LAUSR

Abstract This work presents the design of a robust decentralized PI control system for a small scale, grid isolated concentrated solar power (CSP) – biogas hybrid unit. The biogas is readily available in remote and rural areas in the developing countries and its hybridization with a CSP unit as a supplementary source of heat for enhanced power backup is an attractive option. The considered system utilizes an organic Rankine cycle (ORC) for power generation. The control system is designed to supply the user demanded power to the extent possible with appropriate override controllers to ensure safe and stable operation as the thermal energy storage (TES) approaches the high or low limits. These overrides encompass shutdown and start-up of the biogas burner firing and the ORC at low TES level as well as appropriate reduction in the captured solar flux at high TES level. Closed loop results demonstrate the robustness of the control system to very severe disturbance scenarios with the TES storage never breaching the full or empty limits. Results also show that the hybridization with biogas heating gives extra back-up varying from 1.1 h to 6 h depending on the power demand.