Due to the fast-growing of green energy, projects of wind-farms are planed closer and closer to the minimum regulation distances of radio navigation devices (radar, VOR ...). To assess the impact of this windfarms close to radio-navigation devices, modelling tools are in developments [1-4]. Generally, robust modelling methods (MoM) are used to compute the field scattered by the windturbines [1, 2]. However, assumptions must be done to save memory and computation time and different modelling methods are based on physical optics [3, 4] or UTD [2]. Besides, in literature, interactions between windturbines are always neglected. This paper investigates the relevance of the latter. Indeed, to lower their impact, a simple idea would be to place windturbines behind the one closest to the transmitting antenna to take advantage of the shadowing effect. Therefore, the shadowed windturbine scattering would be reduced. Nevertheless, this effect mainly depends on the distance and the frequency. In this paper, the necessity to account for the shadowing effect between windturbines is established at VOR and radar frequencies to notify wind-energy developer about the shadowing effect of windturbines. The interactions between the windturbines is shown to be negligible at VOR frequency while at radar frequencies, it is not the case and need to be taking account in simulation tools.