Energy and photosynthetic performance investigation of a semitransparent photovoltaic rooftop greenhouse for building integration

Abstract

The present article aims at evaluating semitransparent photovoltaic rooftop greenhouses based on organic photovoltaics and ethylene-tetrafluoroethylene. A RADIANCE/TRNSYS model is proposed. Five configurations (greenhouse roof with 0%, 25%, 50%, 75% and 100% photovoltaic-module covering) and two cities (Barcelona; Paris) have been evaluated. The findings reveal that an increase of the photovoltaic-covering surface reduces the overall energy demand of the greenhouse, but it also reduces the illumination that reaches the crops. For Barcelona, the optimal configuration for proper crop development (tomato; lettuce) is the one with 50% covering. For Paris, the optimal configuration is the one with 25% covering. In terms of energy, in the case of Barcelona, the part of the electricity demand of the greenhouse covered by the photovoltaics ranges from 14% to 63% whereas, in the case of Paris, these percentages range from 6% to 25.3%. As for the thermal behaviour of the building (adjacent office floor), the installation of the rooftop greenhouse reduces air-conditioning demand (around 30% for Barcelona and 37.7% for Paris (0% covering)). For Paris, the effect of the photovoltaic-covering percentage on the thermal demand of the adjacent floor is minimal. However, for Barcelona, it can reduce the air-conditioning demand by 35% (scenario: 100% covering).