Title:
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Life cycle assessment in engineering design
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Making correct design decisions during the early stages of the engineering
design process is increasingly seen to be important, as changes during the
later stage can be costly. Life Cycle Assessment (LCA) is used as a method
to evaluate the design from 'cradle to grave'. In concept design, decisions are
made that have a most significant influence on the life cycle, but at this stage
the lack of detail makes LCA very difficult if not impossible.
This thesis introduces a method that enables an 'order-of-magnitude' life
cycle assessment during the concept stage of the design process. This
is achieved by modelling the life cycle inventory as a function of design
parameters for complete product families used in engineering design. The
hypothesis is that relatively few so-called life cycle parameters determine the
largest part of the life cycle inventory. Furthermore, design parameters are
related to life cycle parameters, which are mathematically modelled. Design
parameters are chosen so that they can be estimated early during the design
process. The models of the life cycle parameters are expressed in terms of
upper and lower limits, summarising data from many product families. More
detailed models describe the relationships of single product families. The
method is suitable for software implementation, which will especially aid the
handling of sensitivity analysis.
Two case studies (sealed lead acid batteries, three-phase asynchronous
motors) are used to illustrate how the life cycle parameters are related to the
design parameters. An overall outline of how the method is implemented into
the overall design process completes the thesis (evaluation of parallel and
series configuration hybrid electric vehicle).
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