Optimizing Building Geometry to Increase the Energy Yield in the Built Environment

Abstract

A crucial element in the use of wind as a source of energy in the built environment, is finding ways to maximize its flow. As flow approaches the windward façade of a building's structure, it accelerates causing an increase in velocity both at the roof's edge and above the separation bubble. Devices such as small scale wind turbines are usually placed in this flow region for energy harvesting purposes. The present research aims to further investigate the accelerated flow by modifying the building's structure to be a concentrator of the wind, maximizing the available wind energy. Using Computational Fluid Dynamics (CFD), preliminary investigations explored sloped facades at four arbitrary angles. Simulations show that at an angle of 30 degrees, there is a velocity amplification of more than 100% at the separation point directly above the roof (Figure 1). In addition, there is little to no reversed flow in the decreased separation bubble minimizing turbulence intensity. Conducted wind tunnel experiments simulating flow behavior over the models support the findings presented and show that with a simple façade change, the flow characteristics are greatly affected. Using the 30-degree slope as a guide angle, elliptical facades were also investigated. Two-dimensional CFD optimizations were used to find angles that gave the highest power density directly above the rooftop. Results show that at higher angles, when the elliptical façade is steeper, there is further velocity amplification. The optimized elliptical façade will provide a base for a three dimensional structure where both optimization tests and eventual wind tunnel testing will be done to support the findings.