Modelling of an off-grid roof-top residential photovoltaic nano grid system for an urban locality in India

In modern era of energy self-sufficiency and its personal preference, an off-grid rooftop solar photovoltaic nanogrid for private use in a single household or among limited number of households poses a promising futuristic prospect. However, several critical aspects need investigation to realize its viability. The present work investigates the techno-economic-space feasibility of an off-grid rooftop photovoltaic nanogrid for residential sector of a cosmopolitan urban locality with unreliable electricity in India. A novel combination of RAMP for load modelling, HOMER PRO for techno-economic analysis and an innovative technique for space feasibility analysis was implemented. 269 houses were surveyed and innovatively classified, based on number of dwelling rooms and demand profile similarity. Correlation and sensitivity analysis were conducted to understand the impact of individual and grouped load profiles, plinth area per household, number of dwelling rooms, climatic conditions , building types and component specification availability in market on the overall cost, configuration and feasibility of the system. Sharing of photovoltaic nanogrids and higher durations of daily occupancy in houses reduce the Levelized Cost of Energy (LCOE) from the system due to reduction in percentage variations of load. The LCOE of shared nanogrids ranged between 0.151 $/kWh to 0.195 $/kWh in India. The study recommends 50 % subsidy on system capital cost against grid prices. Batteries operated at higher depth of discharge (DOD) and having longer life at higher DOD reduce the system LCOE. Apartments in locations with high annual solar radiation, low annual temperatures, large plinth area, low monthly demand and unobstructed rooftops are good candidates for PV nanogrids. In India, high-rise buildings with monthly loads up to 30 kWh/household, mid-rise buildings with loads up to 50 kWh/household, low-rise buildings with loads up to 100 kWh/household and double-storey buildings with loads up to 200 kWh/household can successfully adopt autonomous rooftop PV nanogrids.