Numerical Optimization and Analysis of 3D-Printed Porous Structures for Open Volumetric Receivers

Solar tower power plants with open volumetric receivers using air as the heat transfer fluid present an alternative to existing molten salt or steam receiver systems, offering high robustness, high availability, and effective storage capabilities. As the central component of this receiver type, volumetric porous structures are responsible for the absorption of the concentrated solar irradiation and the heat transfer to the air flow. Manufacturing techniques such as 3D-printing make it possible to purposefully design the porous structures down to sub-millimeter scales. A new numerical optimization approach has been developed which allows the derivation of new porous structures precisely tailored to the available manufacturing techniques. Potential absorber designs are first characterized via three-dimensional CFD and raytracing simulations. The resulting effective properties are then used by a 1D LTNE homogeneous model to evaluate the absorber performance. The variation of the absorber geometry is controlled by an optimization method, both an exact and a heuristic method have been implemented within the new approach. A key feature of the design process is the explicit incorporation of the limitations and capabilities of the associated manufacturing technologies. This allows to directly ensure the manufacturability of the optimized absorber designs. The approach has been applied to derive optimized absorber designs which were then created via 3D-printing and experimentally evaluated confirming their potential as solar absorbers.