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BMW Announces Market Introduction of the BMW Hydrogen 7

BMW Hydrogen 7.

BMW today announced the market introduction of its 7 Series dual-fuel hydrogen combustion engine luxury sedan, the BMW Hydrogen 7. (Earlier post.) BMW will build the car in a limited series and deploy it to selected users in the US and other countries in 2007.

Fueled by liquid hydrogen, the BMW Hydrogen 7 is equipped with a 260 hp (191 kW) 12-cylinder engine and accelerates from 0-62 mph in 9.5 seconds. Top speed is limited electronically to 143 mph (230 kph). The BMW Hydrogen 7 features a dual-mode power unit—controlled at the touch of a button—that can switch from hydrogen to conventional premium gasoline. Engine power and torque remain the same regardless of mode.

The BMW Hydrogen 7 has successfully completed the entire Product Development Process (PDP) obligatory for all new BMWs. In this process, all components of the new technology were integrated into the overall vehicle according to the same criteria applied to standard production cars. The new hydrogen model is built at BMW’s Dingolfing Plant parallel to the other models in the BMW 7, 6 and 5 Series, with the drive unit in BMW Hydrogen 7 coming like all BMW twelve-cylinders from the engine production plant in Munich.

Current status in terms of weight, volume and cost of various hydrogen storage technologies. Targets are those set by DOE. Click to enlarge. Source: DOE

Fuel and storage. BMW Group has given preference to the use of liquid hydrogen as the appropriate source of energy for the automobile. Compared with gaseous compressed hydrogen, liquid cryogenic hydrogen offers higher gravimetric and volumetric densities (see chart at right).

Compared to gaseous hydrogen compressed to 700 bar in a tank of the same size, liquid hydrogen offers 75% more energy—and therefore a longer cruising range. Liquid hydrogen storage also offers a lower cost per unit of energy stored.

If one of the two types of fuel is fully consumed, the system automatically switches over to the other type of fuel. The cruising range in the hydrogen mode is more than 125 miles (200 km), with another 300 miles (500 km) available in the gasoline mode.

The Hydrogen 7 comes with both a conventional 74-liter (19.5-gallon US) gasoline tank and an additional fuel tank for liquid hydrogen that holds approximately 8 kilos or 17.6 lb of liquid hydrogen.

Cutaway view of the LH tank, with the insulating layers visible between the two walls.

The hydrogen tank is made up of a double-wall tank structure consisting of two-millimeter-thick stainless steel plates and featuring a 30-millimeter-thick vacuum super-insulation layer between the inner and outer tank. This configuration reduces heat transfer to a minimum, the interim layer offering the same insulating effect as approximately 17 metres or 56 feet of styropor. The connection pieces between the inner and outer tanks are made of carbon-fibre bands minimizing the conduction of heat.

BMW uses an analogy to convey the temperature consistency: if a tank of this kind were filled, with boiling coffee, the coffee would remain hot for more than 80 days before cooling down to a temperature suitable for drinking.

The tank insulation keeps liquid hydrogen at a pressure of 3-5 bar and at a consistent temperature of approximately -250° C over a long period. Boil-off management limits the inner pressure within the tank caused by any increase in temperature, and ensures a controlled purge of evaporated hydrogen.

Gaseous hydrogen able to escape in this way is diluted in a venturi pipe and oxidated in a catalyst to form vapor. The period in which a half-full hydrogen tank will be emptied completely in a controlled process is about 9 days, and even then the car is still able to cover approximately 12 miles (20 kilometers) in the hydrogen mode with the fuel remaining in the tank.

To fuel the engine, liquid hydrogen is evaporated in a specific, controlled process within the tank, building up a gas “cushion” under defined pressure. Gaseous hydrogen extracted from the tank uses heat from the engine’s coolant circuit to be warmed up for the subsequent fuel mixing process. This heat is generated by a system of two interacting heat exchangers. The heat exchanger in the secondary system capsule (SSC) receives its heat from the engine’s cooling circuit and delivers this heat, first, via the second heat exchanger to the hydrogen tank and, second, to the hydrogen itself warmed up for the subsequent fuel mixing process.

Engine and Emissions. The 6.0-liter Hydrogen 7 engine is based on the 12-cylinder unit carried over from the 760i. Maximum torque is 390 Nm (287 lb-ft) at an engine speed of 4,300 rpm.

The hydrogen engine uses fully variable VALVETRONIC valve management and variable double-VANOS camshaft control. Gasoline is supplied through direct injection and hydrogen is delivered with a hydrogen supply pipe integrated in the engine’s intake system.

Under full load the power unit in BMW Hydrogen 7 runs under stochiometric conditions: a complete balance of oxygen and hydrogen (lambda = 1). This mixture ratio also provides the highest level of performance and output on low emissions in the hydrogen mode.

Although unlike fossil fuels, the combustion of hydrogen generates neither hydrocarbons (HC) nor carbon monoxide (CO), it does produce NOx at high combustion temperatures. To reduce NOx the Hydrogen 7’s engine runs with a lean burn under partial load (lambda > 2). The lean burn keeps temperatures in the combustion process are relatively low, keeping NOX emissions to a minimum.

Such a lean burn mode can be maintained throughout a particularly wide range of operation in the engine control map. And since hydrogen offers particularly broad ignition limits and burns at a fast rate, only a small amount of fuel is required in the mixture to generate a high level of efficiency, according to BMW.

As the engine moves to a richer burn to boost engine output (reaching a max of lambda = 1), the engine management system helps to reduce the engine-out NOx. Remaining NOx is handled by a regular three-way catalyst.


fyi CO2

Any indication on MSRP?
How bad is the MPG running on petrol?


A six litre engine and 0-100 km/h in 9.5 seconds. That will not be very appealing to potential buyers.


If they had made this a PHEV instead by ditching the hyrogen storage tank etc and just putting in a LiIon battery and motor, they'd get...

1) Far better economy
2) Far lower per mile running costs
3) Lower production costs
4) Lower overall CO2
5) Regenerative braking benefits
6) A technology they can easily adapt to every car in the range
7) More interior / boot space

and finally....

Blistering performance, which is what they claim they are always aiming for. What's going on?


Wow, close to 15mpg on gasoline with only 260hp output on premium. That is just awful (even if the car does weigh around 4500lbs). I hope the hydrogen refilling stations are fully automated because you will NEVER get me to mess with liquid hydrogen out in the open. Then again I'm not in the target income bracket for a 7 series.

They could have used a 6-cylinder valvetronic direct injection engine and achieved better gas mileage & power than the 12 cylinder they used.

That would be an awesome cooler for the beers though! You could go camping all week long with just a single pack of ice.

Sid Hoffman

I suspect this technology will never fly. They wait until near the end of the article to admit that the tank will empty itself from half-full in just 9 days and don't even let you know what happens if you top it off. I suspect that it's even worse when the tank is full. Probably only 4 days to self-vent from full to half full. If this estimate proves accurate, this means a full tank of hydrogen would self-empty in around two weeks, which is terrible.

fyi CO2

This is a very high profile, low results oriented program that sugar coats BMW and their chosen few Hydrogen 7 drivers so that they appear to be promoting ICE alternatives.


I'm sure this is a technological tour-de-force, but to what end? Zero HC and CO emissions at point of use (when burning H2) is nice, but when you take a whole-systems view of the car and supporting infrastructure it comes across as very expensive and impractical (your fuel investment disappears in a few days while you're parked??). I'd love to see a well-to-wheels analysis of the efficiency of this thing in real-world use.

Looks like a case of engineering tunnel-vision to me.


What a sad, sad shame ...

Ron Fischer

This BMW is shamed by comparison to the new high-end Lexus hybrid. Liquid hydrogen? Complex hydrides? 9 days to lose a full tank of fuel? I suppose this evaporation rate takes 'planned obsolesence' into a new realm.

John McConnell

It's so nice to see that this site has intelligent people who aren't brainwashed into thinking this is a good idea!! I mean really, give me a break -- it's creating a complicated solution to a simple problem. We need to take all the money being put in to hydrogen and move it toward creating increased battery storage for electric cars, with PHEV as an interim vehicle until we get to electric cars that go FURTHER than cars do now without being recharged.

Harvey D.

Well said John McConnell. It seems that BMW is not looking for the obvious solution, PHEVs as a primary stepto EVs.

Bob Tasa

>Blistering performance, which is what they claim they >are always aiming for. What's going on?

OK here comes conspiracy theory because I dont understand this choice either. Hydrogen is not something the common person can generate or afford to produce. So, if you wanted a fuel that could be controlled with parts that had to be special, what kind of a car would you make? Electric (whose parts are are easily duplicated and interchangable) or Hydrogen?

I normally dont get into conspiracy stuff but the lack of effort GM and others have put into Hydrogen makes no sense with LiIon. A new LiIon car with a 200 mile range would be good enough for most people.

So thats my thought on why Hydrogen.
Yeah nuts I know.

Bike Commuter Dude

Hypothetical scenario:

The world wakes up to climate change and fossil fuel depletion. They switch to EVs in droves. Petrochemical companies are forced to alter their business strategies to survive.

Eve wants to drive her new EV from here home in San Fransisco, to her parents house in Denver. She will charge her car before hand, and deplete it's charge in approximately 300 miles (I'm optimistic in this future that batteries shall have advanced). She will then be forced to wait whilst her battery recharges for a few hours (even with future-tech LiIon batteries). Or, alternately, she could use a chemical energy carrier (hydrogen) to "recharge" her battery using the onboard fuel cell, PEM or otherwise.

The energy from the fuel cell charges the battery, which in turn powers the electric drivetrain, moving the vehicle. The fuel cell could operate at a constant rate, constantly maintaining the batteries charge. Current hybrid technology would then flesh out the rest of the electrical system.

I believe the automobile industry is at a crossroad. They are moving toward a hydrogen economy. Would any huge multinational company throw millions of dollars into research and development of a technology, if they didn't honestly think it would benefit them in some way?


By the way, do you know that 8 kilograms liquid hydrogen take 113 liters of volume (or 30 US gallons, for the international units challenged) ? So if the "cruising range" (no acceleration ?) is 200 km / 125 miles, that means 56,5 liters for 100 km, or 4.2 miles per US gallon of liquid hydrogen... funny, eh ?

But wait a minute : energy density is not the same for gasoline and liquid hydrogen, of course. So let's give the equivalent volume of gasoline that contains the same energy : 56,5 liters translate into roughly 15 liters gasoline, and that corresponds to a whopping 16 MPG on the gasoline EPA scale.

Another great idea like this, BMW ? You really want to compete with the Big Three ? You can relax, you're already far ahead in the race.


BMW claims to provide the "Ultimate Driving Machine" not the ultimate drag racer so handling is just as important to them (they tout their 50/50 weight distribution more then they do the power of their engines in many cases).

Bike Commuter dude:
Lets say she travels 300 miles at 75mph (quite fast and faster than the speed limits in many if not most states). That gives that she just drove for four it that hard to believe that she would be ready for lunch and a short break that could total 1 to 1.5 hours of charging time? "Future-tech" batteries could well charge in 1-1.5 hours given a 220V source.

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