Energy, exergy, environmental and economic analysis of hybrid waste-to-energy plants

Recently, studies have been evaluating the thermodynamic performance of new configurations of integrated waste-to-energy/gas turbine cycles, but a question still remains: Instead of building new natural gas power plants or installing conventional waste-to-energy facilities, should one be investing in flexible efficient hybrid plants? This article aims at presenting a novel comprehensive approach to help answering this question. The strategy intends to demonstrate how to integrate four known key procedures (energy, exergy, economic and environmental analysis) in an original manner in order to evaluate the feasibility of such systems. The technique consists of a conventional Energy-Exergy analysis followed by a new Environmental-Economic approach. The novelties are in the economic and environmental parts, namely: (i) the use of multiple cost equations for estimating the plant's initial investment range and (ii) the indirect estimate of the pollution abatement system cost through an energy-ecological efficiency indicator. A case study configuration (similar to the existing plant of Bilbao) is used as exercise to demonstrate the method and its comparability potential, as well as to allow discussion using tangible results. The case-studied plant has a power output capacity of 107 MWe, thermal efficiency of 36%, ecological efficiency of 89%, thermal waste input capacity of 155 MWt and levelized cost of electricity production of US$ 64-89 per MWh. It is compared to several existing single-fueled waste-to-energy facilities and other energy sources, including renewable and non-renewable. As unique findings of this research, it is shown that the proposed economic method allows to predict costs quite accurately and that the specific investment costs of such technology are very attractive compared to existing single-fueled waste-to-energy facilities in Europe and other electricity sources in the Brazilian context. The proposed method proved to be a comprehensive procedure to analytically evaluate the feasibility of hybrid waste-to-energy power plants, which present good potential in the Energy conversion field.