As part of development of a new integrated collector storage, we experimentally studied the convective phenomena in an inclined cavity with a high aspect ratio (height: H = 1.3 m and thickness: L = 0.1 m). This integrated collector storage has a secondary circuit collecting the irradiation and transferring it at the bottom front face of the cavity. This transfer results in the concentration of the solar heat flux. To simulate the storage, the cavity was partially heated with a constant heat flux at the bottom front face over 0.2 m height. We investigated three inclined angles (30 degrees, 45 degrees and 60 degrees) and three heat flux densities, 1800, 3600 and 5400 W m(-2). Flow was essentially 2D (two-dimensional) in the lower part of the cavity and 3D (three-dimensional) in the top part. The temperature profiles showed the need to develop a system that improves stratification within the cavity. The addition of a plate parallel to the cavity's front wall creates a channel that separates the upward and downward flows, reduces the mixing effect within the storage and slightly improves the stratification. The plate causes the fluid flow to become 2D in the study plane, allowing the use of 2D numerical models. (C) 2013 Elsevier Ltd. All rights reserved.