SMARTER STRATEGIES

Addressing the Looming Urban EV Problem

Salvatore Salamone | Date: 03-24-11 | Comments

Utilities might need smart software that intelligently distributes electricity between urban substations to accommodate the additional loads expected from daytime charging of plug-in electric cars.

As plug-in electric vehicles become more common, they are expected to place new loads on the electric grid.

Most of the attention has focused on the potential problems these cars might cause in the suburbs. While one car charging overnight, here or there, won't have a significant impact on the grid, clusters of cars all charging at the same time in a particular neighborhood might stress the transformers at the local substation. The hope is that with a combination of smart meters, time-sensitive electric rates and intelligent demand response systems, utilities will be able to handle the additional loads from the cars.

Getting much less attention are the potential problems that might arise when people take their electric vehicles into work in urban areas and need to charge them during the day. Unlike the suburban drivers who charge their cars at night when power demands are at their lowest, daytime charging will occur during the time of peak power demands.

Most industry experts expect charging stations deployed in urban parking lots and other municipal facilities to use what is called Level 2 systems. As opposed to plugging a car into a standard 120-volt outlet, a Level 2 plug operates at 240 volts.

A Chevy Volt recharging at a municipal charging port (Source: Chevy)

The advantage of using a Level 2 charger is that batteries can be rejuvenated in a much shorter time. The downside, from the electrical grid perspective, is that there is a much larger load placed on the electrical grid.

A single car charging using a Level 2 system is comparable to the electric load of three or four houses. Again, one or two cars here or there are not a problem for the grid. But when electric vehicles become more common, major problems can arise.

Studies by the Electric Power Research Institute, the National Renewable Energy Laboratory and others find that the load from electric vehicles in urban areas can be substantial. A 20 percent adoption rate of electric vehicles (with half using Level 1 and the other half using Level 2 chargers) could increase the load by about 150 megawatts in small cities like Atlanta, Boston and Baltimore. And larger cities like New York and Los Angeles would need to provide an additional gigawatt of power just for the electric vehicles.

One way to address this potential problem is to use a combination of intelligent software and grid modernization. The idea envisioned is to use smart meters to gather real-time information about charging, analyze the charging load distribution throughout a city, and then use additional intelligence to balance loads across geographically dispersed substations.

Grid modernization will be needed to carry the additional loads between substations. One solution being evaluated today is to use superconducting cables to link the substations. Such cables can carry 10 times the amount of power as conventional cables and significantly increase power distribution efficiency.