Photovoltaics are considered a promising technology to supply energy to buildings and help decarbonize the sector. Solar cell panels can be integrated in the building envelope in different ways: they can be placed on the rooftop, or as shading elements fitted to windows, or — if panels are made semi-transparent — used as glazing. While numerous studies have investigated the impact of photovoltaic integration on the energy performance of buildings, the interplay between the different photovoltaic elements has not yet been comprehensively elucidated. Now, Jinqing Peng and colleagues at Changsha University of Science and Technology and Hunan University in China simulate how rooftop, window, and shading photovoltaics can be used in combination to meet the energy demand of buildings across different climates in China.

The researchers find that the combination of rooftop with shading photovoltaics can generally better match the daily energy load of a building as the two photovoltaic systems generate peak power at different times of the day — rooftop photovoltaic electricity generation peaks around noon, while shading photovoltaics exhibit one peak in the morning and one in the afternoon. Peng and team note that the different photovoltaic elements have different impacts on the properties of the building envelope, affecting the building energy profile. For example, the shading effect caused by photovoltaic windows increases the energy needs for lighting. This is an aspect to take into consideration when selecting the appropriate photovoltaic system combination for a certain climate zone (for instance, lighting is the largest factor contributing to the energy needs of buildings in temperate zones), to avoid exacerbating energy needs. The insights provided by Peng and colleagues offer some guidelines for the integration of multiple photovoltaic elements in buildings.