AFS Trinity @ NAIAS - Plug-in VUE

[pow]

Closing the Power Gap Between a Hybrid’s Supply and Demand

By MATTHEW L. WALD

Published: January 13, 2008

A HYBRID that drives the first miles of each trip on batteries charged from the electricity grid — and burns no gasoline at all until the batteries have been drawn down — is a widely sought antidote to $3 gasoline. But no automaker has yet shown a battery pack for such a vehicle, known as a plug-in hybrid, that would be durable enough for mass production.

Now one company, AFS Trinity Power of Bellevue, Wash., says there is no need to wait for advanced batteries to be invented — that a successful plug-in hybrid can be assembled from components that are already available. The company, which specializes in energy storage devices, is displaying a running prototype at the North American International Auto Show in Detroit, which opens Sunday for press previews and runs through Jan. 27.

The prototype is based on a Saturn Vue Green Line, a hybrid crossover that General Motors builds using a low-cost belt-alternator system for its electric drive. With extensive modifications, AFS Trinity’s Vue can run 40 miles on electricity alone, the company says, drawing its power from a combination of lithium-ion batteries and scaled-up versions of common electrical devices called capacitors.

With a second electric drive system added to the standard gas-electric setup of a Vue Green Line, it would not be a stretch to call AFS Trinity’s creation a hybrid hybrid.

G.M., which is not involved in the AFS Trinity project, will also make announcements in Detroit about Vue hybrids on the way, including a version that uses the two-mode hybrid system recently introduced on large S.U.V.’s. Saturn promises an update on the production of its own plug-in version of the Vue as well.

Typically, hybrids exploit the synergies of electricity and internal combustion by using only an electric motor at low speeds; the gas engine kicks in as speed increases, and both are used when maximum output is called for. AFS Trinity, on the other hand, took a purist position. In its system, the gasoline engine is not started until the batteries run down, an approach that Edward W. Furia, chairman and chief executive of the company, calls an “extreme hybrid.”

By designing the system to operate that way, the AFS Trinity Vue can achieve the equivalent of 150 miles a gallon. But technical issues arise because it carries only a few batteries, putting a big strain on each one during acceleration — a serious problem for an automaker that must provide a long-term warranty. An electric-only vehicle would avoid the problem by carrying four or five times as many batteries, though that would greatly increase the vehicle’s cost.

In fact, the problem in a hybrid is not only how much energy the batteries hold, a quality called energy density, but how fast they can deliver it, called power density. The difference between energy density and power density is like the difference between a wine jug and a peanut butter jar — the containers may have the same capacity, but the size of their openings differ greatly.

Battery choices for a given application are based on the task. For a hybrid car, which needs a deep reserve of energy to go long distances, one of the most promising types is lithium ion, because it offers favorable energy density, carrying many watt-hours in each pound. That is what AFS Trinity chose for the Vue, with about 16 kilowatt-hours of usable capacity.

A typical battery for a household device can empty in an hour without damage, and it can sustain momentary discharge rates three or four times as high, said Don Bender, the company’s chief technology officer. Specialty batteries can empty in six minutes, but they are far more expensive, and running a regular battery that way “would be like driving your engine at the red line for three or four minutes,” he said.

But the discharge requirement for the Vue is even higher than that, and the consequences can be dire. Emptying a battery too fast makes it heat up, causing damage or even a fire.

To cover the gap between the batteries’ ability to supply energy and the demand of the hybrid’s electric motor, the experimental Vue uses ultracapacitors, which are the electrical equivalent of the peanut butter jar. Larger versions of the devices used to manage power flow in all sorts of electronic circuits, the ultracapacitors can be filled from the lithium-ion batteries and then emptied quickly into the motor that drives the wheels as the driver demands.

The rate of energy flow is also an issue as a hybrid car slows down, when its electric drive motor turns into a generator. This process, known as regenerative braking, converts the car’s motion into a powerful stream of electric current, but today’s hybrids capture only about half of the energy produced this way. Ultracapacitors can absorb a much higher percentage.

The ultracapacitors take up about as much space as the lithium ion batteries, although they store a total of less than one kilowatt hour. Mr. Bender described the entire package as looking like an 18-pack of Red Bull cans, shrink-wrapped.

In use, the capacitors function much like the water tank on a toilet. That reservoir lets the toilet get by with a small supply pipe, yet still delivers a large volume at once for flushing. The idea is not unique to AFS Trinity; General Electric, for example, is considering capacitors for a hybrid electric bus.

Because the AFS Trinity Vue runs long distances as a pure electric, it needs a full-size electric motor to go along with the full-size gasoline engine it uses in hybrid operation. While G.M.’s design for the Vue Green Line can get by with a small electric motor connected to the drivetrain by a belt, the AFS Trinity version has been modified with a 200-horsepower electric motor under the rear floor. The Vue Green Line’s standard hybrid system drives the front wheels, and the motor added by AFS Trinity drives the rear wheels.

So in its first 40 miles, the Vue is a rear-wheel-drive vehicle, and after that it is intermittently a four-wheel-drive vehicle, with the energy from regenerative braking captured by the capacitors and funneled through the motor driving the back wheels. “It saved us from mechanical integration and made it basically a software integration,” Mr. Bender said. But the ultracapacitors could be used in any kind of design, he said.

The idea behind the AFS Trinity is based on a widely accepted rule of thumb: the vast majority of drivers travel fewer than 40 miles a day. According to AFS Trinity, a driver who went 40 miles or less a day six days a week, and 100 miles once a week, would be traveling 150 miles for each gallon of gasoline burned, spending a little less than $8 for the gasoline and a little less than $8 for the electricity. The total fuel cost of $15.49 is about one-third of what it would cost for the gasoline to propel a conventional hybrid like the Lexus RX 400h the same distance, by AFS Trinity’s calculation.

In the AFS Trinity prototype, ordinary house current to charge the lithium ion batteries enters the car through a plug behind the rear license plate. In mass production, the plug-in version would cost $8,600 more than the ordinary hybrid, according to the company, whose calculation of the payback period is in the range of 3.5 years.

Payback time would be somewhat shorter if the United States puts a price on carbon dioxide emissions as a way to reduce global warming gases. The Vue Green Line, as Saturn builds it, emits nearly one pound of carbon dioxide for each mile traveled; the AFS Trinity version, running on the average kilowatt-hour, produces about six-tenths of a pound.

http://www.nytimes.com/2008/01/13/automobi...amp;oref=slogin

VIDEOS: http://www.afstrinity.com/video.htm

[PurdueGuy]

What's that? 40 mile electric range from existing battery tech in an SUV? Gee... think maybe the Volt has a better chance than some people seem to think?

[pow]

What's that? 40 mile electric range from existing battery tech in an SUV? Gee... think maybe the Volt has a better chance than some people seem to think?

The AFS Trinity car uses an ultracapacitor, which allows electricity to be quickly generated to power the motor and spin the wheels, while keeping the strain on the battery constant. Think of it as a water tank on a toilet: "the reservoir lets the toilet get by with a small supply pipe, yet still delivers a large volume at once for flushing (acceleration)."

GM does not plan on using such as system on the Volt, so they need a lot more batteries, which must also endure a lot more charging/discharging. At the moment, GM has one pack from LG Chem/CPI; the one from A123/Continental has yet to arrive. Neither of them exist in quantity. I'd say there's still a lot more work to be done.

[Robert Hall]

That's a cool concept.

[PurdueGuy]

The AFS Trinity car uses an ultracapacitor, which allows electricity to be quickly generated to power the motor and spin the wheels, while keeping the strain on the battery constant. Think of it as a water tank on a toilet: "the reservoir lets the toilet get by with a small supply pipe, yet still delivers a large volume at once for flushing (acceleration)."

GM does not plan on using such as system on the Volt, so they need a lot more batteries, which must also endure a lot more charging/discharging. At the moment, GM has one pack from LG Chem/CPI; the one from A123/Continental has yet to arrive. Neither of them exist in quantity. I'd say there's still a lot more work to be done.

Yes, I read the article. Of course GM will have issues to work out, but it's not really that far out there.

[enzl]

Yes, I read the article. Of course GM will have issues to work out, but it's not really that far out there.

Actually, it is. If original timeframe is to be met, these batteries (some of which are not yet being tested) must be 100% foolproof out of the box.

That's alot to ask of a new tech. 2 yrs. road testing is a very tight schedule on the Volt, a vehicle which must reinvent most major and minor systems in a unique matrix of seamless function.

Most car companies cannot do that. I'm not picking on GM, just confused as to how promises could be made without working tech already being available.