mtu Fuel Cell Soon Ready for Volume Production

Posted on May 07, 2001

The HotModule, a fuel cell developed by MTU Friedrichshafen, has successfully completed its first year of practical field trials. 723 MWh of electrical energy and 550 MWh of heat have been supplied within the space of a year to the Bielefeld municipal electricity company by a field trials installation with a rated output of 250 kilowatts.

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  • HotModule enters second year of successful field trials
  • Relatively Low Operating Temperature Means Durability
  • First Installation in A Medical Establishment
  • Eight New Installations in 2001
  • Volume Production in 2004

Friedrichshafen - The HotModule, a fuel cell developed by MTU Friedrichshafen, has successfully completed its first year of practical field trials. 723 MWh of electrical energy and 550 MWh of heat have been supplied within the space of a year to the Bielefeld municipal electricity company by a field trials installation with a rated output of 250 kilowatts. Over the 600 hours for which the HotModule was connected to the power grid in the year 2000, an electrical efficiency of 47 percent was measured for the installation as a whole, while the fuel-cell block on its own achieved a level of 56 percent.

An efficiency of 47 percent is a record for 250-kW installations. It is achieved firstly by the special design of the plant, and secondly by the high output of the cells. the HotModule operates a temperature of 600 degrees Celsius. That high temperature allows expensive noble metal catalytic converters to be dispensed with. Nickel is adequate for initiating the fuel cell reaction. Furthermore, there is another welcome effect that occurs at 600 degrees. When natural gas and water are combined inside the fuel cell at such temperatures, the catalytic converter produces hydrogen - precisely the gas, in other words, that is required to operate the fuel cells. This means that the HotModule can do without expensive gas reforming processes. The cell components of the Bielefeld HotModule are also highly efficient because they produce a smooth voltage - an extremely important quality feature. They are supplied by mtu's American partners, Fuel Cell Energy Inc (FCE), a quoted-stock corporation.

Relatively Low Operating Temperature Means Durability

For mtu, demonstration of the operational viability of its HotModule is an important step on the road to volume production. The theoretical projections have been confirmed by the operational performance of the Bielefeld HotModule at electrical outputs up to the maximum achieved of 225 kW (direct current). The durability of the materials used has, in essence, proved to be trouble-free. One of the reasons for this is that it has been possible to keep the operating temperature at a lower level than originally estimated.

According to the projections, the HotModule was supposed to run at a temperature of 650 degrees Celsius, but in the field trials, marginally under 600 degrees has proved to be sufficient to keep the reactions in progress. This means that the materials are subjected to considerably lower thermals stresses than had been assumed. There was potential for optimisation only in the distribution of intake air in the HotModule and the distribution of the fuel gas within the cell stack. In both cases, these are aspects of flow mechanics that are to be improved in successor plants.

First Installation in A Medical Establishment

One of those plants recently entered service at the Rhön Klinikum hospital in Bad Neustadt in Germany's Franconia region where it supplies the hospital's private mains system. Michael Bode, head of mtu's New Technologies division and in overall charge of development of the HotModule, is confident of making significant progress in terms of intake air and fuel gas distribution with this second field trials installation: "The Bielefeld plant has allowed us to identify weaknesses and systematically eliminate them. For that reason, the later plants should no longer have the gas flow problems experienced in Bielefeld".

The fuel cell plant for the Rhön Klinikum has thus been given a new supply unit for gas and water and an improved cell stack, both of which were tested prior to delivery. Michael Bode believes that this has solved the problems: "On the basis of the test results, we are expecting the new HotModules to achieve overall efficiency levels of 50 percent and more".

Eight New Installations in 2001

mtu is planning to put a total of eight new installations into service in 2001 - four of them in Japan, two in the USA and two in Germany. They are all based on the improved technical concept which is to be further refined from installation to installation. One of the important aims of these modifications to bring down production costs even further. In that connection, every single individual component is meticulously examined in the search for potential improvements in the economy of the design. Such potential may be found, for example, in the choice of materials. The outer shall of the Bielefeld plant, for instance, was made of expensive V2A steel. "This is entirely unnecessary," observes Bode, "because, after all, the installation is operating at atmospheric pressure.

And for that, ordinary steel is quite sufficient. An economical price is more important to our customers than highly sophisticated materials - which is why the future plants will be made of grey steel[?]". mtu is also looking for potential savings in production. At present, the building in which the HotModules are manufactured looks more like a research laboratory than an assembly line. In addition, conditioning and testing the fuel cells also takes too long. But that is due to change very soon. mtu is planning to construct its first production line in the next few years.

Volume Production in 2004

By 2004 all materials and production processes are expected to have been optimised to the point where the company can start volume production. From 2005, mtu expects to be able to offer the system at prices that allow economically viable operation in the prime attractive applications. "As far as prices are concerned, we calculate ultimately on on the basis of life-cycle costs," explains Bode. "What counts is the overall cost that we have to pay for a certain amount of electricity and heat. Therefore, the higher acquisition price of our technology works out in the end because of the significantly higher levels of efficiency it offers."

Michael Bode can see the progress of the HotModule to a marketable product clearly mapped out. Technical refinements and cost reductions are, he says, all set down in a definite time schedule which is being worked through step by step. "We are even slightly ahead of schedule at present. We are capable of supplying, the plant has very good efficiency levels and we can already offer prices that compare very favourably to the state of the art of the various fuel cell technologies."