MODELING THE ENERGETIC AND EXERGETIC SELF-SUSTAINABILITY OF SOCIETIESWITH DIFFERENT STRUCTURES

The paper examines global energy and exergy flows in various models of organized human societies: from primitive tribal organizations to teo cratic/aristocratic societies, to the present industrial (and post-ind ustrial) society, to possible future highly ''robotized'' or ''central control'' social organizations. The analysis focuses on the very gene ral chain of technological processes connected to the extraction, conv ersion, distribution and final use of the real energetic content of na tural resources (i.e., their exergy): the biological food chain is als o considered, albeit in a very simplified and ''humankind'' sense. It is argued that, to sustain this chain of processes, it is necessary to use a substantial portion of the final-use energy pow, and to employ a large portion of the total workforce sustained by this end-use energ y. It is shown that if these quantities can be related to the total ex ergy pow rate (from the source) and to the total available workforce, then this functional relationship takes different forms in different t ypes of society. The procedure is very general: each type of societal organization is reduced to a simple model for which energy and exergy flow diagrams are calculated, under certain well-defined assumptions, which restrain both the exchanges among the functional ''groups'' whic h constitute the model, and the exchanges with the environment. It is argued that not all societies are unconditionally self-sustained, and that certain size and technology-related restrictions apply to virtual ly all types of societal organizations examined here. These restrictio ns limit in general the distribution of the active workforce among dif ferent productive sectors; this distribution cannot be arbitrarily ass igned, but depends quantitatively on the technological level of the ch ain of processes connected with energy extraction, transformation, dis tribution, and use. The results can be quantified using some assumptio ns/projections about energy consumption levels for different stages of technological development which are available in the literature; the procedure is applied to some-models of primitive and pre-industrial so cieties, to the present industrial/post-industrial society, and to a h ypothetical model of a future, high-technology society. No attempt has been made to study transient behavior ( ''evolution'' or ''decay'' of a certain type of society), nor to relate quantitatively the steady-s tate case to resource conservation and environmental protection. For m ost of the cases examined here, neither resource scarcity nor finite b iosphere capacity were considered as constraints.