# Developments in Electric and Green Marine Ships
## 4 Calculating onboard PVs and Battery Capacity  
The table below includes all the symbols that will be used in the present section and their definitions, Table 2. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Descriptions**} & \multirow{3}{*}{**Bluefin’s**} & \multirow{3}{*}{\begin{tabular}{c} **CDL** \\ **Subsea** \\ **Battery** \\ **Pack** \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} **Southwest** \\ **Electronic** \\ **Energy** \\ **Group** \\ **(SWE)** \\ \end{tabular} } & \multicolumn{3}{c}{\begin{tabular}{c} **Furukawa** \\ **Battery** \\ **Company of** \\ **Light** \\ **Marine** **Batteries** \\ **Power** \\ \end{tabular} } & \multicolumn{1}{c}{\
\begin{tabular}{c} **PBES** \\ **Lithium** \\ **Industrial** \\ **Batteries** \\ \end{tabular} } \\  & & & & & & **Marine** & **Batteries** \\ \hline Cell Type & Lithium- &
\begin{tabular}{c} Nickel-metal \\ poly \\ battery \\ \end{tabular} & Lithium-ion & Lead-acid & Lead-Carbon & Lithium-titanate \\ Dimensions & & & & & Technology & Lithium-titanate \\ Length (mm) & 384 & 500 & 1910 & 457 & 508 & 580 \\ Width (mm) & 133 & 400 & 1890 & 305 & 303 & 320 \\ Height (mm) & 210 & 450 & 650 & 327 & 172 & 380 \\ Area (m\({}^{2}\)) & 0.051 & 0.200 & 3.610 & 0.139 & 0.154 & 0.186 \\ Volume (m\({}^{2}\)) & 0.011 & 0.090 & 2.346 & 0.046 & 0.026 & 0.071 \\ Mass (Dry) (kg) & 14.3 & 46 & 75 & 49 & 75 & 90 \\ Energy Capacity (kWh) & 1.5 & 0.95 & 3.2 & NA & 2 & 3.5 \\ Energy Density (tors/MWh) & 23.34 & 24.02 & 23.438 & NA & 27.500 & 25.714 \\ Area per MWh (m\({}^{2}\)/MWh) & 34.048 & 210.526 & 21.091 & NA & 76.962 & 53.029 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Marine batteries. Figure 7: UB 5012 Battery Pack [61], © 2019 The Furukawa Battery Co., Ltd.  
As it has already been mentioned, the total power needed for a ship's operation depends mostly on the category to which this ship belongs (cargo, ferry, cruise, etc.). Hence, the number of solar panels in order to produce the required power differs. Due to that, the present research investigates ships that belong in different categories. Apart from the difference in power requirements among ships from different categories, there is also an important difference concerning the produced power by the solar panels. To be specific, it is commonly known that solar radiation is not constant, neither throughout the day, nor throughout the year. Furthermore, the duration of sunlight varies significantly depending on the season of the year and the area of the world. Therefore, two different methodologies exist when calculating solar radiation. The first is to calculate the radiation for an average day of the year, with average weather and at an average geographical sea location. The second is to decide a specific case scenario, on a specific location and time of year, and use the regional available weather data. Each methodology has advantages and disadvantages. In the present research, the second way is chosen. Specifically, the location chosen is in the Aegean Sea (Greece), in the area near Attica, and the time of the year is an average day of July. A summer month was chosen, because during that period, tourist activity--and thus ship travels--reaches its peak. Additionally, this is also when solar radiation in the area is the strongest. For an average day of July in the Aegean Sea near Attica, solar radiation equals [68]:  
\[\mathbf{I_{total}}=528.7\ \text{W/m}^{2}\text{, on a horizontal plate} \tag{1}\]  
In our days, solar panels have had the biggest technological advancements. The peak efficiency of a solar panel can reach 22.2%. In the present research, a panel of 22% efficiency, 1.6 m\({}^{2}\), and 18.6 kg is assumed. The efficiency could be considered utopic, but is selected as such on purpose. If this proves insufficient, then PVs can be considered incapable of powering a ship's power requirements wholly or at least significantly.