ENERGY EFFICIENCY AND ENVIRONMENT

In this paper, we intent to review and reconsider the concept of efficiency applied to energy systems and processes. It is shown that due to increasing use of energy, we must refine the criterions that serve as objective functions to characterize and optimize systems and processes. Moreover coupling between energy uses and environment appears more and more important. This question starts to be explored : present state of the art is summarized; some suggestions and perspectives are evoked, particularly the relation to economy, even if the main aspects developed remain centered on the scientific part and technical consequences.