Exergoenvironmental analysis for evaluating coal-fired power plants technologies

Abstract

Coal is a source of fundamental importance for the global electrical matrix due to its massive use, its abundance, worldwide distribution, low price, and etc. Despite emerging environmental concerns, projections have shown that coal usage will be kept for a long time. This work brings the quantification of environmental impacts by the exergoenvironmental approach based on the Specific Exergy Cost (SPECO), establishing a baseline of impacts for conventional subcritical plants and providing data so far unavailable for comparison with other alternatives. The sensitivity analysis has identified the importance of the coal composition in the process. Changing from a subcritical power plant to a supercritical one represents a gain of 2.0% in exergy efficiency in the plant and also a reduction in the total environmental impact concerning electricity generation of 5.7%. Electricity generated by the subcritical system has an environmental impact rate of 41.40 mPts/kWh, and the total impact produced by the system to generate a unit of electricity is around 48.26 mPts/kWh. For the supercritical system the environmental impact is 38.90 mPts/kWh, and the total environmental impact produced in the generation of electricity is 45.50 mPts/kWh. The impact rates related to exergy destruction and the formation of pollutants were identified as the principal sources of environmental impact. Changes in the coal composition led to a strong influence on the environmental diagnosis, being responsible for a variation of more than 60% in the impact rate.