Environmental Assessment of Air-conditioning Systems. Design Considerations for Swedish Conditions.

Doctoral thesis, 2007

There is an increased awareness about global environmental changes, and a need for products and systems with the lowest possible impacts on the environment, without trade-offs on the original function or quality. The need for air-conditioning and comfort cooling in commercial buildings has increased and an appropriate design of the air-conditioning system is thus important in order to reduce the environmental impact related to air-conditioning of buildings. The aim is to describe how the environmental performance of air-conditioning systems can be assessed at the design stage. The focus is on the application of existing methods. The life cycle assessment (LCA) based weighting methods are used for the environmental assessment of these systems. This approach is exemplified in five case studies. The case studies form a basis for identification of the major sources of the environmental impacts and enables recommendations on how to improve the environmental performance of the systems. Furthermore, environmental consequences of various requirements on the indoor thermal climate are analyzed. It is shown that life cycle assessment (LCA) based weighting methods can be used for environmental assessment of air-conditioning systems. The required effort to use these methods is reasonable in relation to design practice, but the interpreters of the results and decision-makers have to be aware of the limitations and trade offs of these methods in order to draw appropriate conclusions. It is also shown that the major contributor to the environmental impact of air-conditioning systems is the electricity used for the operation of fans. A design with a low specific fan power is thus an advantage from an environmental point of view. The environmental impact from the production of the components is comparably low, especially if recycling of used materials is considered. The influence of thermal comfort criteria is also comparably low, especially, if the system is designed with a low specific fan power. It should further be noted that the environmental performance is strongly affected by assumptions about the electricity mix used.