JPH02847Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a free electrolyte fuel cell that uses, for example, an alkaline aqueous solution as the electrolyte and continuously flows the electrolyte during operation. This article relates to improving the configuration of fuel cells for the purpose of reducing fuel consumption.

First, with reference to FIG. 1, the basic structure of the conventional fuel cell and the electrolyte circulation circuit will be explained. In the figure, the fuel cell comprises a cell stack 2 in which a large number of single cells 1 are stacked in series in the forward direction, and electrical output is obtained from output terminals 3 at both ends. Furthermore, as is well known, the single cell 1 has an electrolyte chamber defined between a pair of isolated electrodes.
By supplying an electrolytic solution to this electrolytic solution chamber and, on the other hand, supplying a reactive gas to each electrode, an electromotive reaction takes place within the battery. Further, an electrolyte tank 4 is provided externally to the cell stack 2, and an electrolyte circulation line 6 including a liquid feed pump 5 connects the electrolyte tank 4 and the cell stack 2.
is configured to circulate and flow an electrolyte to each unit cell 1 in parallel through this circulation line 6 and a common electrolyte flow path 7 extending between each unit cell 1 inside the cell stack 2. There is. As a result, the heat generated in the cell due to the electromotive reaction is taken out to the outside using the electrolytic solution as a medium, and is cooled and removed in the electrolytic solution tank 4.

On the other hand, in the fuel cell described above, an electrically closed loop is formed between the single cells 1 which are electrically connected in series between the output terminals and communicate with each other through the electrolyte flow path 7. It turns out. For this reason, in the fuel cell, a current i due to the potential difference between the single cells flows through the electrolyte flow path 7, regardless of whether the output circuit is open or closed. This current becomes a leakage current and results in output loss. Therefore, in order to improve the overall efficiency of the fuel cell, it is desirable to suppress the leakage current to as low a value as possible and to reduce the resulting output loss as much as possible.

As a countermeasure to this problem, as shown in Figure 2,
The cell stack is divided into a plurality of cell blocks 8, 8 each having a plurality of single cell laminates as one block, and each cell block 8 is connected to a header piped externally so as to span between the inlet and outlet sides of the cell blocks. Conventionally, an electrolyte circulation system has been implemented in which the electrolyte circulation line 6 is connected in parallel to the electrolyte circulation line 6 via the piping 9. According to this system, the electrolytic solution is supplied in parallel to the single cells within each cell block 8, 8 as a unit, and is supplied to the cell blocks 8, 8 through a separate header pipe 9. Therefore, power loss due to leakage current, which increases exponentially as the number of single cells connected in parallel increases, can be reduced by dividing the cell block into two by halving the number of single cells. can.

However, the cell block sectioned flow system described above also
In the electrolyte flow circuit shown in FIG. 2, since the stacking direction of the adjacent cell blocks 8 and 8 is in the forward direction with respect to the current flow direction, the cell blocks 8
If the voltage of each cell block is V, a potential difference of 2V is applied between both ends of the header pipe 9 spanning the cell blocks 9 and 8, and the leakage current i flowing therein becomes large. According to a trial calculation, the loss due to the leakage current flowing through the header pipe 9 reaches 30 to 40% of the power loss due to the leakage current in the entire cell stack. Therefore, if the leakage current flowing through the electrolyte passage in the header piping can be reduced by some means, it will be possible to take advantage of the cell block sectioned flow system and greatly improve the overall efficiency of the cell stack as a whole. .

This idea was developed in consideration of the above points, and without changing the conventional piping structure,
It is an object of the present invention to provide a fuel cell with excellent output characteristics in which leakage current can be further reduced by only slightly changing the arrangement of cell blocks constituting a cell stack.

This invention will be explained below based on illustrated embodiments.

In FIGS. 3 and 4, cell stack 2
is divided into a plurality of cell blocks 8 as in FIG. Two adjacent cell blocks 8 and 8 are set as a set, and the single cell stacking direction of each cell block is made to face each other with respect to the current flow direction. That is, as shown in the figure, the batteries are arranged so that their polarities are opposite. This is similar to changing the stacking direction of one cell block 8 by 180° in FIG. Note that, as a matter of course, the cell blocks 8 and 8 are electrically connected in series via the crossover wiring 10. In addition, the header piping 9, which is piped between the cell blocks 8 and 8 so as to connect the cell blocks 8 and 8 in parallel to the circulation line 6, has a long pipe length to reduce the electrical resistance of the electrolyte passage. to make it bigger,
As in FIG. 2, connecting piping is provided across the farthest opposite end between the cell blocks 8,8.

According to the above configuration, the piping circuit for electrolyte flow is the same as that in FIG.
The potential difference applied to both ends of the structure is reduced to 1/2 compared to the forward stacked structure shown in FIG. As a result, even though the length of the electrolyte passage in the header piping 9 spanning between the cell blocks 8 and 8, and therefore the electrical resistance of that passage, is the same as that in Fig. 2, there is a potential difference between the two ends. is reduced to 1/2, so the leakage current flowing there is halved and power loss can be reduced accordingly. According to the inventor's calculations, when cell blocks 8 and 8 are each configured with 20 single cells 1, the power loss due to leakage current in the configuration shown in Figure 3 is equal to the power loss in the conventional configuration shown in Figure 2. Can be reduced to 85%. If the cell stack is divided into a large number of cell blocks, each cell block may be divided into a plurality of groups, and each group may be constructed and implemented as shown in FIGS. 3 and 4.

As described above, this design consists of a set of two cell blocks arranged next to each other, with the single cell stacking directions of each cell block facing each other with respect to the current flow direction, and furthermore, the header piping is connected between the opposite ends of both cell blocks. Therefore, while maintaining a large electrolyte flow path resistance of the header piping that spans between the cell blocks,
Moreover, the potential difference applied to both ends can be reduced to half that of the conventional one, and the leakage current can be greatly reduced, thus improving the overall efficiency of the entire fuel cell.
Furthermore, the configuration of this invention can be easily implemented by rearranging one side of the conventional cell block shown in Figure 2 with the battery polarity reversed. It can be used as is and improved upon.

In addition to fuel cells, this invention can also be applied to electrolyte circulation type zinc-air stacked batteries and the like.

[Brief explanation of the drawing]

Figures 1 and 2 are electrolyte flow circuit diagrams of different conventional fuel cells, and Figures 3 and 4 are electrolyte flow circuit diagrams and structural external views of fuel cells according to embodiments of this invention, respectively. It is. 1... Single cell, 2... Cell stack, 6... Electrolyte circulation line, 7... Common electrolyte flow path in the cell, 8, 8... Cell block, 9... Header piping, i... Leakage current.

Claims (1)

[Scope of utility model registration request] For a cell stack made up of a large number of single cells stacked in series, electrolyte is supplied in parallel to each single cell making up the cell stack through an external electrolyte circulation line and a common electrolyte flow path spanning each single cell within the cell. In a free electrolyte fuel cell configured to flow electrolyte, the cell stack is divided into a plurality of cell blocks, and each cell block is connected to the electrolyte circulation line via external header piping that spans the cell blocks. , a set of two cell blocks arranged next to each other is arranged such that the single cell lamination direction of each cell block faces each other with respect to the current flow direction, and the header piping is connected astride between opposite ends of both cell blocks. A free electrolyte fuel cell characterized by piping.