A multidisciplinary design optimization of the 5 MWth, demonstration-scale Small Particle Heat Exchange Receiver (SPHER) developed under the U.S. DOE SunShot Initiative is presented. SPHER is a revolutionary, high-temperature central receiver designed to drive a Brayton cycle or combined-cycle CSP plant that is expected to increase the overall efficiency of solar plants. The design space considered here consists of the geometry of the window of the receiver, the lateral wall angle of the receiver, and the radiative properties of the walls. As a result of the optimization, the receiver efficiency is increased by 6% with respect to the baseline design. (C) 2014 Published by Elsevier Ltd.