Thermal 3D model for Direct Solar Steam Generation under superheated conditions

Abstract

Parabolic-trough collectors (PTC) solar systems are one of the most promising of a wide range of the available solar technologies. Continuous breakthroughs are being achieved. Mainly due to the considerable amount of solar PTC plants that are being under operation in different countries. Within this continuous improvement effort, Direct Steam Generation (DSG) has been under development. DSG will lead to cheaper systems, not only for electricity generation but for heat process requirements. Working with superheated steam as thermal fluid, implies thicker pipe walls. Current numerical models neglect the radial dimension. In this context, simulating DSG absorbers implies considering radial domain discretization. A single phase model has been developed in order to work the 3D temperature field out on the solid parts, including the glass cover. Vacuum annulus has been assumed between stainless steel absorber and the glass envelope. The thermal radiative interaction between those parts has been considered without constant temperature assumption over the glass envelope. Finally, unidimensional approximation has been applied to the fluid domain. The whole code has been developed from the elemental (PDEs) governing equations and has been implemented in Matlab®. The numerical model has been validated from experimental results. These results have been gathered from an experimental DSG test facility with parabolic-troughs.