On the Convenience of Using Simulation Models to Optimize the Control Strategy of Molten-Salt Heat Storage Systems in Solar Thermal Power Plants

Abstract

Thermal oil has been used as heat transfer fluid in many solar thermal power plants, which also use molten salts as thermal energy storage system. Since the engineering of these plants is relatively new, control of the thermal energy storage system is currently achieved in manual or semiautomatic ways, controlling its variables with proportional-integral-derivative (PID) regulators. Once the plant is running, it is very difficult to obtain permission to try new control strategies. Hence, most plants keep running on these simple, sometimes inefficient control algorithms. This paper explores the results obtained with different control strategies implemented on a complete model of energy storage systems based on molten salt. The results provided by the model allow the optimum control strategy to be selected. Comparison of the results obtained by simulation of these control strategies and actual results obtained from a real plant, confirm the accuracy of the selection made.

Model Predictive Control of a Solar Power System with Microturbine and Thermochemical Energy Storage

“…In most TES-based solar systems, flow rate control is the most popular control strategy. The execution units are either pumps , or valves, , or the combination of both. − In some cases, the classical PID controller can satisfy the control requirements. ,,, However, with the increasing system complexity, more advanced methods were attempted in TES-based solar system control. For example, the supervisory control structure is applied to solar cooling systems with storage tanks , and a combined cycle power plant with double-tank molten-salt storage, respectively.…”

“…Leo et al used linear quadratic regulator with integral action of output to regulate the outlet oil temperature and the tank level of the molten-salt TES. Prieto et al ,, compared different control strategies, namely, feed-forward PID, feed-forward advanced PID, and feed-forward adaptive-predictive control and found that the third strategy presented the best stability and setpoint tracking performance. The hierarchical control scheme is also performed in the power industry.…”