Object-oriented modeling for the transient performance simulation of parabolic trough collectors using molten salt as heat transfer fluid

• A detailed transient 1-D parabolic trough collector performance model is presented.
• Modelica is used as modeling language and the model is build upon existing standard modeling approaches.
• The model is explained and referenced in detail, allowing for a complete reproduction, also independent of Modelica.
• The model is successfully validated for molten salt as heat transfer fluid.
• Proposals of suitable levels of discretization for a full-size molten salt PTC loop are given.

Concentrating solar power (CSP) is a promising way of providing renewable electricity. Several plants are already successfully operating, dispatching power to the grid. The majority of them are based on the parabolic trough collector technology, where a heat transfer fluid (thermal oil) is pumped through solar absorber tubes that are concentrically placed to the focal lines of the parabolic mirrors. This work is focused on the transient modeling of parabolic trough solar collectors that use molten salt, a mixture of 60% NaNO3 and 40% KNO3 (weight percent), as heat transfer fluid, instead of the conventional thermal oil. The presented model has been successfully validated against measurement data obtained at the SOLTERM facility (Casaccia, Rome, Italy). The modeling approach and all modeling assumptions are explained in detail. In addition to the results needed for validation, a selection of important simulation results is presented, allowing for future model comparison studies. Furthermore, appropriate levels of discretization are proposed for CSP performance simulations as well as for solar field control design, offering a good trade-off between accuracy and computational effort. Modelica is used as modeling language.