A common enabler for all alternative fuels

[quadraphonics]

Meanwhile, the real improvements in bus efficiency are likely to come from a recent Dutch invention than from aerodynamics:

http://en.wikipedia.org/wiki/Whispering_Wheel

These guys developed a bus wheel with the electric motor built right in, which eliminates the drivetrain. This approach also allows much more energy to be recaptured through regenerative braking, so the overall boost in efficiency runs to 50%. As of yet, it's still quite expensive, and so unsuited to individual cars, but hopefully that will change with time.

 

[Billy T]

Meanwhile, the real improvements in bus efficiency are likely to come from a recent Dutch invention than from aerodynamics:

http://en.wikipedia.org/wiki/Whispering_Wheel

These guys developed a bus wheel with the electric motor built right in, which eliminates the drivetrain. This approach also allows much more energy to be recaptured through regenerative braking, so the overall boost in efficiency runs to 50%. As of yet, it's still quite expensive, and so unsuited to individual cars, but hopefully that will change with time.

It still used fossil fuels - contributs to the pollution of urban air. Your reference stats:
" The bus utilizes an in-wheel electric motor for propulsion which is powered with electricity from a generator, which in turn is propelled by a diesel engine."

I prefer the zero urban pollution (perhaps zero pollution anywhere) system I describe in my post 17. I could not find a wiki link to superflywheels, but recal that they have already very significantly exceeded the specific energy density of storge (I.e. per pound) of all batteries, even those at a comprable stage of development. They were being investigated at JHU/APL 40 years ago* when I worked there. I did find:
http://space-power.grc.nasa.gov/ppo/projects/flywheel/techdet.html#storeenergy
where my memory is confirmed in their "table 1" which states (but is not easy to copy here - go there and see photos of it also.)


Energy storage characteristics:5-10+ times greater specific energy

Long life (15 yr.) unaffected by number of charge/discharge cycles {Billy T note: Few if any battries can do 300 deep discharges without either total failure or significant lose of capacity.}

Reduced logistics, maintenance, life cycle costs and enhanced vehicle integration

85-95% round-trip efficiency More usable power, lower thermal loads, compare to <70-80% for battery system High charge/discharge rates & no taper charge required

{Easily and very accurately from the RPMs} Deterministic state-of-charge

Improved operability

-------------------------------------
*See: http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0697906
Where a factor of 10 improvement on batteries is projected back in 1969. I suspect that they have not been funded well as they have the potential for elimination of much oil consumption if used in a bus based public transport system. Only NASA is currently continuing their development due to to the vastly superior energy stored to weight potential and unlimited number of deep discharge cycles.

 

[quadraphonics]

It still used fossil fuels - contributs to the pollution of urban air.

Ummm... the point was that it is more efficient, not that it doesn't require fuel. In any case, the benefits would be the same regardless of how the electricity was generated, so...

 

[Billy T]

Ummm... the point was that it is more efficient, not that it doesn't require fuel. ...

I understood that, but like the all electric system (no diesel engine) I just described (and earlier in post 17) that consumes ZERO fuel in the city. Like your recomendation, it also has regenerative breaking with in wheel motors.

 

[Harmonic_Subset]

New numbers (you may have to refresh your browser).

Since this is my own analysis, I decided to take some creative license with the input parameters. Same formula (and I stand by its correctness), but I tried plugging in some numbers that I don't believe for a second are remotely correct, just to see what the result is. I did this for the last 5 entries, buses and tractor-trailers.

For a tractor-trailer, in order to match the published fuel consumption I had to decrease the drag coefficient to 0.54 from 0.70. This is not as low as an SUV, but almost. I also had to reduce the mass by nearly 2/3rds, and increase the engine efficiency to 35%. Although the calculated mpg seems to match the published value now, I'm wrinkling my nose at these input parameters. Nevertheless, with these input parameters, the tractor trailer burns 61 percent of its mechanical energy fighting air resistance, and 38 percent fighting rolling resistance.

For a commuter bus, I used the Orion VII diesel-electric hybrid. This bus is bigger and heavier than most, but at least I have some more accurate specifications from the manufacturer. Still, in order to get 8 mpg diesel-equivalent fuel consumption I had to reduce the drag coefficient to 0.6 from 2.1, and you'll never convince me that this is remotely correct without some serious wind tunnel tests. This bus still looks like a rectangular box to me, more so even than older buses. I also had to increase the effective engine efficiency to 47 percent, and IMO this is ludicrous. I'd be screaming for some experimental verification here. These conditions suggest that 46 percent of mechanical energy is wasted fighting aerodynamic drag, and 53 percent is wasted fighting rolling resistance. Total mechanical energy spent is worse than a tractor-trailer, although the engine is more efficient, so the mpg is slightly better.

I compared the hypothetical Superbus to the Orion VII with commuter input parameters. I assumed that the Superbus would be half the weight, using aluminum and composite materials, would be all-electric with 60 percent efficiency (same as Tesla Roadster), with same width as the Orion VII but only as high as an SUV, and with a drag coefficient of only 0.2, as per the Superbus website. The result suggests that the commuting Superbus would get 3.5-times better mpg than a diesel-electric hybrid, around 28 mpg diesel equivalent which is about as good as a full size family sedan. Only 1/4 of its mechanical energy would be wasted on air resistance, and 3/4 on rolling resistance.

I also compared the same two buses under city bus conditions, with stops every 1/2-km, and speed never exceeding 30 mph. The diesel-electric Orion bus burns 4-times more fuel under these conditions, getting between 2-3 mpg fuel consumption rather than 8 mpg. This fact is reflected in a study by the US gov't which puts fuel consumption of hybrid city buses at between 2.50 - 2.75 mpg.

http://www.nrel.gov/docs/fy02osti/32427.pdf

The Superbus theoretically achieves triple this performance, at around 6 mpg diesel equivalent fuel consumption. The mechanical energy wasted between kinetic energy, rolling resistance, and air resistance is similar for both the Superbus and the Orion hybrid, but the Superbus simply does better with only half the losses to air resistance, less than half the total mechanical energy expended, and a far higher equivalent engine efficiency (pure electric).

 

[quadraphonics]

I understood that, but like the all electric system (no diesel engine) I just described (and earlier in post 17) that consumes ZERO fuel in the city. Like your recomendation, it also has regenerative breaking with in wheel motors.

Uh... first of all, it's not "my recommendation." It's a link to an actual test program producing actual results. I'm not here on some crusade in favor of diesel engines or anything. In any case, the company that invented and sells the in-wheel motors is also in favor of all-electric solutions. The reason a diesel engine is used is because it's a *test prototype* and the city in question uses diesel busses.

Finally, all you seem to be suggesting in your post 17 is the use of flywheels instead of batteries or fuel cells. As I understand it, this is problematic in the context of in-wheel motors. That is, the rotational energy in the flywheel must be converted to eletrical energy to power the motors, which reduces the benefits of in-wheel motors (the elimination of intermediate drive stages). You would normally put the flywheel between the power source and the wheels. Moreover, as far as I know, superflywheels are not up to the point where they can be used as the primary energy storage element in a transport system. To date, they're only used as intermediate accumulators. My suspicion is that a flywheel capable of storing the kinds of energy you get out of a tank of gas would be either too big, too heavy, too dangerous or too expensive for use in such a setting.

 

[Billy T]

...Finally, all you seem to be suggesting in your post 17 is the use of flywheels instead of batteries or fuel cells.

Yes.

As I understand it, this is problematic in the context of in-wheel motors. That is, the rotational energy in the flywheel must be converted to eletrical energy to power the motors, which reduces the benefits of in-wheel motors (the elimination of intermediate drive stages).

I fail to see how this differs from the need to convert the mechanical energy produced by the diesel into electric energy for the in-wheel motors. Yes, the rotational energy of the flywheel must be also converted to electric energy but this does not seem to me to be a problem.

I am not current with the modern superflywheel developments but they all must run inside a vaccuum chamber to avoid air friction losses. This chamber also serves as the containment vessel in case of failure. (Those using carbon fibers as the stressed material make carbon dust when they fail and creating all that new surface disipates most of the energy.)

Magnets inside the vaccum chamber on a small diameter section of the same shaft, co-rotating with the larger diameter flywheel, induces AC voltages in pickup coils. Modern electronics can pick up the dynamic magnetic field to generate AC and efficiently convert it to DC for good low speed torque in the in-wheel motors.

The main difference I see (compared to the diesel system of your reference) is that the diesel can not be "reversed" to remake the fuel it consummed, but the flywheel can be speeded up again during the re-generative breaking.

I.e. your reference system must also have some other from of energy storage (batteries?, but a superflywheel would be lighter and more efficient, even in your diesel system.)

... as far as I know, superflywheels are not up to the point where they can be used as the primary energy storage element in a transport system. To date, they're only used as intermediate accumulators. My suspicion is that a flywheel capable of storing the kinds of energy you get out of a tank of gas would be either too big, too heavy, too dangerous or too expensive for use in such a setting.

Flywheels are never a "primary energy sources." They all require a primary energy source, but will be re-energized infrequently, perhaps only at the end stations of the bus route.

 

[Harmonic_Subset]

Just kicking around some more numbers. It seems that if the government made a law requiring all new vehicles to have a drag coefficient of 0.20 or less, then our country could reduce its dependence on oil drastically.

For a Honda Civic, a very popular vehicle, reducing drag coefficient to 0.20 would increase its fuel economy to 49 mpg. In other words fuel consumption would drop by 1/3rd.

For a tractor-trailer, reducing drag coefficient to 0.20 would increase fuel economy to 11 mpg. This is a 57 percent reduction in fuel consumption.

For a city bus, making frequent stops, reducing drag coefficient to 0.20 would increase fuel economy to 3.5 mpg. This is a 40 percent reduction in fuel consumption. This would benefit diesel and hybrid buses alike.

I'm astonished actually. I started this thread thinking that reducing mass would be a great way to reduce fuel consumption and make limited quantities of alternative fuels more "able" to displace fossil fuels. Remember that fuels like ethanol may never displace more than 30 percent of current gasoline consumption. We just can't produce enough of it. But I never realized that modern motor vehicles had such poor aerodynamics. I still think reducing mass is a great idea. For example, if a honda civic reduced its drag coefficient to 0.20 and reduced its weight by half using aluminum and composites then it would achieve a 70 percent reduction in fuel consumption. But, I think drag coefficient reductions are easier to engineer into a vehicle since they can be applied and improved regardless of the size and function of the vehicle. Weight reductions are more difficult because of the variety of sizes, functions, cargo & passenger carrying capacities of vehicles made today. Both should be done eventually, but we should do the easy thing first.

If I were a legislator, I would start by requiring all vehicles to have a drag coefficient of 0.20 or less, with a full-up version of the vehicle (with all the trimmings and accessories) tested in a wind tunnel before production begins, proving that it does. Drivers might not care much about fuel economy, since the cost of fuel is relatively small compared to the overall cost of a vehicle. But when a technology like motor vehicles causes such strenuous demand for a resource such as fossil fuels, such that it affects inflation and the general health of the national economy, then that technology should be curtailed. That's my opinion. I just wish I were in a position to do something about it.

 

[leopold]

i really appreciate you answering my questions harmonic_subset.

the facts of the matter are that if you can reduce the rolling resistance to zero then the weight you are trying to move is irrelevant isn't it? in fact you can throw it out the window can't you?

some fine expertise you have there.

 

[quadraphonics]

Yes.I fail to see how this differs from the need to convert the mechanical energy produced by the diesel into electric energy for the in-wheel motors.

It doesn't, and that would be a really good point if anybody was suggesting diesel-fueled electric cars as an ultimate solution. But nobody is. These test systems were installed on diesel busses because that's what the city already had, and they wanted a relaible backup system in case the test systems should fail.

I.e. your reference system must also have some other from of energy storage (batteries?, but a superflywheel would be lighter and more efficient, even in your diesel system.)

For the last time, it's not "my diesel system." Nobody is advocating diesel busses as the ultimate in energy efficiency. It just happens that the test prototypes of the in-wheel motors are being tested on a diesel bus.

Flywheels are never a "primary energy sources." They all require a primary energy source, but will be re-energized infrequently, perhaps only at the end stations of the bus route.

Way to be pedantic. I think context made it clear that I meant "primary energy storage for the vehicle."

 

[Billy T]

...These test systems were installed on diesel busses because that's what the city already had, ....It just happens that the test prototypes of the in-wheel motors are being tested on a diesel bus. ...

City must have had a crazy set of bus specks if they bought a diesel powered bus with in-wheel electric motors as "what they had."

BTW, there is a point not widely recognized about "in-wheel motors"

They add to the "un-spriung weight." This is not very important in a bus as they are still not much of the total, but if you put the motors inside the wheels in a car, the rid will be worse. For a smooth ride you want as much of the vehicle weight to be supported by the springs, not compelled to go up and down with the holes in the road.

 

[quadraphonics]

City must have had a crazy set of bus specks if they bought a diesel powered bus with in-wheel electric motors as "what they had."

That sentence doesn't make any sense. Here's the (very simple) situation: the city in question (Apeldoorn, Netherlands) already operates a diesel bus fleet. The company that makes the in-wheel motors (e-traction) approached them with the idea and suggested they try out some prototypes on actual buses. So, they modified two city buses to put in-wheel motors and associated batteries and electronics on them, and now drive them around to see how the system performs in the real world. If things go well, the city will buy more buses like this, and also think more about how to improve efficiency and emissions. Nobody is pitching the diesel/in-wheel motor bus as an ultimate integrated solution, so it's specious of you to criticize it on those grounds. I gaurantee you that, if your flywheel system was feasible, somebody would be doing it already.

Incidentally, Mitsubishi is currently testing a passenger car with in-wheel motors.

 

[Billy T]

That sentence doesn't make any sense. Here's the (very simple) situation: the city in question (Apeldoorn, Netherlands) already operates a diesel bus fleet. The company that makes the in-wheel motors (e-traction) approached them with the idea and suggested they try out some prototypes on actual buses. So, they modified two city buses to put in-wheel motors and associated batteries and electronics on them, and now drive them around to see how the system performs in the real world. If things go well, the city will buy more buses like this, and also think more about how to improve efficiency and emissions. Nobody is pitching the diesel/in-wheel motor bus as an ultimate integrated solution, so it's specious of you to criticize it on those grounds. I gaurantee you that, if your flywheel system was feasible, somebody would be doing it already.

Incidentally, Mitsubishi is currently testing a passenger car with in-wheel motors.

Ok that makes some sense - they are road testing the in wheel motors with the help of a local bus that happens to be diesel powered. Not testing the prototype of a diesel bus driven by motors in the wheels as I first understood your post.

Yes, the loss in ride comfort (with motors as un-sprung weight) may be well compensated for to many (including me) if they permit regenerative braking to be economical, but that is not the case if the primary power for the system comes from burning fuel in an on-board diesel engine. This is for the simple reason I stated earlier: The energy recovered during breaking can not be applied to the diesel to "un-burn the fuel." Thus if regenerative breaking is to be used, some other storage system must also be included (rechargable batteries, reversible fuel cell or super flywheel, being the main candidates I think.)

While not yet ready for market, the superflywheel has the potential to be nearly an order of magnitude higher in specific energy than batteries (and some other desirable features related enhanced stability. Large torques are required to change the direction of the stored angular momentum but that can also cause gymbal limit problems, if you need to go up or down steep hills. I.e. trucks with a superflywheel would never flip over on their side just because the driver took a curve too fast if the angular momentum was basically vertical.) Also buyers of buses and trucks tend to at least consider the life cycle costs. The fact that the super flywheel is good for at least 10,000 discharge cycle means it wil last as long as the vehicle (unlike batteries with about 300 deep discharge cycles of life) and the materials for one are not excessively expensive (carbon or glass fibers, vaccuum tank, magnetic bearing and magnets for AC induction etc. - in mass production probably will someday cost less than a diesel engine for the truck or bus as many fewer parts to machine etc.!)

I think the initial market will be for trucks and busses, not cars, especially those that have a regular route and recharge flywheel to full speed at the two ends of it only. Many years ago, (more than 30, I think) in Sweeden there was a flywheel bus with a simple old iron flywheel that had to recharge from "electric lamp posts" at some of its stops along the route. Modern design super flywheel store dozens (if not a hundred - I forget) times more energy per pound. Probably in most urban bus routes would only recharge at the end termainal, while the driver had his rest/coffee break etc. As urban pollution becomes ever more of a problem and liquid fuel for IC engines more expensive, the flywheel bus and electric car will both return - I predict.

 

[ibm.eub]

Our transportation system will be our downfall!!!

 

[mikenostic]

Factors that might reduce weight in any car:
- 2-cycle engine has more power per cubic inch, and therefore less weight, than a 4-cycle

Yeah, and a 2 stroke engine will produce about 10,000 times more CO emissions than a 4 stroke engine of equivalent size. Not to mention a 2 stroke uses more fuel and oil than a 4 stroke of the same size. So the emissions they produce, and the fuel they consume negate any weight advantages they would have over a 4 stroke.
Why do you think that they are being phased out?

- two or three wheels instead of four eliminates tires

Yep, they're called motorcycles.
As for three wheels...
http://www.go-t-rex.com/



For these below, most everything you mentioned are good suggestions, however, the ones I've quoted have some disadvantages which would negate the 'green' cause.

Additional factors include:

- high compression ratio improves carnot efficiency of the engine

Higher compression also means more fuel, and the engine runs hotter.

- removing catalytic converter improves fuel economy

I agree, but the engine would have to burn as clean as if it did have a CC, in order to keep emissions down

- removing muffler improves fuel economy

But then noise pollution comes into play

- turbocharger improves fuel economy

Uhh, no. Forced induction (turbo/supercharger) improves fuel efficiency. A turbocharged engine will use more fuel than an identical normally/naturally aspirated engine. It's essentially rasing the compression (first point above). And like higher compression, it will actually produce much more heat as well.

- slick tires can reduce coefficient of friction

But can become extremely volatile in even the slightest wet weather. A case in point is during F1 races back when they were using slicks on their race cars; whenever it rained, they would have to pit and have the slicks removed and wet weather tires (which were tires with tread) installed.

- no air conditioning or other power-hungry gadgets improves fuel economy

I agree, but try to sell a car w/o a/c to a person who commutes to and from work in hot weather wearing a business suit or something similar.

 

[Harmonic_Subset]

If vehicles had a drag coefficient of 0.20, they would look more sophisticated as well as get better fuel economy. But every car looks the same these days. Same truncated rear-end. Same box-top and sloping windshield, front and back. Same uncovered wheels. K-Cars, all of them.

 

[Harmonic_Subset]

The "embodied energy" of something is the amount of energy it takes to manufacture or recycle, and is usually stated in units of MegaJoules per kilogram (MJ/kg) for various materials used. Alot of people including myself have wanted to know how much energy it takes to manufacture and scrap a car, compared to the energy consumed as fuel over its operational lifetime. A study done by Argonne Lab in the 1990s compared the benefits of using lightweight materials in cars (Aluminum Intensive Vehicles), on a cost basis:

http://www.transportation.anl.gov/pdfs/TA/106.pdf

The study lists mass fractions for various materials used in vehicles, and how much embodied energy they have. I've summarized them here:

 

[Harmonic_Subset]

I applied the above data for embodied energy into my formula for calculating mpg, in order to estimate how much total energy is consumed by a vehicle over its operational lifetime. Energy used in manufacturing is significant enough in some cases that simply using mpg to determine which cars are most energy conservative isn't enough.

The simplest way to decide which car consumes the least energy over its lifetime is to divide the curb weight by the mpg. This allows one to use published numbers which are readily available, and also takes into account the amount of materials used in manufacturing and the fuel used driving. The car with the smallest value of this "Critical Parameter", a value which is otherwise meaningless, probably has the lowest total lifetime energy consumption.

 

[Harmonic_Subset]

One more point:

In keeping with the theme of this thread, it seems that reducing vehicle weight also reduces energy consumed in manufacturing & recycling, in addition to reducing kinetic energy, rolling resistance, and air resistance (via lower frontal area).

Lose weight. It's a winning strategy.

 

[Billy T]

lot of good points here, but they may all be moot as China (Chery Motors and others) and India (Tata's $3000 dollar four-door four-wheel efficient car) enter the market with much cheaper cars. Here is link to Chery Motors factory / cars photos.

http://online.wsj.com/article/SB119626663742706650.html
(It down loaded slowly for me - you may want to do something else while it does.) Text with photo 13 is:

"Chery may have duplicated Western practices in its plant, but it has an advantage on its American rivals in the cost of labor. Assembly line workers, such as the man at left, earn an average of slightly more than $1 an hour -- a sought-after wage in the poor province of Anhui."

I.e. much of the Chery factory came from Europe as a "turn key only for start up" deal. I.e. is very state of the art. Production is rapidly growing and export sales (> 25% of production) are more than doubling about every year. Will sell 400,000 vehicles this year and more than a million by 2010. More details at:
http://online.wsj.com/article/SB119671314593812115.html