Towards zero energy solar households – A model-based simulation and optimization analysis for a humid subtropical climate

Energy conservation and efficiency in the residential building sector is an important field to control carbon emissions worldwide. Solar energy integration in domestic buildings decreases the grid dependency and carbon emissions. This paper investigates techno-economic feasibility, energy, exergy, and life cycle emissions analysis of solar energy integration to achieve an annual net-zero energy balance for a household. A local survey is carried out in the regions of Pakistan to define the representative building structure, services, and schedules. A representative household is then analyzed. TRNSYS is used for modelling and annual transient simulation of household thermal load and energy systems. TRNSYS-GenOpt co-simulations determine the optimal insulation thickness of the building envelope to minimize the thermal load. The on-site renewable energy supply system consists of solar PV, solar space heating, solar domestic hot water generation, and solar absorption cooling. The envelope insulation results in a 37.2% reduction in annual thermal load. Solar PV system supplies 93.4% of annual electricity demand. Solar collectors provide hot water during winter and thermal comfort during 92.4% of air conditioning hours. Energy and exergy analyses are used to evaluate the thermal performance of solar PV, thermal collectors, and absorption system. The life cycle cost analysis performed for a conventional and the proposed building shows that the net present value of the zero-energy solar household (ZESH) becomes lower than that of the conventional household in 8 years. Also, the life cycle emissions are calculated for conventional and ZESH. The CO₂ emissions of ZESH are only 8.7% of that of a conventional household. This study reveals that a ZESH is technically as well as economically viable in humid subtropical climate regions.