Dynamic simulation of the operation of a molten salt parabolic trough plant, comprising draining procedures

The dynamic simulation of a molten salt operated parabolic trough plant is presented. The simulated plant is a typical 9 MWe CSP unit comprising 10 loops with 8 collectors in series (in turn this can be a "module" of a larger CSP solar field) a Two Tanks TES and a molten salt Steam Generator. This type of plant represents a challenge due to the large extension and relative complication of piping network operating with molten salt, in comparison to e.g. a molten salt Tower. The simulation model, implemented in Isaac Dynamics environment, is able to represent the normal operation of the plant with circulating HTF at variable mass flow depending on input DNI, and night circulation at reduced mass flow. In addition, in molten salt operated CSP plants draining operations are of prominent importance, given that these operations should be operated within a due time (depending on boundary conditions) avoiding the possible freezing of the salt mixture. Moreover also emergency draining (e.g. as a consequence of faults in the pump and/or in heat trace equipment) should be analyzed. At this purpose, the model has been modified and utilized to represent also circuit draining, involving flow reversal, that normally requires use of specialized thermo-hydraulic codes like Relap (Reactor Loss of coolant Analysis Program). In conclusion, the paper shows how the simulation environment is able to represent most of the dynamics that affect the operation of a molten salt parabolic trough plant. © 2013 The Authors.