Glass-ceramics For Efficient Fuel Cells

The international technology group has developed extremely heat-resistant glass and glass-ceramics as long-lasting sealing materials for high temperature fuel cells. With an operating temperature of between 650°C and 850°C, Solid Oxide Fuel Cells (SOFC) generate electricity and heat in a highly efficient manner. They are used all over the world in small power stations, domestic power supplies and as auxiliary power generators for vehicles.
 
Our atmosphere continues to heat up. This is mainly caused by the high levels of CO2 emissions that result from the combustion of fossil fuels. According to the International Economic Platform for Renewable Energies (IWR), despite the prices of fossil fuels climbing to new heights, the global output of greenhouse gas rose by nearly 40 percent from 1990 to 2008. The key to sustainable and environmentally-friendly growth lies in energy efficiency. Here, the fuel cell, and particularly the Solid Oxide Fuel Cell (SOFC), represents a promising solution.

Hydrogen is the source of energy for the fuel cell. Nevertheless, this gas only occurs on earth in a chemically bound form. It is won using renewable or fossil energy sources. Although an infrastructure for supplying hydrogen on a comprehensive basis has not yet been established, an SOFC is able to internally reform fossil fuels such as natural gas, biogas, fuel oil or diesel directly into usable energy. This gives this technology an important competitive advantage.
 
Fast retrofitting in industry and households possible
 
SOFCs can be attached directly to the connections for fossil fuels that are already being used in industry, as well as roughly half of all households in Germany and many other countries around the world. Natural gas is particularly well-suited as an energy supplier. The gas mainly consists of methane, which, in turn, is composed of one carbon and four hydrogen atoms. It offers an extremely advantageous hydrocarbon ratio and thus a high energy yield. SOFC technology is attributed with having the greatest potential for covering the energy requirements of the industrial, commercial and domestic sectors in an environmentally-friendly manner in the future. The galvanic cell converts approximately 80 percent of the chemical energy into usable electricity and heat. Its advantages include high efficiency, flexibility with respect to selecting the type of fuel, and extremely low CO2 emissions. Water is even the fuel cell’s main waste product.
 
The high temperature fuel cell is “ready for the mass market”
 
"The infrastructure already exists and in terms of the technology, as well, the SOFC is basically now ready for the mass market,” explains Claire Buckwar, Director of Marketing at SCHOTT Electronic Packaging, the leading manufacturer of powders made from glass and glass-ceramics for hermetic encapsulation and passivation of electrotechnical components. “Manufacturers of high temperature fuel cells now need suitable industrial partners who meet the highest international quality standards and offer high security of supply.”
 
This is why SCHOTT has developed special glass and glass-ceramic seals that are perfectly suited for the high operating temperatures of the SOFC of between 650 and 850°C with respect to their physical and chemical properties. The coefficients of thermal expansion have been selected to suit those of the cell and interconnector materials. This allows for the stresses that result when the hermetically sealed glass-to-metal connections cool down to be reduced. In addition, the seals have a defined crystal phase in order to increase the thermal stability of the seals.
 
Hermetically sealed, even at the highest temperatures
 
"The high operating temperatures of the Solid Oxide Fuel Cell place huge demands on the material that is used. Therefore, in order for the cell to be able to generate energy both reliably and efficiently over the long term, the gas channels at the anode and the cathode and the interconnectors of the fuel cell stacks must be hermetically sealed and partially electrically insulated,” explains Dr. Jörn Besinger, Director of Development at SCHOTT in Landshut (Germany).
 
In many ways, fuel cells function like batteries that have a continuous fuel supply. Today’s high temperature fuel cells usually consist of flat galvanic cells that are stacked together in order to achieve higher energy performance. The layout of the fuel and air supply elements on the macroscopic and microscopic scales, as well as the sealing and bonding technology used in the stack components with glass-ceramic soldering, represents a basic prerequisite to ensuring that the cells perform for sustained periods.
 
A 125-year history of innovation SCHOTT Electronic Packaging (EP), with its headquarters in Landshut (Germany) and Singapore, is the leading manufacturer of special glass powders with unique physical and chemical properties. With its many competence centers around the world, SCHOTT EP offers the most modern glass and glass-ceramic powders and pastes for the hermetic encapsulation and passivation of electronic components. The company that is part of the international SCHOTT technology group and has approximately 17,300 employees all over the world relies on 125 years of experience in the development, manufacturing and reliable supply of special solutions for customers around the globe.