Direct Methanol Fuel Cells

[VolkerP]

Green Overdrive: We drive a fuel cell fork lift!

DMFC from oorja as explained by CEO:

1500W
3 gal Methanol tank
12-16 hours of continuous operation
estimate of fuel costs: less than $2 per gallon
refill in <1min

more specs on the web site: Oorja Protonics - Enabling Power

About Oorja Protonics
Founded in 2005, Oorja Protonics is the leader in providing reliable and economical liquid fuel
cells for the material handling industry. By leveraging its breakthrough technologies, Oorja
manufactures the most efficient and powerful portable liquid Fuel cells that significantly
reduce operating costs and green house gas emissions.
The company is headquartered in Fremont, CA.

Let's fit 2 of them (each at 170lbs) in the frunk and drive the Model S with 40kWh pack at 55mph drive, which takes ~3hours. The fuel cells would produce 9kWh in that time, which give another 36 miles or 22% range extension. Not worth the hassle yet .

[doug]

For a practical range extender, the power output needs to be the average power the car needs to keep moving. The battery takes up the slack. You do get into some trouble if you have a prolonged high power usage situation, such as hill climbing or high speed, where you exhaust your battery buffer.

I'd say the constant power output at 55 mph is a good benchmark. So lets look at the Model S.




From the graph, lets say the Model S uses 260 Wh/mile at 55 mile/h. That would mean the power output would be 260 * 55 W = 14.3 kW. Ooja needs an improvement by about a factor of ten.

[VolkerP]

For a practical range extender, the power output needs to be the average power the car needs to keep moving.

That would not be range extending but a 100% fuel cell driven car with a small battery for buffering purposes. If you have a sufficiently large battery, the fuel cell can continue to fill the battery while you take a break from driving or after you arrange at your destination. I would be fine with a range extender that provides some 80% of energy needed at 75mph, as this is my average traveling speed even on the German Autobahn, drawing the rest from the battery for a 3hour driving period.

Ooja needs an improvement by about a factor of ten.

Agree, but a system of >300lbs cannot be added without pains. I imagine a user-swappable "power brick" with suitcase form factor, weight <80lbs, and some methanol fuel cans. But it looks like this will stay a dream for the next years.

[doug]

That would not be range extending but a 100% fuel cell driven car with a small battery for buffering purposes.

No. The range extender really needs at least enough power output for average power requirements. Otherwise it doesn't actually extend your range much. The range extender has to sustain some minimum the charge buffer. The larger your battery, the more electric-only range you get in a "charge depleting mode" as GM calls it.

If you have a sufficiently large battery, the fuel cell can continue to fill the battery while you take a break from driving or after you arrange at your destination.

That's not really the goal of a range extender. If that were the case, you might as well charge from an outlet at 20 kW or even 90 kW (Tesla's supercharger) which is much faster than the 15 kW I suggested.

I would be fine with a range extender that provides some 80% of energy needed at 75mph, as this is my average traveling speed even on the German Autobahn, drawing the rest from the battery for a 3hour driving period.

Well lets do the same math I did above. From the graph, the power usage of the Model S at 75mph is about 370 Wh/m * 75 m/h ~= 28 kW
80% of that is about 22 kW.

[Robert.Boston]

I don't quite agree with the absolute "this high or nothing" approach you're proposing, @doug. Any fuel cell will add some range, and @VolkerP makes the valid argument that the fuel cell can continue to operate even when the car isn't being driven, effectively making the vehicle self-charging. The question really boils down to, what rate of "trickle charge" from the fuel cell is meaningful? I agree with @VolkerP's math, that the extra bump isn't worth the hassle and cost. But with a better fuel cell, sure: if we could get 10kW of fuel cell generation, that would add about 25kWh of power during the time it takes to discharge the 60kWh pack at highway speeds, equaling the power available from the 85kWh pack.

[brianman]

I don't quite agree with the absolute "this high or nothing" approach you're proposing, @doug. Any fuel cell will add some range, and @VolkerP makes the valid argument that the fuel cell can continue to operate even when the car isn't being driven, effectively making the vehicle self-charging. The question really boils down to, what rate of "trickle charge" from the fuel cell is meaningful? I agree with @VolkerP's math, that the extra bump isn't worth the hassle and cost. But with a better fuel cell, sure: if we could get 10kW of fuel cell generation, that would add about 25kWh of power during the time it takes to discharge the 60kWh pack at highway speeds, equaling the power available from the 85kWh pack.

Assuming that current regen is capped at some "practical maximum" (effective but limited to protect the battery), then you wouldn't want the fuel cell trickle charging while regen is underway. Thus, it might be somewhat complicated, but you'd only want the trickle charge when not regenning. One simple algorithm would be "only when the vehicle is idle".

I dub it "idle regen". Do any cars -- even prototypes -- exist that "increase range" while sitting idle and not plugged in (beyond the apparently trivial solar contribution on some)?

[Eberhard]

I like the idea, but would prefer first, to use the wast heat from the fuel cell to heat the car while cold outside and secondt overcome the range anxiety. Wait one hour to recharge and then drive slowly to the next charging station.

[doug]

I don't quite agree with the absolute "this high or nothing" approach you're proposing, @doug. Any fuel cell will add some range, and @VolkerP makes the valid argument that the fuel cell can continue to operate even when the car isn't being driven, effectively making the vehicle self-charging. The question really boils down to, what rate of "trickle charge" from the fuel cell is meaningful? I agree with @VolkerP's math, that the extra bump isn't worth the hassle and cost. But with a better fuel cell, sure: if we could get 10kW of fuel cell generation, that would add about 25kWh of power during the time it takes to discharge the 60kWh pack at highway speeds, equaling the power available from the 85kWh pack.

I guess it depends on how you define "range extender". You're right that it doesn't have to be "this high or none" to provide some benefit. But if the power output is not high enough you essentially remove what I think is the main purpose of a range extender (under the current expectation of the term), which is quick refuel time enabling you to drive as far as you want. Meaning the car essentially turns from an EV into a hybrid (or a "100% fuel cell driven car with a small battery for buffering purposes" as Volker put it).

So what you're talking about is a more limited range extender. While you get more range than you'd get with the energy capacity of the battery alone, once that battery is depleted you still have to stop and wait for a recharge, even if you have fuel left in the range extender's tank. There's still some benefit to that, depending on cost. (I think Tesla has a patent on a similar concept but with mixing different types of batteries. ) Though, I don't think the goal should be the generator/fuel cell charging the battery. That energy is better used going directly to the motor, displacing energy that would have come out of the battery.

[Robert.Boston]

Though, I don't think the goal should be the generator/fuel cell charging the battery. That energy is better used going directly to the motor, displacing energy that would have come out of the battery.

Good point.

[dpeilow]

I could be wrong, but from what I read it seams like the Robert Boston / VolkerP idea is what BMW is planning with the i3 range extender, albeit a small petrol engine. And it's definitely what Audi did with that A1 test fleet with the small wankel engines.