Benefits and limits of a Constraint Satisfaction Problem/Life Cycle Assessment approach for the ecodesign of complex systems: a case applied to a hybrid passenger ferry

This article aims to respond to the absence of ecodesign tools for products in the early stages of the design process especially in the domain of complex systems. A complex system has numerous interdependent sub-systems, each of these having several design alternatives and variable conditions of use which affect the choice of technological solutions and environmental performance. A complex system is also one which evolves throughout its life cycle, interacting with the external environment. These characteristics rapidly result in a great number of configurations which must be assessed in order to identify the optimal system for the environment (using many criteria and over the whole of the life cycle). To ecodesign such a system in the early stages of the design process, we have investigated, from the literature, 3 different methodological approaches, each of which uses Life Cycle Assessment (LCA). Approach 1 is the intuitive approach of the designer based on simple rules or on a Pareto combined with LCA. Approach 2 is based on Design of Experiments (DoE) combined with LCA and in approach 3 the Constraint Satisfaction Problems (CSP), based on the calculation of intervals, are combined with the LCA. These three methods (Pareto/LCA, DoE/LCA and CSP/LCA) have been tested in an ecodesign project for a complex system: a hybrid passenger ferry. The results of each method are evaluated according to the following criteria: time consumed, training, exploration of fields of possibility, interpretation of results and reusability. These results show that the CSP/LCA approach has certain advantages, in particular for exploring the fields of possibilities, interpreting results and the time saving through reusing results obtained for similar systems.