Exergoenvironmental analysis for evaluation of the environmental impact of energy conversion systems

Abstract

To improve the ecological performance of energy conversion systems, it is essential to understand the formation of environmental impact at component level. A method has been developed that (a) reveals the extent to which each component of an energy conversion system is responsible for the overall environmental impact and (b) identifies the sources of the impact. The approach of exergoeconomic analysis is modified to deal with an evaluation of the ecological impact instead of an economic problem. The basic idea is that exergy represents a proper basis for allocating both costs and environmental impact to components of energy conversion processes. The proposed exergoenvironmental analysis consists of three steps. In the first step, a detailed exergy analysis of the system under consideration is conducted. In the second step, the required values of the environmental impact are determined by applying an appropriate method involving an appropriate quantifier of the environmental impact. Here the Eco-indicator 99 impact assessment method is applied in conjunction with the method of life cycle assessment. In the last step, the environmental impact associated with each component is assigned to the product exergy streams of the component; subsequently exergoenvironmental variables are calculated and an exergoenvironmental evaluation is conducted. As a case study, an energy conversion system consisting of a high-temperature solid oxide fuel cell integrated with an allothermal biomass gasification process has been analyzed. Exergoenvironmental analysis allows us to identify the environmentally most relevant system components and provides information about possibilities for design improvements.