A linear mathematical programming model for optimization of the energy consumption in construction projects

In this study, a linear mathematical programming model is formulated to manage the consumption ofelectrical energy and fossil fuels in the construction projects simultaneously. The aim is to determine atwhat time period and for how long each electric machine is employed in the whole project, the optimalnumber of periodic services for the machines with fossil fuels and optimal service time so that the totalobjective function value is minimized. The objective function of the proposed problem is the sum ofelectricity consumption costs, service costs and fossil fuel consumption costs in the whole project. Inthe proposed model, different intervals are considered for electrical energy consumption and the effectsof the average speed of each machine with fossil fuel consumption and the time required to these machinesin each day are also applied in decisions-making. For solving the mathematical model, the LINGOoptimization software package is employed. For a better understanding of the behavior of the proposedproblem, sample problems with different sizes are investigated and the results are interpreted graphically.The results show that the objective function value of the proposed problem increases with an incrementin the project completion time and number of machines, the consumption cost of the fossil fuels machinesaccounts for a significant portion of the objective function value in all samples and also, the contributionof service costs is more than that of the electric machines. Also, the proposed model is implemented fora sample problem and its sensitivity to some parameters are tested. The results of sensitivity analysisshow that by increasing the project completion time, the number of intervals selected for the daily use ofelectric machines, number of service times required for the fossil fuel machinery and consequently theamount of objective function are increased. Also, the model solving time increases logarithmically withan increment in the project completion time.