The combination of building greenery and photovoltaic energy production—a discussion of challenges and opportunities in design

Abstract

In the case of building surfaces, the installation of green roofs or green facades can be used to reduce the temperature of the environment and the building. In addition, introducing photovol-taic energy production will help to reduce CO2 emissions. Both approaches (building greenery and photovoltaic energy production) compete, as both of them are located on the exterior of buildings. This paper aims to give an overview of solutions for the combination of building greenery (BG) systems and photovoltaic (PV) panels. Planning principles for different applications are outlined in a guideline for planning a sustainable surface on contemporary buildings. A comprehensive literature review was done. Identified solutions of combinations were systematically analysed and dis-cussed in comparison with additional relevant literature. The main findings of this paper were: A) BG and PV systems with low sub-construction heights require shallow substrates/low growing plants, whereas in the case of the combination of (a semi)-intensive GR system, a distance of a min-imum 60 cm between the substrate surface and lower panel edge is recommended; B) The cooling effect of the greenery depends on the distance between the PV and the air velocity; C) if the substrate is dry, there is no evapotranspiration and therefore no cooling effect; D) A spectrum of different PV systems, sub-constructions, and plants for the combination of BG and PV is necessary and suitable for different applications shown within the publication.