An advanced control system for the operation of solar process heat plants and a simulation program for the design were developed. A flexible test facility was installed in order to qualify the control system and the simulation model. It consists of different small collector fields, two storage tanks, an auxiliary electric heater and an adjustable heat sink for simulating any load profile. The advanced control system provided a fast control of the necessary collector field outlet temperatures and an effective compensation for any disturbances. The simulation program based on TRNSYS was extended to meet the requirements for the design of solar process heat plants.