Reference state temperature influence in the thermoeconomic costs of a building thermal facility

Résumé

In 2018, residential buildings were responsible for 17.1% of the energy consumption in Spain. To improve the energy efficiency of buildings, several actions have been taken by the European Union and later transposed by national governments. In our environment, located in the north of Spain, buildings have three main types of energy demand: electricity, DHW and heating demand. Usually, the proposals for reducing the primary energy consumption consider just the first law of thermodynamics that establishes the principle of energy conservation. Although energy quantity is conserved, energy quality degrades in energy exchange processes as the second law of thermodynamics establishes. Therefore, both the first and second laws must be taken into account to achieve an improvement in energy efficiency and the consequent energy savings. Exergy analysis applied to buildings allows quantifying the energy quality degradation, this is, the exergy destruction, since exergy is the thermodynamic property that characterizes the energy quality. Nevertheless, exergy is a relative property, in the sense that its value depends on the reference state chosen. Further, thermoeconomics allows quantifying the exergetic, economic and environmental costs of the exergy destruction.