In this paper, thermal performance of a direct absorption based solar thermal collector seeded with water dispersed copper nanospheroids (having different aspect ratios, such as A=2, 3, 4, 5 and 6) has been investigated. For the investigation, a 2-D channel has been simulated and the effect of different parameters (mass flow rate, intensity of the incident radiation, height of the solar collector and the volume fraction of the nanoparticles) on the collector efficiency has been investigated. For the simulation model radiative transfer equation (RTE), Navier-Stokes equation for a fully developed laminar flow and 2-D heat transfer equations have been solved simultaneously. It has been seen that the absorbed energy fraction is dependent of aspect ratio and the volume fraction of the nanoparticles and A=5 is an optimum aspect ratio. Further, the collector efficiency increases with increase of mass flow rate of the nanoparticles laden fluid inside the solar collector and collector efficiency decreases with the increase of the height of the collector. It has been found that the solar thermal collector performs efficiently at an optimum volume fraction of the nanoparticles. The results of this study will be helpful in developing the nanoparticles-laden fluid based solar collector using prolate copper nanospheroids nanoparticles.