If a sufficiently extensive network of energy connections is considered, it is evident how all production and technological systems are directly or indirectly supported by relationships with the ecological systems of the biosphere that surrounds them. As a consequence, some of the energy flows, consumed inside production processes and technological devices, cross the limits of the control-volume and finally, in order to take into account the effects on the whole macro-system of the optimal design choices that we are looking for, the following question has to be answered:
“How much primary energy has been used by the macro-system to maintain each one of those flows at a defined value?”
In spite of some similarities, the two widely used methodologies show important differences, too, so that the answers to the previous question are often not-consistent, even if very simple systems are considered. Nevertheless, an almost complete integration among the two methodologies appears to be at hand, while all major differences can be explained, if we think of the possible behavior of the different components inside the system, instead of the axioms of previous formulations. The integrated approach is expected to enlarge the options the analyst can use to define and optimize the system and to allow the correct use of the result of both methodologies.
