Velocidade econômica de escoamento e composição de custos de sistemas de irrigação por aspersão

Abstract

Several factors can act as limiting for the irrigated agricultural activity, including energy used in the systems. In this work simulations were made in order to determine the most economical diameter for galvanized steel and PVC pumped supply. It was found that, for galvanized steel pipes, the economical speed ranged from 0.67 to 1.63 ms-1; and, for PVC, ranged from 0.62 to 1.97 ms-1. Based on simulations, it was evaluated the influence of raising the energy cost and the pipe cost on the economical flowage speed. It was observed that when the increment of the electricity cost is higher than the increment of the pipe´s cost, the economical flowage speed tends to decrease. On the other hand, it tends to increase when the increment of the cost of the pipe is larger than the energy´s increment. The increment of cost of electricity causes a further reduction on the economical flowage speed when the length of the pipelines is small. When the increment on the cost of the pipe is larger, the economical flowage speed increases more in pipelines of bigger lengths. It was also aim of this work to determine the required power and energy consumption for the simulated situations in areas irrigated with conventional sprinkler, traveler irrigation machine and central pivot. It can be observed that the power and consumption vary extensively with the local characteristics and the systems, making impossible the use of averages to represent them. Based on simulations were also obtained the total cost and unit cost for the considered systems. The total cost increases with the irrigated area, while the unit cost decreases. The average cost is not a good representation for those systems due to the wide variation presented, due to local and operational characteristics.