(756h) Control System Design for Small Size Isolated Concentrated Solar Power Generation Units

Electricity generated by small size concentrated solar power (CSP) driven Rankine cycle (RC) is an increasingly explored alternative for powering isolated homes / small communities. In these units, solar energy is captured to raise the temperature of a heat transfer fluid (HTF). The hot HTF drives a low temperature Rankine cycle to generate electricity for the household(s). Since the solar flux follows the diurnal transient cycle along with high variability in the power consumed, very large inventory of the HTF is needed to store the solar energy and supply heat to the Rankine cycle as per power demand, including when the solar flux is zero at night. There then is no steady state for the process and it must be designed for inherently transient operation over a very large operating window. A well designed control system that provides robust operation for such a large operating window is then essential. In particular, it should effectively handle process constraints such as maximum/minimum HTF tank level limits etc. This paper evaluates robust control system design for a small size isolated CSP-RC power generation unit. A robust control strategy with appropriate overrides for handling process constraints is developed and tested using rigorous dynamic simulations. The closed loop dynamic simulation is also used for sizing the necessary HTF inventory.