Flexible and efficient feedforward control of concentrating solar collectors

In this work, a static feedforward strategy for concentrating solar energy harvesting is proposed to confront the weather and load fluctuations. In order to counteract the disturbance and maintain the outlet temperature by regulating the mass flow rate, we derived and deployed a generalized disturbance-control equation, which could precisely describe the relationship of the disturbance-manipulated-controlled variables. Based on this equation, disturbance-rejection and setpoint-tracking tuning issues are individually studied. Besides, the rationality of this proposed almost-linear feedforward scheme has been numerically assured regardless of whether phase-change occurs. Finally, the result temperature deviation ranging between −2 °C and 2.5 °C is still tolerable in spite of harsh operating conditions with big share of thermal loss (6% relative to effectively-received radiation), poor optical efficiency (50%) and steep change ratio of effectively-received radiation (±20%). Compared with the widely-adopted PID feedback control scheme in numerical simulation, the feedforward scheme demonstrates the feasibility and superiority in targeted regulation. The feedforward strategy directly determines the manipulated mass flow rate to answer the imposed disturbance, whereas the optimized PID scheme costs respectively about 896 s ~ 1504 s and 658 s ~ 1174 s for the current disturbance-rejection and setpoint-tracking tuners. Moreover, the controlled outlet temperature costs about additional 200 s on the basis to approach to the setpoint, of which the delays are at least two times of the feedforward scheme. A detailed feedforward measurement-control program has also been presented. Notably, the present methodology is conducive to identifying the principal portion of regulation output, which is of particular value to further construct high-performance control schemes.