Hot source of energy

Stacks of ceramic plates are capable of transforming fuels like natural gas into electricity using an electrochemical process.

High-temperature fuel cells are suitable for use in power supply systems for buildings and vehicles. A young firm is planning their commercialisation.

High-temperature fuel cells, unlike other types, are capable of producing electricity and heat not only from hydrogen or methanol but also from cheaper and more readily available energy sources such as natural gas, gasoline, diesel or biogas.

A front-end reformer converts these fuels to hydrogen and carbon monoxide. But the high operating temperature of over 800°C requires a correspondingly long period of pre-heating.

For that reason, such fuel cells are best employed in situations where they continuously operate - particularly providing energy for buildings and vehicles. In many cases they can often be designed to even use the process heat - achieving an energy efficiency of over 90%.

Solid-oxide fuel cells have been researched at the Fraunhofer Institute for Ceramic Technologies and Sintered Materials IKTS since 1992.

They are cast or silk-screened in ceramic paste and then sintered to form plate electrodes of the required thinness.

"We are the first to have developed a ceramic that prolongs the life of the plates by a factor of around 10 with respect to previous types of material," emphasises institute director Prof Alexander Michaelis.

"Moreover, they achieve the highest energy efficiency so far produced using a solid-oxide fuel cell."

A single membrane electrode assembly, complete with connectors, has about the same dimensions as a CD and delivers an output of around 20 W.

By grouping them together in stacks, they generate sufficient power for the envisaged applications. A stack can serve as an auxiliary power unit for boats, campers and other vehicles.