| Title | Thermodynamic assessment of cities applying exergetic efficiency as evaluation index |
|---|---|
| ID_Doc | 43776 |
| Authors | Hartmann, RM; Garcia-Acevedo, LE |
| Title | Thermodynamic assessment of cities applying exergetic efficiency as evaluation index |
| Year | 2022 |
| Published | |
| Abstract | Thermodynamic assessment of cities is presented based on the classic concept of cities. Energetic analysis of cities is a challenging task, due to the lack of a concise, general thermodynamic parameter to evaluate energetic output streams that is applicable to every city. Therefore, exergetic efficiency was applied as comparative index, given that it encompasses concepts of first and second laws of thermodynamics, thus providing a figure of merit similar to those applied to equipment and thermal systems. The proposed concept was employed to assess five cities, classified by its main economic sector: power plant city (Foz do Iguacu), industrial city (Ingolstadt), sink city (Hawaii), service city (Florianopolis), and petroleum city (Singapore), the last being also classified as a Smart City. Results show that the power plant city presented low CO2 emissions (1.553 ton CO2equi/person-year), high global exergetic efficiency (98.77 %), but low internal exergetic efficiency (17.26 %). The service city presented similar behavior, with low emissions (1.104 ton CO2equi/person-year) and also low internal exergetic efficiency (19.49 %). The sink city presented the highest emissions (13.51 ton CO2/person-year) and an intermediate internal exergetic efficiency (28.02 %). The smart city presented a high global exergetic efficiency of 85.3 %, due to mainly the good performance of its refinery sector, but at the same time presented high emissions (9.730 ton CO2equi/person-year). The industrial city presented the highest WtE (Waste-to-Energy) yield of 6.210 GJ/person-year, thus improving its internal exergetic efficiency in about 6 %. Comparisons among the five cities show a linear trend of increasing per capita CO2 emissions with increasing per capita generation of municipal solid waste. Also noteworthy is a similar figure of per capita CO2 emissions normalized by destroyed exergy within the city (3.1 ton CO2equi/TOE) for four cities, while for the industrial one this figure is 5.73 ton of CO2equi/TOE, caused mainly by a broad utilization of electric mobility. Regarding limitations of the proposed methodology, it is clear that exergetic assessment of power plant and petroleum cities demands further study, since the calculation of their exergetic efficiency as a global figure impairs the proper observation of internal exergetic flows. Also, the analysis of the industrial city is complex because it is difficult to define usefulness of industrial production in terms of thermodynamic properties. As general conclusion, the study shows the broad applicability of exergetic analysis to assess any city, despite its economic function, geography or other characteristic of interest. |
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