## 4 Discussion and Conclusions
### Conclusions  
Five designs with different channel shapes and gas flow patterns were simulated numerically using computational fluid dynamics (CFD). Using this approach, it was possible to conceive of, detail, and analyze each design. The electrical current distributions of the two different serpentine channels with square or rounded flow bends were tested. At higher loads, the serpentine channels with abrupt changes in flow direction (Design 1) exhibited slightly lower electrical current distributions comparedto curvilinear bends (Design 2). This minute difference within single cells across designs can have a large effect in a stack configuration. It is recommended that the serpentine channel configuration should consist of curvilinear bends. Because of its better performance, Design 2 was selected for the second part of this investigation. The dimensions of the serpentine channel design with curvilinear bends were then modified (Design 3). Afterwards, Design 3 was compared to crisscross (Design 4) and straight parallel channels (Design 5). The results showed that Designs 4 and 5 produced more uniform electrical current distributions than Design 3. This can be explained because the intakes were efficiently located. Therefore, it was concluded that the effective placement of the intakes was as important as the shape of the channel configuration. The parallel channel flow field (Design 5) was the best alternative for current collectors due to its superior performance.  
Some of the most important components of a fuel cell are the bipolar plates and the geometries of the channels for the distribution of the gases, on which the efficiency of the cell will depend. Fuel cells are an excellent alternative for the use of renewable energy. Mexico is a developing country, which has the highest demand for electricity in the world with values of 5.8%-6% per year. Increasingly stringent environmental policies across the planet demand prompt solutions to pollution problems and demand lower and lower emission levels. The instability of oil prices is forcing countries like Mexico to stimulate an economy less dependent on this energy, looking for solutions such as the one shown in this paper. Fuel cells are an alternative, but developing this technology is a very expensive process in Mexico and in many countries around the world that are opting for the use of renewable energy. Simulation represents an alternative to continue with the development and applications. Some of its main advantages we can mention and that have motivated us to develop the research work are: (a) it provides many types of possible alternatives to explore; (b) the simulation provides a simpler method of a solution when mathematical procedures are complex and difficult; (c) it provides total control over time, because a phenomenon can be accelerated; (d) in some cases, simulation is the only means to achieve a solution; (e) it is generally less expensive to improve the system via simulation than to do it in the real system; (f) it helps the innovation process since it allows the experimenter to observe and play with the system; (g) it is much simpler to visualize and understand simulation methods than purely analytical methods; it gives a deep understanding of the system; (h) it gives solutions to problems \"without\" an analytical solution; (i) it allows analyzing the effect on the overall performance of a system; and (j) it allows experimentation in conditions that could be dangerous or that have a high economic cost in the real system. It is important to mention that there are not many reports about similar cases in which the use of the numerical simulations to develop PEM fuel cells has been employed. In this sense, the innovation degree of our work suggest a transcendental relevance in the PEM fuel cell design field. The objective was met.