Study of methodological approaches for improving environmental performance in complex system design
The tendency towards a homogenous mode of development modeled on that of Western countries means that sustainable development has become increasingly urgent. In order to implement such development, it is not enough to make superficial reductions of environmental impacts; it is necessary to thoroughly redefine products and their expected performances in such a way that the consequences are compatible with sustainable development. Many ecodesign tools have been developed to meet the requirements of sustainable development. However, these tools are not generally suitable for the design of complex systems because there are either too specific, too general or based on rules of thumb often unverifiable. That is why we propose in this research to develop a methodological approach for ecodesign complex systems. This research work has led us to develop four methodological approaches each time to provide answers to the identified problem areas: 1. Are the current eco-design tools adapted to take into account the multiple dimensions of system design? 2. How to identify and hierarchize the most promising areas of environmental improvement at the early stages of the design process? 3. How to determine technological solutions adapted to a complex system and guarantee the best environmental performance? 4. Which are the necessary features for optimal environmental performances for a complex system? First, the Pareto / LCA approach, introduced in Chapter 3, is based on a simplification of the system considering that the main sources of impact are generated by a small part of it. It consists of a succession of LCA for each proposed alternative; it is a tedious process optimization. However, this approach provides “good” results and is well suited to designers’ reasoning. Indeed by their industry experience and knowledge of the product, the designer can easily identify the main contributors to impacts. Then we developed an approach presented in Chapter 4 that combines Design of Experiment (DoE) and LCA. This approach is based on a complete modeling of the product. The main contribution of the DoE / ACV approach is the ability to prioritize the system parameters according to their influence on the environmental performance of the system. To address the limitations identified in the study of the two previous tools we have proposed a new methodological approach based on Constraint Satisfaction Problem (CSP) combined with LCA and presented in Chapter 5. The most time consuming step is to model the system (definition of design parameters, constraints, equation and performance). It is necessary to gather information about each process and system components, the use phase, maintenance, etc. The advantage over previous tools is the ability of the approach to ensure a complete set of solutions, allowing the designer to choose a good one that complies to environmental performance and constraints specified in the definition specifications. In addition to the CSP / LCA approach, we propose an EcoCSP approach, in Chapter 6. In it, the functional specifications are no longer “frozen”. The approach EcoCSP allows us to understand the configuration of the product corresponding to a change in functional performance. The EcoCSP is used to make functional trade-offs that affect the functional unit of the system with the consequences this entails.