Serviceability analysis and feasibility study of ballasted rooftop PV system on existing concrete roof slab buildings

Abstract

Solar Photovoltaic (PV) installation on existing structures became popular for the purpose of reducing carbon emission and improving energy efficiency of buildings. Ballasted PV systems which can impose an additional dead load are preferred by building owners as direct roof penetration method can pose a potential threat to the insulation, water proofing as well as the warranty of roof membranes. Ballasted PV systems have been questioned for structural capability, economic feasibility as well as sustainability stand points. This study focuses on determining an the optimal ballast number to resist uplift wind pressure. It additionally considers concrete roof slab serviceability with respect to long-term deflection, and provides a feasibility study of PV installation. Based on the results of the study, the ballasted PV system does not yield a significant influence on structural serviceability of building. The economic feasibility analysis considers the current level of incentives. Economically a ballasted PV system can be an attractive investment with approximate payback period of 7.6 years. Without incentives, the payback period is 24 years.