## 6 Conclusions  
In this paper, the thermo-optical performance using novel cooling strategy improvements for a hybrid photovoltaic/parabolic dish concentrator with a conical thermal receiver using a beam splitter filter (PV/PDC-CTR-BSF) is investigated. The results show that the PV/PDC-CTR-BSF system performance can be enhanced by improving the effectiveness of the cooling ducts through appropriate selection of the cooling duct cross-section and its placement and orientation with respect to the back sheet of the PV panel. With the advent of 3D printing technology, the back sheets could be 3D-printed with embedded cooling ducts of different cross-sections at different locations and orientations that allow for increased heat transfer and thus improve PV/PDC-CTR-BSF's thermos-optical performance. Typical cooling ducts are employed for dissipating excess heat from under the PV panels that have either a rectangular or circular cross-section and are usually placed right under the back sheet of the PV panel. The novel aspect of the current study is that, in addition to the typical rectangular cooling ducts, ducts with semi-circular, semi-elliptical and triangular cross-sections were considered. Furthermore, for each of the cooling duct cross-sections, several positions and orientations, which include flush below the back sheet layer and  
Figure 12: The back sheet bottom-side (**left**) and cooling duct mid-plane temperature distributions for the triangular duct for the four locations and orientations. (**a**) Triangular duct flush on the outside bottom; (**b**) triangular duct flush on the inside bottom; (**c**) triangular duct embedded in the middle; (**d**) triangular duct flush on the inside top. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Investigators** & **Type of Study** & **Type of CS System** & **Type of Cooling System** & **Optical CR** & **Cooling Fluid** & \(\Delta\)**T** (°C) \\ \hline [PERSON] et al. [9] & Numerical and experimental & One-axis tracked east-west parabolic trough concentrator & Thermosymbon external to the system & 20 suns & R-11, R-22 and water & 21 \\ \hline [PERSON] et al. [33] & Experimental & Compound parabolic concentrator & Fins external to the system & 1.86 suns & air & 18 \\ \hline [PERSON] et al. [12] & Numerical & Compound parabolic concentrator & Duct external to the system & 2 suns & water & 7.7 \\ \hline [PERSON] et al. [34] & Numerical & Linear flat mirror concentrator & Channel external to the system & 24 suns & liquid & 23.9 \\ \hline \multirow{3}{*}{Present work} & \multirow{3}{*}{Numerical} & Hybrid photovoltaic/ parabolic dish concentrator & Channels embedded within the PV back sheet with different cross-sections and locations & 6.4 suns & water & 29-33 \\ \cline{1-1}  & & & & locations & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison with previous studies. embedded inside the back sheet but positioned at the bottom, middle and top of the back sheet, were examined. The following important conclusions can be gleaned from this study:  
* The results prove that the conventional rectangular cross-section cooling duct is the least effective configuration in cooling the PV panel back sheet and removing heat as compared to the other cross-section considered in this study. * The results show that cooling ducts that are an integral part of the back sheet, i.e., the ducts that are embedded within the back sheet, are more effective in removing the heat from the PV back sheet. * Amongst the cases studied, case (a), representing ducts flush at the bottom of back sheet, irrespective of the cross-section, resulted in the lowest heat transfer rate \(\dot{q}_{out}\) as well as the highest cooling fluid temperature \(T_{out}\) at the exit of the duct.