Society exergy analysis: a comparison of different societies

Data from exergy analyses for a number of different countries found in the literature are compared and the differences are discussed. In studies of Sweden, Ghana, Japan, Italy and Norway, the exergy in material flows had been considered, in addition to the flows of energy carriers. In other studies, the use of energy carriers was analyzed for the USA, Finland, Canada, Brazil, Turkey, the Organization for Economic Co-operation and Development (OECD) countries and the World. The exergy of material flows in these societies was estimated. The total annual exergy input per capita to the societies ranged over one order of magnitude. The total exergy efficiency varied from approximately 0.1 to 0.3, whereas the end-use exergy efficiency in general was slightly higher. It was found that different investigators had made somewhat different assumptions on exergy efficiencies in specific sectors, and these assumptions are discussed. However, the structure of the energy system appeared to be more important for the total exergy efficiency than the assumptions on the sectors. In particular, the residential–commercial sector represents major irreversibilities in many societies. In countries where electricity from thermal power plants has a significant contribution to the end use, this also caused large irreversibilities. Finally, the method of society exergy analysis is discussed. It is pointed out that, because of structural dissimilarities, different countries should be compared with care. However, the development within each society can be evaluated using exergy analyses. Furthermore, such analyses can be used as a means to increase the awareness of the notion of energy quality and degradation.