Abstract: The energy property of products is considered as the research object, and the Life-cycle theory is applied in the energy analysis. Based on the analysis of energy-consuming characteristic of mechanic products, the energy-consuming framework of product system and the product life-cycle energy model is set up, and the dynamic characteristic of the energy property is expounded. By adopting the theory of bond graph and the recycle union, the energy factors in each stage of product life cycle are analyzed, which influence product energy consumption. Then the quantitative energy formula and the dynamic characteristic for each stage are presented. At last, by the application of the energy model and the dynamic characteristic analysis, the design alternative can be selected and the design parameters can be optimized, and the electricity kettle is demonstrated that the model and method are applicable and effective.

Key words: Design alternative selection, Design parameter optimization, Energy function, Energy model, Product life cycle