The Benefit of Horizontal Photovoltaic Panels in Reducing Wind Loads on a Membrane Roofing System on a Flat Roof

Yasushi Uematsu,Hirokazu Ikeda,Tomoyuki Watanabe,Tetsuo Yambe

doi:10.3390/wind1010003

Yasushi Uematsu, Hirokazu Ikeda + Show 2 more

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https://doi.org/10.3390/wind1010003

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Abstract

The present paper proposes a measure for improving the wind-resistant performance of photovoltaic systems and mechanically attached single-ply membrane roofing systems installed on flat roofs by combining them together. Mechanically attached single-ply membrane roofing systems are often used in Japan. These roofing systems are often damaged by strong winds, because they are very sensitive to wind action. Recently, photovoltaic (PV) systems placed on flat roofs have become popular. They are also often damaged by strong winds directed onto the underside, which cause large wind forces onto the PV panels. For improving the wind resistance of these systems, we proposed to install PV panels horizontally with gaps between them. Such an installation may decrease the wind forces on the PV panels due to the pressure equalization effect as well as on the waterproofing membrane due to the shielding effect of the PV panels. This paper discusses the validity of such an idea. The pressure on the bottom surface of a PV panel, called the “layer pressure” here, was evaluated by a numerical simulation based on the unsteady Bernoulli equation. In the simulation, the time history of the external pressure coefficients, measured at many points on the roof in a wind tunnel, was employed. It was found that the wind forces, both on the PV panels and on the roofing system, were significantly reduced. The reduction was large near the roof’s corner, where large suction pressures were induced in oblique winds. Thus, the proposed method improved the wind resistance of both systems significantly.

Highlights

Attached single-ply membrane roofing systems are widely used for flat roofs in Japan because of their high workability, low installation cost, and consideration of environmental conservation; the amount of adhesive used for this system is much lower than that of conventional adhesion methods
Tions, these values are specified as α = 0.20, IZ = 0.24, and Lx = 57.7 m value of α of the wind tunnel flow was larger than the specified value, IZ and Lx of the wind tunnel flow were smaller than the specified valu cies can be accepted, because the main purpose of this study was to disc of PV panels for the improvement of the wind resistance of mechanica ply membrane roofing systems and not to evaluate wind loads for des and a roofing system
The positive and negative wind force coefficients of PV panels installed on flat roofs are specified in JIS C 8955 [38]

Summary

Introduction

Attached single-ply membrane roofing systems are widely used for flat roofs in Japan because of their high workability, low installation cost, and consideration of environmental conservation; the amount of adhesive used for this system is much lower than that of conventional adhesion methods. In this system, a waterproofing membrane is fixed to a roof’s substrate with many fasteners, which are generally arranged in a square lattice-like form with a spacing of 0.45–1.0 m. A waterproofing membrane is fixed to a roof’s substrate with many fasteners, which are generally arranged in a square lattice-like form with a spacing of 0.45–1.0 m Note that this construction method is somewhat different from that generally used in Europe and North America, where membranes are anchored to a roof’s substrate by a series of fasteners arranged along the seams of the membranes (see Baskaran and Borujerdi [1], for example). In any case, roofing systems are generally sensitive to wind actions. They are often damaged by strong winds [2]. Cook [4] experimentally investigated the wind-induced

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