Dual Actuator Control Strategy for Temperature Stability in High-Temperature Solar Receivers

Abstract

Fluctuations in incoming solar energy adversely affect the temperature stability within solar receivers, leading to a decrease in thermal efficiency. Therefore, it is essential to design a control system with the capability to maintain quasi-steady temperatures inside the reactor consistently throughout the day. This study introduces a dual-actuator control technology to regulate the temperature within a high-temperature cylindrical cavity-type gas receiver. The actuating system comprises two primary components. The first component involves a variable aperture mechanism, executed through a rotary mechanism made of stainless steel. This mechanism features seven holes of fixed diameters arranged in a half-circle configuration. The rotary mechanism is powered by a stepper motor regulated by a feedback control system. The second actuator is a mass flow controller (MFC) responsible for meticulous adjustment of the inlet gas flow directed toward the solar receiver. The direct normal irradiance (DNI) is simulated using a 10 kW high-flux solar simulator (HFSS) with a variable power supply ranging from 80 to 200 A. This setup enables the simulation of different operational conditions. The dual-actuator method concurrently adjusts both gas flowrate and aperture size. While utilizing each of these methods individually can achieve reasonable temperature control performance, the hybrid approach leverages the strengths of both control methods, resulting in a significant improvement in the temperature regulation performance of the solar receiver. Two control strategies, namely, proportional integral (PI) and model predictive control (MPC), were implemented to regulate the temperature inside a cavity-type gas receiver. Experimental tests indicate that the incorporating the dual-actuator controller is a promising technique, and its application can be extended to include additional parameters for utilization in a multi-input multi-output (MIMO) control system.