Achieving annual and monthly net-zero energy of existing building in hot climate.

This paper demonstrates the possibility of converting a public building from inefficient energy consumer into a net-zero energy building (NZEB). This task is achieved through cost effective energy efficient measures (EEMs) and integration of solar energy systems. Three scenarios that utilize the same roof area are proposed to convert the building into NZEB. The first two scenarios use only PV system with the second scenario that incorporates replacing current chillers with more efficient chillers while the third scenario combines both PV and solar cooling systems. The first scenario attains NZEB on annual basis only whereas the other scenarios achieve NZEB on both annual and monthly basis. The second scenario has distinct advantages over other scenarios with respect to energy saving, interaction with energy grids and economic consideration. Both implemented and proposed EEMs result in about 1480 MW h saving of the building consumption and about 1021 ton avoided CO 2 emission annually with payback periods ranging from half to 3 years for the considered measures. Annual avoided CO 2 emission of about 748 ton is achieved for first or second scenario and about 848 ton for third scenario with payback periods 14.1, 11.8 and 15 years for the 3 considered scenarios, respectively. [ABSTRACT FROM AUTHOR]