BMW Dual-Fuel Hydrogen 7

You have to give BMW credit for refusing to build boring cars, even as the call for clean, renewable fuels reaches a fevered pitch. The famed engine maker believes it can eliminate emissions and preserve the driving performance that BMW buyers expect by continuing to build the same engines, but run them on clean-burning hydrogen. BMW has been experimenting with this idea since the early 1980s, but this sixth-generation iteration is the first that BMW says is ready for everyday use.

Why? The dual-fuel Hydrogen 7 has a practical range, thanks to a gasoline operation mode that adds 310 miles to the otherwise limiting hydrogen-only range of 125 miles. Plus, the Hydrogen 7 is the first of BMW’s hydrogen-powered cars to com­plete the same series development process of any full-production BMW. One hundred will be built at BMW’s plant in Dingolfing, Germany, alongside standard gasoline- and diesel-powered 7-Series variants.

Driving through downtown Berlin and the surrounding areas, we were hard-pressed to tell which one BMW had given us. The only major change to the interior is an important one: a small steering wheel-mounted button labeled “H2” that switches operation between hydrogen and gasoline fuels. The switchover is nearly instantaneous, and the car is happy to run on either. Punch the throttle in hydrogen mode and the sound from the engine is almost diesel-like, which BMW engineers attribute to the faster combustion of hydrogen.

The 6.0-liter V-12 engine is the same as that in BMW’s top-of-the line 760i and 760iL models, with a few exceptions. The intake manifold is changed to handle two different fuel injection systems, with the gasoline injected directly into the cylinders and the hydrogen-air mixture formed in the intake ducts. Plus, engine control management is modified to handle the two very different combustion regimes. This means output is reduced to a maximum 260 horsepower and 287 lbs-ft of torque, the same for both fuels.

That said, 0-60 mph acceleration feels slightly quicker than the 9.5 second time that BMW claims, and the car is more than eager to approach its 143 mph top speed on those blessed blasts of speed-limitless autobahn. Taking full advan­tage of this, our observed fuel economy numbers were a little bit less than the expected 16.9 mpg on gas mode and the equivalent of 17.7 mpg on hydrogen. The solid driving feel was still there, but per­haps a little too solid, with the Hydrogen 7 feeling somewhat heavy through sharp turns and under braking.

While the standard 7-Series is no light­weight, the extra 200 kg that the Hydrogen 7 carries is certainly noticeable. The bulk of that weight gain comes from the mas­sive liquid hydrogen storage tank behind the rear seats that can carry up to 8 kg of liquid hydrogen. In addition to the weight penalty, the tank shifts the rear seats for­ward a bit, cuts trunk space in half, and reduces rearward visibility.

Still, BMW engineers show a rare hint of giddiness when describing the tank. Indeed, double stainless steel walls with a vacuum layer in between are right off a heat transfer specialist’s wish list. The resulting cooling ability is equivalent to 56 feet of Styrofoam insulation, according to BMW.

Unfortunately, since hydrogen is only a liquid at -253oC or below, even this tank is unable to keep it a liquid for very long. If the car isn’t run for 17 hours, boil-off pressure will have built up sufficiently to trigger an automatic system that converts the excess hydrogen gas into water and releases it out a pair of portals near the exhaust pipes. If the car sits for 30 to 40 days, there won’t be enough left to run the car on it.

Refueling, thankfully, is straightforward. Most of it is automated – the computer runs through a series of safety checks first – with the driver left simply to connect the hose. We found the hose a bit unwieldy to handle, and the coupling system a bit frus­trating, but we suspect we’d get used to it with time. The whole affair was over in less than six minutes. Unfortunately, it costs over $80 to fill up the hydrogen tank, even on government-subsidized hydrogen, and the station we refueled at in Berlin is one of only a handful of liquid hydrogen filling stations in the world.

There are inevitable safety concerns with hydrogen but, as is often the case, technology advances faster than safety regulations. BMW is working with international com­mittees to draft uniform safety standards for hydrogen-powered vehicles. In the meantime, the company assures us they’ve taken every precaution. Since the gas is invisible and odorless, a warning system will flash lights and lower the windows if a leak occurs. A portal in the roof will vent the hydrogen in the event of a major storage failure, and the car is also prohibited from parking indoors. Nevertheless, the Hydrogen 7 meets the same stringent safety standards as any production BMW.

For all these challenges, the major ben­efit is that, once the hydrogen is drawn from the tank and burned in the engine, no CO2 is produced. Nitrogen in the air still reacts to form NOx pollutants, but even these are a small fraction of those allowed under the most stringent emis­sions standards in the world. Of course, emissions head back toward conventional levels when running on gasoline, but BMW considers this a short-term sacrifice for practicality’s sake.

In the long-term, BMW sees much room for improvement. Better tank integration from the early design phase, rather than fitting a simple tank design into an existing model as is done here, can save interior space. The weight penalty could potentially be eliminated through the use of lighter materials. Test engines have already shown much better specific output numbers, and efficiency could be much improved with smaller engines utilizing technologies such as forced induction and direct injection. One BMW engineer we spoke with is convinced that a 3-Series sized car with a 310 mile hydrogen range is realistic. Make that happen, and that’s the game, folks.

Of course, we won’t see cars like this in large numbers for some time. BMW’s logical top-down approach to technology integration dictates that buyers at the high­est price points, like the 7-Series, have the easiest time paying the premium for new technology. Furthermore, BMW has identi­fied what it calls an “Eco-Luxury” trend, in which some buyers – in their uncompro­mising demands – are starting to expect environmental awareness as part of the package. BMW is hoping it will appeal to this kind of sensibility with the Hydrogen 7 during its upcoming public roll-out.

Fifty of those aforementioned 100 cars will be offered through cost-free, short-term leases to high-profile figures in en­tertainment, business, politics, and sports in the U.S. starting this year. Shorter test drives and other events will be held for the general public as well. This is not a developmental test: BMW has over 620,000 developmental miles already under its belt, and is pursuing this program as a communication tool to show that hydrogen power, BMW-style, is the real deal.

After driving the car, we have no prob­lem believing BMW’s claim. The biggest hitch facing BMW is not the car itself, but the infrastructure. To be cost-effec­tive and a wise environmental solution, hydrogen ultimately needs to be produced renewably and distributed on a massive scale. The Hydrogen 7 makes one thing clear: should all of this come to pass – and there’s plenty of money and engineering might pushing for it – BMW’s long-held penchant for driving passion won’t get lost in the transition.