This paper introduces a new photovoltaic module passive cooling system that works with natural cooling water circulation. The heat was removed from cooling water by a PCM-based cooling system. A special zig zag geometry of PCM container was considered to increase the heat transfer surface. At the first stage of experiments, a composed oil consisting of 82 wt% coconut oil and 18 wt% sunflower oil was used as PCM. Then, in order to increase the performance of heat transfer between PCM and cooling water, the composed oil was mixed with Boehmite nanopowder (0.009 (w/w)). The cooling performance of the composed oil and nano - composed oil was assessed by monitoring the temperature and the generated electrical power of the panel at various radiation intensities. The results reveal the reliability of the proposed system for cooling of the PV module without need to any pumping system. Moreover, the results show that using nano - composed PCM is more efficient than the plain one. The highest increase in the maximum produced power relative to the reference case were obtained in the presence of nano composed oil, which were 44.74, 46.63, 48.23% at the radiation intensities of 410,530,690 W/m(2), respectively. (C) 2019 Elsevier Ltd. All rights reserved.