The reference environment: Utilising exergy and anergy for buildings

The utilisation of exergy and anergy concepts for low exergy system design extends the potential of performance optimisation of buildings. We propose a new perspective for buildings and their external environment. It recognises exergy as the utilisable potential that maintains comfort inside relative to outside ambient conditions. It considers environmental heat sources as a form of transiting exergy that is utilised internally to increase second law effi ciencies and then returned to the environment. These sources are not chosen to optimise energy inputs, but rather temperature inputs. They are optimised as anergy sources coming from a dispersed state, which are transited through the building system and deposited back in an anergy sink, which defi nes the reference environment. A major obstacle in the application of exergy analysis to buildings is the lack of an accepted defi nition of the reference environment. The absence of this factor leads to ambiguity in analysis and hinders comparisons between studies. Choosing the reference environment infl uences the amount of exergy contained in buildings and with the low quality levels often dealt with in buildings, the infl uence can be signifi cant. The perspective we present clarifi es the use of the ambient environmental conditions as the reference environment for exergy analysis of whole buildings. It also validates the unencumbered use of free ambient anergy sources from the ground, water, air and the sun to increase exergetic performance.