Two-way charging electric cars

[California98Civic]

http://www.nytimes.com/2013/04/26/bu...ml?ref=science

"In Two-Way Charging, Electric Cars Begin to Earn Money From the Grid
Tim Shaffer for The New York Times"

By MATTHEW L. WALD
NYT April 25, 2013

WASHINGTON — Finally, payback for the plug-in.

A line of Mini Coopers, each attached to the regional power grid by a thick cable plugged in where a gasoline filler pipe used to be, no longer just draws energy. The power now flows two ways between the cars and the electric grid, as the cars inject and suck power in tiny jolts, and get paid for it.

This nascent form of electric car commerce will be announced on Friday by the University of Delaware, the regional grid operator and an electric company. They have developed a system to collect payments for work (balancing supply and demand moment to moment) that is normally the domain of power plants.

The possibilities of using electric cars for other purposes are being realized around the globe. Electric cars like the Nissan Leaf and Chevrolet’s plug-in hybrid Volt, are generally not sold in the United States with two-way chargers that could feed back into the grid. But Nissan is offering a similar device in Japan that allows consumers to power their houses when the electric grid is down.

In the Delaware project, each car is equipped with some additional circuitry and a battery charger that operates in two directions. When the cars work with the grid, they earn about $5 a day, which comes to about $1,800 a year, according to Willett M. Kempton, a professor of electrical engineering and computing. He hopes that provides an incentive to make electric cars more attractive to consumers, and estimates that the added gadgetry would add about $400 to the cost of a car.

Granted, the scale of this project, using 15 two-passenger Mini E models, donated by BMW, is indeed minuscule compared with the task of keeping the grid system that serves two-thirds of North America in balance, making sure that supply matches demand as precisely as possible.

The frequency of electric current in the United States is supposed to be stable at 60 cycles a second, but if the supply from a wind farm or solar plant changes suddenly, or demand shifts, frequency gets out of whack.

The market that Professor Kempton is tapping into, known as frequency regulation, has become increasingly important as the mix of generators on the grid has changed.

If electric cars become more popular, proponents say that a network of thousands of plug-in cars could help stabilize the grid.

Michehl R. Gent, a former president of the North American Electric Reliability Corporation, the entity designated by the federal government to write and enforce grid reliability rules, called the Delaware idea “tiny but promising.”

“If we can get our electric vehicles to do more than just be electric vehicles, it will be very well received,” said Mr. Gent, who is not associated with the project.

Professor Kempton has had this “vehicle to grid” system in the works for 10 years. He plans to double the size of his fleet by the end of the year. Half the cars are permanently parked and the other half will provide service for all the hours they are plugged in, which could be as much as 20 hours a day.

The cars listen for a signal from the headquarters of the regional grid operator, the PJM Interconnection, in Norristown, Pa., that comes every four seconds. The signal could tell the batteries to charge, or to discharge, or to do neither. Alternatively, if the cars need charging, they can provide the same service by varying the amount of current they draw. For the grid, the effect is to add or subtract load in a coordinated way that aids stability.

Two-way chargers are not generally available to drivers of electric plug-ins right now. Professor Kempton said he is working with five companies that build electric cars and are interested in a two-way system that could collect revenue from the grid: BMW and four other firms he said he could not name because of confidentiality agreements.

One of those four, he said, was working on a two-way charger that was three times more powerful than the current one, vastly increasing revenue possibilities.

A Nissan spokesman, Brian Brockman, said the company is exploring such possibilities, and recognizes the benefits of moving toward helping power the grids.

[ConnClark]

Nice pipe dream but this is going to take its toll. First Batteries are only 85 to 90% efficient with charging and about 90 to 95% efficient discharging. So any power put back into the grid there is going to have to have about 20% more be supplied at another time. Furthermore the wear and tear on the battery pack on the car could easily cost more than what you get paid from the utility.

[Cobb]

I recall the rail road companies connecting trains to the grid when CA had power problems and even rolling black outs before the enron scandal.

[Ryland]

The battery pack is going to have a pretty light load on it because the charging plug can only handle so much, most people have their electric car charging off a 20 or 30 amp 220v breaker, 6kw chargers are becoming more common and that's under 30 amps and the drive motor can draw 100's of amps, the battery management system also protects the battery pack from over discharge and because the vehicle is not moving then the charge and discharge can be programmed to be pretty kind to the battery pack.

If it really does provide $5 per day of income by leveling off peek loads (the most expensive grid electricity) then that's $150 per month and you can lease a Nissan Leaf for $200 per month, even if you have to pay the extra $400 out of pocket to have this feature added to an EV as a dealer option and lets say worse case is $1000 extra for a charging station that can handle two way connections you are still getting to drive an EV for less per year then a lot of people pay just in gasoline.

[oil pan 4]

Originally Posted by ConnClark

Nice pipe dream but this is going to take its toll. First Batteries are only 85 to 90% efficient with charging and about 90 to 95% efficient discharging. So any power put back into the grid there is going to have to have about 20% more be supplied at another time. Furthermore the wear and tear on the battery pack on the car could easily cost more than what you get paid from the utility.

That's what I was going to say.

[Cobb]

FYI, Eli of bumble bee batteries is cycling an IMA stick at full charge/discharge at a 20-35 amp load to simulate real world use in a Honda. He has it actively cooled and is going to cycle it til failure. Be interested to see how long it can go.

We know the prius as a taxi has been a great success and we know many Honda IMA systems die due to lack of use. With the limits of the plug I dont think its anything to worry of.

Power on a grid is like economics, the price of money or power when needed. Power is almost always being generated rather its needed or not. Its just diverted to other parts of the grid and many of the plants have some wiggle room to throttle up or down for demand, but demand is constantly increasing and many systems are already at capacity.

[Ryland]

You, or more so your vehicles battery management system has 100% control over your battery pack while connected to the grid, while your vehicles battery management system should be designed for the harsh use that is seen while driving, extreme heat and cold, pushing the vehicles range, short term high amp draw, extended high amp draw and when it's connected to the grid it can throttle back or shut down all together on a whim, something that you don't want to do while driving.

People are already doing this kind of thing with lead acid batteries in grid connected solar electric systems that have battery back up, buy power at night at off peek rates and sell back in the day time at peek rates, it of course requires that you have a power company that goes along with this plan and has prices that make it worth while, but it's not a new idea at all and if done right can turn a profit.