Feasibility analysis of a Darrieus vertical-axis wind turbine installation in the rooftop of a building

The renewed interest that is being paid by architects, project developers and local governments to small-size wind turbines is mainly connected to the attractive prospects of future applications in the urban environment; the delocalized power production of these systems could indeed provide an effective answer to both the growing demand for renewable energy and the increased attention in buildings with a sustainable and low-energy design. In particular, Darrieus vertical-axis wind turbines (VAWTs) are being considered as one of the most attractive solutions due to their low visual impact, the reduced acoustic emissions and their better response to a turbulent and skewed oncoming flow. The feasibility of this scenario has, however, to be proved yet; in particular, doubts are still connected to the real producibility in a complex terrain like the urban one and to the compatibility of microeolic machines with a densely populated area. On these assumptions, the aim of this work is to critically evaluate the energetic suitability of a Darrieus VAWT installation in the rooftop of a building in a reference European city. With this goal in mind, a numerical CFD analysis was carried out to characterize the flow field in the rooftop area of buildings with different shapes and geometrical proportions: the flow velocity modulus and direction were calculated for different oncoming wind profiles and the results were projected into a net available wind distribution in the rooftop of each building. As a second step, in order to provide a reliable estimation of the real functioning of the turbine in the investigated environment, a specific numerical model has been developed to account for the effects of a skewed flow on the power performance of the Darrieus rotor. The results of these analyses were finally combined and synthesized in an energy-oriented study to evaluate the feasibility of a rooftop installation.

[1]  C. Ratti,et al.  Analysis of 3-D Urban Databases with Respect to Pollution Dispersion for a Number of European and American Cities , 2001 .

[2]  G.A.M. van Kuik,et al.  Wind Energy in the Built Environment , 2005 .

[3]  T. Stathopoulos,et al.  CFD simulation of the atmospheric boundary layer: wall function problems , 2007 .

[4]  Lorenzo Ferrari,et al.  Start-Up Behavior of a Three-Bladed H-Darrieus VAWT: Experimental and Numerical Analysis , 2011 .

[5]  Yoshihide Tominaga,et al.  AIJ guidelines for practical applications of CFD to pedestrian wind environment around buildings , 2008 .

[6]  Michael Schatzmann,et al.  Recommendations on the use of CFD in wind engineering , 2004 .

[7]  Ervin Bossanyi,et al.  Wind Energy Handbook , 2001 .

[8]  Christina Beller.  Urban Wind Energy - State of the Art 2009 , 2009 .

[9]  P. Richards,et al.  Appropriate boundary conditions for computational wind engineering models using the k-ε turbulence model , 1993 .

[10]  S. Hoerner.  Fluid-Dynamic Lift , 1985 .

[11]  Xin Wang,et al.  Evaluation of CFD Simulation using RANS Turbulence Models for Building Effects on Pollutant Dispersion , 2006 .

[12]  S Mertens,et al.  Performance of an H-Darrieus in the Skewed Flow on a Roof , 2003 .

[13]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[14]  Jörg Franke,et al.  The COST 732 Best Practice Guideline for CFD simulation of flows in the urban environment: a summary , 2011 .

[15]  Martin Gallagher,et al.  Ultrafine particle fluxes above four major European cities , 2009 .

[16]  T. N. Croft,et al.  Benchmark experiments for simulations of a vertical axis wind turbine , 2013 .

[17]  S. Mertens,et al.  The Energy Yield of Roof Mounted Wind Turbines , 2003 .

[18]  Emma Dayan,et al.  Wind energy in buildings , 2006 .

[19]  Wen Tong Chong,et al.  Early development of an energy recovery wind turbine generator for exhaust air system , 2013 .

[20]  Brad C. Cochran,et al.  Harvesting Wind Power from Tall Buildings , 2008 .

[21]  I. Paraschivoiu.  Wind turbine design with emphasis on Darrieus concept [ressource électronique] / Ion Paraschivoiu , 2002 .

[22]  P. Bradshaw,et al.  Momentum transfer in boundary layers , 1977 .