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Q: Direct Carbon Fuel Cells ( Answered,   0 Comments )
Question  
Subject: Direct Carbon Fuel Cells
Category: Science > Technology
Asked by: joy677-ga
List Price: $50.00
Posted: 25 Sep 2006 08:25 PDT
Expires: 25 Oct 2006 08:25 PDT
Question ID: 768241
What DCFC continuous operation energy density,   either electrical
output (watts) per DCFC anode or cathode surface area (cm squared)  or
 electrical output (watts) per total DCFC stack weight (kg), is
presently being achieved in the lab?  [ electrode energy density and
total stack mass energy density, respectively ]
Answer  
Subject: Re: Direct Carbon Fuel Cells
Answered By: keystroke-ga on 26 Sep 2006 16:05 PDT
 
Hello joy677,

The continuous energy density measured for the DCFC in the lab varies
depending on what type of carbon material is being used for the
experiments. A wide range of densities has been measured.

Lawrence Livermore National Laboratory -- Carbon Conversion Fuel Cell
http://www-cms.llnl.gov/s-t/carbon_con.html

"Among carbon blacks, a range of reactivities has been measured. For
example, one carbon material had a peak power density of about 8
milliwatts per square centimeter while a second material measured
almost 50 milliwatts per square centimeter. A third, the best material
tested, yields energy at about 100 milliwatts per square centimeter
and 100 milliamperes at 0.8 volts, sufficient for many fuel cell or
battery applications."

"In repeated tests, the cells deliver up to 0.1 watt continuously per
square centimeter and are 80-percent efficient at 80 milliwatts per
centimeter."

This goes along with this image:
Comparison of Carbon Power Densities
http://www-cms.llnl.gov/s-t/carbon_con_images/Cooper6.jpg

"Three carbon blacks are equally pure, are made by pyrolysis, and cost
about the same, but they differ significantly in structure on the
nanometer scale. As a result, their electrochemical reactivities are
quite different. The two graphs depict the three carbons? voltage and
power?two different functions of electrical current?as tested in a
direct carbon conversion cell. Power densities (bottom) show carbon-3
reacting at a rate 10 times greater than carbon-1, providing about 100
milliwatts per square centimeter at 850C. (Graphite, by comparison,
is about 1,000 times less reactive than carbon-3.)"




This paper outlines the potential density of the DCFC.

"Direct Carbon Conversion" 
by Thomas Tao
http://www.netl.doe.gov/publications/proceedings/03/dcfcw/Tao.pdf




"The highest energy density and long lasting battery
C(s) + O
2
(g) = CO
2
(g) (+4 e
-
)
9.2 kW.hr/kg
21 kW.hr/liter
Potential Applications:
A few watts up to thousands watts"


Search terms:
"direct carbon fuel cell" + watts

If you need any additonal clarification, let me know and I'll be glad to help.

--keystroke-ga
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