If the premise is accepted that the fuel cell is the next generation transformer technology for the motive industry, then the development of such a technology must be advanced to the point that it becomes a viable both physically and economically. That is not to say that a fuel cell system must achieve the same cost targets as those of the internal combustion engine, rather the new technology must present itself as an economically viable alternative when issues like the environment are taken into account. Determining the cost that the market and environment will bear is up to the economist and environmentalist. Bringing the cost of manufacture for the fuel cell down to the lowest possible level is the responsibility of the engineers, and as such formed the basis of my thesis.
As it stands, the cost of several key fuel cell components must be reduced. The bipolar plate is one component that has a significant contribution to the overall system cost and also has the greatest potential to be reduced. When considering how to reduce the cost of bi-polar plate manufacturing, several issues were considered. The manufacturing process and the material costs are the two largest contributors to the overall cost. Material costs are insignificant when compared to manufacturing costs, leading to the conclusion that it must be the process that undergoes the development. Traditional plate manufacturing techniques apply a sculpturing approach, where a CNC milling machine is used to cut out the fuel and oxidant delivery channels. A unique and novel approach to the task is to build up the required channel thickness rather than sculpt the material away. Several possibilities exist that may perform the building up task, of which screen printing is the most promising.
The initial goals stipulated that the screen printing process was had to be capable of printing an electrically conductive material onto a suitable substrate to the height of 0.7 mm. When compared with current CNC milled flow field plate manufacturing techniques, the screen printing process developed exhibits the following desirable features: low manufacturing and capital costs, the ability to rapid prototype, flexibility in flow channel design and material properties, mass and batch production capability and little material wastage.
Investigation into conductivity issues of the inks revealed that investigations into the microstructure and percolation theory proved valuable when trying to formulate a ink as conductive as possible. Future work in the area of ink conductivity is recommended.
Screen printing techniques were applied and developed to the problem and successfully met the requirements outlined at the beginning of the project Fuel and oxidant delivery plates were successfully printed and at a considerable cost savings over the CNC milling approach.