## 3 Results  
### Types of Fuel Cells  
Fuel cells can be classified according to the type of electrolyte that they employ. It determines the type of catalysis necessary, the operating temperature, and reactions into the cell such as steam reforming. Finally, fuel cells are classified as a function of the temperature at which the stack operates [19,20]. As seen in Table 1, a high operating temperature fuel cell does not require expensive catalysis such as platinum, and allows steam reforming (internal transformation of light fuels into hydrogen). The major issue with this type of cell is that quick starts are not allowed, which makes application to transportation impractical. To solve this problem, electrical resistances can be used, but this is a huge waste of energy. For instance, 4 Wh are necessary for a 200-W SOFCs stack to warm up from 20 \({}^{\circ}\)C to 700 \({}^{\circ}\)C in five minutes [21]. Nissan managed to build the first SOFC vehicle in 2016, using a 5 kW stack as an extender for the 24-kWh battery [22]. Low operating temperature fuel cells allow quick start, but they do not allow steam reforming, which limits the usable fuel type. Due to the high power density, low operating temperature condition, lower environmental impact than Phosphoric Acid Fuel Cell (PAFCs), and non-sensitivity to the CO2 present in the air, the PEMFC is the most suitable fuel cell type for a transportation application. This includes personal and mass transit vehicles. As an example, Toyota sells the Sora, which is a fuel cell bus using two 114 kW PEMFC stacks of the same type as found on the Toyota Mirai fuel cell passenger car [23]. When PEMFCs are supplied with ethanol or methanol, the chemical reaction releases CO2 as follows [24]:  
\[\mathrm{C_{2}H_{5}OH+3O_{2}=2 CO_{2}+3H_{2}O} \tag{22}\]  
Finally, pure hydrogen PEMFCs are more suitable than direct ethanol or methanol PEMFCs to comply with standards regarding CO2 emissions, since the chemical reaction only releases water as follows:  
\[\frac{1}{2}\mathrm{O_{2}+H_{2}=H_{2}O} \tag{23}\]  
Figure 6: Vehicle speed through the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) driving cycle. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Name of Fuel Cell** & **Solid Oxide Fuel Cell (SOFO)** & **Molten Carbonate Fuel Cell (OCFC)** \\ \hline Electrolyte & Hard, non-porous ceramic & Molten carbonate salt mixture \\ \hline Operating Temperature & & 600–1100 \({}^{\circ}\)C & 650 \({}^{\circ}\)C \\ \hline Fud & & Pure hydrogen, biogas or light fossil fud & Hydocarbon fuels \\ \hline \multirow{5}{*}{High operating temperature} & \multirow{5}{*}{Benefits} & \multirow{5}{*}{Benefits} & \multirow{5}{*}{Non-process metal for catalysts} \\  & & Allee to reform methanol and ethanol & \multirow{5}{*}{Non-process metal for catalysts} \\  & & Mechanically simple it is a solid-state device. & \multirow{5}{*}{Efficiency: from 50\% to 85\% with cooperation} \\  & & Videide auxiliary power units, medium to large scale power & \multirow{5}{*}{No carbon monoxide or dioxide poisoning} \\  & & generation and Combined Heat and Power (CHP), off grid & \\  & & power and micro CHP. & \\ \hline \multirow{5}{*}{Drawbacks} & \multirow{5}{*}{Drawbacks} & \multirow{5}{*}{High operating temperature} \\  & & Complexity of heat management & \multirow{5}{*}{Fusioning by sulphur} \\  & & The ceramic materials used are expensive to manufacture, & \\  & & and are also fragile. & \\ \hline \multirow{5}{*}{Low operating temperature fuel cell} & \multirow{5}{*}{Berefits} & \multirow{5}{*}{Berefits} & \multirow{5}{*}{Berefits} \\  & & & \\ \cline{1-1}  & & & \\ \  
The high operating temperature of a SOFC allows the internal reforming of light fuels into hydrogen, but it produces CO\({}_{2}\). In the case of pure hydrogen as fuel, even if the chemical reactions at the cathode and the anode are different than the PEMFC's ones, the global reaction is the same as that of Equation (23). Nevertheless, the compactness of a SOFC stack is far lower than that of a PEMFC.