Solar facades for future cities

Buildings in urban environments offer large areas available for the deployment of solar energy technologies. Photovoltaic (PV) systems are often considered for installation on rooftops, with facades usually being disregarded due to their non-optimal inclination. However, PV facades not only convey a cleaner image to buildings but may also act as optimizers of distributed generation. The contribution of differently oriented and tilted PV surfaces varies seasonally and depends on the urban layout, therefore the aggregation of rooftop and facade PV potential in a neighbourhood or a city might satisfy a relevant fraction of its combined electricity consumption even at off-peak production hours. The optimization of PV systems towards load-matching is crucial for the success of future solar communities. This review aims to provide an overview on the rooftop versus facade PV paradigm in the context of future cities. The advantages of facades are highlighted along with methods to estimate their potential, and innovative technological approaches for their implementation are discussed.