PITTSBURGH, PA - Generating power close to the consumer
- a concept called distributed generation - may be one way to take the
future strain off the nation's electric grid. Two of the best technologies
for distributed generation are the fuel cell and the micro-turbine - but
an even better approach may be a "hybrid" of both technologies.
The Department of Energy's Office of Fossil Energy is already testing one
type of fuel cell-turbine hybrid, and this spring will begin running a second
type of test unit. Now, the Department, through its National Energy Technology
Laboratory, plans to add a third hybrid system to its fossil energy research
The Laboratory has selected Honeywell International of Torrance, Calif.,
to begin the first stages of development for a new type of "planar
solid oxide fuel cell" hybrid system. The development effort is planned
as a three-and-a-half year effort valued at approximately $5 million.
The Energy Department will fund about $3.48 million.
Honeywell's planar solid oxide fuel cell will be made up of stacked sheets
of flat ceramic material - anodes, electrolytes and cathodes - that resemble
a stack of record albums sealed at both ends. Natural gas and air will
be fed into the fuel cell, and an electrochemical process - much like
the process a battery uses to generate electric current - will produce
one source of electricity.
For the initial development effort, Honeywell will test three 5-kilowatt
planar fuel cells connected to a turbocharger. The turbocharger is a key
component of the company's advanced turbogenerator technology and is also
used as a compressor to boost the operating pressure of the fuel cell.
In the mature version of the technology, linking the fuel cell with a
microturbine will provide a way to tap the significant energy remaining
in the high-temperature exhaust gases exiting the fuel cell. The gases
can spin the blades of the microturbine to produce a second source of
This dual source of power generation boosts efficiency (the amount of
electricity generated from a given amount of fuel). Fuel cell-turbine
hybrids may be able to extract from 65 to 80 percent of the energy value
from a fuel and convert it to useful electricity. A conventional power
plant operates at much lower efficiencies, typically in the range of only
30 to 35 percent. Boosting efficiencies is one of the best ways to reduce
the amount of greenhouse gas emissions, such as carbon dioxide, released
per unit of electricity generated.
The Department is already testing a tubular version of the solid oxide
fuel cell technology in a hybrid unit. In this system, the ceramic materials
are arranged in concentric tubes. Later this year, another type of fuel
cell configuration - one that uses a molten carbonate as the electrolyte,
rather than ceramics - will be tested in a hybrid configuration.
Each of the systems has its advantages, but the Honeywell flat planar
design may offer greater power density -- that is, more kilowatts of power
per cubic inch of material. Power density is an important factor in reducing
The system envisioned by Honeywell would be a low cost, small size, highly
efficient power unit that would have such low emissions that it could
be sited virtually anywhere. Future applications could include hospitals,
military installations, or computer centers -- all of which need a reliable,
uninterruptible source of power.