Tchertchian Nicolas
email: nicolas.tchertchian@univ-tln.fr

Optimization of maintenance strategy of Renewable Energy Production System (REPS) for minimizing production loss

Optimization of maintenance strategy of renewable energy production system (REPS) for minimizing production loss

Nicolas Tchertchian, Dominique Millet

Introduction

The Renewable Energies Production System (REPS) do not generate direct emissions and do not produce hazardous waste. Nor do they deplete natural resources. However the production of this energy generates indirect pollution due to the high failure rate of the industrial production system, the maintenance and the unavailability of energy source [START_REF] Christensen | Availability of wind turbines in remote places.A statistical and a real-time view[END_REF]. The life cycle of the REPS is defined Figure 1.During the use phase the power system (wind turbine, Marine current power, photovoltaic panels…) can fail and need Operations and Maintenance (O&M).During O&M, technicians are transported to the production site. The impacts generated by this mean of transport should be accounted in environmental assessment.During the period of unavailability of the renewable energy source, the energy that is not produced must be elsewhere. This creates economic costs and generates additional environmental impacts associated with the production of non-renewable energy (nuclear power plant, thermal power plant…). One way to reduce these indirect impacts is to optimize the REPS lifetime while minimizing environmental losses due to maintenance by mobilizing the concept of Eco-Maintenance.The structure of this paper is as follows. In Section 2, we provide a brief overview on optimization of operational resources for the maintenance of REPS. Section 3 deals with the Complex system modeling for environmental optimization of REPS then for Wind Energy Production system. Section 4 presents some O&M scenarios and their environmental impact through Life Cycle Assessment method.Subsequently, the relevant parameters influencing the overall performance of REPS are identified then and operational issues are discussed in Section 5.

Optimization of operational resources for the maintenance of REPS

The maintenance optimization is the process that seeks to balance the constraints of maintenance (legislative, economic, technical, and environmental) and the resources used to run the maintenance program (human resources, spare parts, equipment, arrangements, etc.) [START_REF]Maintenance Optimization[END_REF]. The main objective of the maintenance optimization is to determine the strategy which provide the best balance between direct cost service (labor, materials, administration ...) and the impact on the system if maintenance is not performed as expected (loss of production and profits) while avoiding the consequences on health, safety and environment by mobilizing the concept of "Green" Maintenance [START_REF] Ajukumar | Evaluation of green maintenance initiatives in design and development of mechanical systems using an integrated approach[END_REF].

Figure 1:Life cycle of REPS

To optimize the maintenance of REPS two types of action are possible; first by acting on internal factors (organizational improvement of the maintenance process: fault detection as early as possible [START_REF] Tavner | Reliability of different wind turbine concepts with relevance to offshore application[END_REF], automatic detection of deviations performance of WTs [START_REF] Sainz | Robust filtering for the characterization of wind turbines: Improving its operation and maintenance[END_REF], planning maintenance [START_REF] Nielsen | Planning of O&M for Offfshore Wind Turbines using Bayesian Graphical Models[END_REF] ...); then acting on the external factors in improving the performance of system of maintenance (optimization of logistics scenarios [START_REF] Scheu | Maintenance Strategies for Large Offshore Wind Farms[END_REF], fleet composition, type of truck, vessel, helicopter … *8]).

In practice, two strategies are confronting:

• Identify the risks of failure to intervene earlier

•

Repair as soon as possible in difficult weather conditions to avoid extended downtime of Power system.

In this paper we deal with the second option.

The achievement of maintenance activities such as inspection, preventive maintenance, and replacement of wear components increases the direct costs of maintenance. In return, the risk of incidents or consequences of failure to complete the required maintenance decreased [START_REF]BS3811 Glossary of maintenance terms interotechnology[END_REF].

Complex system modeling for environmental optimization of REPS

3.1. Scope of Reps REPS are complex system composed by 3 linked subsystems.

1. The industrial system responsible for converting renewable energy into electricity source.

2. Location of these systems.

3. External resources maintaining the industrial system.

Modeling parameters for industrial system (solar panels, wind turbines, submarine turbines…) are the power, the lifetime and the reliability of its components.

Location of REPS is characterized byweather conditions (sun, wind, swell…), distance and mean of transport to reach production site (trucks, helicopter, ship, submarine…).

For the maintenance of the industrial system (repair breakdowns or preventive maintenance), external resources are mobilized to transport the technicians on the production site, store and carry tools and spare parts. The performance of these resources will influence the environmental impact of REPS The performance of Maintenance Systems (SM) is characterized by the time to access to the site, the range of use according weather conditions and its life cycle (Raw materials/ Manufacturing, fuel consumption, maintenance: replacement of wear parts, and end of life).

Offshore Wind Energy Production System

The remainder of this paper reports findings from environmental assessment and influences of external factors for wind energy production system (Figure 2) [START_REF] Münsterberg | Design and Evaluation Tool for Operations and Maintenance Logistics Concepts for Offshore Wind Power Plants[END_REF].

The turbine is the power system of REPS. In a simplified way, the wind turbine blades transform the kinetic energy of wind into mechanical energy and then into electricity by a generator. The characteristic of a wind power curve gives the electric power according to wind speed for a wind turbine.

The number of turbines in wind farm and their power are used to quantify the energy generated by the wind farm according wind conditions on the production site. The lifespan of the components is used to design corrective maintenance (by randomly generating failures based on the failure rate of various components defined by a group of experts [START_REF] Ribrant | Survey of Failures in Wind Power Systems With Focus on Swedish Wind Power Plants During 1997-2005[END_REF] and planned preventive maintenance.

The location of offshore wind farms in high sea makes them more difficult to perform O&Ms.

Technicians must be transported with ships on production site, eventually by helicopter. Then the transfer on wind turbines requires optimal weather conditions to ensure their safety.

Distance from shore results in two types of maintenance strategies [START_REF] Tavner | Reliability of different wind turbine concepts with relevance to offshore application[END_REF]; the first based on maintenance made from shore: technicians return to port after each intervention; the second strategy for wind farm away from the coast, technicians are permanently close to the farm.

Weather conditions (average wind speed and significant wave height) are defined for a given wind farm location. These data are needed to evaluate the energy production of the wind farm and to plan the schedule of preventive maintenance. More the wind is powerful and constant more the load factor is better but in return the transfer of technicians is difficult (depending of the system of maintenance used).

Our work is focused on the search for an optimized maintenance system.To develop logistics scenarios, the model integrates different parameters:

• The ability to transfer technicians (number of technicians)

• The speed of response depending on the distance to the site and performance in weather conditions (wind and significant wave height limits).

The different types of SM for offshore wind farms are:Crew Transfer Vessels (CTV), helicopters and Fast Support Vessel (FSV). CTV is used to transport between 12 and 16 technicians on production site located until 30 nautical miles (nm) form shore at 20 knots maximal speed. But they are limited by weather condition. The significant wave height limitations of CTV are usually assumed with 1.5 m. When sea conditions are harsh, operators could charter helicopters. When the distance from shore is more than 30 nm, others solutions exists. Operators need a third type of SM. These vessels (also called "floatel") are bigger and stay near the wind farm on a 24h/7 days basis for several weeks. For example Fast Support Vessel (FSV) is able to accommodate up to 48 technicians. These boats are capable of transferring technicians with the worst sea conditions between 1.5m and 3m.

Figure 2: Subsystems for Wind Energy production system

During the winter season, sometimes access to turbines is inaccessible for long periods, resulting in a long periods of downtime and production losses [START_REF] Obdam | O&M Cost Estimation & Feedback of Operational Data[END_REF]. Thus, these constraints are arguments in favor of investment in more robust vessels able to safely transfer the technicians to the turbines in harsh weather conditions (> 1.5m). But the sophistication of maintenance systems not she leads to an increase of impacts and costs over the full life cycle of the system?

Figure 3shows the distribution of impacts generated by the wind power production under different scenarios.Wind energy production system, in perfect case (i.e. without maintenance), produces clean energy with a yield of 40%. The rest of the energy is to be produced in a conventional manner (non-renewable) and the impact is due to manufacturing of the turbine.

Figure 3: Distribution des Impacts dans la production d'énergie éolienne

In reality wind turbine fail and their efficiency fall under 40%. Consequently more non-renewable energy must be produced and in addition to the manufacturing impact of wind turbine, the impact of the life cycle of SM has to be accounted. The goal is to obtain the best efficiency of the wind energy production system with the least impact.

Case Study: Assessment of Wind farms maintenance

Unplanned maintenances are modeled using Annual Failure Rate (AFR). The model is built around an event generator. The principle of this generator is to randomly assign failures on all WTs over their lifetime and deduct the planned maintenance affecting the wind farm. The generator is built around a global optimization method of the maintenance system, detailed on [START_REF] Tchertchian | Eco-Maintenance for Complex Systems: Application on System of Renewable energy production[END_REF].

We assumed that repair time is 6 hours per turbine and planned maintenance time is 4 hours per turbine.Preventive maintenance is stopped when a turbine fails. Maintenance operations resume when the turbine is repaired.

The functional unit of the Wind Energy Production System is defined by a 20 years lifetime, a wind farm composed by eighty 6MW turbines.

 Environmental assessment of O&M scenarios for wind farms at 50 nautical miles from shore Three different systems are evaluated, a CTV and 2 bigger vessels ("floatel"): a 90 meters long FSV able to accommodate up to 48 technicians and an alternative system capable of transferring up to 24 technicians through a Small Waterplane Area Twin Hull (SWATH) boat coupled to a dynamic stabilization system on a 24 hour/7 day basis and up to 3m of significant wave height.

To comply with the functional unit, four vessels need to be deployed against one SWATH and one FSV. Figure 4 shows the impact of the life cycle of three SM on raw materials manufacturing use and end of life phases the impact due to the non-renewable energy to produce when wind turbines are stopped. To perform all the tasks planned it is necessary to have several CTV. On Figure 5, maintenance performed by CTV is optimal solution when production site is located at less than 10km from shore. However at 50km from shore the situation becomes less obvious, SWATH vesselis the best solution but the difference is not substantial. At 100km from shore the optimal solution is obviously SWATH vessels. Indeed, the environmental gain is about 30% less impactful than CTV for reason mentioned above.

Conclusion

This approach should be applied at the same time as designing WT. It would be interesting to assess the size of the wind farm coupled with the power of WT. For example, is it better to design a 500 MW wind farm composed by 80 * 6MW, or composed by 62* 8 MW WTs.

The failure rate of these turbines is assumed to be different (because the technologies used are different).

Unavailability of 8 MW WTs may be more important generating more environmental impact with production of non-renewable energy. In exchange, the maintenance of a smaller wind farm may induce fewer resources in terms of maintenance. In conclusion, the environmental performance of Systems of Energy Production and system of maintenance are interdependent.

Figure 4 :

 4 Figure 4:Environmental assessment of O&M strategy for windfarm at 100km from shore

Figure 5 :

 5 Figure 5: Influence of distance from shore on environmental assessment of O&M strategy


Nicolas Tchertchian

Haining Liang

Dominique Millet

INFLUENCE OF THE MULTIPLES LIFE CYCLES ON THE ENVIRONMENTAL IMPACT OF A PRODUCT

Keywords: LCA, Modularization, Remanufacturing, Multiples Life Cycles (MLC)

d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

The introduction of environmental dimension in design became a priority in our modern societies. The prospect to see the mining and energy resources becoming exhausted in medium term associated with the environmental problems [START_REF]Bilan 2007 des changements climatiques[END_REF] must lead the great industrial nations to deeply reconsider the way of manufacturing and consuming in order to reach a new model of more sustainable development: The Brundtland report defines sustainability as: "The ability of current generations to meet their needs without compromising the ability of future generations to meet their own needs" [START_REF]The European Parliament and the Council of the European Union[END_REF]. This new kind of development is built on 3 fundamental pillars:  Environmental protection.  Economic growth.  Social equity. Today the need for setting up new strategies as regards sustainable development like the "precious" material recycling or the re-use of components at high added values is increasingly strong. Shown by the increasingly consumption of electronic goods. Under the pressure of the marketing and requirements of the customers who wish always more functions, the technological change generates an accelerated obsolescence of these products. These thrown products, although become "used", are however always mainly functional; thus the majority of their components could be re-used in the manufacture of new ranges of products. In addition to the economic aspects, the remanufacturing makes it possible to answer the WEEE directive which imposes to the manufacturer minimum rates of recycling, of re-use and energy valorization [START_REF] Umeda | Product modularity for life cycle design[END_REF]. However, the methods suggested at the present time do not make it possible to answer in a satisfactory way the technical potentialities of the multiple remanufacturing; the aim of this article is to fill this lack by proposing a method which make it possible to meet the new requirements that imposes the definition of sustainable development i.e. to decrease our consumption of resources and production of waste, to support the emergence of a new model of production associated with a new economy, without loss of quality of life. In the first section of this paper, a state of the art of research undertaken in the field of the remanufacturing and the design of modular products (Design for Modularity) will be presented; it will make it possible to put forward the lacks of the methods suggested in the literature. In the second part, we will propose a methodological support allowing an evaluation of existing products, starting from modular groupings operated according to definite criteria (criteria of values, reliability, technical, technological stability…). The evaluation is based on an analysis of product life cycle alternatives (the number of reusable modules, product lifespan and the number of use cycles under consideration for each module). In third part, this approach is tested within the framework of a comparison of 3 machines espresso (a traditional machine without doses, a machine with aluminum doses and a machine with plastic doses). In the last part the benefit and limits of this new approach will summarize.

LITERATURE REVIEW

The review of literature shows that the interest for the remanufacturing is growing [START_REF] Lund | The Remanufacturing Industry: Hidden Giant[END_REF] [START_REF] Steinhilper | REMANUFACTURING The Ultimate Form Of Recycling[END_REF]. By definition, the remanufacturing is "The process of returning a used product to at least Original Equipment Manufacturer performance specification and giving the resultant product a warranty that is at least equal to that of newly manufactured equivalent" [START_REF] Ijomah | A model-based definition of the generic remanufacturing business process[END_REF]. It gathers several fields of the design: evaluation of the remanufacturability and Re-design of product to facilitate the remanufacturing [START_REF] Laan | Production planning and inventory control with remanufacturing and disposal[END_REF] [8] [START_REF] Duflou | Efficiency and feasibility of product disassembly: A case-based study[END_REF], research on remanufacturing operation (disassembly, cleaning, inspection and sorting, reconditioning, reassembly) [START_REF] Lund | The Remanufacturing Industry: Hidden Giant[END_REF] [5], environmental analyzes [START_REF] Gehin | Développement d'une Méthodologie de Conception de Produits Durables[END_REF] and economic analyzes [START_REF] Kerr | REMANUFACTURING AND ECO-EFFICIENCY:A case study of photocopier remanufacturing at Fuji Xerox Australia[END_REF] [START_REF] Mont | A new business model for baby prams based on leasing and product remanufacturing[END_REF]. In spite of that, various works treats often only one part of the problem. At the same time as the optimization of the product disassembling for its valorization became a very dense subject of research [START_REF] Gungor | An evaluation methodology for disassembly process[END_REF] [14] [START_REF] Desai | Evaluation of disassemblability to enable design for disassembly in mass production[END_REF]. In order to allow the separation of sub-assembly (reusable, which can be recycled or not, dangerous) of many research was carried out in order to systematize and optimize the process of dismantling. The difficulty increases with the number of component and the time of dismantling varies according to several parameters (interconnection of the components between them, joint types, direction of dismantling…). Gungor proposed since 1997 an algorithmic method making it possible to approach an optimal sequence of disassembling [START_REF] Gungor | An evaluation methodology for disassembly process[END_REF]. But this method does not take yet counts of them the economic and environmental aspects: the complete dismantling of a product in the shortest possible time would have a cost not justified. In fact, the justification of the remanufacturing must take into account of many criteria, as underlined by Kara [START_REF] Kara | Selective Disassembly Sequencing: A Methodology for the Disassembly of End-of-Life Products[END_REF]: "Full disassembly of a product tends to be unproductive due to technical and cost constraint…".For Zuidwijk "A product recovery strategy determines the degree of disassembly of a product and the assignment of recovery options" [START_REF] Zuidwijk | Strategic Response to EEE Returns: Product Eco-Design Or New Recovery Process[END_REF]. According to [START_REF] Zuidwijk | Strategic Response to EEE Returns: Product Eco-Design Or New Recovery Process[END_REF] four options of valorization can coexist:  Remanufacturing on a component level which implies a complete dismantling.  Recycling of materials after a complete dismantling.  Recycling of materials after a partial dismantling to respect quotas.  Setting in discharge. Among these four options it misses an important option, that which privileges the remanufacturing with an optimal dismantling corresponding to the extraction at the lower cost of the modules with strong added value. In 2002 Lambert introduced the concept of "incomplete disassembly" [START_REF] Lambert | Determining Optimum Disassembly Sequences In Electronic Equipement[END_REF] justified by certain technical constraints: irreversible connections and economic constraints since the costs of dismantling are inversely proportional to the profits obtained by the re-use of the disassembled components. Using software CAD it is possible to determine if the dismantling of one part is blocked by another part always present. This necessary profitability of dismantling made emerge a new research field in design: "Design For Modularity". The modularization of products is indeed the first step for a sustainable design [START_REF] Seliger | Modularization as an enabler for cycle economy[END_REF]. The modular products make it possible to improve valorization of materials by differentiating the modules which can be recycled from the modules which cannot be recycled [START_REF] Kimura | Product modularization for parts Reuse in inverse manufacturing[END_REF]. In this direction, the design of the future products must take into account in the definition of the modules and architecture. But the majority of the products on the market do not have clearly defined modules; this largely complicates the evaluation of the end-of-life scenarios. In the products comprising a great number of components, those can be gathered in sub-unit, corresponding to functional groups of the product (washing machine case study [START_REF] Kara | Selective Disassembly Sequencing: A Methodology for the Disassembly of End-of-Life Products[END_REF]). In spite of that, various works treat often only part of the problem. The modular decomposition is a means of optimizing dismantling and making environmental and financial gains. The remanufacturing is a strategy which makes it possible to re-use products or modules on several use phases according to the requirements of the customers or the market evolution (e.g. computers system updating) [START_REF] Seliger | Modularization as an enabler for cycle economy[END_REF]. Tomiyama proposes a concept "Post Mass Paradigm Production" [START_REF] Tomiyama | The Post Mass Production Paradigm, Knowledge Intensive Engineering, and Soft Machine[END_REF] which aims at reducing the consumption of the natural resources as well as the production of waste all while maintaining the standard of living current or higher. The satisfaction of this new model passes by an increase in the products lifespan, posing the problem of functional obsolescence. The increase in the period of utilization and thus the limitation of obsolescence pass by a specific strategy according to the value of the component (repair, update, re-use…) "longer-life products should have functional upgradability besides reliability and faulttolerance" [START_REF] Kondoh | Development of Upgradable Cellular Machines for Environmentally Conscious Products[END_REF] [START_REF] Umeda | Product modularity for life cycle design[END_REF]. One of the aspects little developed consists in integrating this modular aspect in the product life cycle in order to evaluate either the product on only one life cycle but to extend the evaluation (economic and environmental) on several use cycles of the modules. The product is not then any more seen like a material assembly and manufacturing process but as a sum of modules interconnected which will become central units of the model construction. This vision is in particular approached in work of Alexis Gehin [START_REF] Gehin | Développement d'une Méthodologie de Conception de Produits Durables[END_REF]. He proposed a concept (brick of life cycle) making it possible to develop a product model taking into account the strategies of revalorization of the components on several use cycles. The approach suggested by A. Gehin allows an environmental evaluation of a product according to these modules, the fact of considering several use cycles imposes operational costs (Supply chain, refurbishing…). However few works gives a report on the performance of systems whose components are re-used beyond two use cycles: environmental impact and economic costs according to strategies of modules life cycle. Although the remanufacturing is a sustainable strategy of end-of-life, there must be a link between the current products and the future products. The problematic of this article is to define the optimal life cycle of a product for Re-design from a modular point of view and Multiples Life Cycles (MLC) by respecting the 3 pillars of sustainable development.

EVALUATION METHOD FOR THE END-OF-LIFE OF REMANUFACTURABLE

PRODUCTS The originality of this article is to consider the impact of the product either through its life cycle but to extend this one to the life cycle of the modules which compose it and this by considering their re-use. For consumer goods, the re-use of modules presents a theoretical environmental profit; however, its application in the industrial world must take into account many constraints: technically better, functional and economic.

Optimization of product architecture.

Majority of the consumer goods designed is based on architectures which marginally take into account the environmental problems. Electronic products for example, have many components manufactured with great material diversity (ferrous materials or not, plastic materials, glasses…), connected by varied joint types (clip, screw of various diameters, sticks, spring retaining ring, rivet…). With the installation of WEEE directive, the disassembly process became an important requirement that it is for recycling (separation of the materials mixtures) or for the remanufacturing of components. The current and future rates of valorization stipulated in this directive generate and will generate additional financial costs. These new requirements in terms of design made emerge new tools in engineering of the life cycle. Among these tools, software (like ProdTect ® [START_REF] Herrmann | ProdTect -Integrating End-of-Life in Product Development[END_REF] or EIME adapted to the study of the electronic print board [START_REF] Mathieux | Proposition of new recoverability indicators as support for the product design process: the electr(on)ic sector experience[END_REF]) enables according to certain parameters of design (joint types, direction of dismantling, materials, manufacturing processes…) to know the dismantling times (or the costs) and the rates of recycling. To use these tools the knowledge of the product structure is a major requirement; this limits the use of this kind of tool in downstream stage of design. The designers input the properties of components (materials, shape, dimension, orientation, etc), the connections between components and the priorities (the relations of anteriority between two components make it possible to define the sequence of dismantling). The software determines the level of dismantling corresponding either at a minimal cost, or optimal rate of valorization. The product is evaluated according to a specified scenario. The time of disassembling is an important criterion in the construction of end-of-life scenario. A component with high value added can require the integral disassembling of the product: the environmental benefit can then be counterbalanced by crippling economic costs. The tools for optimization of product architecture like ProdTect ® and LCA tools are very complementary. The first one makes it possible to design a dismountable product. And the second one makes it possible to legitimate the manufacture of the product but especially to design an optimal endof-life scenario by taking into account recycling rates to satisfy the regulation and to optimize the costs.

Criteria of modular concept

The modularity is an important aspect to optimize the remanufacturing. In the field of the B2B, there are many examples of success in literature like Xerox [START_REF] Kerr | Eco-efficiency gains from remanufacturing -A case study of photocopier remanufacturing at Fuji Xerox Australia[END_REF], baby prams [START_REF] Mont | A new business model for baby prams based on leasing and product remanufacturing[END_REF] or Velo'v [START_REF] Maussang-Detaille | Méthodologie de conception pour les systèmes produits-services[END_REF], being inspired in particular by the concept of Product Service System (PSS). However in small household appliances (B2C market) it is difficult to follow these examples without falling into the second-hand market. The small household appliances put on the market currently are not optimized for the remanufacturing processes; certain parts can be technically re-used but the installation of reverse logistic and the associated costs constitute a major issue. To cure it, it is necessary to call upon the concept of modularity: Design for Modularity consists to design elements of the product (The modules) which carry out some function satisfying a whole of need and being removable [START_REF] Agard | Design of assembly for mass customization[END_REF]. In other words a modular concept makes it possible to reduce the number of interactions between modules. With this intention, it is necessary to determine, a priori, the modules which must respect certain criteria (price of the components, functionality, lifespan, etc.). The difficulty is to define the borders of a module, knowing that the preexistent modularity in the product is only the reflection of the aptitude for the assembly or maintenance. In the continuation of this paper we will regard a module as an assembly of components achieving a specific function. To define a module, it is necessary to gather components of the product according to criteria. These criteria are more or less well defined: in literature we find many works treating of these criteria (Table 1). The idea of these various concepts is to gather the components having close characteristics (e.g. Ease to repair [START_REF] Kimura | Product modularization for parts Reuse in inverse manufacturing[END_REF] [START_REF] Erixon | Modularity: the basis for product and factory reengineering[END_REF]) in order to simplify the process of end-of-life [START_REF] Umeda | Life Cycle Option Selection Based On The Difference Of Value And Physical Lifetimes For Life Cycle Design[END_REF].

Table 1. Modules characterization

End of Life Strategy [START_REF] Umeda | Life Cycle Option Selection Based On The Difference Of Value And Physical Lifetimes For Life Cycle Design[END_REF] Modules properties [START_REF] Erixon | Modularity: the basis for product and factory reengineering[END_REF] Modules properties [ One of the blocking points of the remanufacturing is the economic aspect. Indeed we must take into account additional costs related to a requirement of essential quality (according to the definition of the remanufacturing) but also costs of reverse supply chain (RSC). This cost of logistics associated with the product returns and the transport of the modules can be optimized in the design of modules: the components of the same supplier can be gathered in order to reduce the distances of RSC.

Modular vision of life cycle.

In most of the case the electronic products have one value lifespan much less important than their physical lifespan, the main cause being the obsolescence of a component or a module including the components whose technology develops quickly (for example the computer material). This report shows that it is difficult to remanufacture a machine completely because its lifespan will depend on the most fragile components, on the components whose obsolescence is fastest or on the "housing" components which most strongly deteriorate. Excepted this non reusable modules, some modules (less sensitive to the technical, more reliable or less visual evolutions) can be re-used for the manufacture of new machines (identical or more advanced).

In a traditional outline when a product is not functional any more it is either put in discharge, or recovered by manufacturing which must manage its end-of-life in accordance with the legislation.

According to these directives it is either incinerated (energy recovery), or recycled, or re-used. With the last process, the functional components are not destroyed any more but reused as many cycles as its lifespan allows it. Thus, if a product become nonfunctional or obsolete beyond 5 years but it has a component which can resist 20 years, this component could be re-used 3 times. We talk about modular life cycle because in this vision the module is an individual product. It is independent of the product in which it is inserted (they can be in particular inserted on different product ranges). The characteristic of their life cycle is to integrate additional stages of refurbishing: disassembling, cleaning, repair, test, reassembly [START_REF] Steinhilper | REMANUFACTURING The Ultimate Form Of Recycling[END_REF]. These additional stages generate always additional economic costs and environmental loads. In order to determine the best compromise it is necessary to simulate various scenarios while varying the lifespan of the modules as well as the number of cycle and the lifespan of the product. This approach is built on a judicious parameter setting of the system product-modules and their life cycles.

Design parameters for the end-of-life of reusable products

Today the majority of the consumer goods are designed according to constraints on the respect of the environmental standards imposed by the institutions. LCA methods make it possible to evaluate the products in the last phases of products design, reducing the designer's degree of freedom. Within the framework of the products remanufacturing, many factors are concerned, the lifespan of the product, the lifespan of the components, the number of reusable component and the "remanufacturing process" [START_REF] Ijomah | Development of design for remanufacturing guidelines to support sustainable manufacturing[END_REF]: Inspection -Cleaning -Disassembly -Storage -Repair -Reassembly -Testing. Each one of these operations produce new constraints of designs: ease of Identification, ease of Checking, ease of Handling, ease of Access, ease of Stacking, ease of Separation… We make assumptions on the composition of reusable modules to evaluate the performance of existing products. Also we define virtual modules (modules gathering of the components checking the criteria of classification section 2.2) in order to carry out the environmental evaluation of end-of-life for remanufacturing scenario. According to these criteria the modules could be recycled, re-used or upgraded (figure. To define the parameters well, the first step is to evaluate the various scenarios. One of this parameters must be the lifespan of the product (or value time), it's important because it influences the functional unit. Then we decompose the product in modules according to the criteria defined into section 2.2. Each module is defined by a parameter. Finally the last parameter is the number of life cycle feasible by a particular module. The number of life cycle corresponds to the number of times where a module could be re-used in the manufacture of another product or a higher range. With these three parameters input (table . 2) and also the data of usage (electricity consumption, consumable…) we obtains a number of products according to Z n , a logistic scenario, end-of-life scenario (with various recycling rates, re-use, incineration, landfill)

Methodology: Multiples life cycle analyzes

The construction of the model can be realized directly with LCA software like Simapro ® . In order to improve comprehension of the method it will be supposed that Z1 =… = Zn = constant.

Construction of the model

We look at the life cycle either from product point of view but of these constitutive modules. In this case it is not any more one product which we must model but a succession of products depending on the number of modules life cycle. Product modelization is carried out as if it were about an "Empty box" in which we would add the modules according to their lifespan. Either Z the number of reusable modules life cycle, in order to evaluate the impact of the remanufacturing of the module we will have to analyze Z machines. Among these machines, the first corresponds to completely new product without use of materials recycled or used modules. Z-1 remaining machines will be "Empty box" in which would come to be added the remanufactured modules (Figure . 2).

According to the composition of the machines in recoverable modules the end-of-life scenario will be different (for example material rate which can be recycled, refurbishing of the modules). The choice of the remanufacturing imposes other constraints which we must integrate using new parameters. Product disassembly outside assembly center brings additional distances as well as transport to collect them when the product is thrown at the end of life. These Modules must then be repaired (refurbished). By using the parameters RSC (Reverse Supply Chain) and R (Refurbishing) we can extend simulation in order to have a more realistic vision of the life cycle.

Functional unit for multiple life cycles.

The definition of the functional unit [START_REF] Duflou | Efficiency and feasibility of product disassembly: A case-based study[END_REF] is a fundamental aspect, especially in this parametric modeling. Indeed while varying N and Z we modify the Functional Unit (FU), but to compare the various life cycle scenarios resulting from a choice of different parameters it is necessary to define an adequate functional unit in this type of evaluation. The idea would be to bring back FU to a functional constant (FC) calculus. To obtain an Environmental Score for a MLC scenario (EnS MLC ) we propose to convert the environmental impact (EI) of each stage in annual impact. Environmental score calculation [START_REF]Bilan 2007 des changements climatiques[END_REF] i: manufacturing stage, transport stage, use stage, EoL stage…

Framework.

The performance evaluation of a product on several cycles of use requires a coordinated use of several tools (LCA, ProdTect, Economic assessment).

We must initially know the components of the product: their failure rate, their price, their lifespan, the technical stability of the component in time. Then according to the definite criteria of modularity (section 3.2) we establish modular groupings. The description of the product must make it possible to define realistic scenarios, particularly for the choice of reusable modules and process of refurbishing. The choice of these modules (potentially reusable) will make it possible to simulate several disassembling sequences according to various scenarios. Product analysis software will model these disassembling sequences, thus we will be able to determine time and the cost necessary to the recovery of all modules for one scenario. In addition to disassembly costs, the software makes it possible to validate the coherence of the scenarios. The second part of the approach, being based on the parameter setting of the life cycle (section 3.4), allows systematically to evaluate the life cycle of a product according to the number of modules life cycle Z and the product lifespan N. The designer builds initially his product using the Bills Of Materials (BOM) in the following way: Part-process, component-process, module-process and finally Product-process, for that it must use a database (Ecoinvent, Buwal, Idemat). It must then build its life cycle by taking into account all parameters which will make it possible to simulate several cycles of use: usage (energy consumption: Cx), lifespan of the product N, the modules which designer chooses to reuse in the following cycle M n , the number's cycles of reused modules: Z, the scenario of refurbishing (according to the modules) R, logistic scenario: RSC… The designer can be helped by a "graphic" interface directly connected to LCA software using Macro Excel.

In the same time we carry out an economic study (figure . 3). At the end, according to the choices of the designer, we will have a performance evaluation (environmental and economic). The results will be given in the form of 3D histograms allowing a quick analysis of the results.

CASE STUDY: MACHINES EXPRESSO

In order to validate this approach, we propose to apply it on an industrial case study: the espresso machine. This last decade they are been an emergence of the machines with coffee doses revolutionizing the sector and with a strong competition. That's why we privileged the study of several machines with different technologies: A manual espresso machine and two concurrent machines with doses.

Perimeter of study.

LCA study has been limited initially to the environmental impacts related to MLC in extractionmanufacture-distribution-use and end-of-life of the machines stages. Then we have looked the influence of the MLC compared to different usage: doses or not, sleep mode or not… Protocol: 1. MLC Evaluation: variation of the factors M, N R and Z. 2. Evaluation Use 1: impact of the doses on the environmental performance. 3. Evaluation Use 2: Impact of electricity consumption on the environmental performance.

Modular decomposition.

We applied our experimental approach on the three following Espresso machine:  Product A (P A ): manual machine without doses.  Product B (P B ): manual machine with doses.  Product C (P C ): automatic machine with doses. Before to begin the evaluation for the 3 different machines, their modules must be defined: The pumps and the boilers are very near technologically. On the other hand the 3 products are dissociated by a "quite different Infuser module" because their technology (patented) makes it possible to dissociate competitors. These 3 modules answer at the remanufacturability criteria (section 3.2):  The vibrating pump have a great lifespan (because short cycles), a great technological stability (in 20 years the pumps of espresso machines evolved slowly).  The boiler is a central element of the system which often determines the lifespan of the machine (its breakdown leads generally to a reject of the machine) because of its high value, descaling seems to be an environmentally and economically interesting option.  The infuser answers at the criterion of fast dismantling with a simple cleaning. The Espresso machine is a simple case of study because it gathers 3 modules potentially reusable according to the criteria determined above limiting the number of possible combinations for a first experimentation. Our approach must make it possible to make arbitration on the choice of modular grouping economically and environmentally advantageous. In order to simplify calculations we will limit ourselves to the analysis of 4 scenarios:  WEEE Scenario: The current scenario recommended by WEEE directive.  Re-use of the infuser  Re-use of the infuser and the boiler.  Re-use of the infuser, the boiler and the pump.

Economic assessment.

For each scenario we calculated the cost caused by the modules end of use cycle, this cost takes into account the transport, the storage and the treatment of end-of-life. Global cost calculations:

C global = C tps + C w + C t (2)
C tps : Transport cost for ton/km: 0. Because the machine is transported completely to the production center, the transport cost and the warehousing cost are not influenced by the number of modules to be remanufactured, only the treatment cost which will vary from a scenario to another. (3)

Environmental assessment.

At the same time as this economic assessment, we carry out a Life Cycle Assessment for each configuration (re-used modules, number of cycle of use, lifespan…) to define an Environmental Score according formula (1) section 3.5.2.

For each of 4 scenarios we vary the number of cycle Z for one lifespan and N constant, we make again the operation until N=5. Three cycles of use are enough because beyond the technological rupture would be too large for this type of products. The upgrade can prove to be an option to take some into account according to the compatibility of the module with the architecture of the new product. For each of the 3 machines we represented the results on 3 diagrams separately (Figure 6). Each section represents the aggregate environmental score and an economic score corresponding to the economic costs generated by the remanufacturing. Each simulated configuration is represented by a point P A (M, N, Z) positioned in a Cartesian chart according to its economic costs and its environmental impact (Figure 7). (P A representes product 1, M the number of re-used module, N product lifespan and Z the number of cycle). This graph shows that some products are more impacting or more expensive than others but the remaquable point is the grouping of product configurations which we can make. By representing the results in this form a designer can qualitatively select a modular arrangement among a more or less large choice of configurations (choice of the reusable modules, modules life cycle, producted lifespan…). To carry out this case study we selected competing products but the goal is to use this approach in phase of design. The impacts of fhe products are not only related to their Extraction-Manufacture and End-of-life phases (Phases which are influenced by the remanufacturing). In the case of the Coffee machine the use phase accounts for approximately 90% of the environmental impacts mainly due to the doses utlisation and the electric consumption of the machine in sleep mode. The compararaison between MLC scenario and WEEE scenario shows that the share of the impacts due to the manufacture phase decreases by approximately 5% with the remanufacturing of 3 modules. On this type of products the use of consumable masks the performance.

CONCLUSION

The development of product life cycle is a big step aiming to design a sustainable product. The choice of this life cycle must intervene as soon as possible and must be responsibility for the designer or group of design. The approach suggested in this article is to allow an evaluation of several concepts (various arrangements of modules) on multiples life cycles. In the suggested study this evaluation takes into account two important factors, the environmental performance and the economic performance: This is two of the three pillars of sustainable development. The integration of this approach in design process makes it possible to technically isolate the most powerful systems taking into consideration the constraints of treatment at the end of life (optimization of disassembly time, optimized modules recovery, refurbished modules and re-use them in new products) but also the level of the organizational constraints (logistic costs, environmental regulations…). The first results go in this direction, the product decomposition in module with several cycles of use for reusable modules have a better environmental and economic performance. For the continuation we plan to apply this method for a B2B product in an industrial sector. We also wish to answer a lack of the consideration of the customers' needs in products design.

Figure 3 .

 3 Figure 3. Framework overview

Figure 4 .

 4 Figure 4. Framework analyzes environmental

Figure 5 .

 5 Figure 5. Modules characteristics

Figure 6 .

 6 Figure 6. Simulation for one product

Figure 7 .

 7 Figure 7. MLC selection chart for Espresso machine

Table 2 .

 2 End of Life for closed loop manufacturing

	Parameters Input dated
	N	Value time (years)
	M n	Module n remanufactured
	Z n	Number of life cycle of
		module n (X times)

  4 € for one lorry of 20t.

	C w : warehousing cost
		For 1m3 in/2€;
		For 1m3 off/2€;
		For 1m3 stocked during one day, 0.6 €.
	C t : treatment cost According to the "Prodtect ® " report, we suppose that the treatment costs are:
		Cost of dismantling.
		Cost of recycling with resale of materials.

Table 3 .

 3 Remanufacturing cost for each scenario

				Warehousing
		Scenario	Transport cost	cost	Treatment cost	Global cost
		WEEE	0.412	0.19	4.84	5.442
		1 module	0.43	0.27	3.99	4.69
		2 modules	0.51	0.27	3.28	4.06
		3 modules	0.56	0.27	3.71	4.54
		C infusion system : Supply cost of a new modules "Infusion system" = 3 €
		C

boiler : Supply cost of a new module "boiler" = 5 €  C pump : Supply cost of a new module "pump" = 4 € Economic score calculation: j = Infusion system, boiler and pump.

Table 4 .

 4

	Environmental & economic
	assessment for product C with 3
	modules reused
	P=NxZ N Z	EI	EnS	EcS
	1 1 1 3.49 3.49	4.54
	2 1 2	3.8 1.90	-2.92
	3 1 3 4.13 1.38 -10.38
	2 2 1	3.9 1.95	4.54
	4 2 2 4.63 1.16	-2.92
	6 2 3 5.35 0.89 -10.38
	3 3 1 4.32 1.44	4.54
	6 3 2 5.46 0.91	-2.92
	9 3 3 6.59 0.73 -10.38
	4 4 1 7.73 1.93	4.54
	8 4 2 6.29 0.79	-2.92
	12 4 3 7.84 0.66 -10.38
	5 5 1 8.86 1.77	4.54
	10 5 2 7.13 0.71	-2.92
	15 5 3 9.09 0.60 -10.38

Table 5 .

 5 Distribution of Environmental impact:

		Produit C (3,5,3)
	Manufacture
	&	Use
	EoL
	Machine P C (3,5,3)	Doses Landfill recycling	Electric Consumption No Sleep Sleep mode mode
	5%	92,3%	5,3%
	7%	89,2%	7,4%
	6,3%	80,7%	16,3%
	4,6%	85,5%	12,1%

Table 6 .

 6 Distribution of Environmental impact: Produit C (3.WEEE)

	Manufacture
	&	Use
	EoL
	Machine P C (3.WEEE)	Doses Landfill Recycling	Electric Consumption No Sleep Sleep mode mode
	9,2%	87,8%	5%
	12,6%	83,5%	6,9%
	11,4%	76%	15,4%
	8,6%	81,8%	11,5%


El Korchi

A method helping to define eco-innovative systems (Product Architecture + Reverse Supply Chain structure + Use Cycles Scenario)

Keywords: Eco-design, Product architecture, RSC structure, Usage

Environmental issues involved by emerging markets and rapid development of goods' consumption require a new model to design product more sustainable. While traditional eco-design methods (LCA, Check-lists, Guidelines, DfX tools…) are generally limited in local optimization of product or macro-rules for environmental strategy, this article presents an eco-innovative method consisting in: identifying three lists of potential Use-cycles Scenarios (pUS) (SADT activity A2), three lists of potential Products Architectures (pPA) (A3) and three lists of potential Reverse-supply-chain Structures (pRS) (A4), associating pUS, pPA and pRS to form viable concepts of product evaluating these concepts by the way of a multi-criteria approach: environmentally friendly, economically viable for companies and attractive for users and stakeholders. The purpose is to help the design team to develop various levels of change from existing product concept (Use cycles + Product + RSC): optimized, improved and innovative. Every concept is established by separating at first Architectures produced and structure RSC. In the first time information necessary for the project is collected (current products, current RSC and current usage). An identification of the new usage provides on one hand the Product design stage and on the other hand the RSC structure construction stage. The best Architectures and structures are finally associated then assessed environmentally, economically as well as the attractiveness of the customers and the actors of the system in order to select the most successful concepts.

INTRODUCTION

The introduction of the environmental dimension in product design is a fundamental priority in our society. Today human kind is at once an actor and a spectator of the first effects of the global warming. The environmental crisis resulting from an increase of the consumption and from a decline of the resources is put however in the background in front of social aspects coupled with the economic challenges. The major industrial nations have to rethink profoundly the way of manufacturing and of consuming to reach a new mode of development: "which meets human needs while preserving the environment so that these needs can be met not only in the present, but also for future generations" [START_REF]World Commission on Environment and Development (WCED) (the Brundtland Report)[END_REF]. Some measures to reduce the impacts were adopted since around ten years within companies subjected to the public pressure of the policy, the regulations always more restricting and the sensibility of the population in ecological concerns. These measures rely on the development of reprocessing sectors (collecting, recycling and remanufacturing), on the elaboration of new materials (Biofuels, biodegradables materials, eco-materials) [START_REF] Dovì | Cleaner energy for sustainable future[END_REF] on the development of new manufacturing processes (cold injection moulding, thin film deposition), on mechanisms allowing to change the direction of user's behavior (ecofeedback) [START_REF] Lilley | Design for sustainable behavior: strategies and perceptions[END_REF] [4] … The current ecodesign methods available for the designers are numerous; however they do not allow to cover all these aspects (materials, processes, usage, end of life) and, consequently do not answer completely the requirements of a sustainable development (cf. table 2). Besides, that it is about methods based on LCA evaluations or about the methods based on rules / heuristics recommendations, they are not or little adapted to the practice and to the constraints of the design team [START_REF] Millet | How to identify the most promising areas of environmental improvement at the early stages of the design process?[END_REF]. General requirements expected from an Ecodesign method and formulated by Ernzer [START_REF] Ernzer | An international study on utilisation of design for environment methods (DfE) -a pre-study[END_REF] are the ease to learn, understand and use, lead to relevant, non abstract and understandable results, the usability in early phases of the product development process or by Fargnoli and Kimura [START_REF] Fargnoli | Sustainable design of modern industrial products[END_REF] are the effectiveness of the method in assessing environmental performance, the usability, the possibility to review the design activities, and the ability to provide new solution, the ability of the method in fitting into a certain design process. Others requirements are the multidisciplinary implication, the ability to correctly define the performance of product in a exhaustive way (product architecture, usage, organization -Supply chain) An Ecodesign method must be a tool helping the multidisciplinary design team to take into account all different aspects of the product on the life cycle associate (R&D, Marketing, Customers services, Supply chain, Innovation…). Current methods do not allow to satisfy generally the requirements of the sustainable development. Indeed they focus mainly on one dimension of the problem without to take into account other dimensions. An ideal method would handle simultaneously technological, functional/usage, economic, environmental and organizational dimensions.

REQUIREMENTS FOR A GOOD ECODESIGN

METHOD? A good Ecodesign method must be exploitable by the design team and, more widely the industrial organization (2.1) but also provide all the results/ criteria necessary for the resolution of problems of the sustainable development (criterion of sustainability 2.2). Once these two macro-criteria are defined, the main developed methods of Ecodesign are estimated through an evaluation grid (2.3).

Definition of the macro-criterion design team usability

To assess current Ecodesign methods it is necessary to define the functions that they assure for the design team, and more widely the industrial organization. The Ecodesign has an impact in the various departments of the company. The team has to gather the persons in charge of the divisions the most concerned by the process of products development. Indeed they are the most qualified to identify the most relevant working axes to be investigated. Multidisciplinarity is a characteristic which must be assured by the method, with the aim of taking into account the numerous dimensions of the system. Brezet identifies 5 services: Management, Marketing, Purchases, Production and R&D [START_REF] Brezet | ECODESIGN -A promising approach to sustainable production and consumption[END_REF]. An environmental expert must be integrated in a design team, who can be an internal person to the company or to intervene as to external advisor; in this last scenario it is necessary to establish a learning support allowing to train the members of the design team. In the literature two types of approach are distinguished: the approaches which are situated in upstreams and the one who takes place at the end of design process. Brezet defines the various levels of Ecodesign in 1998 [START_REF] Brezet | ECODESIGN -A promising approach to sustainable production and consumption[END_REF]:

Ÿ Level 1 : Product improvement Ÿ Level 2 : Product redesign Ÿ Level 3 : Function innovation Ÿ Level 4 : Systems innovation
Products improvement requires an adjustment of the existing products. The redesign of products involves that the components of the product are developed or replaced by others. These two levels concentrate exclusively on products. On the other hand, the functional innovation aims at replacing the services proposed by products, the innovation of the systems involves that new products and services appear, requiring modifications in infrastructures and organizations.

Definition of the macro-criterion Sustainability

Is the method exhaustive? Does it allow to report all the dimensions of the problem. The approach which we wish to put in to the test aims at handling the economic, environmental and societal aspects.

Ecodesign methods assessment

The state of the art in Ecodesign approaches shows the existence of numerous approaches which extend from general methods like check-lists or "guidelines" to methods more complex and specialized as the life cycle analysis. We have distinguished four Ecodesign approach:

Ÿ

Table 1: Assessment of Ecodesign methods according design team point of view

The first tools consist in exploiting in a iterative way a software of Life Cycle Assessment. The LCA tools applied to the current product indeed allows to identify the most impacting components and life cycle stages. Alternative solutions can be proposed; their environmental gain can be finally assessed by modifying the modelling of the life cycle of the current product and by generating simulations with LCA method.

This first category of approach presents advantage and inconveniences associated to the use of the LCA tools. Through a multicriteria evaluation led on the whole life cycle, it allows a rigorous identification (standardized methodology ISO14040 [START_REF] Goedkoop | The Eco Indicator 99: A Damage Oriented Method for Life Cycle Impact Assessment-Manuel for Design[END_REF]), but this approach uses up too much of the design team's energy as they concentrate on understanding the reasons of environmental impact [START_REF] Millet | Does the potential of the use of LCA match the design team needs?[END_REF] of past products. This is detrimental to their work of interpreting and seeking means of improving future products [START_REF] Fussler | Driving Eco Innovation: A Breakthrough Discipline for Innovation and Sustainability[END_REF]. The development of tools focused on end of life optimization accelerated these last years. The emergence dismantling optimization methods (DfD) [START_REF] Hallmann | ProdTect, the Tool for Product Architects: Turning Challenges of Predicttive Design into Uniques Selling Points[END_REF] [21] as well as of design of modular products (DfM) [START_REF] Kimura | Product modularization for parts Reuse in inverse manufacturing[END_REF] [15] aim at reorientating the end of life of products towards a better management of the recycling and more at privileging the re-use of modules. While the traditional Ecodesign methods allow a superficial environmental improvement of the current products the Eco-innovation is an approach which allows to decrease radically the environmental impacts while offering some added value to the users and to the economic actors of the product [START_REF] James | The Sustainability Circle: a new tool for product development and design[END_REF]. Among these tools of the product life cycles environmental QFD, Eco-TRIZ, Product System service or Eco-compass is most often found in the literature. The last category of approach is based on the use of simplified tools. Guidelines or check-lists allowing to identify specific axes of improvement with the considered product. Amongst the most known the general guidelines such Ecodesign Pilot [START_REF] Wimmer | ECODESIGN Pilot, product-investigation-, learning-and optimization-tool for sustainable product development[END_REF] or Ten Golden Rules [START_REF] Luttropp | Ecodesign and the Ten Golden Rules: generic advice for merging environmental aspects into product development[END_REF] they appear very abstract or very quality focused thus of limited applicability for the design of new systems. More specialized guidelines such as ' electrical and electronic: practical ecodesign guide ' exist [START_REF] Castells | Electrical and Electronic Practical Ecodesign Guide[END_REF]. These rules are more numerous and detailed generating a local focus which is detrimental to both a more global and a more systemic viewpoint [START_REF] Boothroyd | Cutting out the excess[END_REF]. This limitation of vision may distract the team from the 'right' solutions. Other tools are based on simplified environmental assessments. They distinguish themselves from LCA approach, by being more qualitative and simpler of integration within the company. Amongst these tools MET (materials, Energy, and toxicity) [START_REF] Brezet | ECODESIGN -A promising approach to sustainable production and consumption[END_REF] is a multi-criteria tool which allows, quite as the LCA, to identify the environmental concerns during the entire life cycle of the product.

A new approach to set up

The current Ecodesign methods do not allow to satisfy all the functions to design innovative system compatible with sustainable development. Indeed they are mostly limited to one or two dimensions. The LCA approach allows to treat in a rigorous way the environmental problems but requires an expert whereas the environmental check-lists treat in a more empirical way a complex problem which can be use by multidisciplinary team. Most of the assessing methods allow only local optimizations of the product (LCA, Checklists, Dfd tools). Few methods allow to design innovative systems getting radically new solutions. The societal aspects, as the customers' needs consideration, as well as the economic, are not still taken into account. Now the implementation of new end of life scenarios as the remanufacturing of modules imposes an adaptation of the reverse logistics networks with all the consequences that it involves in terms of infrastructure, localization and management of flows. There are many dfD tools, which allow to optimize the architectures in according product characteristics and the end of life strategy. Unfortunately they generally do not go beyond a simple optimization of the dismantling sequences. The study of some tools shows an inadequacy of the current methods (cf. Table1 & 2) to match the requirements of design of eco-innovative systems.

DEFINITION OF THE FOUNDING PRINCIPLES OF THE NEW PROPOSED METHOD

For answering to dissatisfactions revealed by an analysis of the current Ecodesign methods 7 principles were formulated as foundations for a new methodology:

A guide helping the designers

The method has vocation to help the design team to develop more relevant solutions. In this particular case, it has to help the members of the design team (Engineering department, Marketing, Supply Chain, Production, R&D) to define the various dimensions of the problem, to generate innovative solutions from new ideas and to assess then to select the most promising on the environmental and economic aspects and which satisfy the users and the other actors of the life cycle of the product. The structure of the method has to give to the design team the guidelines to execute the task of the method: which data to gather and how to use them to create new solutions, when and how to estimate these solutions and finally how to determine the most relevant solutions for a specific situation.

A support learning

The method has to facilitate the learning of the design team on various aspects of the environmental concerns; in other words, it has to bring to the foreground and make easier the exchanges between services and the transfers of environmental information. It also has to reveal the profits of an environmental orientation of design team's work and generate a motivation to act.

A method to act in early design stage

The objective of this method is to help the design team, in the upstream design phases; the final report of this method is the best concept of Eco-innovative system (Product Architecture + RSC Structure + Use-cycles Scenario) on the economic and environmental aspects and on users'/stakeholders' attractiveness. Indeed we focused our efforts on the earlier stage because it corresponds to the stage where the freedom degrees of the design team allows to envisage solutions radically new to be more compatible with a sustainable development.

A multidisciplinary approach

The design methodology proposed rely on a benchmark of the current product (in terms of usage, product architecture and end of life management) made by all the disciplines involved on the design process; this strategy aims at guaranteeing a progressive evolution of the current industrial system towards a future industrial system more compatible with a sustainable development.

Besides, it reveals to the design team (RD, Marketing, supply chain, Engineering department, RSC) ideas and curbs of an orientation towards Eco-innovative products.

A multi-dimensional design

According to us, any environmental improvement of a product / system recovers either from the improvement of the Use-cycles phase (A2) in particular for products with strong energy consumption or with long lifetime, or the improvement of the materials or processes the most impacting in products specifications in Pre-Life (A3), or implementing end of life treatment to reduce the impacts generated in End-Life (A4). The method is based on the separate developments of a list of potential Product Architectures (pPA) of and a list of potential Reversesupply-chain Structure (pRS), both lists being fed by a definition of potential Use-cycles Scenario (pUS). The idea is to find the maximum of pPA independently from pRS and pUS, pRS independently from pPA and pUS and pUS independently from pPA and pRS to open in a most exhaustive way the design space.

An exhaustive method without a priori knowledge

The concepts are obtained by association of the product architectures, of RSC structures and scenarios of potential Use-cycle allow to cover a large number of possible solutions without a priori. The strategy used for this new method consists in privileging no solution a priori (Life cycles scenario, technology or end of life treatment), considering that certain ways can create in A6 unexpected profits (for example economic gains associated to the remanufacturing of a module with strong value added on several life cycles). However, as these Architectures / Structures / Scenarios were independently developed in the previous 2 phases, they are not necessarily compatible; in this fact an adaptation of the architecture of the product can be necessary to adapt itself to a structure of RSC given (and respectivelly).

A simultaneous assessment: Environmental, Economic and Attractiveness

Final report of the method is one (or several) concept of Eco-innovative system viable: by viable, we understand a system which is at once acceptable on the economic criterion for the company (and for stakeholders), better for the environment and for all stakeholders implied in one or several life cycles of the product and finally attractive for the user (first and others cycles). The final principle of the method is to classify the various concepts proposed in a trihedral (economic, environmental and attractiveness criteria).

A METHOD HELPING TO DESIGN ECO-INNOVATIVE SYSTEMS

The general structure of the method is based on 7 founding principles expressed in the chapter 3, contains six stages. The SADT formalism (fig. 1) is used to synthesize the main inputs, outputs, resources and controls of these 6 actigrams:

1. Identify needs in information of the project. 2. Define the pUS of the product / system. 3. Define pPA. 4. Define pRS. 5. Associate pPA and pRS.

6. Assess the potential concepts "Architecture+RSC" and select the best concepts.

A multi-dimensional assessment

This analysis must be driven by integrating all disciplines and the services of the company, in particular the marketing services, R&D, Innovation and Supply-chain. This stage serves just as much to federate all the actors of the design team that to take in all the information necessary for the following stages. This multidimensional analysis is structured in 3 sub stages:

1. The analysis of current product

The current product is decomposed into modules resulting from an internal functional analysis of the product allowing to identify the materials, energy, and information flows. These evaluations will afterward allow to identify components, modules, materials, the most problematic fixtures of the product and thus those for whom the alternatives will firstly have to be looked for.

Current RSC analysis

The analysis of the current reverse supply chain, if it exists, starts by modelling the reverse logistics network and process dealing with end-of-life products recovery. For this aim the design team should gather information about reverse logistics facilities locations, transport, warehousing and end-of-life treatment processes. After this, the modelled reverse supply chain is assessed environmentally and economically to identify the cost and environmental impact of the current end-of-life product recovery.

The analysis of the current Usage

This sub-stage consists in analysing the current part of service associated with the product (maintenance, repair, optimization of the usage, return). And evaluate the physical lifetime and value lifetime of product.

Definition of potential Use-cycles Scenario of system

It uses studies on external product aspects, as the analysis of Users trends, Competitors trends or technological trends during several generations to unveil the future products trends. The actigram A2 delivers the following main outputs: A list of the fixed / necessary functions A list of Short-term upgradable functions: Their integration into the product can't be defined at the beginning of first cycle.

A list of long-term upgradable functions: Their integration into the product can be only functionnaly defined.

Figure 1: Framework of Method helping to define eco-innovative systems The phase A2 provides data for the phases A3 ("Pre-Life") and A4 (" End-Life ").

Definition of potential product architectures

The purpose of the actigram A3 is to propose pPA: that is modular architecture consisted of remanufacturables modules, recyclable modules and upgradables modules. Three levels of architectures are distinguished (optimization, improvement and innovation) corresponding to the various evolutions of usage identified in the precedent actigram (necessary functions, short-term upgradables and long-term upgradables functions). The actigram A2 delivers the following main outputs: Optimized pPA: The fixations are modified (types, quantity and orientation), facilitating the extraction of reusable modules, some materials are substituted with the aim of optimizing and homogenizing the process of recycling. Improved pPA: Some modules can be modified (i.e. to improve reliability) or added into the product architecture allowing a functional short-term upgrade. Innovative pPA: The product architecture is modified; modules are added or removed without limitation allowing a functional short-term and long-term upgrade.

Definition of potential RSC structures

After the analysis and the evaluation of the current RSC structure, different ways of improvement can be imagined. This is the object of the activity A4 of the SADT. The input is a set of 18 generic structures of RSC (gRS). The Improved pRS: The selected generic structures are adapted to specificity of the firm's business to obtain potential improved RSCs. For this aim, a radical change on the role of actors and locations for end of life treatment would be necessary.

Innovative pRS: The selected generic structures are adapted to specificity of the firm's business to obtain innovative pRS. the innovation the reverse supply chain should supported by the innovation in the product design and a radical change in the customer culture.

Association of better PPA and PRSCS

The association of the phases A2, A3 and A4 allows to constitute associations between product architectures, RSC structures and life cycle scenario. Designed independently, it is necessary to adapt them each other. This work must be done with help of the design team

Multi-criteria assessment (environmental, economic et functional) of potential product + RSC concepts

The activity A6 is a phase of multi-criteria assessment and selection of the final concept (Product + RSC + Usecycle scenario). The final selection is connected to the performance of the concept in three criteria "sustainable development": acceptable for environment, viable economically for the company and attractive for the user. We proceed by 3 parallel evaluations which can be independently made: an environmental assessment bringing some value to the society, an economic assessment for the company and an evaluation of the attractiveness with regard to the values perceived by the customer. Finally all the estimated concepts are organized into a hierarchy in on a trihedral for choice.

CONCLUSIONS

The objective of this research was to formalize a new method to help the design team to define eco-innovative systems (product architecture + RSC structure + Usecycle scenario) enabling them to choose the most promising solutions/options as early as possible in the design process. The proposed tool responds to the general requirements for Ecodesign tools formulated by Ernzer [START_REF] Ernzer | An international study on utilisation of design for environment methods (DfE) -a pre-study[END_REF]:

Eeasy to learn, understand and use Lead to relevant, non-abstract and understandable results Useful in early phases of the product development process Not be a stand-alone activity or by Fargnoli and Kimura [START_REF] Fargnoli | Sustainable design of modern industrial products[END_REF]:

Ability to correctly define the performance of product Usability Effectiveness of the method in assessing environmental performance Ability to provide new solutions Possibility to review the design activities Ability of the method in fitting into a certain design process. The research work is in an initial stage of development: further studies concerning both the definition of more precise assessment criteria of the methods, as well as their verification throughout different industrial applications are certainly needed.

  generic structures are obtained by varying the role (Inspection and Sorting of Modules: ISM, Dismantling and Cleanig: DC and Inspection and Sorting of Products: ISP) of each actors (Customers: C, Grouping Center: GC and Product Center: PC), three level of change can be found corresponding to the following potential reverse supply chain structures: Optimized pRS: The Optimized RSC structure is obteined by changing the location and the number of facilities in the current reverse logistics network.

Table 2 :

 2 Assessment of Ecodesign methods according sustainability

			Sustainable criteria
		Economic Aspects	Environmental Aspects		Social Aspects
			Eco indicator
	LCA [9] [10]	None	CML, EI99 (quantitative)	None
			Qualitative environmental impact: Greenhouse
	E-FMEA [11]	None	effect, Ozone depletion etc)	None
		Extension possible	Rough assessment
			Mono-criteria (qualitative or quantitative)	Voice	of	Extended to voice of
	QFD E [12]		e.g. Aggregated Method EI99	Customers		stakeholders
	LiDS-Wheel [8]	None	Base of rules : Materials, Energy, EoL	New concept development
		Indirect considerations	Materials	Services extension
	Eco compass [13]		energy
			Materials (qualitative)
			Exhaust gases (qualitative)
	MAIECO [14]	None	Toxicity (qualitative)	None
	Eco Design Pilot [15]	None	Base of rules (guidelines)	None
			Material
			Fixtures
			End of Life optimization: reusable part, recycling
	Prodtect [16]	Disassembly cost (maximizing profit)	parts and hazardous substances	None
		Material cost
		Manufacturing cost
	DfM [17]	Assembly cost	Aggregated Method EI99	None
				Voice	of	Extended to voice of
		Life cycle costing	Mono-criteria	Customers		stakeholders
	Total performance Analysis [18]	Life cycle value	CO2 emissions [kg-CO2]	Obsolescence, technological value
	Design methodology for upgradable					Tends of competitors
	products [19]	Rough price of each generation	No environmental assessment control	Customers' needs	Company's policy