(369s) Modeling of a Solar Thermal Reactor for Control Purposes

A solar thermal reactor receives concentrated solar irradiation and uses this energy to thermally convert biomass into synthesis gas (H₂, CO and CO₂). The operation of this reactor is affected by the presence of clouds, which act as a disturbance for this process. During a partially cloudy day, operation of the reactor is still possible but flow rate manipulation is required in order to avoid complications in the separation processes downstream. Thus, a robust control system that will allow continuous high performance operation of the reactor is required to make the process more feasible. The proposed control system is a model predictive control system (MPC), which uses a model of the process in order to obtain the required control signal. Therefore the first step for the development of the control system is to develop a dynamic model of the process that is simple enough to be executed in real time on site. A dynamic model was developed, based on unsteady mass and energy balances, and simulated using COMSOL Multiphysics. Simulation results from this model were used to fit a time series model to be used in the control algorithm. Model validation was performed at the High Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL) using different power level inputs. In this work, a description of the model and a comparison with the experimental results are presented.