Hybrid and organic photovoltaics for greenhouse applications

Reducing the energy demand and dependency on fossil fuels is crucial for improving the sustainability of greenhouses, which are the most energy intensive systems in the agricultural sector. Renewable technologies represent a key option to meet the greenhouse energy demands. Agrivoltaics has recently emerged as a strategy to combine farming activity and power generation through photovoltaics (PV). However, PV systems retrofitting needs to consider the interactions with the existing greenhouse structure, as well as the energy requirements of the equipment for climate control. The influences of PV shading on agronomic parameters have also to be carefully considered. Firstly, this review examines the response of plants to the light and the fundamental aspects of greenhouse facilities. Then, the state-of-the-art of PV systems applied to greenhouses is thoroughly analysed. Simulation studies and experimental works are examined to highlight the effects of PV technologies and module arrangements on energy production and plant growth. Particular attention is devoted to new PV technologies, i.e. organic, dye-sensitized and perovskite solar cells, because of their semi-transparency and flexibility, allowing the easy integration of PV modules into existing or newly conceived greenhouse structures. The review has highlighted that the new PV technologies have an enormous potential due to the possibility of tuning their spectral features according to the characteristics of plants and to the capability of optimizing the use of solar energy into high-tech greenhouses. Shading through these innovative systems has also demonstrated to create a suitable atmosphere for crop growth especially in hot and tropical regions.