Techno-economic analysis of a hybrid combined cycle applied to sugarcane plants

Abstract

Hybrid combined cycles, fueled by natural gas and biomass, have been present in several power plants. As shown by different authors, it is possible to increase the overall efficiency of these plants by means of waste heat recovery from exhaust gases of gas turbines. The main disadvantage, for some cases, is the higher natural gas consumption, making some plants economically unfeasible. The present work applies the concept of a novel hybrid combined cycle (HCC), adapted for sugarcane mills, burning sugarcane bagasse and natural gas. In order to evaluate the potential of application of this concept, a new hybrid configuration, starting from an existing plant, is proposed. A thermodynamic performance study has shown an electrical efficiency improvement (from 6.8% to 17.8%) for the same amount of bagasse originally burnt, thus allowing the plant to operate throughout the year, increasing the electricity generation (from 108.9 to 323.0GWhel) as well as meeting the same steam demands for sugar and ethanol production processes. The economic evaluation, considering investments, operating expenses and plant requisites, has pointed to an internal rate of return (IRR) of 22.89%. Furthermore, this new configuration does not depend on a large natural gas consumption (gas share of 11.4%), making the plant’s economic feasibility less dependent on fluctuations of natural gas prices. Finally, a sensitivity analysis of four different hybrid plants have shown the techno-economic feasibility of hybrid combined cycles applied to sugarcane mills, including during the off-season period.