An integrated receiver-storage (IRS) system for a concentrating solar power (CSP) beam-down system is analyzed for optimal performance and to enable efficient round-the-clock operation. For this purpose, a new in-house programme based on a transient 2-D simulation model coupling a cavity receiver and heat storage together was developed. The programme employs the Matlab (R) software and it was successfully validated against previous simulation results. The IRS-system was analyzed under realistic radiative boundary conditions. Charging and discharging processes considering radial and axial heat transfer were simulated. It was found that the impact of differences in the heterogeneous radiative boundary conditions on the system efficiencies were limited. The differences between the 2-D coupled model and a decoupled 1-D thermal models were at largest in the start-up of the IRS with a relative error of 5.6%, but the differences smoothened out over time. Analyzing the overall efficiency of the IRS system indicated that the performance of IRS is very good and the IRS could well be applicable for beam-down CSP. Charging and discharging efficiencies of 99% and 93% and a solar-to-exergy conversion ratio of 0.53 could be reached.