## 2 Methods
### Practical Case Study
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **Feeder Vessel (reefer) *** & **Ro-Pax Vessel *** \\ \hline \multirow{6}{*}{**Technical Features**} & & & Pax:1000 \\  & & & Lane length for \\  & & & trailers: 1600 m \\  & & & Cars: 160 \\  & & & Reefer cargo’s plugs: 100 \\ \hline \multirow{6}{*}{**Electricity demand**} & Lbp (m) & 78.15 & 153.25 \\  & B (m) & 14.46 & 28.65 \\  & D (m) * & 7.41 & 13.85 \\  & GT & 2456 & 26,916 \\  & Service Speed (kn) & 19.49 & 23.00 \\  & Main Engine (kW) & 7000 & 2 \(\times\) 15,600 \\  & Type of Main Engine & Tier III (MGO) & Tier III (MGO) \\  & Auxiliary engines (kW) & 2 \(\times\) 662 & 3 \(\times\) 1254 \\  & Power take off (PTO) (kW) & 1500 & 2 \(\times\) 1000 \\  & Bow thruster (kW) & 350 & 2 \(\times\) 1000 \\ \hline \multirow{2}{*}{**Electricity demand**} & Maneuvering (kW) & 1620 & 4936 \\  & Berthing (\(kW\))-_PBJ-_ & 1200 & 1880 \\ \multirow{2}{*}{**Electricity support**} & Maneuvering & PTO + 1 auxiliary engine & 2 PTO + 3 auxiliary engines \\  & Berthing & 2 auxiliary engines & 2 auxiliary engines \\ \hline \multirow{6}{*}{**Maritime-Route 1**} & \multicolumn{2}{c}{_Vigo(Spain)–St. Nazaire (France)_} \\  & **Maritime-Route 2** & \multicolumn{2}{c}{_Las Palmas (Gran Canaria island)–Huelva (Spain)_} \\  & **Maritime-Route 3** & \multicolumn{2}{c}{_Las Palmas (Gran Canaria island)–Sta. Cruz de Tenerife (Tenerife island)_} \\ \hline \hline \end{tabular}  
* Depth to upper continuous deck for Ro-Pax vessel. *** More technical features in [PERSON] et al. [20]. *** More technical features on the base vessels: “Sorolla” (_[[http://www.bjharreras.es/?page=lis-ferriesGidp=10_](http://www.bjharreras.es/?page=lis-ferriesGidp=10_)]([http://www.bjharreras.es/?page=lis-ferriesGidp=10_](http://www.bjharreras.es/?page=lis-ferriesGidp=10_))) and “Marti i Soler” (_[[http://www.bjharreras.es/?page=lis-ferries.26_](http://www.bjharreras.es/?page=lis-ferries.26_)]([http://www.bjharreras.es/?page=lis-ferries.26_](http://www.bjharreras.es/?page=lis-ferries.26_)) \(\mathit{\&}\)_dfp=35_).  
\end{table} 
Table 1: Technical features of the fleets considered for the application cases. It should be borne in mind that the vessels' boiler emissions have not been considered in the analysis, since shore power is not an alternative for their activity [4; 14]. Consequently, even though the vessel is plugged into the land grid during the berthing stage, the vessels' boilers are working to provide the steam required for the fuel tanks' heating coils (among other uses). Table 1 also shows the maritime routes selected for the case studies. These routes involve ports that belong to electricity grids with large differences in terms of sustainability. The first, between Vigo in the northwest of Spain and St. Nazaire in Brittany (France), was selected mainly due to the different environmental footprint of the electricity grids of both countries (see Section 3.1). Additionally, this route currently operates as a European Motorway of the Sea (MoS), having been a frequently studied route for optimizing fleets in the past [20; 21]. This permits us to widen the analysis by comparing unconventional vessels (e.g., optimized feeder vessels) to the conventional ones. Case study 2, between the Canary Islands (Las Palmas port) and the Iberian Peninsula (Huelva, Spain), represents a habitual kind of shipping between continental Europe and its islands. Each island is supplied by its own electricity plants and therefore the sustainability of its grid is completely different from that on the continent (see Section 3.1). Finally, case study 3, between two islands of the Canary archipelago (Las Palmas and Sta. Cruz de Tenerife), introduces one of the most frequented maritime routes in Europe (interisland), but with the singularity of a scarce share of renewable energy sources in their electricity generation. The operation times in port were estimated through expressions published by [PERSON] et al. [21] for SSS vessels (feeder and Ro-Pax vessels).