In this study, carbon-based nanofluids (CBNFs) were prepared using a revised vortex trap method and applied in the direct absorption solar collector (DASC) to evaluate the feasibility of CBNFs in DASC. The thermal storage performance of water and different concentrations of CBNFs (0.01, 0.025 and 0.05 wt%) was assessed with a 1000 W halogen lamp as a simulated light source under different volumetric flow rates (1.5, 3.0, and 4.5 L per minute [LPM]) at a constant thermal storage load (2.4 kg of water) and ambient temperature of 26 °C. The thermal storage capacity, system efficiency factor (SEF), and heating rate of the CBNFs as the working fluid were higher than those of water in most cases. The thermal storage capacity and SEF of 0.05 wt% CBNF at a volumetric flow rate of 3.0 LPM were 10.36% and 9.36% higher than that of water, respectively. The relevant experimental results demonstrate the great potential of CBNFs in DASC.