Five-cell stack

An overall DMFC stack energy conversion efficiency of 35% was achieved over a range of stack operating conditions of 0.46-0.57 V per cell. An extended life test over llOOh on a five-cell stack made of identical cell components and stack configurations was also performed. 

The newly assembled 30-cell stacks (one is shown in Figure 2.2) were immediately run in the DMFC mode at a fixed stack voltage at 60 °C with a 0.5 M methanol solution fed at the anode manifold and dry ambient air fed at the cathode manifold, without subjecting the stacks to any H2/air break-in conditions. The stacks gradually reached the reported levels of performance within a few hours and remained stable for at least the initial week of testing in our laboratory before they were sent to our partner for system integration. An extended life test over 1000 h on a five-cell stack built identically revealed stable stack performance. During the initial run, the... 

A five-cell stack (with a structure identical with that of the 30-cell stack) and a column of Drierite (anhydrous CaSO (W.A. Hammond Dryerite) used for trapping water vapor in the stack cathode exhaust stream were placed inside a convection oven set at the stack operating temperature. A T-valve was used to separate the water vapor and liquid water by gravity. The liquid water was directed to the outside of the oven with a peristaltic pump set at a flow rate of 1 mLmin , which was slightly higher than the flux of liquid water from the stack cathode exit but significantly lower than the cathode feed rate. The liquid water thus separated from the stack cathode exhaust stream was collected vdth a conical beaker placed... 

Table2.1 Test results for a five-cell stack fed with a 0.5 M methanol solution at 25 mLmin and dry oxygen at 0.76 atm at 0.69-1.58 SLPM.

An extended stack life test was performed on a five-cell stack built with cell components and stack configuration identical with those of the 30-cell stack. The... 

Figure 2.15 Life test results for a five-cell stack at 60°C for the initial 200 h.Thestackwasfed with aO.5 M methanol solution feed at 20 mL min at the anode and with 0.76 atm dry air at 1.5 SLPM at the cathode.

Figure 2.16 Life test results for a five-cell stack at 60°C for the entire 1150h.

Thermal stress calculations in the five cell stack for the temperature distribution presented above were performed by Vallum (2005) using the solid modeling software ANSYS . The stack is modeled to be consisting of five cells with one air channel and gas channel in each cell. Two dimensional stress modeling was performed at six different cross-sections of the cell. The temperature in each layer obtained from the above model of Burt et al. (2005) is used as the nodal value at a single point in the corresponding layer of the model developed in ANSYS and steady state thermal analysis is done in ANSYS to re-construct a two-dimensional temperature distribution in each of the cross-sections. The reconstructed two dimensional temperature is then used for thermal stress analysis. The boundary conditions applied for calculations presented here are the bottom of the cell is fixed in v-dircction (stack direction), the node on the bottom left is fixed in x-direction (cross flow direction) and y-direction and the top part is left free to... 

EAP-6230 101.6 mm diameter five-cell stacks, DEB type Voltage 28.5 f 3.5 V... 

EAP-6266 I0l.6mm diameter, five-cell stacks Voltage 27f3V... 

One spare electrochemical cell stack is installed in the primary anolyte circuit. Manual intervention is required to connect the spare cell stack and disconnect a faulty cell stack. Five spare cell stacks are kept in storage, allowing replacement of all primary or secondary electrochemical cell stacks (but not both at once) in the case of common-mode failure, e.g., severe blockage. The inventory of spare cell stacks was not deemed necessary to cover common-mode failure of both primary and polishing (secondary) electrochemical cells, because their anolyte circuits are separate and the catholyte circuit is much less likely to be the source of failure (AEA, 2001a). 

Figure 6-13 Voltage Current Characteristics of a 3kW, Five Cell DIR Stack with 5,016 cm Cells Operating on 80/20% H2/CO2 and Methane (85)...

Institute for Chemical Technology of the Technical University of Graz (hosting also the CD Laboratory for Fuel Cells). Here, development of advanced fuel cell electrodes is in progress. This Institute also makes and assembles fuel cell stacks and accessory equipment. Five prototype Apollo Fuel Cell have been produced. 

Fig. 5.11 Maximum principle stress contours in the slice near the gas inlets of the five cell SOFC stack predicted using the temperature from pseudo 2-D stack model and ANSYS (after Valluru, 2005).

Fig. 5.13 Prediction of y-current density (A/m2) distribution for five cell co-flow SOFC stack obtained using DREAM-SOFC. (a) Contours at the top and bottom surfaces of the stack, (b) Profiles along the direction of channels at the center of each cell.

Fig. 5.22 y-current density (A/m2) distribution inside the five cell co-flow SOFC stack calculated using FLUENT SOFC module. 

---