Is modernization making villages more energy efficient? A long-term comparative end-use analysis for Cheranatzicurin village, Mexico

摘要

A detailed analysis of the change in the patterns of energy use in a Mexican village, from the year 1986 to 2012 is presented. The satisfaction of energy needs is analyzed according to the first- and second-law efficiencies of thermodynamics, for a total of 22 end-uses. The analysis covers both the end-use devices used for energy conversion and the energy and exergy used in the related thermodynamical tasks. The final energy per capita was 11.0 GJ/year in 2012, about 10% less than in 1986. In the study period, the overall first-law efficiency of the community increased from 17% to 23%, while the second-law efficiency rose from 6.4% to 8.2%. The increments in useful energy and minimum exergy (total and per capita), relative to 1986, occur at the expense of a small increase in the per capita consumption of final exergy of the community. The rise of both energy efficiencies is a consequence of the reduction in fuelwood consumption and on the use of draft-animals, whose conversion efficiencies into final energies and useful work are extremely low. Also, there is 314% increase in the village's fossil fuel use, especially due to an increase in the penetration of gas and electric appliances into the household sector and of vehicles. The energy use in the productive sector including agriculture fell dramatically. CO_2 emissions from the community's energy use rose by 279%. Despite the increase of commercial energy use, and a rapid penetration of LPG cookstoves, fuelwood still represents 68% of the village final energy consumption. Also, there is a large mismatch between sources and needs in thermodynamic terms: while 72% of the energy needs correspond to work and heat at less than 100 ℃, 99% of the energy sources imply combustion processes (fuelwood, LPG, gasoline and diesel) to mid and high temperatures. However, in order to reduce CO_2 emissions, the electricity and transport devices have to increase their efficiencies, and primary energy ought to come in higher proportion from renewable sources.