MILP Algorithm for outlet temperature optimization of a hybrid concentrated solar system for SHIP considering a 1D solar field and a dual phase thermocline storage
Résumé
Solar Heat for Industrial Processes (SHIP) is in an increasing trend in research for industrial decarbonization. Process heat demand and solar energy can both present large intermittencies. Storage gives a degree of freedom on which mathematical optimization can be performed. Lowering the working temperature of the solar field decreases the heat losses and therefore maximizes the production; it also reduces heat losses from the storage while increasing its use in the operational phase. In this paper, the investigated system is a solar field consisting of low-cost Parabolic Trough Collectors in series with Linear Fresnel Receivers, in series with a dual-phase thermocline storage. A MILP (Mixed Integer Linear Programming) algorithm is used in order to obtain a control trajectory of the system; then, this control trajectory is injected in a non-linear and more accurate plant model to evaluate its performances. Comparison is performed with another control approach, consisting in producing at the process temperature whenever possible. The MILP control shows an absolute increase of the solar fraction of 2.5%. The way the thermocline is handled is not standard (as compared to what is done for electricity production) but shows a great interest for heat applications.
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