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Benchmarking of low "exergy" buildings

: Schmidt, D.

Rode, C. ; Technical University of Denmark -DTU-, Lyngby:
8th Nordic Symposium on Building Physics in the Nordic Countries 2008. Proceedings. Vol.2 : Copenhagen, June 16-18, 2008
Lyngby, 2008 (DTU Byg Report 189)
ISBN: 978-87-7877-265-7
Nordic Symposium on Building Physics in the Nordic Countries <8, 2008, Kopenhagen>
Conference Paper
Fraunhofer IBP ()

There is an obvious and indisputable need for an increase in the efficiency of energy utilisation in buildings. Heating, cooling and lighting appliances in buildings account for more than one third of the world's primary energy demand. In turn, building stock is a major contributor to energy related environmental problems. There are great potentials, which can be obtained through a more efficient use of energy in buildings.
An optimisation of the exergy flows in buildings and the related supply structures, similar to other thermodynamic systems such as power stations, can help in identifying the potential of increased efficiency in energy utilisation. Through analyses, it can be shown that calculations based on the energy conservation and primary energy concept alone are inadequate for gaining a full understanding of all important aspects of energy utilisation processes. The high potential for a further increase in the efficiency of; for example, boilers, can not be quantified by energy analysis - the energy efficiency is close to 100%; however, this potential can be showed by using exergy analysis, the exergy efficiency of a common gas boiler is about 8%.
The Low Exergy (LowEx) approach entails matching the quality levels of exergy supply and demand, in order to streamline the utilisation of high-value energy resources and minimise the irreversible dissipation of low-value energy into the environment. This approach is the key concept for the work of Annex 49 on energy use and supply structures in the built environment.
Using a typical case, the advantages of the analyses and the difference between energy and exergy analyses are demonstrated. In conclusion, based on an analysis of a real and existing building suggestions for a benchmarking system for so-called LowEx buildings are presented. In order to achieve an exergy optimised building design, loads on the building service system have to be reduced as much as possible. The suggested benchmarking method gives an engineering approach to archive those building system configurations.
The presented research work is related to the ongoing international cooperation work in the IEA ECBCS Annex 49 "Low Exergy Systems for High-Performance Buildings and Communities", the established Network for "Low Exergy Systems in Buildings - LowExNet" and the ongoing German activities in the collaboration project in the exergy field from industry partners and research institutes.