A Concept of Smart Agro-Photovoltaic Tunnels

This paper is a review of chosen reports on the integration of photovoltaics and agrotechnics and also presents the concept of an agro-photovoltaic foil tunnel module. This concept assumes the possibility of integrating modules into intelligent agro-photovoltaic fields. The proposed solution combines cultivation in a foil tunnel with a photovoltaic farm. The paper reviews electronic solutions to control ambient parameters, particularly those influencing the rate of photosynthesis in foil tunnels. The article also presents an analysis of the energy and water balances of the module in 4 different climate zones, including locations in Poland, Spain, Algeria, and Colombia. The module's water requirements include drip irrigation and fogging systems. Water is assumed to be obtained from rainfall, desalination, non-conventional (treated, desalinated) resources, groundwater, and sub-artesian wells. The module's energy needs include electricity consumption for pumping freshwater, desalination and water treatment, irrigation and fertilization, additional lighting and heating of plants, folding and unfolding of foil covers, and energy consumption related to automation. The article also analyzes crop shading by solar panels and its impact on the selected crop. The functionality of the presented solution was assessed for tomato cultivation in the four selected areas. A 240 m2 foil tunnel was considered. 60 m2 of the tunnel was covered by PV panels. The analysis results show that the most energetically effective agro-photovoltaic cultivation of tomatoes appears to be in the Saharan region of Africa where a 16 MWh annual energy surplus was obtained. Cultivations in Spain (Cartagena) and Colombia (Cali) seem to be slightly less effective, with approximately 15.5 MWh/a. The least effective agro-photovoltaic cultivation of tomatoes proved to be in Poland where the energy surplus reached 8.5 MWh/a. However, the economic return from cultivation strongly depends on local energy and tomato prices. The system of smart tunnels proposed by the authors combines photovoltaics with controlled protection of crops against unfavorable and extreme climatic conditions. In addition, the system allows plants to be grown with the maximum possible days with natural growing conditions, i.e. with uncovered tunnels, with natural bio-fertilization, and with natural sunlight.