Flow enhancement in and around buildings for wind energy harvesting

Abstract

Decentralised small-scale wind energy harvesting in urban environments, as one of the potential solutions to tackle the energy crisis and climate change, requires the development of flow enhancement techniques in a fairly turbulent urban wind condition. This study proposes two types of building and facade configurations, including adaptive Double Skin Facade (DSF) and aerodynamic through-building openings, to enhance wind energy harvesting in and around buildings. Depending on their layout configuration, the two proposals form various types of confined aerodynamic duct-shape corridors suitable for installing wind turbines. The desirable wind flow characteristics for wind energy harvesting including speed, uniformity and unidirectionality of the wind flow and undesirable wind turbulence were investigated inside the different layout configurations of the corridors. The effect of wind speed and direction, urban terrain, aerodynamic modifications of layout configurations and wind turbines on the flow characteristics, and the effect of local wind data on annual energy production of the two proposed designs were studied. A series of wind tunnel tests in two phases were conducted utilising flow measurement techniques including hot-wire anemometry, Cobra probe measurements, tuft visualizations and Particle Image Velocimetry (PIV). Several Computational Fluid Dynamics (CFD) simulations using steady and unsteady RANS were also performed to investigate the mechanisms and characteristics of the flow inside different layout configurations of DSF and through-building openings. CFD results were properly validated against the wind tunnel data using statistical performance analysis, which showed the capability of the steady RANS, SST k-? in particular, to estimate the mean flow characteristics inside the corridors. The results showed that the DSF with proper aerodynamic modifications including recessed regions and curved walls effectively channel and enhance the wind flow inside corridors for a wide range of wind directions, and hence, is a potential technique for enhancing wind flow in urban environments. It was found that proper aerodynamic modifications of the DSF maintain the amplified wind velocity inside the corridors up to the wind direction of ±45° to the corridor's axis. Within this range of wind directions, the mean velocity inside the leading side corridors of the layout with the proper modifications got almost doubled as compared with the free-stream velocity. The results showed that the aerodynamic modifications and the confined area of the corridors contribute substantially to the reduction of turbulence intensity by about 25%. Considering wind coming in any direction, the middle region of the corridors, where wind flow is relatively uniform and unidirectional, is a suitable location for installing wind turbines.

Date of Award	2019
Original language	English