Electric Power Generation Using Buoyancy-Induced Vortices Sustained by Entrained Solar-Heated Air

Abstract

Thermally-stratified air layers over solar-heated ground are exploited for a scalable, low-cost method of power generation by the deliberate formation of intense buoyancy-induced vertical columnar vortices, similar to naturally-occurring desert “dust devils.” Such vortices collect low-grade thermal energy in solar-heated air in regions with high surface heating rates, and convert the (gravitational) potential energy in the concentrated buoyant air into “solar-induced wind” with significant kinetic energy. Unlike dust devil vortices that are typically free to wander laterally and are therefore susceptible to cross winds, the anchored columnar vortex is deliberately triggered and anchored within a cylindrical domain bounded by an azimuthal array of stationary ground-mounted vertical vanes sustained by continuous entrainment of the heated air through these vanes. Solar energy collected by the ground plane sustains the anchored vortex and electric power is generated by using the air motion to drive a vertical-axis turbine to form a simple, low-cost electric power generating unit. In terms of cost-of-energy, intermittency, mechanical simplicity, and environmental impact, the approach has significant advantages compared to solar PV, CSP, and conventional wind turbines. Meter-scale laboratory experiments have demonstrated the nucleation, anchoring, and sustainment of strong, buoyancy-driven vortices centered within an azimuthal array of stationary vertical vanes above a controlled thermal ground plane. Outdoor tests of a meter-scale prototype have demonstrated autonomous start-up, formation, anchoring, and sustainment of a buoyancy-induced vortex generated solely by absorbed solar energy.