The hydrogen age is here. Mankind's search for increasingly environmentally-friendly individual mobility and independence from fossil sources of energy has led to a world-wide search for the fuel of the future. To ensure both environmentally-friendly mobility and a smooth changeover to a long-term, sustained supply of energy, the fuel used must be fully sustainable, that is suitable for ongoing regeneration in a constant cycle. It must also fulfil a whole range of economic, qualitative and quantitative criteria. Researchers and experts around the world have found only one single source of energy able to reach this ideal: hydrogen.

Hydrogen stands out clearly from fossil sources of energy by the simple, but all-important fact that in its recovery and use it can be embedded in a regenerating, natural cycle: Whenever hydrogen is recovered through regenerating sources of energy such as solar, wind and water energy, it is indeed available in unlimited quantities and virtually without the slightest emissions.

BMW was the first car maker in the world to focus consistently on the medium- and long-term development of its cars on the use of hydrogen. And on this basis the Company has developed a logical, all-round concept: BMW CleanEnergy, the BMW Group's Energy Strategy. The long-term objective is to avoid emissions and use energy recovered in a regenerating process.

There are important reasons for this strategy: In July 1998 the Association of the European Automobile Industry (ACEA) made a commitment to the European Union to reduce the CO₂ emissions of all newly registered European cars to an average of 140 g CO₂/km by the year 2008. This equals a reduction in CO₂ emissions by 25 per cent versus 1995 and amounts to average fuel consumption of just 6.0 liters/100 km (47.1 mpg Imp).

A further reduction of CO₂ emissions by 14 per cent from 2008-2012 is also being considered. It is a fact, however, that ACEA's targets going beyond 140 g CO₂/km cannot be achieved by vehicle-related, technical improvements for reducing fuel consumption alone. It also calls for the use of fuel either low in carbon or completely free of carbon. And the long-term solution in this context is hydrogen.

Depending on the type of drive system used, the energy stored in hydrogen can be converted into two forms of energy for driving a car: either through a conventional combustion engine serving to convert this energy directly into drive power or through so-called "cold" combustion in a fuel cell generating electrical energy. BMW uses both of these options, focusing on the combustion engine for the actual process of driving a vehicle. The combustion power unit, given the sum total of its features, still offers the greatest number of benefits. At the same time BMW sees the fuel cell as a source of energy supplying electric power to the on-board network in lieu of a conventional alternator and offering brand-new options in air conditioning the car as well as other comfort functions.

BMW has worked hard for international leadership in hydrogen technology throughout 20 years of research and development. The focus in this process has been not only on engine technology as such, but also on the recovery, storage and transfer of hydrogen into the car itself. Hence, the BMW Group is consistently promoting the introduction of hydrogen as a source of energy, establishing partnerships with other companies in developing components and technologies, and sensitizing both decision-makers in politics and the energy industry to the need to start the actual process of implementation now.

Hydrogen, designated by its chemical symbol H, is the most common and, at the same time, the lightest element in the Universe. Forming part of water and all organic compounds, it is part of the biological cycle and therefore fully compatible with the environment.

Hydrogen can be stored either in gaseous form or as a cryogenic fluid and is relatively easy to transport. A non-toxic color- and odorless gas, hydrogen is combustible and has approximately one-quarter the calorific value of gasoline in its liquid phase (in terms of volume). In terms of weight, on the other hand, liquid hydrogen has almost three times as much energy as gasoline. Combustion of hydrogen generates water (H₂O), but no carbon dioxide (CO₂). And given the sum total of its properties, hydrogen, in the opinion of experts, has the potential to become the fuel of the future.

In nature hydrogen is virtually non-existent in its pure form outside of compounds. It is to be found most frequently in water, in various forms of hydrocarbon, and in other chemical compounds. Therefore it always requiring a conversion process before it can be used for the generation of energy.

Currently more than 600 billion cubic meters of hydrogen is recovered worldwide each year. This hydrogen comes, for example, from the reformation of natural gas, from the production of coke or electrolysis of chlorine alkali, a process which generates hydrogen as a by-product. Annual production of hydrogen in Germany amounts to approximately 30 billion cubic meters.

Half of the hydrogen recovered in this way is required for synthesizing ammonia used for the production of artificial fertilizer and for the synthesis of plastics. A quarter of the ammonia serves for processing petroleum, and the final quarter is used for synthesizing methanol, an alcohol used in the textiles, dye, and plastics industry, and is also applied in a large number of metallurgical production processes.

Hydrogen may be recovered in various ways and through various processes crucial to the overall ecological balance of hydrogen as a fuel.

The processes applied most frequently today use fossil sources of primary energy:

• Reformation of natural gas, liquid gas, and naphta
• Partial oxidation of heavy oil
• Gasification of coal
• Pyrolysis of coal to produce coke
• Reformation of gasoline

None of these processes offers a long-term, sustained alternative: First, they are based on finite raw materials and sources of energy; second, undesired substances such as carbon dioxide are released in the processes involved. Working on behalf of the European Union and the German Federal Government, researchers are examining the options for the so-called sequestration of CO₂. This is the process of separating and retaining this gas, for example in recovering hydrogen from natural gas. For the purpose of long-term storage, the carbon dioxide is pumped into former, now empty deposits of crude oil, natural gas, or coal. Another point being critically debated is the option to deposit such carbon dioxide at the bottom of the sea.

Simple, effective, clean: electrolysis

Electrolysis is the most promising method for recovering hydrogen, using electric power to recover hydrogen from water in virtually unlimited quantities. The principle applied in this case is simple and straightforward: Two electrodes dipped into a water bath are subjected to a flow of direct voltage. The positively charged hydrogen ions (cations) gather in this process around the negative cathode, the oxygen ions (anions) move to the positive anode.

The hydrogen gas generated in this process is retained, as is - where required - the gaseous oxygen. Again, this may be done in various ways:

• through alkalic electrolysis
• through membrane electrolysis
• through alkalic high-pressure electrolysis
• through alkalic high-temperature electrolysis

The highly developed process of alkalic electrolysis is currently the most environmentally-friendly and economical production method among these processes. However, electrolysis makes sense in ecological terms only if the electricity used for the fission of water is obtained from regenerating sources of primary energy.

Free and unlimited: solar energy

Large-scale generation of electric power by way of solar energy, using, the power of the sun to recover hydrogen, is a key factor in finding a global solution for the future. The sun offers the largest potential of renewable energy, transmitting as much energy to the Earth in one hour as mankind consumes worldwide in one year: The solar energy at our disposal each year adds up to approximately 1.1 billion terawatt hours (TWh), roughly 10,000 times the current annual consumption of energy by mankind as a whole.

One way of converting this energy into electric power is through the use of solar cells generating electricity directly in the process of conversion. To try out such scenarios, the BMW Group played an active role from the beginning in the Solar Hydrogen Project in the small Bavarian town of Neunburg vorm Wald. Here, in cooperation with other companies, researchers examined the photovoltaic generation of hydrogen and its use for various purposes.

Judged by the current state of the art, solar power stations with trough-shaped parabolic mirrors are even more interesting in economic terms than photovoltaic conversation facilities. The process applied in this case is to heat oil pumped into a pipe to a temperature of up to 400 °C or 750 °F in the mirror's focal point. This hot oil then serves to evaporate water in a heat exchanger, the steam generated in this way being used in the next step to drive a steam turbine for the production of electric power. Solar-thermal facilities of this kind are already in operation in the Mojave Desert in California where, among others, the Kramer Junction and Harper Lake Solar Power Stations generate environmentally-friendly solar electricity which may also be used for recovering hydrogen.

Here, in the largest solar power complex in the world, 2.3 million square meters of mirrors generate 354 megawatt of electricity - enough energy for approximately 200,000 inhabitants of California. This means that during its overall service life, this solar power plant avoids the emission of 18 million tonnes of CO2 in comparison with facilities running on fossil fuel.

Particularly regions around the 40th latitude are very well suited for solar power plants. But even in Europe solar-thermal plants are seen to have a potential of approximately 1,400 terawatt hours (TWh), equal to almost four million of the solar power plants in California mentioned before. Even photovoltaic technology would be able to generate 600 TWh. The fact nevertheless remains that at least in the mean term wind energy offers the largest energy reserves in Europe not yet tapped, amounting to 1800 TWh offshore and 350 TWh on land. Currently about 60 TWh of electric energy is generated by wind power in Europe, that is roughly 2.4 per cent of the total demand for electricity.

Re-growing raw materials may also be used instead of fossil carbon compounds as input for recovering hydrogen. Using biomass as the source of energy for regenerating hydrogen, the processes applied are unique in two respects: First, they are the only option to recover hydrogen directly from a regenerating source of primary energy. Second, biomass is generally regarded as almost neutral in terms of CO2, since, through photosynthesis, plants take up the same amount of carbon dioxide from the air as they emit themselves when being processed.

Hydrogen can be recovered from biomass either through gasification or fermentation or through other biological processes. For ecological reasons
numerous experts claim that hydrogen should only be recovered from waste biomass, and not from energy-bearing plants. Clearly, this alone applies certain strict limits to the availability of biomass really suitable for practical use.

Studies conducted in the context of the TES Transport Energy Strategy state that in Europe hydrogen recovered from biomass has the potential to substitute approximately 30 per cent of the total amount of fuel generated in conventional processes. The assumption made in this case is that all the biomass available, including the cultivation of energy plants, is used exclusively for the production of fuel for road traffic. But since biomass is also used for stationary purposes in the production of electricity and heat, its real potential for substitution is in the region of 15 per cent. In other words, biomass can make a contribution to the reduction of carbon dioxide emissions, but is far from being able to cater to the actual demand.

Contrary to electrical energy, hydrogen may also be stored in large amounts, generally either in gaseous or liquid form. This provides the option to use electrical energy generated by solar, hydro or wind power for the fission of hydrogen and, going beyond current practice, to subsequently store the hydrogen recovered in this way.

Very large amounts of hydrogen are stored in so called gasometers, medium quantities are kept in gaseous form in pressure tanks at approximately 30 bar. Small amounts, in turn, may be filled into pressure cylinders made of steel or carbon-fiber-reinforced composite materials up to a pressure of 400 bar. New tank systems able to withstand pressure of up to 700 bar are currently being examined.

Hydrogen can be stored in liquid form at a temperature of -253 °C. Since this kind of storage, as opposed to the storage of hydrogen in gaseous form at 700 bar, provides 1.78 more energy density per unit of volume, BMW advocates the use of liquid hydrogen for storage in the vehicle: The more energy one can take along within an existing tank of given capacity, the longer the range of the vehicle. To achieve the same energy density as liquid hydrogen, gaseous hydrogen would have to be compressed and stored at a pressure of 1250 bar.

Another option is to store hydrogen in a so-called hybrid reservoir, where the hydrogen is kept under pressure in metallic powder and then released again as required through the infusion of heat. Hydrid reservoirs are able to take up approximately 2 per cent of their weight in hydrogen, which is not enough for use in a motor vehicle.

One more option being examined is the storage of hydrogen in nano-fiber structures or alanates (= chemical hydrogen compounds). Should these technologies prove viable, they would indeed open up new perspectives for the storage of hydrogen energy.

Transport by pipeline, ships and trucks - already standard practice today

There are already pipeline networks in regions with a high concentration of chemical plants and companies for the long-distance transport of gaseous hydrogen. In principle natural gas pipelines are also quite suitable for this purpose, provided they meet the necessary technical requirements such as ensuring proper sealing without leaks. This is the case throughout most of the European gas pipeline network.

Hydrogen is also well-known in communal use: The city or light gas used in the past was a synthesized gas made up of 50 per cent hydrogen. In many cities this gas was used for purposes such as street lighting until well into the second half of the former century.

Intercontinental transportation of hydrogen is also a routine procedure these days, with the technical solutions required being largely in place. And since liquid hydrogen takes up only about one-tenth of the volume of gas compressed to 30 bar, ships and trucks are designed to carry cryogenic hydrogen. As in the case of nitrogen, oxygen or argon, the tank systems used in this case are high-vacuum-insulated double-jacket tanks.

These facilities allow efficient transportation of hydrogen from its place of production all the way to the car: Immediately after recovery, the gas is cooled to a temperature of -253 °C. From here, ships and tank trucks transport the - now liquid - hydrogen to the filling station, where it is again stored in cryogenic form. Then, at the fuel pump itself, the hydrogen flows into the tank of the car either in liquid form or, after being allowed to warm up, is pumped into a pressurized tank under the pressure required. Both of these processes can be applied at one and the same filling station, meaning that the filling station of the future will be able to offer the motorist not only gasoline and diesel, but also gaseous and liquid hydrogen.

One of the basic prerequisites for the broad-scale introduction of hydrogen as fuel is the availability of a tank-filling system just as easy to use as the system we have today. This applies both to cryogenic, liquid hydrogen and to gaseous hydrogen under high pressure.

The BMW Group advocates the use of liquid hydrogen. The main reason for this decision is that the energy density of liquid hydrogen relative to the tank system is almost twice that of gas compressed to 700 bar, reaching a level of almost 2.5 kilowatt hours per liter.

Cooperating with Magna Steyr in a joint venture, BMW is developing a tank system allowing vehicles to be filled up with liquid hydrogen virtually just as fast, with no loss and no danger of any kind, that is with the same convenience and efficiency as in the case of gasoline or diesel. To offer the customer optimum comfort and convenience, this tank-filling system is already in use at the world's first public "robotized" filling station for liquid hydrogen at Munich Airport. In April 2004 the project partners responsible for installing and operating this filling station were able to look back at five years of experience, so far filling more than 30,000 liters of liquid hydrogen into various vehicles in more than 600 operations.

The procedure applied is very simple and straightforward: Like at every other filling station, cars running on hydrogen drive up to the fuel pump located in the public area of Munich Airport. Then the driver initiates the fully automatic tank-filling process. While the tank is being filled up - this takes roughly as long as a conventional tank-filling process with gasoline or diesel - the driver in theory need not even get out of his car, since he is identified by his tank card or by electronic remote control. Liquid hydrogen at a temperature of -253 °C is subsequently able to "rain" into the tank of his BMW, hydrogen gas in the tank condensing on the droplets via the liquid phase and thus reducing the partial pressure of the hydrogen gas. As a result, absolutely no hydrogen is lost in the process of filling the tank.

In terms of the operations involved, the process of filling the tank manually is again virtually exactly the same as at a conventional filling station. By and large, the system differs only in terms of the pressure- and low temperature-proof connector taking the place of the usual pump nozzle: To fill up the tank, the driver places the connector on the tank filler pipe and locks it in position, enabling the hydrogen to "flow" in.

This process of filling the tank manually is to be studied in a large-scale demonstration project in Berlin, where the first hydrogen tank in Germany integrated in a public filling station will be opened in autumn 2004. And to develop a standardized liquid hydrogen connector suitable for worldwide use on the automobile as soon as possible, the BMW Group and General Motors/Opel established an open consortium in April 2003 together with Linde and Walter.

Crash tests with tanks for liquid hydrogen.

In close cooperation with the TÜV South Germany Technical Inspection Authority, the BMW Group has conducted a comprehensive range of tests examining various accident scenarios and determining how the liquid hydrogen tank behaves in the process. One of the test procedures was to destroy full tanks under high pressure after deliberately blocking their safety valves. The predetermined rupture point inside the tank provided for such an extreme case allows controlled discharge of the hydrogen without any major risks or hazards.

In a further series of tests vehicle tanks filled with liquid hydrogen were subjected to various fire conditions in a special test area: In the process the tanks were surrounded by flames at a temperature of almost 1000 °C or approximately 1850 °F for up to 70 minutes. Again, the tanks did not present any problems, the evaporated hydrogen slowly escaping through the safety valves in a smooth, almost imperceptible flow of gas. In the last series of tests, finally, car tanks containing liquid hydrogen were deformed and seriously damaged by hard, solid objects. None of the tanks exploded.

Thorough and very demanding crash tests were also conducted successfully on the overall vehicle as a complete "system" and are described in greater detail in the Chapter on "How Cars Run on Hydrogen". After these comprehensive examinations, the TÜV Technical Inspection Authority arrived at the conclusion that hydrogen can be used just as safely as gasoline.

Liquid hydrogen is always cryogenic

Liquid hydrogen inside the tank of a car warms up in a "natural" process. The pressure inside the tank thus increases in the course of time until a limit currently set at 5.5 bar, the maximum pressure allowed in a tank for liquid hydrogen. Under higher pressure, gas is able to escape in a controlled process through a spillover valve in a process comparable to the evaporation of gasoline from a conventional car tank when parked in bright sunshine.

Currently it takes about one day for the fuel in a hydrogen tank to reach a pressure of 5 bar with the engine not running. And whenever the car is driven in the meantime, pressure decreases and the loss of hydrogen during extended standstill periods may be avoided altogether.

The BMW Group is the first car maker in the world to start series development of a hydrogen car. In the words of Professor Dr. Burkhard Göschel, Board Member BMW AG for Development and Purchasing, "we will start delivering hydrogen cars to customers during the production cycle of our current BMW 7 Series".

BMW has been examining engines and vehicles for the use of liquid hydrogen since 1978. On 11 May 2000 BMW became the first car maker in the world to present a demonstration fleet of 15 hydrogen-powered sedans, in this case the BMW 750hL. "We believe in the combustion engine, since we are convinced that our customers will demand dynamic performance, superior comfort and a long cruising range also in future", states Professor Göschel. The vehicles run by BMW have proven their qualities in everyday use, covering more than 170,000 kilometers.

In 2001 and 2002 some of these vehicles accompanied the BMW Group's CleanEnergy WorldTour, seeking to create an international awareness for hydrogen technology, its benefits and the tasks still to be handled. Visiting five major world cities, the BMW Group invited representatives of political life, the world of science and the media to attend special events held during the WorldTour. And the positive response shown by this international audience made the CleanEnergy WorldTour a great success.

Dual-mode drive for practical customer benefits

Using current technology, only the combustion engine offers the advantage of being able to drive in a dual mode, that is on both gasoline and hydrogen.

Obviously, this serves to bridge any gaps in supply arising in the process of establishing and building up a network of hydrogen filling stations. The motorist opting for CleanEnergy drive, therefore, is not restricted in any way in his cruising range and the destinations he wishes to reach.

BMW working on series development of the hydrogen car

BMW is the first car maker in the world to start the series development of a car driven by a hydrogen combustion engine. Pointing strongly into the future, this progressive sedan is based on the current BMW 7 Series. Top speed will be 215 km/h (133 mph) plus, the cruising range will be in excess of 200 kilometers or 125 miles on hydrogen and 500 kilometers or 310 miles on gasoline.

BMW presented a trendsetting hydrogen concept engine at the 2003 Frankfurt Motor Show. Displacing 6.0 liters, this V12 engine develops maximum output of more than 170 kW or 231 bhp at 5,500 rpm, with maximum torque of 337 Nm or 248 lb-ft at a low 2,000 rpm.

Significantly, the new hydrogen concept engine is able to run on a stochiometric hydrogen/air mixture (lambda = 1). One of the biggest challenges in making this possible was to avoid anomalies in the combustion process overcome by the use of fully variable double-VANOS and Valvetronic drive.

Intelligent combustion avoiding the formation of nitric oxide

Sophisticated engine technologies are able to avoid the generation of undesired by-products in the combustion process. Above 1700 °C or 3100 °F, nitric oxides (NOx) may be generated in the combustion chamber without hydrogen being involved in the process.

To drastically reduce NOx emissions, BMW's engineers are pursuing a special operating strategy:

As long as the engine is running under part load, load management, as with a diesel engine, is based on the concept of quality control, meaning that the engine is run in the lean mode with an air surplus (lambda > 1.7) and with the generation of NOx emissions being kept to a minimum. As a result, there is no need for any subsequent treatment of exhaust gas.

Whenever the engine is required to develop substantial power, on the other hand, engine load is based on quantity control, like in a gasoline engine: In this case the engine runs on a stochiometric mixture (lambda = 1) which, while generating NOx emissions, remains significantly beneath the SULEV limit through subsequent treatment of exhaust emissions.

Fast electronic engine management and flexible valve control enable the engine to switch from one of these operating modes to the other without virtually any delay.

BMW research engine with potential efficiency of 50 percent

This new hydrogen concept engine does not yet fully exhaust the potential of BMW combustion engines for further development. One additional option, for example, is to boost engine power by a turbocharger when operating with external fuel/air mixture formation. A combination of direct hydrogen injection and turbocharging, in turn, serves to further increase the engine's degree of efficiency while at the same time boosting engine output over that of the hydrogen concept engine, in this way raising the specific output of such a hydrogen engine to the same level as that of a petrol engine. The BMW Group's Research Division is working on a hydrogen engine seeking in the long-term to achieve an effective degree of efficiency of 50 percent with the engine running at its optimum point. This demanding objective is to be reached by optimizing the combustion process and capitalizing in this way on the excellent combustion properties of hydrogen (low degree of activation energy required, high rate of flame propagation).

Further improvements serving the same purpose are the reduction of engine friction, the optimization of ancillary systems as well as the enhancement of overall energy management.

Crash tests with hydrogen cars

Complete cars, not only fuel tanks, must prove their high standard of safety. This is why BMW hydrogen cars are already being examined in the usual crash tests such as the Euro NCAP head-on offset collision at an impact speed of 64 km/h, the standard rear-end collision with 100 and 40 per cent overlap, as well as a side-on collision at the car's most vulnerable point on the filler pipe leading to the fuel tank. And the BMW hydrogen car already meets all of these requirements in full. Indeed, in the words of the TÜV South Germany Technical Inspection Authority, "the hydrogen car is at least as safe as a conventional gasoline-powered car".

Fuel cell APU feeding electric power to the on-board network

The BMW Group's hydrogen concept also involves the use of a fuel cell, the so-called APU Auxiliary Power Unit. In this case, a PEM Polymer Electrolyte Membrane supplies electric power for the on-board network.

While a conventional battery has to be charged by an alternator, this system operates independently of the engine and is fed with energy from the hydrogen tank. Even when the engine is not running the APU allows the driver to use the air conditioning or heating. And an Auxiliary Power Unit not only supplies three times more power than an alternator, but also restricts this supply of power to the actual period of use, meaning that power is only supplied when actually required, whereas with conventional technology the engine drives the alternator all the time.

Applying this saving to conventional gasoline fuel, this means a reduction of fuel consumption by one liter per 100 km in city traffic. And if the coolant pump, oil pumps, brake servo and by-wire applications are also supplied with electric power in this way, a fuel cell is able to reduce fuel consumption to an even greater extent. Last but not least, the "drain" of power from the engine is more than 10 kW lower, this additional power then being available to drive the vehicle.

Molded tank replacing the conventional hydrogen cylinder

So far cylindrical tanks have been used in all cases to store liquid hydrogen, since currently they are the only tank configuration able to meet the great demands made in terms of insulation and safety. But development engineers look optimistically into the future also in the area of tank technology, focusing on molded hydrogen tanks making perfect use of the space available within the body. The objective is to integrate the hydrogen tank perfectly into the vehicle, thus offering the customer the usual space and convenience he wishes to enjoy inside his car.

CleanEnergy Partnership (CEP): Thorough test operation and hydrogen trials in Berlin

To promote hydrogen technology in Germany along straightforward, practical lines, the BMW Group joined forces with Aral, BVG, DaimlerChrysler, Ford, GHW, Linde, Opel, and MAN in June 2002 to form the CleanEnergy Partnership or CEP for short. Established for a project term scheduled up to the year 2007 and with a budget of Euro 33 million, the CEP forms part of the German National Sustainability Strategy and is supported by the German Federal Government. It demonstrates technologies pointing into the future and presents the technical and economic prerequisites for the use of alternative fuel in road traffic.

An elementary point of fundamental significance in this context is to prove the positive effects of a new technology on the environment. This is why hydrogen is to be recovered to the greatest possible extent through regenerating energy, that is mainly with electricity derived from solar energy, hydro or wind power. This means that in practice no undesired emissions are generated from the initial recovery of hydrogen all the way to its final use in the car. BMW is participating in the project through the operation of hydrogen vehicles.

Filling station for fluid and gaseous hydrogen under construction.

One of the key activities of the CEP is to build and operate a hydrogen filling station under regular conditions. Integrated in the everyday operations of a conventional filling station, this hydrogen filling station will be opened in autumn 2004. Apart from gasoline and diesel fuel, customers are able to fill their tank here with two types of hydrogen: compressed gaseous hydrogen (CGH2) and liquid hydrogen (LH2). The BMW Group favors the latter for reasons of handling and the range the car is able to cover.

Gaseous hydrogen produced locally

Gaseous hydrogen is produced locally at the filling station by means of pressure electrolysis virtually free of emissions. This technology has indeed been developed for local production of a hydrogen energy supply with a high degree of purity. The principle applied is simple, water being split under pressure by direct current into its two elements hydrogen and oxygen.

The compact facility used for this purpose is designed for fully automatic, ongoing and safe operation. A particular factor is the direct link established between the production of hydrogen and actual demand at the filling pump, with only as much hydrogen being produced as is actually required. A compressor unit compresses the gaseous hydrogen from approximately 15 to 350 bar, that is the pressure at which hydrogen is filled into the cars. And filling pumps are indeed already prepared for a filling process under a pressure of 700 bar.

Tank trucks delivering liquid hydrogen

Liquid hydrogen is produced at a central location and delivered by tanker trucks. At the filling station the cryogenic hydrogen is stored in a highly insulated double-jacket 10,000-liter reservoir. Since evaporation pressure is reduced every time hydrogen is pumped into a car, the loss of hydrogen and the cooling operations required are kept to a minimum.

This supply of liquid hydrogen also serves as back-up for the supply of gaseous hydrogen: Should the supply of compressed hydrogen run low, liquid hydrogen can be converted into gaseous hydrogen to set off any bottlenecks in the supply process. The filling pumps for liquid hydrogen are equipped with a transfer pump and a cold-draw coupling for rapid tanking. The advantage of such a filling station with liquid hydrogen is that it is able to achieve a potentially greater throughput of energy.

Long-term cooperation: the TES Transport Energy Strategy

No single company will be able to produce hydrogen as the fuel of the future all by itself. Precisely this is why the BMW Group, acting as a pioneer, has initiated various joint ventures: The TES Transport Energy Strategy Project started in May 1998 with the support of the German Federal Government and now comprising Aral/BP, the BMW Group, DaimlerChrysler, MAN, Opel, RWE, Shell, TOTAL and VW.
The objective of this initiative is to develop a common strategy for the introduction of alternative energy and drive systems. Further fundamental goals are to make transport less dependent on petroleum, to preserve finite resources, to further reduce emissions such as CO2, and to expand the initiative to the whole of Europe. These objectives are based on the vision of a crisis-resistant, sustained, environmentally-friendly and resource-preserving supply of energy which, in combination with a new generation of highly efficient vehicles, is intended to pave the way into a more ecologically-minded and economical world of mobility in future.

TES: hydrogen is the most sensible alternative in the long term

The TES initiative has carefully studied and assessed all alternative fuels for their possible potentials. Focusing in the process on more than 80 alternatives, the researchers established beyond doubt that hydrogen is the best solution for the future offering the most powerful potential. The main advantage of hydrogen in political and strategic terms is that the process of regenerating production is very flexible and offers substantial opportunities for the future. In practice this means that both CO2 emissions and supply risks may be considerably reduced in the long term both in mobile and stationary applications. And at the same time hydrogen technology offers a substantial potential for innovative mobile applications, thus opening up new growth opportunities for Germany as a centre of industry.

The Transport Energy Strategy has been successfully presented at numerous international events, international corporations in the energy and car industries joining the TES initiative.

A lot has happened recently also in Europe in developing a fully-fledged hydrogen economy: The new European Hydrogen and Fuel Cell Technology Platform (EHP) held its first General Assembly in Brussels in early 2004, expressing its commitment to the development and application of low-cost, competitive European energy systems based on hydrogen and fuel cell technologies for mobile, portable and stationary applications. In the next 10 years the EU will provide up to Euro 2.8 billion in funds in its quest to initiate a hydrogen economy compatible with the environment.
Specialists of the BMW Group have been appointed to bodies such as the Advisory Council and the Deployment Strategy Panel of the EHP as well as the California Hydrogen Highway Implementation Advisory Panel in order to offer their advice and know-how. This ensures an effective transfer of know-how also on an international level, the BMW Group being able to contribute experience from 25 years of hydrogen research.

BMW CleanEnergy - further partnerships and joint ventures

In the series development of the hydrogen car, the BMW Group is working with a network of partners in industry. Magna Steyr, for example, has already become a highly competent BMW partner in the development and supply of the hydrogen tank.

Within an open Development Consortium, the BMW Group has joined forces with General Motors in the development of a liquid hydrogen tank coupling to be established as a global standard.

This projected liquid hydrogen coupling is based on the Draft Directive of the European Integrated Hydrogen Project (EIHP) serving in turn as the basis for compiling the future ECE Directives for Hydrogen-Drive Vehicles (ECE = Economic Commission of Europe of the United Nations). The actual process of developing the coupling is being conducted with the support of Linde and Walter, two specialist companies in this area.

BMW CleanEnergy Partnership in the U.S.: Controlled Hydrogen Fleet and Infrastructure Demonstration Project

The U. S. Department of Energy has awarded a grant to a partnership, which includes BMW and is led by Air Products and Chemicals, Inc., for a combined research project titled "Controlled Hydrogen Fleet and Infrastructure Demonstration Project". The goal of the project is to study hydrogen as a fuel in real-world driving conditions. This 5-year program will use Federal funds, as well as donations from partnership members, to finance construction and testing of 24 hydrogen filling stations in California. Due to the nature of the project, the stations will vary from using renewable resources such as wind power to using a hydrogen pipeline. Some stations will be fixed; others will be relocatable.

Partnership members Toyota, Honda and Nissan will contribute a total of 65 fuel-cell powered vehicles to the project. BMW, as the leader in hydrogen internal combustion engines will provide up to 15 7 Series cars, the only test vehicles using proven internal-combustion engines.

The 2001/2002 BMW CleanEnergy WorldTours were one of several initiatives taken by the BMW Group to establish a greater acceptance of hydrogen and sensitise the public to this essential issue.

In the "H2 - Mobility of the Future Project", the BMW Group has been offering schools throughout Germany comprehensive learning material on the subject of CleanEnergy since 2001. Intended for lessons in Secondary Stages I and II at Higher and Medium Secondary Schools, this collection of materials comprises not only a special folder for the teacher, but also an interactive CD-ROM. The same material is also available in English and, as "Expert Knowledge on Hydrogen" in Mandarin. Last but not least, there is also a special version of this teaching material for young children at Primary Schools. The material is available from BMW Corporate Communications.

"H2 - Mobility of the Future" as a highlight in school classes

Offering the "H2 - Mobility of the Future" learning package, the BMW Group has taken up requests from many teachers and educators confronted increasingly in their classes with questions regarding alternative energy. This material provides not only a sound foundation for dealing with the subject matter in class, but also for inter-disciplinary lessons promoting action-oriented learning and self-initiative on the part of students.

The material is therefore highly suitable for use not only in classes such as Chemistry, Physics, and Technology, but also in subjects such as Geography, Social Science and Economics, where the issue of intelligent and sustained energy supply in future is also of great significance.

The teaching material follows an overriding, interdisciplinary perspective in focusing on the general subject of hydrogen. Particular highlights are the significance of mobility and energy, the reasons for climate problems, regenerating recovery of energy, hydrogen as a source of energy in future in both mobile and stationary applications, and the general topic of switching over to a hydrogen economy.

BMW CleanEnergy in the Transport Centre of "Deutsches Museum" in Munich

In its function as a founding member, the BMW Group offers information on hydrogen mobility of the future in the Transport Centre of "Deutsches Museum" in Munich: Ever since spring 2003, the BMW CleanEnergy Project has been showing how hydrogen paves the way into mobility in future. In an entertaining presentation, visitors to the Transport Centre are made acquainted with the recovery, distribution, storage and use of hydrogen. Interactive exhibits show how electricity gained from renewable energy serves to split water and generate hydrogen gas. The filling station of the future, in turn, demonstrates how cryogenic fuel is pumped into the tank of a car. And naturally the "heart" of the whole concept is also presented at the Museum, a prototype of the world's first hydrogen production car, the BMW 7 Series.

A touchscreen enables the visitor to get acquainted with the technical highlights of the hydrogen car in greater detail, focusing on the engine, the tank and the supply lines all the way to the exhaust system. The range of teaching material is supplemented by the H2 laboratory even accessible from the internet, together with films and graphics. All this gives the observer a good idea of the many benefits of hydrogen and heightens awareness of the steps still to be taken by society to make the fuel of the future reality in our world.

BMW CleanEnergy Projects in China

An Information Manual in Mandarin bearing the title "Expert Knowledge on Hydrogen" has been available to universities in China since April 2004. A BMW CleanEnergy internet portal in Chinese also ensures that this information material is accessible throughout the entire country. This information campaign is part of the BMW CleanEnergy Project in China, with the BMW Group planning a wide range of activities in order to promote the introduction of hydrogen as the ideal source of energy in future in one of the world's largest economies. Accordingly, BMW experts are cooperating with German and Chinese partners in studying ways and means for implementing a hydrogen infrastructure in China.
BMW CleanEnergy Exhibition at the Beijing Science & Technology Museum.

In cooperation with the Beijing Science & Technology Museum, the BMW Group has organized a BMW CleanEnergy Exhibition in the process of enhancing public knowledge in this area. In its concept, the Exhibition follows the approach the BMW Group has already taken at "Deutsches Museum" in Munich, presenting the complete hydrogen cycle ranging from the initial production and distribution of hydrogen all the way to the process of filling the tank and actually using hydrogen in the car.

The bottom line: hydrogen already widely accepted as a source of energy

To ensure successful introduction of hydrogen cars on a broad scale, hydrogen must be accepted by society as the fuel of the future. This is why the Institute for Mobility Research in Berlin has examined the attitude of the population in a comprehensive study, arriving at the conclusion as early as in the late '90s that hydrogen is already widely accepted.

The fact remains, however, that knowledge on hydrogen is still limited, particularly young people knowing rather little about the many ways of using hydrogen. Precisely here, therefore, the teaching material provided by the BMW Group makes an important contribution.

A survey has shown that the image of hydrogen crucial to its acceptance is largely neutral: Although respondents subjectively believe that hydrogen involves greater risks in the operation of a vehicle than gasoline and diesel, they agree that hydrogen should replace conventional fuel in future. The introduction of hydrogen powering an all-round or high-tech vehicle would therefore speed up the process of acceptance. And the benefits of hydrogen technology in terms of society and personal use are seen above all in the area of environmental protection.

Pursuing the BMW Group's energy strategy, BMW researchers and engineers have focused not only on the hydrogen combustion engine, but also on other alternative drive concepts, developing promising technologies in the process.

Hybrid drive

Hybrid drive seeks to set off the weaknesses of individual systems and add up various strengths by pooling different technologies. With this in mind, BMW took a significant step in this direction in 2003, integrating an electric motor in a BMW X5 Experimental Vehicle between the combustion engine and the transmission in order to support the conventional drive system in the process of acceleration. High-performance capacitors serve in this case to provide the energy required.

This Experimental Vehicle not only showed a standard of response never seen before as well as an increase in torque to 1,000 Nm or 737 lb-ft at low speeds, but also enabled the vehicle to reduce fuel consumption by up to 15 per cent in the usual test drive cycle.

A concept imaginable in future is to install a compact "active transmission" integrating both the electric motor and the power electronics into the transmission and thus significantly reducing both the additional weight and the space required for the system. High-performance capacitors in the door-sills could provide a further benefit, offering far higher charge and discharge rates than a battery system. And last but not least, electrical intervention in the drivetrain might serve to optimize driving conditions in, say, stop-and-go traffic or when accelerating.

In the serial hybrid system the combustion engine, alternator, electricity reservoir and the electric motor connected to the drivetrain all operate in series following the flow of energy. This provides the option to optimize the combustion engine for operating conditions with the highest degree of efficiency, the engine starting only when the battery is not able to provide the amount of energy currently required.

The challenge facing the engineer is to keep the space required and the extra weight - both of which are greater mostly due to the additional battery - within reasonable limits. A further factor is that such a vehicle requires two drivetrains at least in part. And last but not least, complex interaction of the two sub-systems presents greater demands in the management and development of the vehicle as such.

Hence, there are two crucial arguments against hybrid drive: As an add-on solution it makes the vehicle not only heavier but also more expensive.
All concepts for intelligent electrification are therefore nothing but a supplementary solution in the ongoing development of the combustion engine.

Electric drive

Electric drive is among the oldest alternative drive concept. It is free of gaseous exhaust emissions and is acknowledged as the most environmentally- friendly drive technology. But this is only the case if the electricity used is generated in a fully ecological process.

The BMW Group introduced an innovative concept for electric drive vehicles in the guise of the E1 as early as in 1991. In terms of its size and range, such a vehicle is suited above all for use in cities and densely populated areas where the inherent disadvantages of the electric motor are less significant:

Unlike the combustion engine, the electric motor develops maximum power at low speeds, while at the usual speeds on the motorway it is far less dynamic and agile than a combustion engine.

Ongoing development of the electric car is moreover linked inseparably to battery performance and efficiency. And it is a fact that battery systems are still quite inadequate in meeting the requirements made by a road vehicle in practical use. The conflict of interests between energy and power density, for example, remains unsolved to this day. While a high-temperature battery is able to store three times as much energy on the same weight as a lead battery, it does not provide the same power output as, say, a nickel metal-hydride battery. To cover a range of 200 kilometers or 125 miles, a battery would have to weigh approximately 500 kilograms.

Yet a further drawback is the battery's inadequate rapid-charging capacity, meaning that "filling up the tank" would take the whole night. And the fuel cell serving as a chemical battery still calls for great concessions in terms of both weight and cost.

Natural gas drive

Natural gas consists mainly of methane (CH4) and is very similar to hydrogen in its properties relevant to the vehicle. In comparison with a vehicle running on gasoline, the combustion of natural gas in the engine reduces the generation of carbon dioxide (CO2) by approximately 20 per cent. But since the process of conditioning and distributing natural gas from the well to the filling station involves higher CO2 emissions than the conventional provision and distribution of gasoline or diesel, the actual reduction of CO2 in practice is only about 10-15 per cent versus a vehicle running on gasoline.

Starting in 1995, the BMW Group became the first European car maker to offer series production cars with natural gas drive able to run in a dual mode either on natural gas or gasoline. Indeed, the BMW 316 g running on compressed natural gas was one of the cleanest cars in the world, right from the start fulfilling the strictest emission limits coming into force in California in 2003.

Knowledge gained in the project nevertheless showed that natural gas drive lacks the appropriate long-term perspective: A vehicle running on natural gas still emits sizable amounts of carbon dioxide. A further point is that natural gas is a fossil source of energy subject to finite supply. And the need to establish a natural gas infrastructure complete with filling stations would make this an unfeasible alternative en route to hydrogen technology. With the market acceptance of the natural gas car also being limited, the BMW Group has decided to discontinue its production of natural gas cars, taking the direct step into the world of hydrogen instead.

Accordingly, the BMW Group is continuing this approach through the series development of the hydrogen car with a combustion engine and its consistent commitment to hydrogen as a sustainable source of energy for the future.