Solar radiation distribution inside a greenhouse with south-oriented photovoltaic roofs and effects on crop productivity

This study assessed the climate conditions inside a greenhouse in which 50% of the roof area was replaced with photovoltaic (PV) modules, describing the solar radiation distribution and the variability of temperature and humidity. The effects of shading from the PV array on crop productivity were described on tomato, also integrating the natural radiation with supplementary light powered by PV energy. Experiments were performed inside an east-west oriented greenhouse, where the southoriented roofs were completely covered with multi-crystalline silicon PV modules, with a total power of 68 kWp. The PV system reduced by 64% the solar radiation available inside the greenhouse, compared to the potential value without PV system (2,684 MJ m-2). The solar radiation distribution followed a north-south gradient, with more solar energy in the sidewalls and decreasing towards the centre of the span, except in winter, where it was similar in all plant rows. The reduction under the plastic and PV covers was respectively 46% and 82% on yearly basis. Only a 18% reduction was observed on the plant rows farthest from the PV cover of the span. The cultivation areas under the transparent cladding and close to the greenhouse side walls were less penalised by the PV system. The distribution of the solar radiation observed is useful for choosing the most suitable crops and for designing PV greenhouses with the attitude for both energy and crop production