Prestressed solar updraft towers for use in greenhouse gas removal

Abstract

Greenhouse gas removal technologies will require huge throughputs of air in order to effectively remove diffuse greenhouse gases: solar updraft towers, which utilise a greenhouse induced stack effect, could provide this airflow. For such a system to be economically feasible, the tower structure must be efficient and, ideally, lightweight; however, existing designs mainly consider slip-formed concrete tubes, which must be relatively stocky to resist buckling. We therefore propose the alternative, lightweight, structural form of a prestressed hyperboloid cable-net, suspended from a central compression mast via a “bicycle wheel” at the top, and covered in fabric to form a chimney. Our objective is to show the feasibility of such a structure: we investigate the structural mechanics via a simplified analytical model and scale physical model, finding good agreement between the models in predicting the lateral stiffness of the tower. These models, combined with estimates of the wind load, are then used to estimate the sizing of a $\text{1000}\text{m}$ tall, $\text{100}\text{m}$ diameter tower. A simple estimate of the maximum CO${}_2$ removal rate illustrates the difficulties of removing greenhouse gases at scale.