Due to population growth and the need to have healthy, comfortable environments, the energy consumption of buildings has increased considerably in recent years. “Worldwide, buildings consume a third of the energy, which is terrible. So it is essential to cut consumption in buildings to limit the demand for energy and improve the construction sector,” said Ana Picallo-Perez, a researcher in the UPV/EHU’s Department of Thermal Engines and Motors.

So this research has sought to apply the concept of thermoeconomics to buildings. Thermoeconomics is a science that blends thermodynamics with economics. According to the first law of thermodynamics, energy cannot be created or destroyed, it is transformed, in other words, energy can be found in different forms (electricity, heat, etc.) and is converted from one form into another. Yet one type of energy cannot be transformed one hundred per cent into another; although the amount of energy is maintained, the quality is degraded owing to losses during conversion. That is the basis of the second law of thermodynamics and that quality is measured by means of exergy. “Exergy is in fact the basis of thermoeconomics,” explained Ana Picallo.

“The basic idea is that even though energy is conserved, exergy is not conserved, in other words, exergy is destroyed in energy transformation. So even though energy cannot be created or destroyed, its quality gradually diminishes. This loss of quality is called the destruction of exergy and entails a cost. So thermoeconomics seeks to prevent this destruction and energy degradation in buildings,” said the UPV/EHU researcher.

Dynamic, complex structures

“Buildings are complex systems. In fact, they are highly dynamic and have major difficulties, among other things because the needs of each user cannot be controlled at all times. In addition, in the case of buildings there is another set of factors to take into consideration besides user needs, such as the external atmosphere, etc.,“ added Picallo.

“By bearing all these factors in mind and adapting thermoeconomics to that dynamic nature of buildings,” said Ana Picallo, “we developed a piece of software that brings together various users and ways of functioning, which helps us to find out the costs arising out of the destruction of exergy; it is the first time that it has been developed for buildings”.

“The demand of a building is broad and each type of energy has a quality. Firstly, the demand for electrical energy for lighting equipment and home appliances of buildings is of high quality. Secondly, demands such as heat or similar are of low quality. Electricity is used to meet the former and natural gas or similar sources to meet the latter. Both sources are of a high level of quality. So in the second case we are using a type of high quality energy to meet a low-quality demand and in this process a lot of exergy is destroyed,” explained Picallo. “Other systems such as renewable energies need to be used. Continuing to meet low-quality demands by using high-quality sources of energy is not viable. So it is essential to ensure the suitability between energy sources and demand in order to cut costs,” added the researcher.

The researcher stressed that “our aim going forward is to develop diagnostic software for buildings in order to quantify and provide evidence of errors. What is more, thermoeconomics helps us to detect where the greatest destruction of exergy takes place and, if this is spotted, we would be taking a significant step forward in optimizing buildings”.

Additional information

This piece of research was conducted within the framework of the PhD thesis by Ana Picallo Perez (Bilbao, 1991) and entitled Thermoeconomics. A tool for energy and economic evaluation of building thermal systems / Termoekonomia. Eraikinen sistema termikoetan energia eta ekonomia ebaluatzeko tresna.  It was supervised by José Maria Sala-Lizarraga, professor of Thermodynamics and Chemical Physics at the UPV/EHU.