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

[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:AC?

[Cassini2]

Installing a motor in every wheel is intuitively a nice idea. Unfortunately, electric motors have a great deal of inertia. At high speeds, the effects of this rotational inertia dramatically affect the stability of the vehicle when it hits a bump.

At lower speeds, vehicle performance is maximized when the motors torque/speed curve is matched to the maximum speed of the vehicle while simultaneously matching motor diameter to wheel diameter. Unfortunately, the wheel diameter, tire diameter, motor diameter, and peak motor RPM rarely agree. Thus mechanical gearing often helps.

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/

Re:AC?

[feepness]

You must be new around here... ever see how much energy an AC-troll post can generate?

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?

Re:AC?

[TheNetAvenger]

Installing a motor in every wheel is intuitively a nice idea

This was the subject of a few papers and subsequent articles in popular automotive and popular mechanics type magazines.

The conclusion was that technology would be needed to offset these effects and even at the time of the articles/papers 20years ago, it was not too farfetched.

With today's high response computers already in cars with active suspension, linear traction, etc. the computer technology to offset these problems is something that can easily be tuned using today's technology.

Some aspects of independent motors, or 'drive trains' to each wheel is 'enhanced' stability and traction control, as well as rotational tricks that would allow the car to rotate one wheel backwards while rotating the others forward. This would give a performance car incredible cornering, handling, as well as make available some interesting turning radius effects.

I can remember back when 'performance' car people hated the idea of 'alternative' energy or electric powered cars and saw them as the death of the sports/muscle cars. At the time I spoke up and tried to explain how wrong they were, as alternative technology could yield faster, better performing and safer sports cars. This is just one area and example of how new technology would achieve these results.

"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.

Re:"Brushless DC" vs "synchronous AC" motors.

[Cassini2]

For this application, they will be using an induction AC motor. This is not a synchronous AC motor. Induction motors eliminate the permanent magnets of Brushless DC motors and the rotating electromagnets of synchronous motors. Replacing the rotating magnets with a "squirrel cage" results in a small net weight savings, and a considerable inertia reduction.

In all likelihood the locomotives that you are talking about are also using induction motors. At locomotive power levels, induction motors allow for some nice tricks that blur the line between a conventional induction motor and a conventional synchronous motor. Specifically, if you have a separate power source / load for the inductive rotor, the resulting motor design looks like a synchronous motor, but is really a specialized induction motor. GE even has patents on this technology.

The power research group at my local university even did a research contract with a major multinational on how to exploit induction motor properties for use in new electric car designs. For weight sensitive applications (like a car) over 1 kW, almost all the motors are induction. Even for high-accuracy applications with servo capability, like CNC machines, all the large spindle motors are induction motors. With modern control electronics, an induction motor is all you need.

Re:AC? - because they are idiots...

[nickull]

Anyone who has a basic knowledge of physics knows hydrogen is stupid. If you have electricity, use batteries - you can skip the 400 pounds of ice and twenty five other major problems with trying to convert good electricity into hydrogen and back again. It will never work for terrestrial applications. See: http://technoracle.blogspot.com/2005/12/hydrogen-a gain-tweedle-dumb-and.html and http://www.tinaja.com/h2gas01.asp Hydrogen is dumb. Hydrogen is a bad idea.