Procedure for the determination of the maximum surface which can be irrigated by a photovoltaic pumping system

Abstract The area which can be irrigated with photovoltaic equipment, of a defined power, is an important design parameter of an integrated photovoltaic irrigation system. In this paper, a procedure has been developed to maximize the area of the surface irrigated. The analysis considers the interaction of four subsystems: local climate, irrigated crops, soil and photovoltaic pumping equipment. At first the mechanical energy available in the shaft of the moto-pump is calculated by the utilizability method. Then an analytical relation between mechanical energy, volume of pumped water and manometric height is obtained and correlated with experimental results. This correlation is used to obtain the volume of pumped water as a function of mechanical energy. Finally, a water balance is done, considering the irrigated surface as a variable. The maximum surface which can be irrigated has to satisfy the following conditions: (a) the water supply has to satisfy the water demand at any time of the year, (b) the water stored in the soil has, for safety reasons, to be no less than 20% of its field capacity. The procedure is illustrated with an example developed for a crop of grapes in the area of Petrolina PE, Brasil. The maximum surface which can be irrigated with a 450 W photovoltaic equipment results, in this example, to be equal to 1.57 ha. When the storage capacity is not considered, the maximum area becomes equal to 1.44 ha. The procedure can also be used to determine the optimum inclination angle of the photovoltaic panels.