This paper investigates the performance of direct and indirect passive cooling systems of phase change material(PCM)/flat heat pipes (FHP) for low-concentrated photovoltaic solar panel (LCPV) via compound parabolic collector (CPC). The study is performed in the case of not including and including the CPC at different concentration ratios and FHP condenser lengths. The system is entirely mathematically modeled and solved using MATLAB software and validated via experimental setup. The study is performed to cool the panel with PCM attached at its back (direct) or transfer the PV's excess heat to the PCM via FHP (indirect). Results show that indirect cooling system outperforms the direct one with and without CPC system for power generation and efficiency. Both cooling systems mitigate the panel operating temperature without the CPC system, compared with the reference panel. However, the direct approach (LCPV-PCM) has a panel's temperature higher than the reference one including CPC. Contrarily, the indirect cooling system (LCPV-PCM/FHP) has operating temperatures lower than the reference panel at C = 2, while at C = 4, LCPV-PCM/FHP has operating temperatures higher than the reference panel. The maximum produced power from LCPV-PCM/FHP at C = 4 and 30 cm condenser length is equivalent to 3.71 times compared with the reference panel.