Proceedings of FuelCell2006
Fourth International ASME Conference on Fuel Cell Science, Engineering and Technology
Irvine, California. June 19-21 2006
FUELCELL2006-97031
ELECTRICAL CHARACTERIZATION
OF A GLUCOSE-FUELED ALKALINE FUEL CELL
1Eugenia
Bubis, 1Lea Mor, 1Nissim Sabag, 1Zeev Rubin,
1Ury Vaysban, 2Kas Hemmes, 1Pinchas Schechner
1Ort
Braude College of Engineering, Karmiel, Israel.
2Delft University of Technology, Delft, The Netherlands.
1
Experimental Determination of:
1)Quasi-static polarization curves, V(J);
2) Power Density as a function of current density,
PD(J)
3) Ohmic internal resistance of the cell, RFC.
Experimental Conditions
1 [KOH]
2 [Glucose]
3
4
0.35 M
0.022 to 1.11 M.
Room Temperature
Sampling Time
0.1 s
2
Procedure
FIGURE 2: FUEL CELL VOLTAGE AS A FUNCTION OF TIME
DURING THREE CONSECUTIVE CONNECTION-DISCONNECTION CYCLES,
[glu]0 = 0.67M;
RL =10.29W., 9.28W, 8.4 W.
3
= V@(tc + 0.1s)
= V@(td + 0.1s)
FIGURE 3: FUEL CELL VOLTAGE AS FUNCTION OF TIME
DURING A CONNECTION-DISCONNECTION CYCLE.
RL = 10.29 W; [glu]0 = 0.67M
4
Polarization Curve for different [glu]0
VD
JL 
RL A
Small Values
5
Power Density as Function of Current Density
of Various [glu]0
2
V
PD(J)  J L VD  D
RL A
Low Values
Maximun
at 0.22 M
Competence with
non-electrochemical
reactions
6
Internal Resistance
Assuming that only
the ohmic resistance
can react immediately
1 - Voltage Divider Method
Current at VIRC
RL
VIRC  i c R L  OCV
R FC  R L
R FC
R L (OCV  VIRC )

VIRC
7
2 – Current Interrupt Method
At the disconnection instant, there is a
sudden increase in the cell’s voltage,
VD, caused by the immediate
annulment of the
ohmic losses
VD  VIRD  VD
The current at the disconnection
instant is:
VD
id 
RL
RFC
VD (VIRD  VD )R L


id
VD
8
Horizontal
continuous
line indicates
the RFCmean
RFC as function of RL computed from the "VOLTAGE DIVIDER“ method
[glu]0 = 0.22 and 0.67 M.
9
Internal Resistance
as function of the
glucose concentration
RFCmean = RK + RC[glu]0
[W]
Glucose
Concentration
dependent
term
Glucose
Concentration
independent
constant
RFC, 0.35 M KOH = 2.02 + 3.54[glu]0
[W]
10
Internal Resistance dependence on Glucose
concentration, RC:
RFCmean = RK + RC[glu]0
[W]
The glucose concentration contributes to the ohmic resistance
only in the volume between the two electrodes. As any ohmic resistor:
RC
c L
[W·M-1]

A
AR C
c 
 0.725R C W·M-1·m
L
Rc(1M glucose in 0.35 M KOH) = 2.56 W·m
11
Internal resistance factor independent of the glucose
concentration, RK.
RFCmean = RK + RC[glu]0
[W]
RK includes ohmic resistances that don’t
depend on glucose concentration,
Rk = Rmetallic mesh + Rconnections + R0.35M KOH
RK = 2.02 W > R0.35M KOH
RK Contributes to the ohmic resistance only in the volume
between the two electrodes. As any ohmic resistor
R 0.35M KO H 
L 0.35M KO H
A
 1.38 0.35M KO H  (1.38)(0.155) 
R0.35M KOH = 0.21 W < 2.02 W = RK
12
Conclusions
At a [KOH] = 0.35M, the cell reaches peak
performance at [glu]0 = 0.22M
The two methods used to measure the internal
resistance of the fuel cell, Voltage Divider and
Current Interrupt, yield practically identical results
Efforts will be directed towards development of
practical glucose-fueled AFC,
as electricity generators for portable devices
Proposed Directions:
• The effect of temperature on cell performance.
• Development of nano-tube electro-catalytic electrodes
13