Bridging the energy gap of India’s residential buildings by using rooftop solar PV systems for higher energy stars

The residential-building sector in India consumes>25%of the total electricity and is the third-largest consumer of electricity;consumption increased by 26%between 2014 and 2017.India has introduced a star-labelling programme for residential buildings that is applicable for all single-and multiple-dwelling units in the country for residential purposes.The Energy Performance Index(EPI)of a building(annual energy consumption in kilowatt-hours per square metre of the building)is taken as an indicator for awarding the star label for residential buildings.For gauging the EPI status of existing buildings,the electricity consumption of residential buildings(in kWh/m2/year)is established through a case study of the residential society.Two years of electricity bills are collected for an Indian residential society located in Palam,Delhi,analysed and benchmarked with the Indian residential star-labelling programme.A wide EPI gap is observed for existing buildings for five-star energy labels.Based on existing electricity tariffs,the energy consumption of residential consumers and the Bureau of Energy Efficiency(BEE)’s proposed building ENERGY STAR labelling,a grid-integrated rooftop solar photovoltaic(PV)system is considered for achieving a higher star label.This research study establishes the potential of grid-connected rooftop solar PV systems for residential buildings in Indian cities through a case study of Delhi.Techno-economic analysis of a grid-integrated 3-kWp rooftop solar PV plant is analysed by using RETScreen software.The study establishes that an additional two stars can be achieved by existing buildings by using a grid-integrated rooftop solar PV plant.Payback for retrofit of a 3-kWp rooftop solar PV plant for Indian cites varies from 3 to 7 years.

Mitigation of the impacts of electric vehicle charging on energy-star ratings for residential buildings in India

The star-labelling programme for residential buildings was introduced by India in 2020 and applies to all residential buildings with no lower limit on the built-up area or electrical demand.The energy-star label for a residential building is awarded against the notified standard by the regulatory body and electric vehicles(EVs)have not been accommodated as a load for residential buildings.The en-ergy consumption of an existing residential building is taken from a study already carried out and compared with the requirement of the Indian residential star-labelling programme with an EV as a plugged-in load.An annual energy gap of 6060 kWh for the existing residential buildings considered in this study for five-star building energy labels increases to 7784 kWh if the EV load is added to the building load.The residential building will lose two energy stars if it caters to the EV load and,to bridge this energy gap,the replace-ment of existing electrical appliances with five-star-rated energy appliances,employing grid-connected rooftop solar photovoltaics(PV)and retrofit of the building envelope are considered.The techno-economic potential of rooftop solar PV and building envelope retrofitting for existing residential buildings is explored using RETScreen®and eQUEST software,respectively.The study establishes that the installation of rooftop solar PV can accommodate the additional load of EVs and can bridge half and three-quarters of the energy gap to achieve five energy stars for an existing building with and without EVs,respectively.It is the most economical option among the options explored in this study.The target Energy Performance Index is achievable by high-end energy consumers(12000 kWh/year)by additional measures,the replacement of inefficient electrical appliances and building envelope retrofitting in addition to the installation of rooftop solar PV.