Wind energy harnessing on tall buildings in urban environments

Wind energy harnessing on tall buildings in urban environments is a rapidly developing renewable energy technology. It is influenced by the terrain type, local wind characteristics, urban environment and building architecture. Considering that so far there has been no systematic review of all the relevant factors influencing urban wind energy harnessing, critical points related to this are outlined in detail in the present study by critically assessing existing literature and indicating future research directions. These important elements include the urban wind environment, wind resource assessment, and wind-turbine design. The combined influence of all these features on wind energy harnessing on tall buildings in urban environments is analyzed in a separate section as a case study. Wind resource assessment may be achieved by field measurements, wind-tunnel experiments and computational modeling, while the optimal approach is to determine local wind resources based on the combined results of all three methods. In urban built environments, global wind characteristics in the atmospheric boundary layer are predominantly relevant for the aerodynamic performance of large-scale engineering structures, while for small wind turbines built on top of tall buildings the relevant aerodynamic features are more due to the local wind characteristics in between the buildings that are affected by the size and shape of the buildings of interest. Vertical axis wind turbines have generally proven to be more suitable for wind energy harnessing on tall buildings in urban environments because they are more efficient in turbulent flow, and are also less noisy. This makes them a better choice than horizontal axis wind turbines, especially if the building is not originally designed with wind-power generation in mind. Nevertheless, there are also some good examples of horizontal axis wind turbines. The case study indicates that wind turbine efficiency on buildings in a built environment is unsatisfactory, with only a few cases of the successful integration of wind turbines on buildings. However, the poor performance of wind turbines in the analyzed engineering structures can be attributed to an inadequately performed wind resource assessment and an unsuitable selection of wind turbine types, thus indicating strong potential for future work in this regard.