## 5 Integration of Sorption Systems On-board
### Feasibility Evaluation of Integrated Configurations  
The evaluation of a specific solution among the proposed ones is strongly dependent on different constraints. Indeed, the installation of the systems previously described might need additional volume compared to traditional solutions. Furthermore, such systems are usually heavy and therefore might lead to a penalization in the fuel consumption during shipping. As a pre-feasibility screening parameter, the possibility of driving the sorption system totally with the waste heat from engines was evaluated. In order to reduce the penalisations due to the sorption units on-board, it is of paramount importance that there is no need for integration of the driving heat source. For the critical analysis, it was assumed that the system works in steady-state conditions, i.e., the heat source temperature, seawater temperature, and user-side temperature are constant. The boundary conditions for each configuration, in terms of temperature levels and efficiency of the sorption and compression units, are shown in Tables 4 and 5. In the evaluation of the performance of the sorption systems, the following parameters were employed:  
* Thermal _COP_, the ratio between the cooling energy delivered and the driving heat needed: \[\mathit{COP}=\frac{Q_{\mathit{cool}}}{Q_{\mathit{heat}}}.\] (8)
* _EER_ (energy efficiency ratio), the ratio of the cooling energy delivered over the electricity needed to drive auxiliaries: \[\mathit{EER}_{\mathit{sorption}}=\frac{Q_{\mathit{cool}}}{E}.\] (9)
* The _SCP_ (specific cooling power), i.e., the normalized cooling power per unit of sorbent that the chiller can deliver: \[\mathit{SCP}=\frac{Q_{\mathit{cool}}}{m_{\mathit{sorb}}}.\] (10)  
Figure 12: Series cooling system configuration. 1—engine; 2—sorption chiller; 3—seawater condensing heat exchanger for sorption chiller; 4—vapour compression chiller; 5—seawater condensing heat exchanger for compression chiller; 6—brine heat exchanger for compression chiller; 7—brine heat exchanger for sorption chiller; 8–9—three way valves for series operation; 10—cold room. (**a**) operation of the sorption chiller only for baseload; (**b**) series operation with combined cooling effect from the sorption and compression chillers. As previously stated, the preliminary condition to be fulfilled by each configuration is the possibility of relying only on waste heat from the engine for driving the sorption cycle. To achieve this, the number of hours, over the total, during which the integrated systems presented can be driven by the waste heat from the engine in each case are presented in Table 6.  
As can be seen, due to the low COP of the AC/ethanol system, application on bigger size vessels (vessel B and C) is possible only in the North Sea, where seawater temperatures are lower and the efficiency of the system is higher. On the contrary, the system can be applied in medium size vessels (type A), for all routes worldwide. For fishing vessel D, i.e., the smaller vessel among the examined ones, even though the cooling load is lower, since the engine is also smaller, the amount of waste heat is still insufficient to drive the system. On the contrary, the CaCl2/ammonia system is suitable for all the examined conditions, since it can be run by waste heat in each case.