Simulation of vertical-axis wind turbines (VAWT) is challenging due to the high-speed rotation of the blades, complex high-Reynolds number turbulent flow with massive separation involved. Addressing such problems requires an efficient numerical approach to robustly handle the dynamics of the geometry while accurately predicting the flow dynamics. DNS simulations have been conducted for the first time to the best of the authors knowledge on a VAWT. This was achieved by using a framework incorporating a moving reference frame formulation (MRF) of Navier-Stokes (NS) equations with the spectral/ hp method within the Nektar++ framework. DNS was performed upon a quasi-3D (homogeneous extrusion of the 2D model in the 3rd dimension), three-bladed, straight-bladed Darrieus VAWT. The environmental conditions were akin to the low pressure, low Reynolds number atmosphere found on Mars allowing for this work to be extended to assessing VAWTs potential as an energy source on extra-terrestrial missions, connecting high-order methods to industrial applications. The effect of the order of the polynomial expansion of the variables as well as the resolution within the extrusion upon the present vortex dynamics and aerodynamic forces has been assessed.