In this paper we investigate and compare two dierent solar receiver technologies for concentrated solar power plants operating with supercritical CO2. The rst receiver is based on conventional surface absorbers, while the second receiver is based on an innovative idea to use volumetric receivers where sunlight is transmitted through a transparent pipe and directly absorbed by nanoparticles dispersed in supercritical CO2. The optical properties of the nanoparticles and the CO2 at high pressures and temperatures have been rst estimated and then used in a Navier-Stokes solver that has been coupled to a radiative transfer solver. The results indicate that for temperatures up to 700C the volumetric receiver achieves thermal collector eciencies up to 65% as compared to surface receivers with 50%.