Exergy in the built environment. The added value of exergy in the assessment and development of energy systems for the built environment.

Abstract

This doctoral research studied the added value of exergy for the assessment and development of energy systems for the built environment, aiming at a reduced need for high-quality energy input. Currently the analysis and development of energy systems for the built environment is based on the energy concept. Energy however gives an incomplete presentation of the performance of energy systems by failing to address the difference between various forms of energy. Exergy is a thermodynamic concept that quantifies the ‘work potential’ of different forms of energy, which can be regarded as the quality of energy. Unlike energy, exergy can be destroyed and the amount of exergy destroyed or lost indicates the thermodynamic improvement potential of a system, which is not revealed using energy analyses. The research firstly includes several additions to the exergy analysis method as found in literature. Secondly, the exergy performance of current energy systems is studied, demonstrating the additional insight obtained with exergy, for example: while energy analyses suggest that the only way to reduce the required energy input is by reducing the demand at building level, exergy analyses reveal a large improvement potential at system level, i.e. in principle the same output can be obtained with significantly reduced input. Lastly, several exergy based approaches to support the development of improved systems are developed and demonstrated, including the use of ‘exergy principles’ for energy concept development and the use of exergy analysis to assist further improvement of a (preliminary) energy concept. It is concluded that there is still significant room for improving current energy systems for the built environment, especially related to heating systems. Also, the exergy based approached developed in this research are promising ‘tools’ to support the development of improved energy systems, reducing the required input by making better use of the potential of the worlds energy resources.