Road Test
First Drive: 2007 BMW Hydrogen 7
We sample a brave experiment to burn hydrogen in a real car
The name tells you immediately what it is: The 2007 BMW Hydrogen 7 is a 7 Series sedan the automaker converted to run on liquid hydrogen. There is no intention to put this or any other hydrogen-fueled car into production yet. The point of the exercise is to gather experience with a hydrogen car in the real world. So let's go straight to the experience.
If no one told you there was a fortune in advanced technology and ground-breaking engineering packed into this car, you might think you were motoring about in a perfectly normal 760Li. Indeed, while looking hard for distinguishing characteristics during our test-drive around greater Berlin, we came up with just three suspects: a slight metallic rattle from the engine when accelerating (sort of like a diesel but less pronounced), an occasional hesitation or engine-transmission miscue on tip-in and less energetic acceleration, thanks to a power cut from 438 horsepower to 260 and a weight gain of 440 pounds.
That's it. Otherwise, the Hydrogen 7 is a perfectly normal luxury sedan. It is definitely not some weird science project that forces us to scale back our expectations about the personal automobile. "A vehicle that is not a BMW anymore is not acceptable to us," says the company in contemplating the future of mobility. And noting that the internal-combustion engine represents available and well-understood technology, BMW is placing a bet on adaptation of existing engines (the 6.0-liter V12 in this case) to burn liquid hydrogen as one way to move beyond fossil fuels.
Proving the concept in a regular car
From the driver seat, this is definitely still a BMW. The H-7 is smooth, polished, poised on the road, and still pretty spritely. Passing maneuvers and uphill on-ramps need a little more careful consideration than in a 760 because you don't have as much sheer thrust. But the difference is not fatal. (BMW quotes 0-62 mph in 9.5 seconds: leisurely but livable.) Furthermore, suspension calibration effectively hides the car's extra mass, so this is another BMW 7 Series sedan that impresses you with how lithe and responsive a heavyweight luxocruiser can be. Overall, there is precious little to indicate that this 7 is running on that wondrously abundant fuel, the one that promises to rewrite all the rules of transportation, economics, energy and environmental stewardship…as long as we can work out a couple teensy problems.
At this moment, the production of hydrogen as a motor fuel typically begins with a petroleum resource such as natural gas and then requires massive amounts of electricity, which is often produced by burning coal. So looking at the entire energy cycle, it's an environmental bust, and BMW fully acknowledges its Hydrogen 7 makes no commercial sense in the near term. But the project is not about replacing gasoline any time soon. It is instead intended to start a dialog, to offer a vision of the future, to demonstrate some possibilities, to encourage development of an infrastructure, and to expand our knowledge about hydrogen as a fuel for vehicles that are otherwise just like what we're used to.
In all those ways, the Hydrogen 7 is a revelation, and BMW earns our congratulations for taking this aggressive step.
If you're lucky, and convincing, you might get a chance to give the carmaker your own congratulations, along with your input in this grand experiment. BMW plans to build 100 Hydrogen 7s and put them into the hands of selected drivers for loan periods of up to several months. About half the cars will come to the States. We have our request in.
Hydrogen is cool
Anyone getting an H-7 to drive will find a vehicle that artfully disguises its progressive technology. Starting with the long-wheelbase chassis of the 760Li, BMW engineers pushed the rear seat forward and pulled the trunk's bulkhead back to make room for the hydrogen storage tank. This barrel-shaped structure with its double stainless-steel walls and "vacuum super insulation" carries about 30 gallons of liquid hydrogen at -253 degrees Centigrade (the temperature at which hydrogen liquefies at ambient pressure). This is enough fuel to carry the car about 125 miles. Realizing road users would not be finding a hydrogen station on every corner, BMW made the H-7 a dual-fuel vehicle. Its 19.5-gallon gasoline tank is good for another 310 miles. This flexibility to get along without access to hydrogen is a critical factor in BMW's plan to log real-world driving experience with the H-7.
There is one tradeoff in that dual-fuel strategy. The engine could not be fully optimized for either fuel, since it had to immediately and seamlessly switch between the two, and so power and running efficiency are somewhat compromised. Hydrogen has very different combustion characteristics, with a much faster, hotter and more aggressive burn. The engineers admitted that clatter we heard was in fact hydrogen's near explosive combustion banging against the engine internals.
At the same time, there was something gratifying about pushing the "H2" button on the steering wheel and knowing we were humming down the autobahn pumping almost nothing into the atmosphere but water vapor. (That's "almost nothing" because traces of crankcase oil do still get burned in the combustion chambers, as in any internal-combustion engine. There can also be minute amounts of nitric oxide formed, but clever engine management keeps the level down to where a three-way catalyst can clean it up.) The transition between fuels is imperceptible, and at light-throttle cruising, even the hydrogen clatter is inaudible. Only the dual fuel-level gauges (one for each tank) and a few other unique readouts and switches give away the fact this is not exactly a typical 760 BMW.
Well-disguised complexity
Of course, beneath the skin, dizzyingly complex systems see to the safe and efficient operation of the H-7. The company is understandably being overly cautious with the technology, since experience and validation history are still limited. But most of this is invisible. Even the refueling procedure is anticlimactic. A filler receptacle lives under a power-operated cover in the right C-pillar, and all you do is plug in the hose fitting until it locks. The car then communicates with the filling station electronically, performs safety diagnostics and initiates the fill. Simple.
Liquid hydrogen rather than compressed gas is BMW's choice for fueling the H-7, based on a greater energy density (more range and performance per tankful). The company accepts a certain degree of technical complexity because of the cryogenic temperatures involved, but since hydrogen will always be transported and stored in liquid form, introducing it to the car in that state does not represent a huge additional challenge. And the ability to maintain that -253 degree temperature in the onboard tank leads to at least one catchy factoid: The tank's thermal insulation is so astoundingly good that BMW calculates a block of ice inside it would take 13 years to melt.
Still, a certain amount of boil-off is always happening to the liquid hydrogen. This creates a cushion of pressurized gaseous hydrogen within the tank, which sensors and bleed-off systems maintain within the desired range. It is this natural pressure, rather than pumps, that transfers the hydrogen from the tank to the engine. The fuel is fed as a gas into the intake tracts of the V12 (though ongoing experimentation shows great efficiency and power gains to be had from injecting hydrogen directly into the combustion chambers).
The Hindenburg effect
No discussion of hydrogen and motor vehicles can get very far before someone mentions safety, and the airship Hindenburg's fiery destruction in 1937. Controversies abound over the relative roles of the bagged hydrogen and the flammable coating on that ship's skin, but whatever the reality, the safety of hydrogen in practice will always get special scrutiny. BMW has intricate systems for managing pressure in the H-7's hydrogen tank and safely handling any bleed-off. It has rigorously tested the crashworthiness of the tank, and even studied its susceptibility to gunfire.
Engineers point out that, even if the worst happens, lighter-than-air hydrogen escapes upward and rapidly dissipates rather than splashing downward on everything the way burning gasoline does. In fact, one school of thought says that if gasoline had not become the motor fuel of choice in the last century, and somebody wanted to introduce it now, it would be outlawed as impossibly dangerous. So yes, hydrogen must be managed carefully, but BMW believes this is not an insurmountable challenge.
The company is also optimistic that the methods for extracting hydrogen and creating motor fuels will become more environmentally friendly. Biomass could serve as the base resource, and electricity from solar and wind could power the processing. In a future like that, the arguments in favor of hydrogen fuel get powerful indeed.
Dr. Klaus Draeger of BMW's board of management, calls the Hydrogen 7 "an important milestone on our way to an era of sustainable mobility," partly because the driving experience is "spectacularly unspectacular." We agree entirely.
Edmunds attended a manufacturer-sponsored event, to which selected members of the press were invited, to facilitate this report.
If no one told you there was a fortune in advanced technology and ground-breaking engineering packed into this car, you might think you were motoring about in a perfectly normal 760Li. Indeed, while looking hard for distinguishing characteristics during our test-drive around greater Berlin, we came up with just three suspects: a slight metallic rattle from the engine when accelerating (sort of like a diesel but less pronounced), an occasional hesitation or engine-transmission miscue on tip-in and less energetic acceleration, thanks to a power cut from 438 horsepower to 260 and a weight gain of 440 pounds.
That's it. Otherwise, the Hydrogen 7 is a perfectly normal luxury sedan. It is definitely not some weird science project that forces us to scale back our expectations about the personal automobile. "A vehicle that is not a BMW anymore is not acceptable to us," says the company in contemplating the future of mobility. And noting that the internal-combustion engine represents available and well-understood technology, BMW is placing a bet on adaptation of existing engines (the 6.0-liter V12 in this case) to burn liquid hydrogen as one way to move beyond fossil fuels.
Proving the concept in a regular car
From the driver seat, this is definitely still a BMW. The H-7 is smooth, polished, poised on the road, and still pretty spritely. Passing maneuvers and uphill on-ramps need a little more careful consideration than in a 760 because you don't have as much sheer thrust. But the difference is not fatal. (BMW quotes 0-62 mph in 9.5 seconds: leisurely but livable.) Furthermore, suspension calibration effectively hides the car's extra mass, so this is another BMW 7 Series sedan that impresses you with how lithe and responsive a heavyweight luxocruiser can be. Overall, there is precious little to indicate that this 7 is running on that wondrously abundant fuel, the one that promises to rewrite all the rules of transportation, economics, energy and environmental stewardship…as long as we can work out a couple teensy problems.
At this moment, the production of hydrogen as a motor fuel typically begins with a petroleum resource such as natural gas and then requires massive amounts of electricity, which is often produced by burning coal. So looking at the entire energy cycle, it's an environmental bust, and BMW fully acknowledges its Hydrogen 7 makes no commercial sense in the near term. But the project is not about replacing gasoline any time soon. It is instead intended to start a dialog, to offer a vision of the future, to demonstrate some possibilities, to encourage development of an infrastructure, and to expand our knowledge about hydrogen as a fuel for vehicles that are otherwise just like what we're used to.
In all those ways, the Hydrogen 7 is a revelation, and BMW earns our congratulations for taking this aggressive step.
If you're lucky, and convincing, you might get a chance to give the carmaker your own congratulations, along with your input in this grand experiment. BMW plans to build 100 Hydrogen 7s and put them into the hands of selected drivers for loan periods of up to several months. About half the cars will come to the States. We have our request in.
Hydrogen is cool
Anyone getting an H-7 to drive will find a vehicle that artfully disguises its progressive technology. Starting with the long-wheelbase chassis of the 760Li, BMW engineers pushed the rear seat forward and pulled the trunk's bulkhead back to make room for the hydrogen storage tank. This barrel-shaped structure with its double stainless-steel walls and "vacuum super insulation" carries about 30 gallons of liquid hydrogen at -253 degrees Centigrade (the temperature at which hydrogen liquefies at ambient pressure). This is enough fuel to carry the car about 125 miles. Realizing road users would not be finding a hydrogen station on every corner, BMW made the H-7 a dual-fuel vehicle. Its 19.5-gallon gasoline tank is good for another 310 miles. This flexibility to get along without access to hydrogen is a critical factor in BMW's plan to log real-world driving experience with the H-7.
There is one tradeoff in that dual-fuel strategy. The engine could not be fully optimized for either fuel, since it had to immediately and seamlessly switch between the two, and so power and running efficiency are somewhat compromised. Hydrogen has very different combustion characteristics, with a much faster, hotter and more aggressive burn. The engineers admitted that clatter we heard was in fact hydrogen's near explosive combustion banging against the engine internals.
At the same time, there was something gratifying about pushing the "H2" button on the steering wheel and knowing we were humming down the autobahn pumping almost nothing into the atmosphere but water vapor. (That's "almost nothing" because traces of crankcase oil do still get burned in the combustion chambers, as in any internal-combustion engine. There can also be minute amounts of nitric oxide formed, but clever engine management keeps the level down to where a three-way catalyst can clean it up.) The transition between fuels is imperceptible, and at light-throttle cruising, even the hydrogen clatter is inaudible. Only the dual fuel-level gauges (one for each tank) and a few other unique readouts and switches give away the fact this is not exactly a typical 760 BMW.
Well-disguised complexity
Of course, beneath the skin, dizzyingly complex systems see to the safe and efficient operation of the H-7. The company is understandably being overly cautious with the technology, since experience and validation history are still limited. But most of this is invisible. Even the refueling procedure is anticlimactic. A filler receptacle lives under a power-operated cover in the right C-pillar, and all you do is plug in the hose fitting until it locks. The car then communicates with the filling station electronically, performs safety diagnostics and initiates the fill. Simple.
Liquid hydrogen rather than compressed gas is BMW's choice for fueling the H-7, based on a greater energy density (more range and performance per tankful). The company accepts a certain degree of technical complexity because of the cryogenic temperatures involved, but since hydrogen will always be transported and stored in liquid form, introducing it to the car in that state does not represent a huge additional challenge. And the ability to maintain that -253 degree temperature in the onboard tank leads to at least one catchy factoid: The tank's thermal insulation is so astoundingly good that BMW calculates a block of ice inside it would take 13 years to melt.
Still, a certain amount of boil-off is always happening to the liquid hydrogen. This creates a cushion of pressurized gaseous hydrogen within the tank, which sensors and bleed-off systems maintain within the desired range. It is this natural pressure, rather than pumps, that transfers the hydrogen from the tank to the engine. The fuel is fed as a gas into the intake tracts of the V12 (though ongoing experimentation shows great efficiency and power gains to be had from injecting hydrogen directly into the combustion chambers).
The Hindenburg effect
No discussion of hydrogen and motor vehicles can get very far before someone mentions safety, and the airship Hindenburg's fiery destruction in 1937. Controversies abound over the relative roles of the bagged hydrogen and the flammable coating on that ship's skin, but whatever the reality, the safety of hydrogen in practice will always get special scrutiny. BMW has intricate systems for managing pressure in the H-7's hydrogen tank and safely handling any bleed-off. It has rigorously tested the crashworthiness of the tank, and even studied its susceptibility to gunfire.
Engineers point out that, even if the worst happens, lighter-than-air hydrogen escapes upward and rapidly dissipates rather than splashing downward on everything the way burning gasoline does. In fact, one school of thought says that if gasoline had not become the motor fuel of choice in the last century, and somebody wanted to introduce it now, it would be outlawed as impossibly dangerous. So yes, hydrogen must be managed carefully, but BMW believes this is not an insurmountable challenge.
The company is also optimistic that the methods for extracting hydrogen and creating motor fuels will become more environmentally friendly. Biomass could serve as the base resource, and electricity from solar and wind could power the processing. In a future like that, the arguments in favor of hydrogen fuel get powerful indeed.
Dr. Klaus Draeger of BMW's board of management, calls the Hydrogen 7 "an important milestone on our way to an era of sustainable mobility," partly because the driving experience is "spectacularly unspectacular." We agree entirely.
Edmunds attended a manufacturer-sponsored event, to which selected members of the press were invited, to facilitate this report.
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