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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Gabriele Bedon University of Padua, Italy
Co-authors:
Gabriele Bedon (1) F Stefano De Betta (1) Hagar Elarga (1) Michele De Carli (1) Ernesto Benini (1)
(1) University of Padua, Padova, Italy

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Mr. Gabriele Bedon is a Ph.D. Student in Energy Engineering at University of Padua, Italy. His main research topics involve the aerodynamic simulation with semi-analytical models of the Darrieus wind turbines and their airfoil optimization with advanced optimization algorithms. He graduated at University of Padua in Mechanical Engineering and at Denmark Technical University in M.Sc. in Engineering, Sustainable Energy. He is currently cooperating with both Universities to improve the design of several projects.


Poster

Poster Download poster (8.92 MB)

Abstract

A Novel Implementation of Wind Energy in Buildings based on Synthetic Jet Concept

Introduction

In the last decade, wind energy has experienced a wide spread both in the onshore and offshore environment. With the aim of reducing the cost of energy, wind turbine technology has undergone a continuous development, which focused mainly on the size increase for the offshore environment. A different approach considers implementing wind energy technology where it is consumed, primarily in the cities and, in particular, by using small wind turbines on the top of the tallest buildings. These sites could provide specific advantages due to the low cost of grid connection, the exploitation of potentially unused space and environmental conditions characterized by higher values of the average wind speed compared to the free-stream due to the hill effect. On the other hand, flow detachment due to the building shape could negatively affects the exploitation of this effect. In the present paper, a novel approach to prevent the flow detachment, inspired by the synthetic jet technology, is developed and analyzed with respect to the building shape.

Approach

The analysis and evaluation of the synthetic jet approach applied to the building is conducted by considering a Computational Fluid Dynamics (CFD) analysis based on the Unsteady Reynolds Average Navier-Stokes (URANS) equations and k-ε turbulence model. Two different models are developed, considering a two- and a three-dimensional approach respectively. The models were validated with respect to experimental data available in the scientific literature, providing good agreement with experimental data both on scaled and real size models. The validated models are applied to obtain a reliable simulation of the flow around a baseline building.

Main body of abstract

The flow around the baseline building is compared to the flow pattern obtained by introducing an air duct on the top of it, which is blowing a fixed air mass flow rate (the jet). The energy required to produce this jet is not considered since it is presumed to be already available from other sources (e.g. ventilation system). Different parameters were varied in order to find the optimal set to obtain a flow reattachment after the separation at the building edge. The geometric parameters such as the duct cross section, the aspect ratio and the tilt angle are varied by considering a constant jet mass outflow rate, modelled in the CFD simulation as a velocity inlet. The analysis provided the velocity profiles on different positions on the roof: a reduction in the flow separation would enable an installation of a wind turbine with a lower support and the interception of a uniform accelerated wind speed provided by the hill effect.

Conclusion

The present work considered the advantages deriving from using air mass outflow from a duct placed on the top of a building roof in order to enhance the flow reattachment after the detachment at the building edge. Different shapes, outflows and environmental conditions are considered, in order to find the optimal parameter set which reduces the detachment area. By obtaining such a reduction, the wind turbine placement is simplified and the increased wind speed due to the hill effect can be exploited. The increased energy production linked to the lower costs deriving from easier operations of maintenance, a cheaper installation and connection to the grid in an accessible urban environment, would lead to a strong decrease in the cost of energy.


Learning objectives
By reading this works, delegates will have the possibility to understand and analyze the details of the innovative concept of synthetic jets on buildings. This new technology would enhance the profitability of exploiting wind energy in urban environment, favoring the possibilities of exploiting new installations sites in the proximity of the most energy consuming areas, the cities. The integration of renewable energy in buildings is, moreover, one of the target area for several projects aimed to transform the modern cities in “smart cities”.