Search

The traditional shading systems that greenhouses use cause some of the solar radiation that is reflected or absorbed to be lost and, therefore, not used by the plants under cultivation. An interesting solution to these problems is to position photovoltaic (PV) panels on the roofs of greenhouses. All of the photovoltaic greenhouses that have been realized in Mediterranean areas are characterized by a fixed position of the PV panels and excessive shading, especially in autumn and winter. The purpose of this study is to describe a prototype of a photovoltaic greenhouse with both fixed and horizontal PV panels that exploit the natural variation in the elevation angle of the sun's rays during the year to allow for "passive" variation in shading. The considerable variation in the elevation angle of the sun's rays (from 24.4° to 71.1°) results in a high variation in shading (from 39.4% to 72.6%), with the highest values in the summer months and the lowest values in the winter months. This trend is favorable for meeting the photosynthetically active radiation (PAR) needs of greenhouse plants. If the plants under cultivation require more solar energy, it is necessary to increase the distance between the panels. We implement a specific mathematical relationship to define the precise distance to be assigned to the photovoltaic panels on the roof pitch. [ABSTRACT FROM AUTHOR]

The cultivation of plants in greenhouses currently plays a role of primary importance in modern agriculture, both for the value obtained with the products made and because it favors the development of highly innovative technologies and production techniques. An intense research effort in the field of energy production from renewable sources has increasingly led to the development of greenhouses which are partially covered by photovoltaic elements. The purpose of this study is to present the potentiality of an innovative prototype photovoltaic greenhouse with variable shading to optimize energy production by photovoltaic panels and agricultural production. With this prototype, it is possible to vary the shading inside the greenhouse by panel rotation, in relation to the climatic conditions external to the greenhouse. An analysis was made for the solar radiation available during the year, for cases of completely clear sky and partial cloud, by considering the 15th day of each month. In this paper, the results show how the shading variation enabled regulation of the internal radiation, choosing the minimum value of necessary radiation, because the internal microclimatic parameters must be compatible with the needs of the plant species grown in the greenhouses. [ABSTRACT FROM AUTHOR]