Numerical Analysis of High-Performance Lithium-Ion and Lead-Acid Batteries with Capacity Fade for an Off-Grid Residential PV System

This paper introduces and integrates effective models to describe the fundamental characteristics of high-performance lithium-ion (graphite-LiFePO4) and lead-acid (VRLA) batteries with capacity fade for use in an off-grid residential photovoltaic (PV) generation system. The lithium iron phosphate (LFP) and VRLA batteries have been simulated using a 1D electrochemical model with thermal and aging components, and using the CIEMAT model, a general analytical model of the lead-acid battery, respectively. In the off-grid PV/battery/demand system, the calculated annual state of charge (SOC) distribution and time history of degradation in the LFP and VRLA batteries describe the internal battery behaviors and the blackout risk; the LFP battery is expected to accomplish a one-third lower annual blackout frequency and a 25% longer degradation time than a VRLA battery with a 24-kWh battery capacity over 15years of operation. According to the calculated loss and surplus electricity indexes, the LFP battery has a remarkably long life and high charge/discharge efficiency, even with a variable current and in long-term operation.