Battery integrated off-grid DC fast charging: Optimised system design case for California

Abstract

Global acceptance and exploitation of electric vehicles (EV) is no doubt a fact. There are two major factors beneath this growth; 1. increasing battery capacity thus rising range and 2. availability of DC fast charging infrastructure. Whereas battery is a topic of chemistry, DC fast charging is significantly related to grid operations. When installed, DC fast-charging stations (above 50 kW), require grid upgrades such as new transformers, underground cabling, LV/HV equipment installations on site. This not only increases the overall cost of installation but also the time from permit applications to operation. This study proposes a novel off-grid DC fast-charging station (FCS) that is integrated with a li-ion battery and solar photovoltaic (PV) that overcomes permitting, grid upgrades, and heavy installation activities on site. The system has 140 kWh liion battery, 100 kW DC fast charging units. In this study, a linear optimization algorithm is developed to assess the installed PV capacity. It is assumed that PVs will be installed over a parking area to make use of vast open land. The modularity of the PV system is considered to achieve scalability. Finally, an in-depth economic analysis is presented comparing conventional grid-tied FCS to the proposed system.