Quantifying the benefits of extending electric vehicle charging deadlines with solar generation

Significant cost reduction in recent years has made solar power an economically competitive power source in many regions today. In view of this, and the widespread introduction of electric vehicles (EVs) to the mass market, we study public EV charging stations with on-site solar generation that are backed up by conventional power from the grid. Since the carbon footprint of conventional power is higher than solar power, charging deadlines can critically affect the total solar energy available to charging stations and therefore the overall carbon footprint of the charging service. In this paper, we propose a method to quantify how much carbon footprint can be reduced as a function of the charging deadline by describing a performance-guaranteed fair power allocation algorithm in a public charging station. This enables us to study the three-way tradeoff between the charging deadline, the utility of EV owners, and the carbon footprint of EV charging. We find that our algorithm makes nearly optimal use of available green energy, while still guaranteeing that solar charging performs no worse than grid charging.