First High-Temp Fuel Cell in Bi-Fuel Service

Posted on September 30, 2004

The first bi-fuel fuel cell went into service at Vattenfall in Berlin on September 30.
  • HotModule taken into service at Vattenfall in Berlin
  • Start-up of series production scheduled for 2006
  • Record high efficiency results achieved
  • New prospects for power generation
  • Great market potential for the technology

The first bi-fuel fuel cell went into service at Vattenfall in Berlin on September 30. The plant, which is located in the "Fuel Cell Innovation Park", runs on natural gas, methanol or both. The "HotModule", as the fuel cell plant is known, is being tested in everyday operation as part of a program of field trials at BeWAG. The test run is intended to prove that the HotModule can be operated on a variety of fuels. This plant additionally demonstrates that the fuel cell is not reliant on the existence of supply networks, because the liquid fuel used is derived from wastes generated in the city of Berlin.

The HotModule was built by mtu CFC Solutions, a company of DaimlerChrysler AG, as a technology which was developed as a decentralized miniature power plant and is presently undergoing practical testing after more than ten years of development work. Plants of this type are being tested for their suitability for everyday use in various areas of application.

While MTU Friedrichshafen, the parent company of mtu CFC Solutions GmbH, has its core business in the production of diesel engines and drive systems for ships, railroads, heavy vehicles and decentralized power supply systems, the company is engaged in developing the HotModule and bringing it to the series production stage as part of a long-term strategy. Michael Bode, Chief Executive Officer of mtu CFC Solutions GmbH, said at the plant opening: "For our parent company, fuel cells represent a long-term addition to the present-day range of products, particularly in the field of power supply systems."

The HotModule is particularly environment-friendly because it produces virtually no emissions. Furthermore, it conserves resources because it requires significantly less fuel than comparable conventional power plants in order to produce the same amount of electricity. The HotModule is particularly well suited for use as a decentralized miniature power plant since it generates not only electricity, but also high-temperature heat. The heat is required for a large number of industrial processes, for example at Michelin for producing process steam for the vulcanization of tires. The HotModule normally runs on natural gas, but, as Bode said, is also capable of operation with other fuels.

Start of series production scheduled for 2006

The HotModule is entirely on schedule as it proceeds toward series production. To date, twelve field-trial plants have been erected, of which eight are currently undergoing practical testing. The other plants already have the testing phase behind them. In 2004 and 2005 it is planned to deliver further plants to customers in Europe, the USA and Asia. Compared with other fuel cell technologies, the HotModule is already comparatively advanced and relatively economical to produce due to its design and construction. This is one reason why series production of the HotModule is imminent, according to Bode: “With every new system we gain valuable experience, which we incorporate during further development, above all with regard to preparation for series production. The preliminary target for us is 2006, when we envisage the start-up of series production.”

Record high efficiency results achieved

The previously erected HotModules achieve electrical efficiencies of almost 50 percent, a value which is not attained by any conventional technology in the 250-kilowatt class. For comparison, modern gas engines in the same size class have a mechanical efficiency of around 41 percent, which does not include the conversion of the mechanical energy into electrical power.

Thus far, two mtu HotModules have been taken into service in the automobile industry and in the power supply field in the USA. The overall plants were delivered by Fuel Cell Energy Inc. (Danbury, Connecticut), a US cooperation partner, which has mtu as its largest single shareholder. The cells of the HotModule, the key components of the plant, are supplied by FCE.

New prospects for power generation

Another technical feature of the HotModule makes it possible to embrace completely new markets beyond the existing markets with this fuel cell. Unlike other fuel cells, the HotModule can be run with other hydrocarbon-based fuels, such as biogas, sewage gas, landfill gas, industrial residue gases and methanol as well as natural gas. “This presents us with completely new possibilities,” says Michael Bode. “Currently, much of this gas in industry and agriculture goes completely to waste or at best is used in thermal applications. The HotModule offers a highly efficient possibility to utilize these gases to produce power.”
Cost-effective construction with potential for further cost reductions

To date, fuel cell technology has not become generally established in the mass market. The reason is that, in comparison with traditional methods of power generation, efficient fuel cells are still too expensive, either because they require complex installations with costly peripherals or because they are dependent on high-grade materials such as platinum. However, the principal reason is that fuel cells are presently not yet in series production.

By comparison, today the HotModule is already a cost-effective option. However, it still has to go down in price, says Michael Bode: "The bar in the market is set high. The pace at present is being set by gas engine plants, which cost less than 1000 Euro per kilowatt of power even though they achieve significantly lower efficiencies than our HotModule." Therefore mtu CFC Solutions is focusing its efforts on further reducing the manufacturing costs of the plant. Within just a few years the company has been able to halve the costs per kilowatt of the HotModule.

In the medium term mtu CFC Solutions intends to bring the costs of its fuel cell down to between 1100 and 1500 Euro per kilowatt of power in order to make the HotModule economically attractive. To achieve this goal, the developers plan to implement technical simplifications in order to make the system peripherals, such as the fuel gas treatment, significantly cheaper to manufacture in the future. They are also taking another close look at the fuel cell itself. The plan is to simplify its construction further, to economize on materials, to increase the power output of the cell and to reduce the number of steps required for production of the cell. However, the greatest savings potential lies in series production. "Today, every HotModule is still a one-off handmade product whose costs cannot be compared with those of series-manufactured products such as engines," says Bode. "When the HotModule reaches the stage at which it is ready for series production, cost savings of a further 50 percent will become possible, enabling us to achieve our cost target."

Simple operating principle with high development potential

The composition of the HotModule is very simple. The entire system consists of three separate components, namely a central steel container with the fuel cell stack – this is the actual HotModule that gave the entire system its name – upstream gas treatment and an electric part, in which the generated direct current is converted into alternating current and the system control is housed.

The HotModule is a carbonate fuel cell, inside which the temperature is 650 degrees. The high temperature eliminates the need for expensive catalytic converters made of precious metal. Nickel is sufficient to initiate the fuel cell reaction. At 650 degrees, yet another effect becomes apparent: combining natural gas and water within the fuel cell results in dehydrogenation. Hydrogen is the fuel that is required to run fuel cells, and it can only be obtained at great expense in the case of low-temperature fuel cells in bulky reformation systems. However, the most welcome of side effects can be found in the waste air emitted by the HotModule: 400 degree heat, with which high-pressure steam can be produced, which in turn is required for many industrial processes.

The actual nucleus of the system is some 350 individual cells, which mtu at present purchases from its US partner company Fuel Cell Energy Inc. They are installed in sequence and are held together by anchor bars, thus creating the cell stack. The individual cells are constructed as flat sandwiches.

Like other fuel cell types, the development of the HotModule is not yet complete. There are various aspects of the HotModule where there is room for development. With this in mind, mtu technicians are working on increasing the energy density of the cell and extending its service life. The individual cells that currently produce 0.7 kW are set to generate 1 kW of power each in future. mtu engineers are also in the process of making the HotModule even more flexible. It should be in a position to continue to generate power independently in the event of problems with the power supply system, even in the event of total power failure.

Technical Data for the HotModule

Fuel Natural gas, biogas, sewage gas, landfill gas, industrial residue gases, methanol
Electrical output of the cell block 270 kW
Electrical output of the system on the grid approx. 230 kW

Thermal output of the system

180 kW
Electrical efficiency of the cell block approx. 56 %
Overall rate of utilization > 90 %
Number of cells approx. 350
Waste air temperature for utilization of heat approx. 400° C