## 3 Evaluation of the Energy Conversion Subsystem and Energy Storage Subsystem
### Trade Study
Upon this, the best ranked fuel option turns out to be liquid hydrogen, followed by gaseous hydrogen, methanol, and then ammonia (cf. Table 1). The span of values in the scaled and weighted final score gives a picture of how each fuel will perform against the others according to the selected trade parameters. The values range from 18.04 for ammonia to 29.44 for liquid hydrogen. Furthermore, the values for \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline \multirow{2}{*}{**Trade Parameters**} & \multirow{2}{*}{**Unit**} & \multicolumn{5}{c}{**Parameter Values**} \\ \cline{3-6}  & & **Liquid** & **Gaseous** & **Ammonia** & **Methanol** & **Weights** \\  & & **Hydrogen** & **Hydrogen** & **Ammonia** & **Methanol** & \\ \hline LCOE & [\(\ell\)cent/kWh] & 24.45 & 18.81 & 38.16 & 22.29 & 10 \\ \hline Environmental friendliness & [-] & 4 & 3 & 2 & 1 & 7 \\ \hline Partial load capability & [-] & 3 & 4 & 1.5 & 1.5 & 5 \\ \hline Displaced water volume & [m\({}^{3}\)] & 62.50 & 164.58 & 144.24 & 158.02 & 4 \\ \hline TRL & [-] & 4 & 3 & 1.5 & 1.5 & 4 \\ \hline Transport infrastructure & [-] & 1.5 & 1.5 & 4 & 3 & 4 \\ readiness level in 2032 & & & & & & \\ \hline Safety of maintenance personnel & [-] & 3 & 2 & 1 & 4 & 2 \\ \hline Scaled and weighted final value & [-] & 29.44 & 27.27 & 18.04 & 20.14 & \\ \hline Rank & [-] & 1 & 2 & 4 & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of trade parameters, their fuel-specific values, and weights used. liquid and gaseous hydrogen are close to each other at 29.44 and 27.27, respectively, which is also the case for ammonia (18.04) and methanol (20.14). Finally, it can be seen that the values of ammonia and methanol are just about two-thirds of the values for hydrogen (liquid and gaseous). As mentioned earlier, it is very complex to decide which fuel is most suitable. The trade study provides a framework for making this decision, although the result may not be completely objective and unequivocal. In the following, some critical points of view and areas of improvement for the trade study are addressed. The fuel options explored sometimes have their own niche use cases (e.g., ammonia is used for the production of fertiliser); in the study, only the use of fuel for heat and electricity generation is taken into consideration. The fuel ending up with a lower score in this trade study might not make it a bad choice for it to be produced on a SailREC System if another application of the generated chemical is the aim. The projected future demand for each fuel, which is used not only for power generation but also as a feed stock for other chemicals and similar applications, could be explored in further studies. Furthermore, when referring to the trade parameter LCOE, it should be clear that a value for each fuel is calculated, which, however, does not correspond to the market price of the fuel. It is just an indicative value and, hence, all the CAPEX and OPEX are not meticulously charted but can still be used for comparison of fuels. The abstraction made in the flow charts is fundamental in nature; detailed design and modelling can be performed in further studies:  
* For example, in the abstract representation of the model, the process for desalination as well as PSA and DAC--in the case of ammonia and methanol, respectively (cf. Appendix B.2)--are not taken into consideration;
* Furthermore, the model can be adapted for a more detailed investigation of seaborne transport and the use of pipelines and railways for transportation on land instead of trucks;
* The processes used (such as liquefier, Haber-Bosch process, etc.) are taken to be continuous processes and are assumed to be performed on the scale of the power rating of the SailREC System. From an engineering perspective, the processes could be considered batch processes. This is not modelled accordingly in the trade study. Considering buffer storage between processes and aptly power-rated processes would need further exploration.