Abstract - "Exergy as buildings efficiency metrics and specific Trnsys tool development" - KEP energy

The exergy analysis is an indirect way to assess the impact of an energy system on the natural resources, the energy sources and the environment. Moreover it allows to read the system-environment interactions from a Second principle of thermodynamics point of view. A building is an energy system that uses energy sources in order to maintain its functionality and to ensure indoor comfort for the occupants. Through the exergy analysis is taken in account not only the energy consumption (energy quantity) but also the energy degradation (energy quality). So it is powerful as buildings assessment metrics.

The buildings energy efficiency targets at European and global scale, summarized by the acronym "NZEB" and by the concept "Low Carbon", imply the use of complex modeling software. How much more should be push the efficiency, the more becomes necessary check with accurate equations and algorithms the calculation during the entire path from input-data to output-data. On the other hand, the technological evolution is putting in the market active and adaptive devices such as building integrated photovoltaics (BIPV) and building automation and control systems (BACS). At the operational level they are spreading heat pump systems and renewable energy sources, whose efficiency is strongly influenced by weather conditions. Consequently the dynamic simulation software, as Energy Plus or Trnsys, rise to prominence, as they allow an high model representativeness in relation to the building-climate-user interactions.

Trnsys is a widely used dynamic simulation software, in the field of the buildings modeling. However, among the Trnsys standard libraries any exergy calculation library lacks. Consequently we thought useful develop a specific library, in order to make able the designers to carry out exergy assessments in Trnsys ambient, coupling buildings dynamic energy analysis with buildings dynamic exergy analysis. The developed library was written in C++, in Microsoft Visual Studio, and then compiled as dynamic link library *.dll. The library is readable in Trnsys Simulation Studio, and linkable to the standard software libraries, so as to form a bidirectional integrated data stream between them. The library is graphically symbolized in the Trnsys libraries tree by an icon drawn in Adobe Photoshop. We compiled a Windows installer in executable format *.exe, in order to automate the library installation. When launched, the installer place automatically the files in the directories and write the relates keys in the operating system registry.

The activity summarized in this abstract allows to calculate in Trnsys ambient the overall exergy entering and exiting from a building in form of energy and mass flows, and so to quantify the destroyed exergy. The exergy destruction rate can be understood as a system efficiency indicator, that is a system impact indicator.

Il poster è stato presentato in Poster Session in Sustainable Places 2015, Savona, 16-18 settembre 2015.