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Team Italy:
Innovative MCFC
Booth Number:
H78/2
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Giovanni Pasquale
Dr. Marianna Teitto
Dr. Francesco Dallegri
IPASS, Perugia, Italy |
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Giovanni Pasquale |
Dr. Marianna Teitto |
Dr. Francesco Dallegri |
IPASS (Italian environmental engineering and sustainable development center) team who focuses in the field of education of physical agent pollution, presented the innovative technology concerning Small Size Molten Carbonate Fuel Cell (SSMCFC) to Prof. Dr. Giuseppe Spazzafumo from the University of Cassino, Department of Industrial Engineering.
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Introduction
An original cylindrical Molten Carbonate Fuel Cell is proposed.
The cell main peculiarity is the original architecture which
involves both elements geometry and gases arrangements. High
benefits may be obtained by the proposed configuration. Cylindrical
elements may be easily obtained by injection printing; this
is a moulding technique which is conveniently used for large
scale productions because of time and cost advantages. Moreover,
cylindrical configuration produces lower heat losses because
of high volume with respect to surface. Besides, sealing is
enhanced and compression strain is kept uniform along cell
surface. The original gases arrangement is attained by stacking
circular holed thin steel rings. We carried out tests on a
single cell to determine voltage/current characteristic at
different conditions: with and without steam into cathodic
compartment at several times along cell lifetime. It was also
verified cell resuming performances when a temperature drop
occurs. Maximum power density was evaluated for different
conditions. Results suggest that the proposed cell design
is a promising solution for FC micro-CHP applications because
of performances, durability and low realisation costs.
The experimental cell
The original cylindrical Molten Carbonate Single Cell (Patent
PG2003A0019, IPASS, 2003) test facility is made by:
1) Single cell which is constituted by nickel anode, electrolyte,
nickel cathode and a gas distribution system. Gas distribution
system is composed by the following steel plates, rings and
nettings for each electrode:
- steel disk;
- steel ring in which a steel netting is placed. Gases
internal flow is kept uniform by choosing a netting diameter
smaller than the ring internal one;
- steel disk which separates the electrode chamber into
two subchambers; holes are realized in the plate central
zone where gases flows from the external subchamber to the
internal one;
- steel netting which is mounted on a ring disk;
- holed steel disk which contacts the electrode.
The distribution system is characterized by high mechanical
stability for high working temperatures. Steel disks are low
rigidity 1 mm thick. Sheets, rings and nettings may be easily
formed by water or laser cutting methods with low realisation
costs.
The proposed distribution system allows to obtain the following
advantages:
- Mechanical: divide each electrode chamber into two subchambers
with uniform stack compression strain;
- Electrical: reduction of internal electric resistance
by enhancing the contact between two consecutive plates;
- Fluiddynamical: uniform gases distribution inside each
chamber.
The proposed distribution system can log catalysts for natural
gas reforming which will be a future cell development.
2) Mechanical frame for cell stacking which is equipped
with cup-springs to compress the stack.
3) Heating system for cell conditioning (dewaxing, start-up)
and gas heating which is constituted by electric resistors.
4) Exhaust and inlet manifolds. The manifold system is integrated
with the steel coat which externally covers the proposed cell.
Exhaust sections are twice than feeding ones both for anodic
and cathodic flows; damages due to gases escapes are minimized
by creating each inlet manifold and placing them between two
equal outlet manifolds. Thus, a possible gas escape follows
from the feeding manifold to the exhaust one, because gas
pressure in the inlet manifold is higher than in the outlet
one.
5) Thermal insulation panels made by ceramic fibers which
guarantee external surface temperature lower than 50°C
when cell temperature is 645°C.
Figure 1 – The experimental cylindrical MCFC
Experimental Tests
Experimental tests were carried out to individuate a single
cell Volt-Ampere characteristic with and without steam at
the cathodic compartment. After dewaxing and start-up procedures,
a 0.06 ohm electric load was applied to the single cell. For
the first 120 working hours cell voltage diminishing rate
is approximately 0,1 V/50 h when no steam is used (see Figure
2); after that period steam was injected into the cathodic
compartment: voltage rose up till a constant value. Working
temperatures were measured by thermocouple into anodic and
cathodic external subchambers: temperatures range is [640,
645]°C during testing.
Experimental Results
Figure 3 shows Volt-Ampere characteristic for the following
conditions:
a) when the electric load was applied (0 working hours, no
steam at the cathodic inlet);
b) 120 working hours (no steam at the cathodic inlet);
c) 200 working hours (steam at the cathodic inlet);
d) cell temperature was reduced to 400°C and feeding gases
were not supplied to the cell after 200 working hours. After
48 hours, cell temperature was increased to 645°C and
gases were supplied again; steam was injected at the cathodic
inlet since a 0.06 ohm electric load was applied and V-I characteristic
was evaluated.
Figure 2 – Cell voltage vs. working time
Figure 3 – Cell voltage/current characteristic curves
for a), b) and c) working conditions
Figure 4 shows cell electric power versus voltage curves
for a), b), c) and d) conditions. It is shown that maximum
power is respectively about 29.1 W for a) condition, 5.3 W
for b) condition, 14.6 W for c) condition and 14.9 W for d)
condition. Single cell area is 250 cm2. Thus, maximum power
densities are respectively:
- 116.5 mW/cm2 for a) condition, which corresponds to a 171.1
mA/cm2 current density;
- 21.4 mW/cm2 for b) condition, which corresponds to a 42.7
mA/cm2 current density;
- 58.4 mW/cm2 for c) condition, which corresponds to a 132.1
mA/cm2 current density;
- 59.6 mW/cm2 for c) condition, which corresponds to a 131.1
mA/cm2 current density;
Figure 4 – Cell power density/voltage characteristic
curve for a, b and c working conditions
Conclusions
Experimental tests showed the performances of the new original
cylindrical cell for different working conditions. Voltage/current
performances, maximum power density and current density were
evaluated. High current densities (approximately 170 mA/cm2)
were obtained; furthermore, performances stabilization was
achieved by steam application at the cathodic compartment.
A resume test was also carried out with positive results.
Findings make the proposed technology suitable for micro-CHP
fuel cell applications because of high performances compared
with low realisation costs and viability for industrialisation
processes.
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