Photovoltaic systems for powering greenhouses

In the paper it is shown that grid-connected PV-plants can be considered and profitably used for powering greenhouses. In fact, in a PV-plant to be installed in a greenhouse, PV-modules can be simply and fully integrated on the greenhouse coverage so allowing to obtain the maximum government economical incentive for generating electricity, also minimizing authorization and tax problems that are more stringent both for large “on-ground” and “on-roof” residential or industrial PV-plants. However, in greenhouse PV-plants with PV-modules integrated on the coverage, the consequent shading effect could limit photosynthesis phenomenon, leading to serious problems related to crop productivity. Transparent or semitransparent technologies for PV-modules don´t fully obstruct the incident light and don´t stop the photosynthesis in greenhouses; then, they can represent a very good solution for reducing negative impact on the crop productivity of shading effect. On the other hand, they are significantly more costly than conventional PV-modules and this may limit their utilization in large-power PV-plants. In this paper, on the basis of progress of a research project that is developing by the authors with the financial support of the “Regione Calabria - Italy”, a novel greenhouse prototype, powered by a PV-plant, is introduced. It is essentially based on a conventional cost-effective PV-plant that generates electricity to be used for fully supplying both an artificial lighting system and a heating/cooling system, properly designed for the optimal control of the greenhouse micro-climate and for maximizing the greenhouse crop productivity. Comparisons with already experienced different solutions are also developed.