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Yesterday on this program we heard about a company in California called Better Place. It hopes to create a network in the United States and other countries for recharging the batteries of all electric cars.

Those plug-in electric cars are now starting to show up in auto showrooms and on the highways, but there are a lot of obstacles, as we're going to hear this morning. NPR's Christopher Joyce reports on concerns facing would-be drivers and the utilities that would have to supply the electricity.

CHRISTOPHER JOYCE: Russell Rankin is an enthusiastic entrepreneur who's got 13 electric vehicles charging up at the back of the Loew's Hotel in Annapolis, Maryland. They're not quite cars, but they're more than golf carts.

Mr. RUSSELL RANKIN (ECruisers): So it has three rows of two seats, so everybody kind of calls it a golf cart on steroids or, you know, something maybe that you'd see at Disney or something like that. So it has a big bubbled roof on it, very futuristic looking.

JOYCE: They're made by Global Electric Motorcars, owned by Chrysler. Rankin's company, ECruisers, uses them to squire people around the city for free. Advertising on the cars pays the freight. After about 30 miles, the cars come back here to recharge.

Mr. RANKIN: Yeah, our vehicles just run off of just a regular household outlet. We have a regular, three-pronged plug that you'd have on any household appliance.

JOYCE: So that's easy. The hard part is keeping cars charged when they're needed.

Mr. RANKIN: But we still got to play a big cat-and-mouse game all day. How many vehicles do you have out? What is current charge? How many electrical outlets do we have that we can charge off of? Because if I've got 13 vehicles, but I only have 13 plugs, then I can't charge them all up as they come in and go out.

JOYCE: Have you ever been in a situation where you got a car that's out?

Mr. RANKIN: Oh, yes. Yeah. We know where every outlet is in three states and the District of Columbia.

JOYCE: That, in a nutshell, is the challenge of electric cars: You need a reliable and widespread source of electrons. That puts pressure on the electricity grid, the power plants and wires and substations that move electricity.

Take transformers, for example, the metal cylinders high up on telephone poles. They convert high voltage to the 120 volts you use in your home. What happens if you plug in a bunch of hungry electric cars in a neighborhood?

Engineer Carl Imhoff at the Pacific Northwest National Laboratory looked into that.

Mr. CARL IMHOFF (Engineer, Pacific Northwest National Laboratory): We found that they could handle one to two to maybe three vehicles per home pretty easily if they are charged slowly, the same voltage that you have in your home for normal appliances, 120 volts.

JOYCE: Slowly means about eight hours. Imhoff says the grid could handle tens of millions of electric cars at that rate. But people will want faster charging than that, which will require bigger transformers and heavy duty power outlets that deliver 240 volts. And running the grid will get more complicated.

Here's why: Grid operators have to match supply and demand of electricity 24/7 because you can't store electricity easily. So when demand drops, they have to turn off power plants somewhere. If demand spikes - say, a hot day in Texas -they've got to fire up extra generators.

Now, add millions of cars to the demand side. Imhoff says one way to keep the system balanced is to use smart chargers that tell grid operators how much juice these cars need.

Mr. IMHOFF: If you use smart charging, you can actually cycle the charge, turn the charge off, turn it on, turn it off, turn it on, to serve the local conditions of the power system.

JOYCE: Nighttime is a good time to charge cars, when there are lots of power plants sitting idle and the electricity is cheaper. And for drivers who care about where their electrons are coming from, that's the most common time for utilities to get energy from wind turbines.

Eventually, grid operators could theoretically draw power from cars when they're hooked up, say, to satisfy a surge in demand somewhere else on the grid. Cars would become sources of energy.

Mark Lauby is with the North American Electric Reliability Corporation, the grid operators' organization.

Mr. MARK LAUBY (American Electric Reliability Corporation): Presumably, automobiles are going to be smart enough to tell me that, hey, I'm here and I want to be charged - or hey, I'm here and I have energy available if you want it.

JOYCE: This kind of power-sharing tango between utilities and drivers could make the grid more efficient, but it's also fraught with difficulties. No one wants to wake up to a drained battery, and to get power back from cars, engineers would have to install equipment to convert the batteries' direct current to alternating current.

So, for now, grid engineers are waiting to see if drivers come over to electric cars. If they do, they will build.

Christopher Joyce, NPR News.

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