TodayApril 17, 2022

The challenges of hydrogen in the BMW 7-Series

BMW Hydrogen Symposium in Berlin, Germany

The challenges of hydrogen in the BMW brand. BMW talks about the specifications of its hydrogen, at the BMW Hydrogen Symposium in Berlin, Germany. We’re in Berlin, Germany, driving the hydrogen 7-series internal combustion engine.

Munich, Germany, May 11th, 2000… BMW presented the world’s first production-based hydrogen car in Berlin, the BMW 750hL. The luxurious sedans will be used as shuttles for the entire duration of the EXPO 2000. These vehicles are built on the same production line in Dingolfing as normal production 7 Series. They will demonstrate to all who experience them that they meet the very highest requirements for comfort, dynamics, and utility value at market-appropriate costs. “And we will be the first automobile manufacturer in the world to offer series production hydrogen cars,” says Dr. Burkhard Göschel, Development Director of the BMW Group.

Thousands of Hydrogen Cars and Adequate Infrastructure by 2010

Dr. Burkhard Göschel: “Our vision is to have a hydrogen fuel station available in the vicinity of the branches of the BMW Group in Germany by the 11th of May 2005.” BMW offers international energy companies close cooperation for the development of a hydrogen fuel station network: “Our aim is to have a sufficient network of hydrogen fuel stations all over Europe by the year 2010,” says the development chief. By then BMW has planned to have sold several thousand hydrogen cars. The prices for the cars and for the fuel are to be similar to those of conventional cars and fuels.

750hL: A Hydrogen Sedan For Everyday Use

The hydrogen technology used in the 12-cylinder sedans has already advanced so far that it permits realistic planning for large series production. BMW has extended its leading position in the development of the CleanEnergy car. CleanEnergy is the generic term for the ecologically ideal, closed energy cycle based on water.

Running on hydrogen, the 12-cylinder engine delivers 204-horsepower and accelerates from standstill to 100 km/h in 9.6 seconds while achieving a top speed of 226 km/h. Fitted with the 140 liter Cryo fuel tank, the fully equipped 7 Series has an additional range of 350 kilometers. The car features a conventional fuel supply too since the availability of hydrogen fuel is limited. After the EXPO in Hanover is over, the sedans will drive back to Munich on their own power using conventional fuel.

The engine itself differs mainly only with regard to the intake duct with additional injection valves for the hydrogen. The production of the 750hL was incorporated as much as possible into the normal production process. The 12-cylinder engines were integrated into production in the Dingolfing plant and assembled together with the conventional spark-ignition and diesel engines.

The hydrogen is stored cryogenically – i.e. in super-chilled and liquid form – at a temperature of around minus 250 degrees Celsius in a double-walled steel tank behind the rear seat-backs. Two safety valves ensure controlled ventilation in the case of excess pressure. They are also part of the comprehensive safety concept which proved its reliability in numerous crash tests. Even in a massive rear-end collision in which the tank would be affected in its protected area, the steel cylinder with its double two-millimeter thick walls did not leak. Even greater deformations that might cause a leak in the tank, would not cause it to explode. For an explosion to occur, hydrogen and air would have to mix but due to the higher inner pressure of the hydrogen, air cannot enter the tank.

The First Production-Based Cars With Fuel Cell

A number of the BMW hydrogen sedans are the first production-based cars to feature a fuel cell for supplying onboard electricity. This “electrochemical” the battery takes on the function it does best: the production of electricity with a very high degree of efficiency of up to 50 percent. The compact fuel cell battery in the 7 Series with hydrogen drive is only as big as a conventional lead-acid battery. However, the five-kilowatt unit outperforms the best of these by far. The so-called fuel cell APU (Auxiliary Power Unit) not only takes on the supply of all conventional electric components but also allows for new functions. The trailblazing 7 Series model features stationary air conditioning which cools the interior even if the engine is turned off.

Pioneering Service Concept: Permanent Checking Function via Radiotelematics

Like the Formula 1 racing cars, all 750hLs are radio-linked to the service computer in the development workshop in Munich – 24 hours a day. This enables the monitoring of all systems continually and facilitates reacting instantly to any situation. Not only is all of the hydrogen data transmitted and checked, but all the data processed by the standard bus system in the 7 Series, as well. “The workshop knows that something is wrong before the driver does”, explains Klaus Pehr, the BMW engineer responsible for hydrogen cars. The insights gained are incorporated into the on-going improvement of the hydrogen fleet. By means of a rotating deployment plan for the environment-friendly 7 Series, all cars are brought up-to-date as quickly as possible. After the world exhibition is over on October 31st, all vehicles will have received the latest developments.

The telematic checking system has already proved its usefulness in the development stage. Thanks to this system, the car check conducted every evening in Hanover is reduced to a short operation in the branch where mainly only the sensors have to be calibrated. There the 750hLs are also refueled with hydrogen using a so-called mobile “Cryo-Can”.

Hydrogen Engines: Lean-Burning Mixtures Prevent Emissions

Since the end of the seventies, BMW has been dealing with the topic of hydrogen drive. Five generations of hydrogen cars have hit the road, each based on the BMW 7 Series of the time. Today too, the basic engine is a series-production engine, but the hydrogen drive calls for some changes ranging from the fuel system to the mixture formation process. An electronic mixture formation system has been developed which precisely matches hydrogen injection and charge changes. Combustion generally takes place with an excess of air. The additional air in the combustion chamber absorbs heat and reduces the flame temperature to below the critical level above which the mixture could ignite by itself. At the same time, the low combustion temperature also prevents the production of nitric oxides (NOx), which have to be detoxified by catalytic converters in petrol-engine cars. So even without additional exhaust emissions treatment, the BMW hydrogen engines operate almost entirely without emissions. This environment-friendly engine layout leads to a reduction in specific output. However, this can be compensated for by means such as increasing the displacement. Engines designed solely for hydrogen operation do not have to make this compromise and are at least on par with spark-ignition or diesel engines as far as specific output is concerned.

Refueling In Only Three Minutes

A further prerequisite for the introduction of hydrogen as a fuel is a filling system which must be no more complicated than filling a car today. The low temperature of minus 250 degrees Celsius requires special refueling technology.

In cooperation with its project partners, BMW has developed a fueling system that can be used to fill vehicles with hydrogen as quickly, loss-free and safely as with conventional fuels. The latest version of this technology is currently being used by the world’s first public robotic fuel station for liquid hydrogen at the Munich airport. The fully automatic hydrogen fueling operation takes less than three minutes and is a simple process for the layman.

BMW Promotes Solar Electricity For Generating Hydrogen

Hydrogen can only be a sensible alternative to conventional fuels if the electricity needed for generating it from water can be produced with renewable energy sources. This can, for example, be achieved by means of solar cells which produce electricity directly. Solar powerplants with groove-shaped parabolic mirrors, which operate on the principle of the steam turbine, are a promising alternative. Such a system is already in operation in the California Mojave desert. In order to test such scenarios, BMW has joined the solar hydrogen project in Neunburg vom Wald at an early stage, where the photovoltaic generation of hydrogen and its use for different purposes was studied. The aim is to produce sufficient amounts of hydrogen economically using solar energy.

BMW Supports Practice-Oriented Hydrogen Initiatives

BMW supports initiatives at all levels that help to create the necessary conditions for the introduction of hydrogen-powered cars. The “European Integrated Hydrogen Project” for example aims at harmonizing hydrogen-relevant regulations internationally. The goal is to provide lawmakers with a sound basis for making decisions. Concepts for standardizing infrastructure and vehicle components are being developed.

BMW has joined together with nine partners from the world of business and research for this purpose. Work is running on two tracks: a top-down process will analyze already existing hydrogen relevant laws in Europe. On this basis suggestions for Europe-wide standardization are to be worked out. The bottom-up analysis examines existing vehicles and infrastructures to identify safety-relevant aspects. They will then be used as a basis for discussions with the authorities. With this project, BMW aims to bring about general licensing for hydrogen-powered vehicles.

HYFORUM 2000: To Strengthen International Alliance For Hydrogen

In addition, BMW has been very active in bringing about the international hydrogen conference HYFORUM 2000 which will take place in Munich in September 2000. It is purposefully aimed at high-ranking decision-makers from industry, finance, insurance, and politics. Its goal is to bring together important partners and to direct their attention to the topic of hydrogen as an energy source. Wide-ranging cooperation is now called for in order to pave the way for hydrogen to move from research to application. To achieve this, not only are technical decisions needed but political decisions as well. It is expected that the HYFORUM 2000 will produce answers to the energy question in the 21st century. As an international forum, HYFORUM 2000 will send out signals to the entire world.

Lou Ann Hammond

Lou Ann Hammond is the CEO of Carlist and Driving the Nation. She is the co-host of Real Wheels Washington Post carchat every Friday morning and is the Automotive, energy correspondent for The John Batchelor Show and a Contributor to Automotive Electronics magazine headquartered in Korea. Hammond is a founding member of the Women's World Car of the Year #WWCOTY, and board member of the Women in Automotive.

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