Managed Approach Could Trim EV Charging Costs by Half

The cost of charging a plug-in electric vehicle could be cut 50% by varying the rate of the charging process, according to researchers at Carnegie Mellon University in Pittsburgh, Pa.

The key is a system that enables the grid operator to control EV charging speed or even interrupt it for short periods to balance fluctuations in the power supply and overall demand for electricity.

Typical EV chargers initially work at a maximum rate. They switch to a trickle mode as the battery approaches full charge and remain in that state until the driver unplugs the vehicle.

The Carnegie Mellon researchers point out that plugging in at the end of the day means tapping into the grid when demand and electricity prices are high. The system they propose would give EV owners the convenience of plugging in their vehicle when they arrive home for the night while benefiting from lower power rates that kick in late at night.

A simple timer that delays the start of charging can capture some of these benefits, notes team co-leader Jeremy Michalek. The Carnegie Mellon approach would provide further advantage by enabling energy providers to maximize their operating efficiency. One example: Dynamically adjusting charge rates for a large number of EVs might avoid the cost of shutting down or starting up a generator to match transient shifts in power demand across the grid.

The Carnegie Mellon research team will detail their findings in the February issue of the journal Applied Energy. They say future study will look at the environmental impact of load shifting, since the cheapest power plants to operate are typically those burning fossil fuels.