Abstract
1.3 billion people are without access to electricity; carbon accounts for 54 percent of the overall Ecological Footprint. Obviously, there is an increasing need for urban generation of electricity from renewable sources; which would in turn lower the demand for energy coming from centralized power plants often relying on fossil fuel. Micro installations also have the advantage of yielding power directly to the user. Throughout the recent years, we have seen many concepts of building integrated wind turbines (BIWT) and building mounted wind turbines; precisely because wind speed increases with eight. However, the high level of turbulence at the roof drastically impairs the performance of conventional horizontal and vertical axis wind turbines. Such BIWT are not cost effective because they miss by far the power expectations. Indeed, the flow past bluff bodies is a highly complex tri-dimensional turbulent flow composed of eddies of different sizes and frequencies. Separation bubbles are high vorticity regions with fluctuating velocities where conventional wind turbines are far from their design conditions. Nevertheless, there is a kind of wind harvester which is well suited for such flow conditions; vortex-induced vibration harvesters turn the unequal pressure distribution on their surface into vibratory motion. Vibration can be used to generate electricity through either piezoelectric or electromagnetic transduction mechanisms. In the present paper, we introduce several vortex-induced harvesting devices of simple structure and also describe the wind flow around several common types of buildings. Finally, we propose several locations to place vortex-induced vibrations harvesters on the building envelope according to the results of Computational Fluid Dynamics simulations for several wind scenarios. Those harvesting devices can be used for low-power electronics and LED lighting; they can become cost-effective when mass produced.