Is the grid ready for electric cars?

Robert Weekley plugs in his electric car as soon as he drives it home from work each day.

Depending on his shift, that may be at times when electricity demand is low, like noon or midnight. On other days, it may be at the same time everyone else returns home, when the power grid is already heaving under the load of lights, ovens and TVs fired up just in time for dinner.

The batteries charge most effectively when they're still warm from the drive, he says, as a layer of snow from a light flurry settles on his silver, converted 1990 Pontiac Firefly. Weekley, webmaster and communications contact for the Electric Vehicle Society of Canada, lives in a low-rise apartment building in Toronto's northwest with no indoor parking. There is also no smart meter, so electricity costs the same all day long and  there's no incentive to charge during off-peak hours.

So far, Weekley is among just a handful of electric car owners in Canada — a microscopic fraction of the country's fleet of 20 million petroleum-powered vehicles. Their impact on the power grid is minimal.

But if 500,000 other highway-capable plug-in electric-drive vehicles are cruising our roads by 2018, as a recent joint federal government-industry paper — Canada's Electric Vehicle Technology Road Map — predicts, how much strain will that put on the national power grid?

So far, provincial utilities say they aren't very concerned. But some people are warning that electric vehicles could usher in unexpected problems, and several utilities are starting to study how electric cars would be used and recharged in order to get some hard numbers about the potential impact on the power grid.

Possible clustering problem

The supply of electricity isn't the main issue. Hydro-Québec says the electricity consumed by one million electric vehicles is equivalent to less than two per cent of the electricity sales in Québec in 2009. Similarly, even in winter when electricity demand is highest, B.C.  has the unused capacity on its grid to charge nearly 2.4 million light duty vehicles — almost all the 2.5 million registered vehicles in B.C., a study by the University of Victoria's Pacific Institute for Climate Solutions reports.

But that doesn't mean utilities can ignore the coming wave of plug-in cars.

"Say 10 houses on the same street are plugged in at the same time — that could be an issue," says Nick Beck, director of transportation energy technology at Natural Resources Canada.

The scenario isn't as unlikely as it might sound. Hybrid-electric cars already tend to cluster within certain neighbourhoods. Plug-in electric cars are expected to do the same as neighbours see each other getting new cars, talk about the benefits of not having to fill up with expensive gas as the pumps, and sell each other on the idea of electric transport.

The problem is that the neighbourhood transformers that convert electricity to the right voltage before it enters people's homes aren't designed for the kind of load created by a number of cars all drawing large amounts of power from the grid at the same time, and they may fail, causing neighbourhood power outages. To accommodate electric cars, those transformers may need to be upgraded, Beck says.

Another problem is human behaviour.

A 2008 report by University of California in Davis found plug-in electric car users don't naturally think about what's best for the grid if they pay a constant rate for electricity, and they often plugged their cars in during the hours of peak electrical demand. But most of the extra capacity within the grid is available late at night and very early in the morning. That means that to minimize the load, people would have to be persuaded to charge cars at night, not during the day or the high-demand evening hours when they've just driven home from work.

Beck thinks that problem will be easily solved through electricity pricing. Already, utilities are installing smart meters  in homes that allow them to impose higher billing rates during peak times to encourage people to switch their electricity use to off-peak hours. Beck predicts "smart chargers" that communicate with the smart meter will soon be available. Such chargers would automatically switch on when the electricity price drops to a certain threshold, making it simple for users to charge at off-peak times, Beck says: "The controller's doing the thinking for you."

Big range, big impact

There are also the unknowns that make it hard for utilities to plan for the rising number of electric cars. Researchers acknowledge that very different impacts on the grid could be created depending on the car models, commute times and charging rates chosen by electric car drivers.

Weekley, for example, drives his electric car just two kilometres a day and plugs his battery chargers into a regular 110-volt outlet that uses "less power than a hairdryer," he says. It typically takes half an hour each day to top up his vehicle's batteries.

But new electric cars such as the Nissan Leaf, which will be available in Canada in 2011, have ranges on the order of 100 kilometres, meaning each one could consume 50 times more electricity than Weekley currently does — and spend many more hours plugged in.

"What people actually end up buying in terms of vehicles is going to affect what grid impact will be," said Curran Crawford, a mechanical engineering professor who co-authored the University of Victoria study.

Many people predict Level 2 chargers, which draw 220 volts just like stoves and clothes dryers, will be widely used for faster charging.  But chargers that draw more may cause problems by placing higher power demand on the grid when they are plugged in, noted the University of Victoria study, even though they result in more efficient charging.

Toronto experiment

To ensure they're prepared for electric cars, utilities will need detailed information about electric car drivers and their behaviour patterns that they don't currently have — when people charge, how much they charge and how it affects equipment such as transformers and the peak load on the grid. To get that data, Toronto Hydro is partnering with Mercedes-Benz Canada to study how 15 daily car commuters use Smart Fortwo plug-in electric cars.

The utility has chosen a group of test-drivers from a group of 600 applications from members of the public is providing them with leased cars, said Tom Odell, manager of the electric vehicles project at Toronto Hydro.

The study intends to include a sub-group of drivers who live near one another to test how the clustering phenomenon will affect the grid. It will also choose at least one driver with a long commute in order to explore the anxiety people experience about the limited range of electric cars compared to traditional, combustion-driven cars that can quickly be refuelled during a drive. That will indicate what kind of public charging infrastructure drivers might need.

For now, drivers taking part in the study will be able to use at least three free public charging stations, including one at Toronto's Hydro's office. The utility is also providing electricity to charge the cars for free using a meter in their homes that is separate from their main home supply to study their usage patterns.

Toronto Hydro anticipates most people will commute during the day and charge a night, Odell said. But soon it will have hard data on real consumers to work with: "We want to prove out what their behaviours are."