Rational use and energy planning: a thermo-dynamic and geographical approach

The rational use of energy resources is the only way to reduce the environmental impact of human activities. Cities are thermodynamic systems that must be organized by relating variable energy demand to minimize entropy production. Here a methodology to analyze energy needs of buildings by a GIS (Geographic Information System) is presented. Spatial analysis techniques were used to connect descriptive data of different plant typologies to the relevant buildings, even when this information was not provided by the original data base. A statistical method was used to evaluate the energy needs of the urban building systems. The method utilises a numerical map to extend to the universe the evaluation obtained from a probability stratified simple random sampling design with the optimum allocation of sample buildings to the strata. The strata considered refer to construction’age of buildings. This statistical approach to the energy analysis of the urban system required the primary definition of the energy characteristics of the universe of buildings. This was necessary to avoid systematic error in the calculation method of sample size and techniques to select the elements of sample units. An equal probability selection method (epsem-design) of stratification by age classes was used. The energy balance of building provided variables connected to the thermo-physical parameters of the building and the energy consumption was evaluated by using a correlation between dimensionless numbers. Dimensional number correlation was extended to each building of the universe of buildings because the sample used has a statistical meaning. Using spatial analysis techniques and GIS, the energy consumptions maps of the population of buildings were obtained. The proposed method was applied to the territorial energy programming of the urban area of Florence (Italy). It was also possible to use it as the base for energy programming and for defining the scenarios of integrated low environmental impact energy strategies and actions using thermodynamic indicators. The variability and spatial distribution of these parameters based on entropy variations provided some indications for reducing energy consumption and developing efficient energy use in the built up area. These parameters and others based on Second Law of Thermodynamics and related Information Theory, allowed evaluation of the sustainability of energy use in the urban area and its spatial distribution in different building meshes superimposed on the area considered, using entropy. The proposed methodology has a low cost in comparison with the face to face interview survey, since it only has to evaluate the sample, the size of which can be reduced in routine applications.