The study is focused on the effects of a high and transverse temperature gradient on the performances of a solar receiver. To better understand these effects, we perform Thermal Large Eddy Simulation on a turbulent channel flow with imposed wall temperatures. The first analysis of the temperature gradient impacts shows that a dissymmetry appears in all the profiles and points out a strong effect on the fluctuation parts. Heat transfer coefficients on the hot wall (wall of interest) decrease with the increase of the temperature ratio. The study of the fluctuations could explain this phenomenon. Indeed, the fluctuations and the turbulence intensity appear to be tightened on the cold side and damped on the hot side. The study in the spectral domain confirms this mechanism. Moreover it reveals that the transverse temperature gradient modifies the energy cascade.