Energy and exergy analysis applied to the built environment

Exergy analysis is useful for assisting building designers in the choice of building and building service concepts with a potential for minimising energy resource depletion. Unlike energy, exergy is not subject to a conservation law. Exergy recognizes that the energy that is carried by substances can only be used ‘down’ to the level that is given by the environment. This paper describes a spreadsheetbased energy and exergy model developed for use by building and building services designers. The lumpedparameter steady-state model provides a simplified description of energy and exergy demand in a building. The model considers exergy dissipation via the building envelope as a result of heat transmission and ventilation, and includes energy conversion steps in the heat emission, heat distribution and heat supply systems. The model focuses on heating loads and systems for non-industrial buildings. The main advantage of this model is that it enables a designer to compare energy and exergy demand for different building and building service configurations, from building envelope through heating system and primary energy conversion. Thereby a building designer can develop insight into which combinations of design options result in the lowest total exergy consumption.