Comparative environmental performance analysis of two air conditioning systems by using Expanded Total Equivalent Warming Impact metric

The greenhouse gas emissions caused by human activities determined an increase of global mean temperature during last decade. The growing space heating and cooling demands in civil sector represent the major driver to environmental emissions. The environmental analysis represents a good strategy for evaluation, comparison, and selection of energy supply system on the basis of users’ demands. Usually, the well-known Total Equivalent Warming Impact index is used to compare the global warming effects of alternative air-condition systems by considering energy consumption, indirect and direct greenhouse gas emissions caused by refrigerant leakages. In this paper an expanded form of Total Equivalent Warming Impact index, Expanded Total Equivalent Warming Impact parameter is proposed to calculate CO2 equivalent emissions from direct and indirect contributions of two alternative air- conditioning systems satisfying the space heating and cooling demand of a building located in Naples. The conventional system is composed by a centralised natural-gas fuelled boiled and a chiller, while the proposed system consists of a ground-source heat pump, a low temperature thermal network and a series of electric heat pumps. The systems and building have been modelled trough TRNSYS 17. The results show that the environmental analysis reward the renewable-based system and the difference between the two environmental indexes is substantial.