NGK develops world's most efficient fuel cell
June 11, 2009
NGK Insulators, Ltd. (President and CEO: Shun Matsushita; head office: Nagoya, Japan) has developed a new solid oxide fuel cell (SOFC) based on a proprietary configuration that achieves one of the world’s highest lower heating values (LHV)-63%-and a remarkable fuel usage rate of 90%. NGK is currently working to develop even higher-performance SOFCs, with the goal of introducing this technology for practical use at businesses and in residences, where fuel-cell use promises to expand.
Using advanced ceramics technologies accrued over many years to develop a unique SOFC cell and stack configuration, NGK has achieved an LHV of 63%, one of the world’s highest LHVs for stationary stacks in the 700-W power output and 800°C operating temperature class, in addition to the high fuel usage rate of 90%. The primary advantages of this new fuel cell are outlined below.
The new fuel cell realizes high output by reducing resistance through a thin film (5 micrometers thick) of electrolyte (zirconia) formed over the entire surface of the cell’s supporting fuel electrodes and by creating a large power-generation surface through air electrodes formed on both sides of the cell.
The fuel cell features spaces (flow channels) to supply fuel gas inside the cell, precisely optimized to ensure even distribution of fuel gas throughout the cell. Power-generation tests with a stack connecting tens of these cells indicate fuel usage rates of 90% or more and LHV values of 63%.
Measuring 1.5 mm thick, the device is the world’s thinnest flat-tubular fuel cell. Since the cell interior contains flow channels for fuel gas, it requires none of the components required to separate fuel gas from air in ordinary flat cells, reducing both size and cost.
NGK has provided this SOFC stack to a leading oil company in Japan, which is currently evaluating the fuel cell’s power-generation performance. NGK plans to pursue further efforts in this area, including potential partnerships with other firms in the form of technology alliances and joint development efforts, as it seeks to further improve SOFC cell performance to enable use of fuel cells in residences and in commercial facilities, including convenience stores and shopping centers.
SOFC stands for solid oxide fuel cell, a type of fuel cell that generates electric power from hydrogen and oxygen. Incorporating ceramics for components such as electrolytes and electrodes, an SOFC can operate at higher temperatures (600 – 1,000°C) than the polymer electrolyte fuel cells (PEFCs) currently available for home use. SOFCs are remarkably efficient, allowing use of generated waste heat not just for cogeneration but for reforming (a reaction that creates hydrogen from fuel), a process that with PEFCs requires a separate heat source. SOFCs are expected to enter practical use as the next generation of fuel cells within the next few years.
Cells and stacks
A stack is a power-generation element formed by electrically connecting multiple cells in series. These cells constitute unit power-generation components of a fuel cell. Since a single cell has low voltage-approximately 1 volt-multiple connected cells are used to increase the voltage to necessary levels.
LHV stands for lower heating value, a measure of power generating efficiency. The LHV is the heating value resulting when all fuel gas is burned completely, minus the condensation latent heat of water vapor.
Fuel usage rate
The percentage of fuel supplied to the SOFC stack that is actually used in power-generation reactions
1. Configuration of a flat-tubular cell (with internal flow channels)
2. Results of power-generation testing
3. An SOFC stack (center) and cell (bottom right)