Development plan for fuel cell modules consisting of 35 two-cell sections and incorporating static moisture control subsystems as integral part of modul

Hess, P. D.

English

NASA Technical Reports Server

t r '  
' .  TECHNICAL MEMORANDUM 
0 November 10, 1964 
To: B. R. Nichols 
From: P. D. Hers : 
Subject: 
Dir tribution: 
Fuel Cell Module Development Plan - Activity 145 - 205 
J. L. Platner, D, P. Ghere, R E. Lochen, 
J. R. Hurley, C. Martin, G. Johnson 
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L O  
2.0 
3.0 
FUNCTION 
The Fuel Cell Module is the power  subassembly that convert6 chemical 
energy to electrical  energy. It consists of 33 two-cell eectioas and has 
the static moirture control subsystem a s  an integral part of the module. 
The requirements and component8 are described in Paragraph 3.1 .1  
of the Centerline Specification (NAS 8-2696-8-00024). 
STATUS 
Two fuel cel l  modules consisting of 35 two-cell sections have been con- 
structed and tested as  a breadboard system. The results of these tes ts  
have shown that a cell performance of 0.80 volts at 160 ASF or  better 
can be expected for required life goals. The testing of these module8 ie  
continuing to verify life data. 
DEVELOPMENT AREAS 
The development a reas  of the fuel cell  module w i l l  be limited to investi- 
gation of the following arear. 
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3. 1 
3.2 
Gold plating of the oxygen plate w i l l  be investigated as an 
alternate to si lver plating. 
conjunction with the silver oxygen electrodes, have a layer of 
si lver plated over the nickel-plated magnesium for additional 
corrosion protection. 
been observed in obtaining a good bond of the si lver to the nickel 
plate and a silver plate of uniform thickness. 
the si lver electrodes develop a bond to the si lver plating and possibly 
cause a gas diffusion limitation to the electrode reactant sites. Also 
rebuilding or re-use of the oxygen plates is difficult and frequently 
requires replating. 
noted which allows corrosion of the nickel substrate. 
The present oxygen plates, used in 
Problems with the si lver plating have 
In cell operation, 
Porosity in thc silver plating has  also been 
Initial testing of gold plating over the nickel-plated magnesium 
oxygen plates had produced good results in bonding, uniformity 
of thicknese and produces a non-porous plate. 
been constructed with gold-plated oxygen plates and the si lver 
oxygen electrode could be readily removed without damage to the 
plating bond, indicating superior rebuild characteristic@. 
A few cells have 
Additional testing should be accomplished to verify initial results. 
Xmproved methods for manifolding reactant gases into individual 
cell  plates should be investigated so as to  minimize localized 
drying effects. The reactant gases a r e  ported into the cells 
through 0.030" by 0. 250" holes that have been cut by the EDM 
process. These EDM holes connect to a 0.062" by 0.093" 
t ransverse slot for distribution of the reactant gases  over the 
face of the electrodes through the 0.030" by 0. 0601g grooves. 
A change in the abrupt transition f rom EDM hole to slot may 
result  in  a better gas distribution. 
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I Tests  should be designed to minimize these adverse effects. 
Designe for  improved intercell reactant manifolding should 
attempt to uae the water vapor and w a t e r  traneport membrane 
for  humidification of reactant gases. 
3 . 3  Methods of dry stacking fuel cell modules should be investigated 
as an improvement over wet stacking. 
Wet stacking of fuel cell  modules requires that calibrated amounte 
of KOH electrolyte be added into the cell  membranes and water 
traneport membranes. 
cult to handle saturated asbestos sheets. 
Additionally, wet stacking makes it diffi- 
Dry stacking could greatly increase the speed of assembly and 
possibly result in a more optimum electrolyte distribution in 
asbestos membranes. Tests should be designed to tes t  thk 
feasibility of dry etacking and to develop technique8 for d ry  
stacking. 
3.4 Modules should be constructed with 20 mil  asbestos and compared 
to the 30 mil  asbestos built cells  for improved capacity and/or 
efficiency, performance and life. 
Decreased capacity and/or efficiency can be realized by reducing 
the internal ohmic resistance of individual cells. Reduced ohmic 
resistance is possible in cells built with 20 mil asbeetoe as  com- 
pared to the standard 30 mil asbestos cell. Tests  should be de- 
signed to evaluate possible performance advantages against the 
poeeible reduced reliability of the 20 mil  system. 
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3. 5 Additional testing, over that accomplished under Part II, 
should be conducted o n  Type  446 and 546 electrodes to allow 
comparison of these electrodes to the standard Clevite elec- 
trode. 
be tested to verify equivalent performance and life. 
A statistically significant number of electrodes should 
3.6 Type HYSAC silver electrodes should be tested and compared 
to SINAC eilver (15 g) for improved capacity and life. 
tically significant number of electrodes should be tested. 
A rtatis-  
3.7 Technique for inatallinc transistorized sensing element6 internal 
to the cell should be investigated for possible improved tempera- 
ture compensation of the vacuum controller. 
4.0 TEST PLAN 
Tes t  specifications detailing the required testing and the required com- 
pletion date for  the testing should be generated ar soon ae porfsible. 
P. D. He59 
nfm 
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Fuel cell module development plan - Activity 145 - 205

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