Comparative assessment of different air-conditioning systems for nearly/net zero-energy buildings

This study deals with the performance of different air-conditioning strategies for achieving the target of nearly/net zero energy in a medium-scale building under various environmental conditions. In particular, vapour compression (VC), vapour absorption (VA), and integration of radiant cooling technology are analysed using renewable energy resources emissions and solar photovoltaic (PV)-based electricity. Four different kinds of air-conditioning configurations are considered: VC-based, VA-based, VC-radiant air-conditioning technology with VC dedicated outdoor air system (DOAS) and VA radiant air-conditioning technology with VC-DOAS. Numerical model validations with the benchmark standards are done for VC- and VA-based systems. In particular, annual electric consumption, electricity generation, thermal load generation among all configurations, emissions and solar fractions are studied. The present study shows that target of nearly/net zero-energy building can be achieved in an efficient manner through radiant VC-based system with VC-DOAS for hot-dry and composite (ie, hot-dry with higher humidity) environment conditions. However, for warm-humid environment, complete net zero is not possible, but up to 74% of net zero target can be assured with VC-based radiant and DOAS. With respect to the conventional VC-based system, the payback period assessment for the most suitable nearly/net zero building cooling system varies in the range of 5-9 years, depending on the environmental conditions.