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Abstract: Industry in the power generation sector today has experienced a very significant development due to the increasing demand for electricity; hence an effort to optimize the generation of electricity is necessary. This study aims to optimize fuel costs and reduce the emissions of a gas and steam power plant in Indonesia, that is the Sengkang Power Plant. The method used is to conduct polynomial regression to find the functions of the fuel cost and the emission. To form an objective function of fuel cost with the consideration of emission, the weight sum method is used. With the newly acquired objective function, the Lagrange method is then employed to find the optimal point between the cost of electricity generation and the resulting NOx emissions. The optimization point of the generator is obtained by processing the operation data of the power plant in the form of peak load and base load that must be fulfilled by the plant on working days and public holidays and the NOx emissions generated at the same time. From the simulation results obtained, there are some combination of active power generation for 2 generator units that produce optimum operating costs with low emissions.

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