How to Reach 200 MPH on Hydrogen Fuel Cells

the_manatee writes "Ford's 999 hydrogen-powered speedster is making waves for its upcoming speed record attempt in the Bonneville Salt Flats, but details on what's actually going on under the hood have been scarce. As it turns out, there are NASCAR-style brakes, steering, and suspension components, along with 16 Ballard Mk902 fuel cells that produce 350 kW of electricity. All that juice spins up a 770-hp motor and the rest is (hopefully) history. One final ingredient: 400 lbs of ice for cooling, which will melt in seconds once the car gets up to speed."

Comments

Power/Weight Density

[Cassini2]

An AC induction motor has the highest power/weight density of all electric motors. Brushless DC motors are only competitive for very small motors. Even so, they could probably get a better power/weight number by burning the hydrogen in a modified internal combustion engine or in a jet engine.

Re:Power/Weight Density

[Firethorn]

From browsing conversion sites, another reason for using an AC motor over a DC one is the ability to do regenerative braking. The DC kits don't offer it. Apparently it's a lot easier to run an AC motor as a generator than a DC one.

Re:Power/Weight Density

[Agripa]

I am not sure why that would be true. If so it is probably a controller issue. Effective DC regenerative breaking would certainly require an impedance transformation via a switching regulator to be effective but that is no different then dealing with an AC motor. High power AC motor control design certainly benefits from large scale use since high power DC motor applications are relatively rare.

AC motors can be used as incredibly effective non regenerative breaks if DC is applied to the field.

Re:Power/Weight Density

[Firethorn]

It may be a controller issue; I can only report what I've seen. Thus far all builds I've seen by auto manufacturers have used AC motors, and even the home brew electric car sites place AC conversions as more effective and efficient than DC conversions. Just more expensive.

Reading through more sites, AC motors are more efficient, last longer, and emit less pollution. Apparently brushes wear out and can spark, leading to ozone creation.

Re:Power/Weight Density

[networkBoy]

Add to this that the power curve of a DC motor meas a transmission is desirable (but robs you of energy), whereas the AC induction motor's power curve is conducive to direct drive-trains.
As to the regen braking issue, DC motors are optomised towards the production of kinetic energy at an expense of not so good generation capability. In fact, some DC motors can not be generators as part of the DC is used to energize a coil as a reaction magnet (rather than having ultra high cost rare earth magnets), to use them as generators would require energizing that coil(s) and since the circuit is integral to the motor that is not possible.
-nB

Re:770 hp?

[msmikkol]

Fuel cell cars usually have some buffer batteries to shave the peak demand on the fuel cell stacks. I would guess that this car is no different - The motor draws juice from both the fuel cells and the batteries.

Re:Sounds impractical and useless

[Anonymous Coward]

Like this one? And this one?

Re:Helium, Hydrogen...hey, it's all the same.

[Cassini2]

The pressurized helium/oxygen mixture allows the fuel cells to generate more power than ambient air because of its higher oxygen content, and high-pressure storage eliminates the need for an air compressor

Nice. I expect the common press to make that kind of mistake, but you'd think that Popular Mechanics would get it right.

I think you misinterpreted the article. The oxygen cylinder contains a helium/oxygen mix. They have 2 additional cylinders to get the hydrogen from. The compressed oxygen is used so the fuel cells can absorb oxygen at a much faster rate than if they were burning regular air. Likely the fuel cells can't absorb 100% oxygen, hence they dilute the oxygen with a light inert gas like helium.

Using a dedicated helium/oxygen tank is not likely to be economical for a conventional car.

Re:Is the ice really necessary?

[PhiberOptix]

quoted from engadget:

The car itself will be cooled through "ice bath cooling" because the front is sealed in order to keep the drag coefficient as low as possible

http://www.engadget.com/2007/07/11/ford-fusion-999 -fuel-cell-car-goes-for-land-speed-record/

FORD = Fscked On Race Day

[the eric conspiracy]

In this case by the 300 mph hydrogen fuel cell Buckeye Bullet.

http://jalopnik.com/cars/alternative-energy/300%25 2B-mph-buckeye-bullet-hydrogen-fuel-cell-streamlin er-259765.php

Re:AC?

[systems_joe]

Probably for the same reason that Toyota chose a permanent-magnet synchronous that runs off of 500V DC for the Prius. Six big honkin' IGPT transistors convert the DC voltage to 3-phase AC with pulse-width modulation and variable frequency control.

Re:The effect of water vapor exhaust?

[dsanfte]

The principal biproducts of current combustion engines are CO2 and... wait for it... H2O.

Yes, water vapor.

Has Arizona turned to a jungle yet?

"Brushless DC" vs "synchronous AC" motors.

[Animats]

An AC induction motor has the highest power/weight density of all electric motors. Brushless DC motors are only competitive for very small motors.

Er, no. A "brushless DC" and a "variable-frequency synchronous AC" motor are the same thing. Smaller motors tend to be called "brushless DC" and are driven by "motor controllers", while larger motors are called "variable-frequency AC" and are driven by "drives" or "inverters". The threshold is around 1KW. The difference in terminology comes from different industries.

All motors are AC at the windings, or they'd reach a steady state position and stop. "Commutation" refers to the means provided to switch power to the windings so the motor continues to chase the minimum position for the magnetic field. Commutation can be performed with brushes and a commutator (which is just a drum of contacts), with external electronics, or simply borrowed from the power line frequency. "Brushless DC" and "variable AC" motors are driven by external electronics. They're usually at least 3 phase devices; this allows starting from a stationary position without the possibility of being stuck at a neutral point.

This concept scales up just fine. Here's the General Electric AC6000, the most powerful locomotive in the world, driven by 3-phase AC variable-frequency motors. The software, written in C++, locks all the wheels together as if they were geared together, even though there's a separate motor for each axle. This allows more tractive effort without wheel slip than any previous locomotive. There are thousands of these locomotives (mostly the smaller AC4400, but a few hundred of the big AC6000) in use today.

After 40 years of reasearch...

[CBob]

They come up w/an impractical, overpriced & crude application of the work they put to better use in a testbed van.

Yep, somewhen in the middle 60's Ford made a experimental Econoline van that was powered by fuel cells.

Need some sleep? Try ,http://www.fuelcells.org/info/library/fchandbook. pdf

Just an Informative AC

[Anonymous Coward]

http://buckeyebullet.com/
http://www.osu.edu/features/2007/bullet/
http://engineering.osu.edu/news/archive/2007/07042 0.php
http://en.wikipedia.org/wiki/Buckeye_Bullet_2

Go Bucks!