## 2 Material and Methods
### Weather Data
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**Cities** & **JAN** & **FEB** & **MAR** & **APR** & **MAY** & **JUN** & **JUL** & **AUG** & **SEP** & **OCT** & **NOV** & **DEC** & **Year** \\ \hline Heraklion & 27.6 & 34.4 & 52.6 & 66.8 & 81.5 & 84.3 & 84.3 & 74.1 & 57.2 & 42.8 & 29.4 & 24.8 & 659.8 \\ Athens & 25.1 & 32.0 & 50.4 & 65.6 & 81.8 & 85.5 & 85.2 & 73.7 & 55.5 & 40.1 & 26.3 & 21.8 & 643.0 \\ Thessaloniki & 21.8 & 29.2 & 47.3 & 64.2 & 82.0 & 86.6 & 86.1 & 73.1 & 53.6 & 36.9 & 23.1 & 18.7 & 622.6 \\ Kastoria & 22.5 & 29.7 & 48.1 & 64.3 & 81.7 & 86.6 & 86.0 & 73.2 & 53.7 & 37.4 & 23.5 & 19.1 & 625.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Data for the daily diffuse solar irradiation on the horizontal surface (\(\rm H_{d}\)) in [\(\rm KWh/m^{2}\)]. Figure 3: The examined cities and the Greek climate zones, Reprinted with permission from ref. [32], Copyright 2015 Elsevier (License Number: 5290151135624). \[\omega_{s}^{\prime}=min\bigg{[} \begin{array}{c}\cos^{-1}(-\tan(\varphi)\cdot \tan(\delta))\\ \cos^{-1}(-\tan(\varphi-\beta)\cdot\tan(\delta))\end{array} \bigg{]} \tag{18}\]  
where (\(\varphi\)) is the geographical latitude of the examined city and (\(\delta\)) is the declination angle of the mean monthly day. More details about the calculation of the declination angle can be found in Ref. [27]. Table 5 gives the results of the solar energy on the tilted surface for different angles and locations. The next step regards the temperature levels of the air and the water. The mean monthly temperature (T\({}_{\rm am,m}\)) and the mean monthly water temperature from the grid (T\({}_{\rm w,m}\)) are the temperature levels that are needed for all the months and all the studied locations. Table 6 includes all the data provided by Ref. [29]. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Heraklion**} & \multicolumn{2}{c}{**Athens**} & \multicolumn{2}{c}{**Thessaloniki**} & \multicolumn{2}{c}{**Kastoria**} \\ \cline{2-10}  & **T\({}_{\rm am,m}\)** & **T\({}_{\rm w,m}\)** & **T\({}_{\rm am,m}\)** & **T\({}_{\rm w,m}\)** & **T\({}_{\rm am,m}\)** & **T\({}_{\rm w,m}\)** & **T\({}_{\rm am,m}\)** & **T\({}_{\rm w,m}\)** \\ \hline JAN & 12.1 & 14.7 & 8.7 & 11.3 & 5.3 & 8.2 & 2.2 & 4.2 \\ FEB & 12.2 & 14.2 & 9.3 & 10.9 & 6.8 & 7.9 & 3.4 & 5.0 \\ MAR & 13.5 & 14.8 & 11.2 & 11.8 & 9.8 & 9.2 & 6.9 & 7.5 \\ APR & 16.5 & 17.2 & 15.4 & 14.3 & 14.3 & 12.8 & 11.5 & 11.5 \\ MAY & 20.3 & 20.6 & 20.7 & 17.7 & 19.7 & 16.8 & 16.4 & 15.7 \\ JUN & 24.4 & 24.5 & 25.7 & 21.6 & 24.5 & 20.2 & 21.4 & 19.8 \\ JUL & 26.2 & 27.3 & 28.1 & 24.7 & 26.8 & 21.5 & 24.0 & 22.2 \\ AUG & 26.1 & 28.2 & 27.5 & 25.7 & 26.2 & 22.8 & 23.2 & 22.7 \\ SEP & 23.6 & 27.2 & 23.4 & 24.2 & 21.9 & 22.1 & 18.9 & 20.2 \\ OCT & 20.1 & 24.7 & 18.2 & 21.1 & 16.3 & 19.4 & 13.4 & 15.9 \\ NOV & 16.7 & 20.9 & 13.8 & 16.9 & 11.1 & 15.7 & 7.2 & 10.8 \\ DEC & 13.7 & 17.2 & 10.3 & 13.5 & 6.9 & 11.0 & 3.0 & 6.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Mean monthly air temperature (T\({}_{\rm am,m}\)) and mean water temperature from the grid (T\({}_{\rm w,m}\)) expressed in [\({}^{\circ}\)C].