Concentrating solar power systems (CSP) with thermal storage units can provide dispatchable power. Here we propose a modified design of a cavity receiver combined with a thermocline heat storage unit for the beam-down CSP. Instead of using a separate receiver and heat storage unit, an integrated unit consisting of an extended cylindrical cavity with a packed bed storage is proposed. The new approach was designed using validated cavity radiation and quasi-1D 2-phase numerical heat transfer models. As the concentrated irradiation can be directly absorbed in such a system, the structure used can be simplified and operation of the unit is more effective. A high solar-to-exergy conversion ratio of 0.52 was reached with an optimized design, charging and discharging efficiencies being well beyond 99% and 92% at 770 degrees C. An important detail in the integrated receiver-storage design was the use of a circulation air flow fan, which enhanced the heat transfer inside the packed bed storage. The proposed design is promising for improving the efficiency and economics of beam down CSP.