Direct absorption evacuated tube solar collectors are a new type of collector that has great potential to use in a solar system. In the present work, energy analysis of the direct absorption evacuated tube solar collectors employing Al2O3 nanoparticles is investigated numerically. A three-dimensional computational fluid dynamics simulation model is developed in ANSYS-Fluent software. The working fluids which are selected in this study are Al2O3 nanoparticles dispersed in water and EG. The effect of the two volume fractions (0.04% and 0.06%) of the nanofluid is investigated on thermal performance of the DAETC. In addition, the temperature distribution of the system is examined based on different volume fractions of the nanofluids. The results show that the outlet temperature difference of 0.04% Al2O3/EG is improved by 19.34% with respect to 0.04% Al2O3/water and for 0.06% Al2O3/EG is improved by 16.45% with respect to 0.06% Al2O3/water nanofluid, respectively. The results also reveal that the collector efficiency of 0.04% Al2O3/water, 0.06% Al2O3/water, 0.04% Al2O3/EG, and 0.06% Al2O3/EG nanofluids are 69.77%, 71.39%, 66.68%, and 69.43%, respectively. The 0.06% Al2O3/water and 0.06% Al2O3/EG nanofluids have the highest collector efficiency and outlet temperature difference, respectively.