## 6 Energy Analysis
### Series Configuration  
The second configuration considered was series configuration, for two different temperatures and fishing vessels tonnage, i.e., the small fishing vessel A in the North Sea and the bigger fishing vessel C in the Indian Ocean, which represents the worst case, in terms of temperatures and cooling load. One of the parameters that can be optimized in the series configuration is the amount of cooling load that each unit can provide. For the present case, according to the temperature levels and schematics presented in Figure 12, the AC carbon/ethanol prototype was sized to cover 70% of the overall cooling load, i.e., the base load needed to bring the fish to a temperature of 2/3 \({}^{\circ}\)C, while the remaining load was provided by the compression chiller. The overall system was a water/water system, meaning that the heat transfer fluid in all circuits was brine (i.e., water/glycol mixture), different from the cascade configuration previously analysed. Indeed, it is intended for refrigeration and storage of fish that require higher temperatures, i.e., \(-5\)\({}^{\circ}\)C to \(-10\)\({}^{\circ}\)C.  
At first, the fraction of waste heat used was calculated: for fishing vessel A in the Indian Ocean it was about 90% of the overall heat from the cooling circuit of the engine, whereas for vessel C in the North Sea it was 70% of the overall heat available from exhaust gases. In the latter case, indeed, the heat from the cooling circuit of the prime mover was too low to power the sorption system and therefore the installation of a waste heat recovery heat exchanger was considered. The results of the energy analysis on the series configuration are reported in Table 10. Compared to the case of cascade configuration, the energy savings were significantly higher, i.e., 71-73% against 33%. This is due to different features linked to the operation of the system: on the one hand, a relevant fraction of the load was covered by the sorption system, with a reduced electricity consumption due to \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **System** & **A** & **B** & **C** & **D** \\ \hline North Sea & Cascade & 1.3 m\({}^{3}\) & 2.4 m\({}^{3}\) & 3.0 m\({}^{3}\) & 1.2 m\({}^{3}\) \\ Indian Ocean & Cascade & 1.5 m\({}^{3}\) & 2.8 m\({}^{3}\) & 3.4 m\({}^{3}\) & 1.4 m\({}^{3}\) \\ North Sea & Compression & 0.2 m\({}^{3}\) & 0.4 m\({}^{3}\) & 0.5 m\({}^{3}\) & 0.2 m\({}^{3}\) \\ Indian Ocean & Compression & 0.3 m\({}^{3}\) & 0.5 m\({}^{3}\) & 0.6 m\({}^{3}\) & 0.3 m\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Volume needed for the installation of the cascade in different fishing vessels and seawater conditions. the auxiliaries only; on the other hand, the temperature lifts for the units were quite different. It can be seen that, for the examined cases, the fuel savings were double the ones reported in Figure 14. On the contrary, as previously discussed, there are some limitations in the installation of such a sorption system, since it is not suitable for all conditions due to the higher evaporation temperatures for the proper operation. Moreover, when considering the activated carbon/ethanol working pair, due to the high amount of heat needed, not all the examined conditions are feasible. Such a restriction, instead, does not apply for the CaCl\({}_{2}\)/ammonia system. The volume needed for the installation was calculated as well: 0.8 m\({}^{3}\) was needed for vessel A in Indian Ocean conditions and 1.6 m\({}^{3}\) for vessel C in North Sea conditions. The reference system, i.e., the R744 compression chiller that covered the whole load, required instead 0.3 m\({}^{3}\) in vessel A the for Indian Ocean and 0.7 m\({}^{3}\) for vessel C in the North Sea. Compared to the previous case, the difference between the waste-heat powered system and the reference one was lower, due to the fact that, in this case, the sorption system was undersized compared to the overall load (which was, in turn, lower, due to the higher storage temperatures).