Installed photovoltaic power has rapidly grown in the last 20 years, with a compound annual growth rate (CAGR) of cumulative PV installations equal to 30% between 2011 to 2021 and a global capacity that exceeded 1.6
During the operation, PV modules absorb incident solar radiation to generate electricity. Only 15%-20% of solar radiation is converted to electricity and the other staggering approx. 80% of incoming solar irradiation is absorbed by the
Due to the implementation of the "double carbon" strategy, renewable energy has received widespread attention and rapid development. As an important part of renewable energy, solar
The unique properties of roofs, such as good sunlight incidence, good ventilation conditions, no redundant shielding, and flexible tilt angle for PV panels, are advantageous for solar energy harvesting. Accordingly, roofs present the highest efficiency potential for PV generation systems in buildings (Lin et al., 2014).
Despite numerous benefits, there are potential negative impacts from rooftop PV implementation. Currently installed photovoltaic panels typically convert only 15–18% of the incoming solar radiation into electricity [ 7 ]. As a result, most of the incident radiation is absorbed into the panel as heat and released into the urban environment.
Due to the cooling effect of green roofs, several studies had investigated the effect of green roofs in buildings with rooftop PV panels. The results of a study on a green roof integrated with a photovoltaic system show electricity generation improvement of PV panels (with 3%).
The shading effect of the photovoltaic panels makes the roof temperature in the shading area higher than that in the unshaded area. This is because the photovoltaic panels store a certain amount of heat during the day when the irradiation is abundant, radiating heat with the shading area at night, causing its temperature to rise.
Finally, a quantitative method for evaluating the comprehensive potential for energy savings is proposed, considering the electricity generation gain of photovoltaic panels and the comprehensive energy-saving efficiency of photovoltaic roofs, which generates a total potential for energy savings rate of 61.06%.
Fig. 1. New installed capacity of renewable energy technologies globally from 2011 to 2021. Building PV generation systems can be applied on roofs (Kumar et al., 2018) and/or facades (Quesada et al., 2012), and the installed PV generation system can share the grid load.
