That means off the line acceleration is surprisingly swift, given that the vehicle weighs about 400 pounds more than a standard version. There is also an eerie lack of the traditional engine and exhaust noises. Even at its top speed of 100 mph, which I reached on the French autoroute, the main sounds audible in HydroGen3 are wind noise and some tire roar. “Powertrain” sounds are limited to a background whine from the electric motor transmission gears, a subdued supercharger-like sound from the stack compressor and occasional clicks and buzzes, as other components kick into operation.
At start-up, the noises are mainly a whine from the hydrogen compressor and a slight rush of the water/air mixture coming from the “exhaust pipe” vent. The compressor whine sound level is related to “throttle” position with a slight delay as the compressor ramps up. There is also a discernable ticking sound from the three injectors, which feed hydrogen into the stack, while the anode side re-circulation pump, which maintains the flow through the membranes of the stack, has a slight squeak.
|GM fuel cell engineer, Bernd Zerbe was along for the ride to make sure everything worked properly. |
A discussion of the underhood hardware with GM fuel cell engineer, Bernd Zerbe, revealed that all the accessory drives are electric. In an internal combustion drivetrain many accessories would be belt driven but the beltfree fuel cell stack means electric pumps are needed for the brakes, steering and cooling loops. There are two cooling loops, one high temperature for the stack, one low temperature for the power electronics. No less than three radiators sit in the engine bay, one for the air conditioning and one each for the low and high temperature cooling loops.
Though much attention has been given to the cold-start problems faced by fuel cell stacks, high temperatures are also an issue. Stack temperatures above 90 degrees C can degrade the fuel cell, explains Zerbe. “The worst situation is going uphill slowly in hot weather, although we successfully managed such a test in Italy,” he says.
The construction of the stack is also being reviewed. The fuel cell in HydroGen3 uses titanium stack plates with etched channels.
Newer versions of the stack are using stainless steel stamped plates. However, stainless steel has issues with corrosion, so GM engineers are looking at composites.
At 16 seconds, the HydroGen3’s acceleration time to 60 mph was leisurely to put it mildly, but in city traffic the car was responsive enough to keep up with the flow. (In London’s appallingly congested streets it took us one hour to cover 12 miles). At 60 mph the dashboard kilowatt output gauge, which replaces the normal tachometer, revealed that we were using about 40 Kw of the fuel cell’s total 94 Kw (125 hp) output. But acceleration from 60 to 100 mph seemed to take forever as HydroGen3 struggles with its extra weight and increasing aerodynamic drag on the bluff Zafira body.
| On the French autoroute heading to Paris. |
Our development car is fueled with liquid hydrogen, as opposed to the less space efficient, but easier to handle compressed variety. The GM engineers riding shotgun with me (we have four people on board, plus luggage) noted that the car averaged about 125 miles between refueling stops on the European marathon. That’s about half what the HydroGen3’s fuel cell system should be capable of, claimed the engineers, were the car not suffering from a number of handicaps. These include range-robbing performance tires, excess weight, unfavorable aerodynamics, a European government restriction on filling the tank to more than 85 percent capacity and last but not least, the fact that the marathon car was being driven by leadfooted auto journalists.
Although the rate of hydrogen consumption comes as something of a surprise to the engineering team, I was told that once the fuel cell powertrain is optimized in a purpose-built vehicle (which is the next step, say GM insiders), then fuel mileage will improve significantly.
Proceeding across northern France, I was thinking less about fuel consumption and more about the refueling procedure. My curiosity was answered as we pulled into an autoroute rest stop and met up with a van, equipped with two large Linde liquid hydrogen tanks and an elaborate pumping rig. It looked daunting but during three scheduled stops the actual act of pumping only took a matter of minutes and we were on our way in less than 30 minutes, or half the time the engineers had expected. I even took a turn at manhandling the bulky rig, which is not unlike a race car refueling device. Needless to say, interested parties, including Linde AG, Europe’s primary hydrogen producer, are at work on a more user-friendly refueling system.
At the end of my turn at the helm of HydroGen3 I was left impressed by its easy driving character, refinement and lack of problems, other than the occasional, usually erroneous sensor reading. It’s clear that the GM development engineers have much work left to do, optimizing the various systems, reducing the overall system cost to a target figure of $50 per kilowatt and conquering the still-daunting challenge of finding efficient hydrogen storage methods.
| Author John McCormick dons the heavy gloves as the Zafira’s tank is filled with liquid hydrogen. |
Bernd points out that freeway driving does not demonstrate the fuel cell car to its best advantage. “Efficiency at part load is the strength of a fuel cell and nearly two-thirds of all driving is at part load.” That said, Zerbe admits that performance needs to improve. Running through other issues, Zerbe suggests that HydroGen3 demonstrates that safety concerns have been met, NVH problems are 80 percent contained and the program is on the right path to meeting durability goals.
These major challenges aside, it’s evident from this demonstration that GM has taken a big stride forward in its march toward a working hydrogen fuel cell vehicle. “This marathon has been an extremely good engineering experience,” notes Zerbe. “We have learned a great deal.”