Influence of User Electricity Load Profile and Calculation Time Step on the Photovoltaic System Balance

Abstract

Realistic energy balance of photovoltaic system has a direct impact on realistic economic evaluation of operation costs for given building. To estimate the realistic electricity power profile with a short-time step, a generator based on appliances power, occupancy and external daylight presence has been developed and used for simulations. Generator allows to create different power profiles for the whole year (all days identical, workdays-weekends, 365 different days) with given time-step resolution (from 1 minute to 1 day). Paper presents and analyses the results from parametric simulations of PV production and building electricity loads balance with different times-steps. Monthly calculation approach used as a standard methodology for building performance evaluation significantly overestimates the solar fraction of PV systems. Only calculations with time steps shorter than 1 hour lead to results close to reality. A methodology for monthly balance correction to realistic results based on yearly PV production to building consumption ratio will be presented.