Low exergy systems for high-performance buildings and communities

There is an obvious, known 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. Furthermore, there are great potentials, which can be obtained through a more efficient use of energy in buildings. As a relatively new approach it can be shown that 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, cannot be quantified by energy analysis - the energy efficiency is close to 100%; however, this potential can be shown by using exergy analysis (Schmidt and Shukuya 2003), the exergy efficiency of a common gas boiler is about 8%. This shows clearly the potential and need for improvements of our energy use structure. A similar picture can be drawn by having a closer look to energy supply structures in our communities. This paper outlines the international co-operative work in the general framework of the International Energy Agency (IEA), the ECBCS Annex 49 "Low Exergy Systems for High Performance Buildings and Communities", which ended in 2010 (Annex 49 2011).