DaimlerChrysler Readying 2nd-Generation F-Cell Test Vehicle; Targeting 2012-2015 for Commercial Intro
|The second-generation B-Class F-Cell.|
DaimlerChrysler estimates that the marketing of hydrogen fuel-cell drive systems will begin sometime between 2012 and 2015, according to a recent fuel-cell workshop held by the company in Germany.
DaimlerChrysler is thus readying its second-generation of F-Cell B-Class fuel-cell test vehicles—announced last year (earlier post)—with an eye toward the beginning of series production with that marketing timeframe in mind.
A total of 60 DaimlerChrysler A-Class vehicles with fuel-cell powertrains are currently in use worldwide, being driven by various customers at six locations in Europe, Asia and the United States.
Representing the largest fuel-cell fleet test to date, all relevant measured values are sent on a daily basis via radio and the Internet to the DaimlerChrysler researchers and developers in Nabern and Ulm.
|The F600 HYGENIUS|
Compared to the current A-Class F-Cell, the second-generation B-Class F-Cell vehicles feature a number of improvements that are essential in order to bring the technology further toward the series-production stage and which have been installed as prototypes in the F 600 HYGENIUS research vehicle. (Earlier post.)
The most important innovations in the fuel cell drive for the F 600 HYGENIUS include:
A newly developed fuel tank that stores hydrogen at 700 bar rather than the previous 350 bar, thereby enabling the vehicle to hold four kilograms of hydrogen and travel a distance of more than 400 kilometers on one tank.
A new membrane technology for the fuel cells and a new humidification system consisting of hollow fibers. Both of these innovations allow for precise heat and water management, which means that water in liquid form no longer collects in the stack. Such water accumulations freeze in the winter and make cold starts difficult. However, the F 600 HYGENIUS starts easily even at temperatures as low as minus 25 degrees Celsius.
A new electric drive unit on the rear axle in the form of a permanently excited synchronous motor that is both smaller and more powerful than its predecessor from the F-Cell.
A lithium-ion battery that produces 30 kilowatts of power in continuous operation and 55 kilowatts at peak loads—twice the output of the nickel metal hydride batteries previously used.
New bipolar plates that are no longer made of graphite but instead consist of metal foils only 0.15 millimeters thick. The metal improves the conductivity and robustness of the fuel cells, and the thinner foils make the stack around 40% smaller than before.
A new electric turbocharger that supplies air (oxygen) to the fuel cells. This turbocharger is three times smaller and seven times lighter than the previously used screw-type compressor.
Together with other innovations, the new technology package is responsible for the improved fuel economy of the F 600 HYGENIUS, which consumes the energy equivalent of only 2.9 liters of diesel fuel per 100 kilometers. The research vehicle’s fuel cell system operates efficiently—in the partial load range, it has an efficiency rating of 60%, according to DaimlerChrysler.
A further goal of the F 600 HYGENIUS test drives is to develop an optimal operating strategy for future B-Class F-Cell vehicles. Questions explored in this research include:
Would it make sense to operate the vehicle only with the stack or only with the high-voltage battery?
Under what conditions and performance demands should the booster function be activated, whereby energy for the electric motor is supplied by both the fuel cell and the battery?
What are the best situations and points in time to shift the vehicle from one mode to the other?
In which charge stage and driving situation should the motor be used as a generator and the battery be recharged?
The stack that will be used in the B-Class F Cell and—as a double pack—in the successor model to the Citaro fuel cell bus will include a series of innovations from the F 600 HYGENIUS.
The most important technological innovations that DaimlerChrysler will take from the F 600 HYGENIUS are:
The 700-bar tanks for storing hydrogen, in order to increase the full-tank range from today’s 160 kilometers to more than 400 kilometers (249 miles).
The electric drive motor. This permanently energized synchronous motor, which stands out through its light and compact design, has a maximum power output of 85 kilowatts and achieves a maximum torque of 350 Nm.
The lithium-ion battery.
The technically simplified humidification and de-humidification system consisting of hollow fiber modules that lends second-generation stacks freeze-start capability.
The all-new fuel cell stack for the B Class F Cell also generates 40% more output and has a higher power/weight ratio.
Two other innovations from the F 600 HYGENIUS will be gradually introduced to new fuel cell fleets. First of all, the bipolar plates in the fuel cells will be made of metal foils in the future, allowing for more space-saving installation than today’s graphite plates. Secondly, a light electric compressor—rather than the heavy screw-type compressor—will be used to supply air to the stacks.
DaimlerChrysler’s H2 argument. DaimlerChrysler defined three objectives for ”sustainable mobility”:
Maximum efficiency and thus minimal energy consumption by vehicle drive systems;
Diversification of primary energy sources used for transport applications and a greater share of fuels from renewable sources in the energy mix; and
Further emission reductions (in view of the effect of greenhouse gases as well), leading to the long-term goals of zero emissions and complete CO2 neutrality.
Hydrogen has proved to be the ideal secondary energy source for achieving the above-mentioned objectives. That’s because when hydrogen is used as fuel for fuel-cell vehicles, it leads to energy efficiency in the resulting drive system that is nearly twice as high as that achieved by the most modern gasoline and diesel engines. Such fuel cell powertrains therefore offer tremendous gains in efficiency that cannot be achieved even with improved concepts for combustion engines, which DaimlerChrysler is also working on.
Even if the primary energy source and the process used to produce the hydrogen are taken into consideration, fuel-cell drives are still superior to all combustion engine concepts when it comes to emissions as well. Fuel-cell vehicles that run on pressurized hydrogen are by their very nature always zero-emission when in motion. If the hydrogen is obtained from a renewable energy source, the entire utilization chain is also free of emissions.
Petroleum’s nearly complete dominance as the primary energy source for today’s motor-vehicle fuels cannot be maintained over the long term. There are several reasons for this, including the finite nature of this fossil resource, its very high price at present (which is not expected to decrease significantly), and the fact that much of the world’s crude oil reserves are in politically unstable regions. In light of this situation, most oil-consuming countries have made it their goal to break dependence on petroleum, which is why they are increasingly demanding and supporting alternative primary energy sources for use in the production of fuels. Such sources include natural gas, wind power, and biomass.
It is very difficult to forecast the course fuel prices will take. Only two or three years ago, for example, practically no expert would have predicted that the price of crude oil would be more than $75 per barrel in 2006—at that time a barrel of crude was selling for just $25. Nevertheless, over the next few years we can expect further increases in the prices of fuels obtained from fossil energy sources; the only thing not certain is how large the increases will be.
Supplies of crude oil will also continue to dwindle, and the need to exploit lower-yielding sources of crude oil, such as oil shale and oil sand (considered too costly in the past), will by itself lead to higher prices. Then of course there is the factor of politics in oil-producing regions, which has a major impact on prices.
At the same time, there are several factors in favor of techniques for producing fuels from renewable sources. For one thing, solar energy and wind power, at least, are essentially inexhaustible resources, which means scarcity can never play a role in their prices. And the technological advancements that will be achieved in the future with today’s emerging techniques for producing energy from renewable sources will mean greater efficiency, which in turn will reduce production costs. This development can be clearly seen in techniques for generating electricity from wind power. In general, fuels obtained from fossil energy sources will become more expensive in the future, while prices for fuels from renewable sources will tend to fall. And the greater efficiency of fuel cell drives will help to reduce overall vehicle operating costs.—DaimlerChrysler