## 4 Experimental Results and Discussion
The description in Figure 2 indicated that the focused light efficiency formed on the focal plane by the CFL array plate was 84% of the incident optical power. However, as shown in Figure 7a, the module transmittance was about 55% under the DNI condition of \(\alpha=0^{\circ}\) and \(\beta=0^{\circ}\). This means that approximately 65% of the incident light power was transmitted through the optical module. Therefore, we conceived that it is feasible to improve the light concentration efficiency to the CCPC end surface by applying a reflective coating to the prism geometry interface, as shown in Figure 15.  
In the illumination analysis model, all optical surfaces except those represented as \"reflective coated surfaces\" in Figure 15 were set as transmission and reflection surfaces considering Fresnel loss. Figure 16 shows the module transmittance and concentrated optical power efficiency to the CCPC end surface of the modified model. In this simulation, the draft angle and the fillet radius of the CFL were set to 20\({}^{\circ}\) and 0.1 mm, respectively. The result shows the light concentration efficiency to the CCPC end surface higher than 2 times that of the \"assembled CCPC end\" shown in Figure 10 in the angular regions of \(\mid\alpha\mid<20^{\circ}\) and \(\mid\beta\mid<1.5^{\circ}\). The transmittance in the regions of \(\mid\alpha\mid<20^{\circ}\) and \(\mid\beta\mid<1.5^{\circ}\) decreased to approximately 35% compared to the results in Figure 10. The magnitudes of the CCPC end surface concentration efficiency and module transmittance are trade-off characteristics, and adjusting the number of surfaces applying the reflective coating in the linear prism geometry of the lightguide can adjust both result characteristics. Figure 14: Transmittance through the module and the measured power efficiency on the CCPC end surface and the incident surface of the Si PV cell according to variation in the incidence angle of the sun, considering experimental conditions: (**a**) transmittance through the module and (**b**) generated power efficiency. In this study, to validate the transmittance and the light collection characteristics of the proposed optical module structure, we designed and fabricated a small-sized unit module with a dimension of 100 mm (X) \(\times\) 100 mm (Y), a suitable size for the fabrication of the prototype. However, for practical implementation of large-scale simultaneous cultivation-power generation systems based on the devised structure, reducing manufacturing costs by producing larger unit modules and arranging them in an array format is deemed feasible. For instance, by manufacturing unit modules of size 100 (X) mm \(\times\) 200 (Y) mm using injection molding, it is possible to produce them for less than 4 USD, considering assembly costs even for mass production. In this case, the size of Si PV cells arranged on the CPC-shaped aspect is 5 mm \(\times\) 200 mm. Meanwhile, the unit cost of high-efficiency mono-crystalline Si PV cells is around 1.0 - 1.5 USD/W, with a power output of 4 W for PV-cell modules measuring 100 (X) mm \(\times\) 200 (Y) mm. Considering this, the material  
Figure 9:0 M Transmittance through the module and the concentrated optical power efficiency on the CCPC end surface according to variation in the incidence angle of the sun, of the modified optical module: (**a**) result of variation in \(\alpha\) and (**b**) result of variation in \(\beta\). Figure 9:1 Modified shape of the optical module with reflective coated surfaces on the prism-shaped surfaces of the lightguide. cost of high-efficiency mono-crystalline Si PV cells with the same area is approximately \(4-6\) USD. Ultimately, this is comparable to the material cost of the optical module capable of simultaneous cultivation-power generation proposed in this study. If the proposed optical module is used, compatibility issues related to power transmission are not expected since the same mono-crystalline Si PV cells can be applied.