IEA ECBCS Annex 49 - Low Exergy Systems for High-Performance Buildings and Communities

The Annex 49 Project

The exergy content required to satisfy the demands for the heating and cooling of buildings is very low, since a room temperature level of about 20 °C is very close to ambient conditions. Nevertheless, high quality energy sources like fossil fuels are commonly used to satisfy these small demands for exergy. From an economical point of view, exergy should mainly be used in industry to allow for the production of high quality products. The new approach is not necessarily focused on a further reduction of the energy flow through a building’s envelope: when the demands for heating and cooling have already been minimized, the low-exergy approach aims at satisfying the remaining thermal energy demand using only low quality energy.

Annex 49 aims at improving, both on a community and building level, the design of energy use strategies which account for the different qualities of energy sources, from generation and distribution to consumption within in the built environment. Annex 49 is based on an integral approach which includes the analysis and optimization of the exergy demand in the heating and cooling systems as well as in other processes where energy/exergy is used within the building stock.

It is known that the total energy use caused by buildings accounts for more than one third of the world’s primary energy demand. There is, however, a substantial saving potential in the building stock. The implementation of exergy analyses paves the way for new opportunities to increase the overall efficiency of the energy chain.
The method of exergy analyses has been found to provide the most correct and insightful assessment of the thermodynamic features of any process and offers a clear, quantitative indication of both the irreversibility and the degree of matching between the resources used and the end-use energy flows.
 

Objectives

The main objective of Annex 49 is to develop concepts for reducing the exergy demand in the built environment, thus reducing CO₂ emissions from the building stock and supporting structures for setting up sustainable and secure energy systems for this sector.

Specific objectives are:

• To use exergy analysis to develop tools, guidelines, recommendations, best-practice examples and background material for designers and decision makers in the fields of building, energy production and politics;
• To promote possible energy/exergy cost-efficient measures for retrofit and new buildings, such as dwellings and commercial/public buildings;
• To promote the exergy-related performance analysis of the buildings, from the community level perspective.

 

Outcome

The tools, guidelines, recommendations, best-practice examples, pre-normative proposals and background material developed within the framework of Annex 49 are oriented and made available to designers, planners and decision makers in the fields of building, energy production and politics. Using results from different research projects of the participant countries, a wide range of cases has been studied. At the building level, both residential and commercial buildings were be taken into consideration.

The integration of energy sources from our environment, e.g. the use of water from abandoned mines for heating or cooling of buildings, requires exergy efficient supply systems at the community level and adapted building service systems.

At the community and supply level, the widest spectrum of possibilities has been assessed. In addition, several climatic conditions were taken into account.

Annex 49 summary report: Exergy Assessment Guidebook for the Built Environment   

Annex 49 final report: Detailed Exergy Assessment Guidebook for the Built Environment 
 

Acknowledgement

This project has been financially supported by the German Federal Ministry for Economics and Technology.