With low exergy systems: High performance energy systems for 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. A more efficient use of energy in buildings can be advantageous in many ways. 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 for increased efficiency in energy utilisation. Through analyses, it can be seen 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 shown by using exergy analysis [1]. The exergy efficiency of a common gas boiler is about 8%. This clearly highlights the potential and need for improvements in the structure of our energy use. In taking a closer look at energy supply structures in our communities, a similar picture appears. 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 was concluded in 2010 [2].