Shading on Photovoltaic Collectors on Rooftops

Avi Aronescu,Joseph Appelbaum

doi:10.3390/app10082977

Abstract

Rooftop photovoltaic (PV) systems in urban environments play an important role in solar electric energy generation. Shading on PV collectors, by self-shading, walls and fences on rooftops, affect negatively the output energy of the PV systems. Increasing the distance between the collector rows, and between the walls and fences near to the collectors, may minimize the shading losses. Practically, this option is usually limited, especially on rooftops. Rooftops may be of different types: horizontal, inclined, and saw-tooth, and may have obscuring structures like walls and fences. The distance between the shading objects and the PV collector rows determine the loss of energy due to shading. The study provides the PV system designer with mathematical expressions for distances from obscuring objects for the deployment of PV systems on rooftops. The optimal inclination and azimuths angles of a PV system on a triangular sloped rooftop are also illustrated.

Highlights

Distributed photovoltaics (PV) currently constitute roughly half of the global PV solar energy installed capacity [1]
Shorter row-to-row distances between the PV collectors are needed for steeper inclined roofs, and larger collector inclination angles require larger row-to-row distances
Literature on the shading of PV systems concentrate on mutual shading and the distances between the collector rows deployed on the ground, but they do not address shading and the distances from protruding objects encountered on rooftops

Summary

Introduction

Distributed photovoltaics (PV) currently constitute roughly half of the global PV solar energy installed capacity [1]. The advantage of distributed energy is the generation of electricity right at the consumer location. Distributed PV is a general term for locally generated electricity in an urban environment, and building-integrated photovoltaics (BIPV) are a subcategory. Rooftops may provide a large amount of empty space that can reduce the use of dedicated land for large PV plant installations [2]. PV fields are usually designed with multiple collector rows. The row-to-row distance is an important parameter of the PV field design. The distance may be determined by maintenance requirements, by the amount of allowed percent of shading, or by a customary rule

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