It's unfortunate that you were not able to post the complete Scientific American critique of P.E.M.technology instead of the misleading information that followed your intro. This tidbit illustrates some of the history of S.O.F.C. technology and was written before Global Thermoelectric's remarkable achievements.
The link for the pictures are at the bottom of page
Solid Oxide Fuel Cell (SOFC)
Solid oxide fuel cell is a highly efficient and compact fuel cell in the next generation coming
after the phosphoric acid fuel cell.
OBJECTIVE
Solid oxide fuel cell (SOFC) is expected to be commercialized as a compact cogeneration device which offers
highly efficient energy conversion from natural gas to electricity. Tokyo Gas has been conducting fundamental
research on cell component materials and developing manufacturing technologies with the aims of understanding
the heart of SOFC as well as infallibly judging and estimating performance, potential applications, and economical
feasibilities. Key technologies required for improvement of electricity generation efficiency and reliability in
long-term operation are also being developed to expedite the commercialization.
PRESENT STATUS
In 1989, Tokyo Gas launched independent R&D programs for planar SOFC. In the early development stage,
basic studies on cell component materials (i.e., electrodes and separators) were performed, and cells and stacks
were manufactured based on the experiences learned from these studies. The size and electrical output of the cells
and stacks increased in the course of development, which carved the milestones of successful manufacturing and
testing of the world-largest single cells (Figure 1) in 1992 and producing the world-largest electrical output of 1.33
kW from the stack (Figure 2) in 1993. Presently, our efforts are focusing on technological innovations for
improving the performance and reliability in long-term operation, for which many findings from fundamental
researches are applied.
Figure 1 The largest single-cell (23 cm sq., 97W)
Figure 2 View of a 1kW-class stack
PRINCIPLE
Planar SOFCs have potential advantages over the other fuel cells. They can generate electricity more
economically, more cleanly, and more efficiently with smaller sizes, and thereby can offer various applications
including residential and industrial uses. As schematically illustrated in Figure 3(a), planar SOFCs are constructed
basically by alternate piling of single-cells and separators, which is called a stack. The single-cell uses stabilized
zirconia as the electrolyte which conducts oxide ions at around 1000øC. The air and fuel electrodes are fired on
both surfaces of the electrolyte sheet (Figure 3(b)). In the air electrode, oxygen is electrochemically reduced to
form oxide ions by accepting electrons from the external circuit. The oxide ions then move through the electrolyte
and reach the fuel electrode. In the fuel electrode, the oxide ions electrochemically oxidize fuels and release
electrons to the external circuit. Thus the electron flow is established from the fuelelectrode to the air electrode
through the external load, which produces DC electricity.
Also, a high operating temperature (around 1000øC) allows reforming of natural gas within the fuel cell (i.e.,
internal reforming). Not only hydrogen but also carbon monoxide, both of which are products of the internal
reforming reaction, can react with oxide ions and be directly used as the fuel. The internal reforming eliminates a
space-consuming and costly external reformer, so that compactness and reduced cost can be achieved.
Figure 3 Schematics of the planar type SOFC
APPLICATION
The high energy conversion efficiency and simplified fuel processing system of the SOFC with an internal reforming
system can make a compact SOFC system. A wide variety of applications can be expected ranging from
large-scale power plants to super-compact cogeneration systems. The applications attractive to gas utilities
include:
large-scale cogeneration systems for distributed power generation plants (multi-MW class)
small cogeneration systems for multi-family buildings (several tens of kW)
super-compact cogeneration packages for residential uses (multi-kW class)
PROSPECTS
Most planar SOFCs ever fabricated and tested in the world are still fueled by hydrogen. In 1996, we are to be the
first to manufacture and operate 1 kW class planar SOFC with the internal fuel reforming system which can use
methane as a fuel. Following is the plan for the development of super-compact systems of multi-kilowatts which
are thermally self-sustaining, and can generate both AC electricity and hot water using pipline natural gas as a fuel.
These systems are expected to be commercialized in the beginning of the 21st century.
For More Information:
Masakazu Hishinuma
Fundamental Technology Research Laboratory
Tokyo Gas Co., Ltd.
16-25, Shibaura 1-Chome, Minato-ku, Tokyo 105, Japan
Tel:+81-3-5484-4641 Fax:+81-3-3453-7583
E-mail:hisinuma@tokyo-gas.co.jp
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