A method for operating a cane preparation unit with an energy optimizing unit, wherein the cane preparation unit includes a plurality of carriers (16, 18, 20) coupled to each other for receiving cane from a cane loading section, cutting the received cane into a desired size, shredding the desired size cane into shredded cane pieces and conveying the shredded cane pieces to a chute of a first mill, wherein each of the carriers (16, 18, 20) is associated with a carrier motor, the method comprising: receiving, by the energy optimizing unit, a working range for at least one operating variable for the plurality of carriers (16, 18, 20) of the cane preparation unit; estimating, by the energy optimizing unit, energy consumed by the cane preparation unit when operated with a first plurality of set points in the received working range for the at least one operating variable; selecting, by the energy optimizing unit, one or more first set points as use set points for the at least one operating variable based on the estimation of energy consumed by the cane preparation unit, the first set points obtained with an objective function for reducing energy consumed for the at least one operating variable, wherein the objective function includes a first term to reduce deviations in a first mill chute level for maintaining uniform feed, a second term to reduce the speed of at least one of the carrier motors and a third term ensuring smooth acceleration of the carriers (16, 18, 20), and wherein the use set points correspond to reduced energy consumed in the operation of the cane preparation unit; and operating the cane preparation unit at the use set points for the at least one operating variable; and monitoring the at least one operating variable for energy consumed at the use set points at distinct time intervals; and re-estimating energy consumed corresponding to a second plurality of set points; and generating one or more second set points corresponding to a minimum energy consumed at the one or more first set points or the second plurality of set points as new use set points; and operating the cane preparation unit at the new use set points; and wherein the objective function is given by: Min d ∑ j = 0 Np − 1 y sp k + j − y ^ k + j 2 + ∑ j = 0 Nc − 1 d k + j T W 1 d k + j + ∑ j = 0 Nc − 1 d k + j − d k + j − 1 T W 2 d k + j − d k + j − 1 subject to X k + 1 = f X k, d y ^ k = g X k, d d min ≤ d ≤ d max where d = speed 1 speed 2 ⋮ speedm; W 1 = w 11 0 ⋯ 0 0 w 12 ⋯ 0 ⋮ ⋮ ⋱ ⋮ 0 0 ⋯ w 1 m; W 2 = w 21 0 ⋯ 0 0 w 22 ⋯ 0 ⋮ ⋮ ⋱ ⋮ 0 0 ⋯ w 2 m; X = x 1 x 2 ⋮ x n; ŷ = f irstmill chute level; Np = predictionhorizon; Nc = control horizon receiving, by the energy optimizing unit, a working range for at least one operating variable for the plurality of carriers (16, 18, 20) of the cane preparation unit; estimating, by the energy optimizing unit, energy consumed by the cane preparation unit when operated with a first plurality of set points in the received working range for the at least one operating variable; selecting, by the energy optimizing unit, one or more first set points as use set points for the at least one operating variable based on the estimation of energy consumed by the cane preparation unit, the first set points obtained with an objective function for reducing energy consumed for the at least one operating variable, wherein the objective function includes a first term to reduce deviations in a first mill chute level for maintaining uniform feed, a second term to reduce the speed of at least one of the carrier motors and a third term ensuring smooth acceleration of the carriers (16, 18, 20), and wherein the use set points correspond to reduced energy consumed in the operation of the cane preparation unit; and operating the cane preparation unit at the use set points for the at least one operating variable; and monitoring the at least one operating variable for energy consumed at the use set points at distinct time intervals; and re-estimating energy consumed corresponding to a second plurality of set points; and generating one or more second set points corresponding to a minimum energy consumed at the one or more first set points or the second plurality of set points as new use set points; and operating the cane preparation unit at the new use set points; and wherein the objective function is given by: Min d ∑ j = 0 Np − 1 y sp k + j − y ^ k + j 2 + ∑ j = 0 Nc − 1 d k + j T W 1 d k + j + ∑ j = 0 Nc − 1 d k + j − d k + j − 1 T W 2 d k + j − d k + j − 1 subject to X k + 1 = f X k, d y ^ k = g X k, d d min ≤ d ≤ d max where d = speed 1 speed 2 ⋮ speedm; W 1 = w 11 0 ⋯ 0 0 w 12 ⋯ 0 ⋮ ⋮ ⋱ ⋮ 0 0 ⋯ w 1 m; W 2 = w 21 0 ⋯ 0 0 w 22 ⋯ 0 ⋮ ⋮ ⋱ ⋮ 0 0 ⋯ w 2 m; X = x 1 x 2 ⋮ x n; ŷ = f irstmill chute level; Np = predictionhorizon; Nc = control horizon