# Developments in Electric and Green Marine Ships
## 4 Calculating onboard PVs and Battery Capacity
Knowing the efficiency of the panel, the area of it, and the solar radiation available gives the total power output of the panel \(Pp\):  
\[\mathbf{P_{p}}=\mathbf{I_{total}}\ ^{*}\mathbf{A_{p}}\ ^{*}\mathbf{n_{p}}=188\ \text{W/panel} \tag{2}\]  
Having calculated the power that a solar panel can produce leads to finding how many panels are required in order to power a ship. Of course, installing an on-board PV system fully covering the operational power requirements of a ship would be extremely difficult, if not impossible, with the current commercial and industrial technology. Such an installation would require a large number of panels that would not be able to fit on-board. The panels must face the sunlight, and that means being placed on the top of the ship. As mentioned before, there are many ship categories with different specs, different power requirements, and thus different required PV installations to cover a fixed percentage of their power \begin{table}
\begin{tabular}{c c} \hline \(I_{total}\) & Solar radiation \\ \(P_{P}\) & Power output of one panel \\ \(Ap\) & Surface area of one panel \\ \(np\) & Efficiency of each panel \\ \(P_{e}\) & Electric power requirements \\ \(A_{deck}\) & Surface area of a vessel’s deck \\ \(L_{ship}\ ^{u}\) & Ship’s useful length for PV installations \\ \(W_{ship}\ ^{u}\) & Ship’s useful width for PV installations \\ \(A_{TP}\) & Surface area required for the total number of panels \\ \(P_{NMHS}\) & Power requirements for the Nissos Mykonos vessel \\ \(E_{NMHS}\) & Energy requirements for the Nissos Mykonos vessel \\ \(T_{trip}\) & Total trip duration \\ \hline \end{tabular}
\end{table} 
Table 2: Symbol definitions. needs. Additionally, the architecture of the vessel plays a decisive role in the feasibility of such an installation. For example, a LoLo (Lift on Lift off) vessel or a cargo etc., is unable to install PV on the deck, and the only available space is on top of the bridge. Starting from the category of cruise ships, a specific one is chosen for comprehensive reasons. The results and conclusions for that ship will also refer to other ships of the cruise category. The cruise ship chosen is the _Voyager of the Seas_ with a length reaching 311 m and 47 m width [69]. The Voyager's capacity is 3184 passengers plus the required crew. The total power output of the ship's engines is around 75.6 MW. The distribution of that power is around 41% for propulsion, 34% for heat production, and the rest is 25% for electric power generation, as shown in Figure 8. So, the actual power needed to cover the electric needs of the Voyager, \(P_{e}\), is around 18.75 MW. The Voyager, being a luxurious cruise ship, has a great variety of outdoor activities, leaving no room for even the smallest solar panel installation. As a result, it cannot incorporate power production with solar panels. Nevertheless, other ships with similar size and power demand to Voyager's could theoretically install solar panels at their top. For such ships, taking the Voyager as an example, in means of size and power needs, an average available area on the top deck \(A_{\text{deck}}\) is around 10,500 m\({}^{2}\). Where:  
\[A_{\text{deck}}=L_{\text{ship}}{}^{u}*W_{\text{ship}}{}^{u} \tag{3}\]  
\[L_{\text{ship}}{}^{u}=300\text{ m},\,W_{\text{ship}}{}^{u}=35\text{ m} \tag{4}\]  
where \(L_{\text{ship}}{}^{u}\), \(W_{\text{ship}}{}^{u}\) are ship's useful length, width. The particular available area could accommodate around 6562 cramped solar panels of 1.6 m\({}^{2}\) each. The calculation of the power output of each panel results in a total power output of 1.234 MW from all the installed panels. That amount of power equals 1.6% of Voyager's total required power, or 6.6% of the power required for electricity production. It is clear that even if there was space available, and thus a capability of installing solar panels in Voyager, the amount of the power produced would be insufficient to cover even 7% of the electrical needs, or 2% of the ship's total power demand.