Reducing the operating temperature of a photovoltaic (PV) module is an effective way to improve efficiency and prevent damage from overheating. The present paper focuses on the study of the effect of inclination on air natural convection in an asymmetrically heated channel (at uniform heat flux), in laminar regime. This configureuration models the passive and natural air-cooling of PV panels by inclined chimneys. The computational procedure solves the unsteady two-dimensional Navier-Stokes and energy equations by a finite volume approach while the projection method decouples the pressure from the velocity. The heat transfer and fluid flow are analyzed for a wide range of modified Rayleigh numbers varying from 102 to 105 and for inclination angles between 15o and 90o with respect to horizontal position. The results show that the mass flow rate and the average Nusselt number increase with the angle of inclination as well as with the modified Rayleigh number. However, a significant reduction in heat transfer rate and induced flow rate is observed for the low angles of inclination. To enhance the cooling of the PV panel, extensions are added at the inlet and outlet of the channel. The simulations show that only the downstream extensions of the channel are effective in improving the induced mass flow rate and therefore the convective heat transfer.