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Finding a suitable aiming strategy for receivers of power towers can be challenging, especially for receivers using molten salt as heat transfer fluid as the allowable flux density decreases dramatically with increasing salt temperature. In this paper a very fast, steady-state model for the molten salt receiver is presented. This model is combined with a ray-tracing software and a metaheuristic optimization procedure. The thermal model is used to calculate the actual temperature and mass flow in the receiver which are then used to calculate the operational limits for the flux density. It is demonstrated that such an optimized aiming strategy can outperform a parameter based aiming strategies by more than 2 %.

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The convective heat losses of cavity receivers for solar thermal power towers are of great importance for the overall efficiency of the whole system. However, the influence of wind on these losses has not been studied sufficiently for large scale cavity receivers with different inclination angles. In this present study the impact of head-on and side-on wind on large cavity receivers with inclination angles in the range of 0 • (horizontal cavity) to 90 • (vertical cavity) is analyzed numerically. The simulation results are compared to data published in literature. When no wind is present the losses decrease considerably with increasing inclination angle of the receiver. In case of a horizontal receiver wind does not have a huge impact on the losses: they remain constant on a high level. In case of an inclined cavity wind increases the heat losses significantly in most of the cases, although the highest absolute value of the losses occurs for the horizontal receiver exposed to head on wind. In some cases, when wind is flowing parallel to the aperture plane, a reduction of the heat losses is observed. The temperature distribution in the cavity is analyzed in order to explain the impact of wind on the heat losses. Wind in general causes a shrinking of the zone with uniform high temperature in the upper region of the cavity, whereas wind flowing parallel to the aperture plane additionally inhibits hot air from leaving the cavity and therefore leads