Urban Wind-Concentrator Tower for Energy Conversion

Abstract

In urban environments the wind speed can increase locally due to two effects acting like vents on the airflow: One is the surrounding natural landscape topology which might enforce a concentration of airflow under certain weather conditions, the other effect comes from the existing development of cities due to their history. Often a checker-board pattern was starting point of the beginning urbanization. Since the historical buildings were relatively low, wind didn’t play a role in town-planning. During town development building heights have been increased, and nowadays, in particular in urban canyons between skyscrapers gale-force like wind speeds can be reached. Besides an uncomfortable microclimate at street level for pedestrians in regard to gusts and pollution, high wind speeds can damage the urban infrastructure by high wind loads. The kinetic energy can be very high as measurements and models show. With the background of the climate change it can be expected that wind speeds in urban canyons will further increase in future, which will lead to more damages and other negative effects. The idea proposed here is to use the wind energy in order to produce electricity and to coincidentally lower negative effects onto urban environments. Thereto, a slender wind-concentrator tower has been developed, which collects and redirects inflowing air to a vortical flow system, making the conversion of kinetic into electrical energy possible. This work is a CFD study to examine the feasibility of the proposed 20 m high wind-concentrator tower, especially designed for the urban environment. The main goal is to analyse the developing vortical flow within the tower and to determine the concentrated energy of the vortices. An optimisation of the wind-concentrator tower is a future task. In this study the concept of the wind concentrator tower will be introduced. Special attention is paid to the constraints coming from the urban environment, i.e. the dimensions of streets or places, which limits the diameter of the tower. Thereafter the relevant CFD simulation setup is explained, and, finally, based on the CFD results an evaluation of the wind concentrator concept in regard to energy conversion will be presented and summarized, followed by a discussion of wind concentrator design variatons.