A 1.2 MWth solar parabolic trough system based on air as heat transfer fluid at 500 °C - Engineering design, modelling, construction, and testing

We report on the realization of a 212 m-long parabolic trough concentrator and associated solar receiver that uses air as the heat transfer fluid at 500 °C. The fully pneumatic solar concentrator is based on a stack of reflective polymeric films mounted on a rigid concrete support structure and protected by a transparent polymeric envelope. The solar receiver consists of an array of helically coiled absorber tubes contained side-by-side within an insulated groove having a windowed opening. The multiple absorber tubes are connected via two axial pipes serving as feeding and collecting manifolds. The 1.2 MWth solar collector unit, comprising the solar concentrator and solar receiver, is modelled by formulating the energy conservation equation coupling radiation, convection, and conduction and solving it numerically using the finite volume technique. Model validation is accomplished by comparison to on-sun experimental data obtained from tests of the first solar collector unit after its commissioning in Ait Baha, Morocco. The mean absolute and RMS deviations between measured and computed air outlet temperatures of the solar receiver are 7.3 °C and 9.5 °C, respectively. The validated model is further applied to identify heat losses and predict year-round operation. For a DNI of 2400 kW h/m2/yr, the solar plant can deliver 1810 MW h of thermal energy at 500 °C.