The performances of a photovoltaic system based on high-efficiency commercial monocrystalline Si solar cell associated with the water flow lens (WFL) system are investigated. This system enables the cooling of the surface of the cell, indirectly cooling the surrounding, and, on the other hand, it allows us to investigate, depending on the position of the cell and the WFL system, the influence of larger and smaller intensities of the light with the inevitable change in the spectrum. All of these effects are very important and can greatly contribute to the better photovoltaic performance of the used cells. Indoor characterization at higher and lower light intensities is performed using both different spectra and intensity of the light. The obtained results show that at low/lower light intensity, spectra are more dominant than the intensity of light itself and that the used WFL system always improves the photovoltaic response leading to a higher efficiency of the tested solar cell. It was found that the ratios of the short circuit current (I-sc) and the input light energy (P-input) are 4.42 and 8.96 without and with the use of the WFL system in the measurements, respectively. The same Si solar cell is also tested in outdoor condition, but this time using the WFL system to concentrate sunlight to produce a larger amount of power and water flow for cooling the surface of the solar cell. Again, a higher efficiency (an increase from 25.7% to 33.5%) by using the WFL system was obtained.