Dutch Invention Uses Electric Engines For Wheels

Makarand writes "A Dutch invention is promising to make vehicles atleast 50% more efficient and also bring down the soot and carbon dioxide emissions. This is made possible by replacing the conventional wheels by 'in-wheel' electric engines which are normal electric engines turned inside out. No transmission is necessary as the in-wheel engines are powered by battery-packs installed on the vehicle. A diesel-powered generator which replaces the original engine on the vehicle charges the battery-pack continuously. The Dutch company E-Traction has built a bus using this technology that will undergo testing for the next six months."

Comments

Oh puLEASe

[chessie]

this is news how? the idea was built and proven over 100 years ago. ferdinand porsche, who was an ENGINE man, did this in like 1900 and won lots of races with his hybrid car. this feat alone put his name on the map beginging his career.
see this this page

Re:Oh puLEASe

[ergo98]

I'm hardly an expert, but have come across this term quite a few times. In a nutshell, handling and control is improved with minimized unsprung weight (and conversely diminished with increased unsprung weight). The premise is that the shocks can "push down" on the tire and wheel assemblies to counteract the upward momentum when they hit a bump in the road, for example. With increased unsprung weight, the kinetic energy is too large for the shocks to counteract, so for brief instants the wheel loses contact with the roadway to varying degrees (or even if it maintains contact, the downward pressure is reduced and thus traction is compromised).

Re:Oh puLEASe

[kfg]

You could put it that way, yes. The issue is inertia. The function of the suspesion system is to move as freely as possible so that the wheels follow the uneven contours of the road leaving the chassis stable and keeping the tires in full contact with the surface for optimum traction.

As the weight of the wheel goes up so does its inertia. It starts to resist movement more and more. This is a Bad Thing. When you hit the right bump at the right speed the wheel hops off the ground rather than moving the suspension up with the irregularity, upsetting the entire car and losing traction at that corner. The sprung to unsprung mass ratio becomes important because with heavy wheels and a light chassis the mass of the wheel reacts more strongly on the mass of the chassis. The suspension can't move with the bump but the chassis does. A loaded bus chassis is much more massive compared to the wheels than a loaded car is.

The people in the car experience this as ride harshness.

Active suspension systems are ones that use sensors and mechanical actuators to move the suspension ( as opposed to springs). They can "anticipate" the movement needed and partially compensate for the added mass, but only partially.

I can'na change the laws of physics.

A heavier wheel rim also takes more energy to accelerate, more so than the same mass on the chassis does, and increases gyroscopic effects.

This is why the solid spoked wheel gave way to the tensioned wire spoked wheel, than the pressed steel wheel and ultimately the "mag" ( which is really only a mag if it's actually made of magnesium. The aluminum wheels you get in the dress up stores are actually often heavier than the cheaper steel wheels they are purchased to replace). The lighter the wheel the higher the ultimate performance of the vehicle in every catagory (this is why bicyclists are absolutely rabid about wheel weight).

Is this system feasable for a car? Oh, absolutely. But you have to be careful to at least keep the motors as low weight and compact as possible. The GM Sunracer managed to contain them within something that looked very much like a standard bicycle hub, although rather heavier. Copper and magnets aren't light.

KFG

Popular approach for ships lately

[PhotoGuy]

Due to my wonderful education from the "Frontiers of Construction" marathon on Christmas Eve, there seemed to be many examples in the marine industry where the generator/electric motor approach is used instead of the traditional approach is used.

I got the impression that one significant benefit is the flexibility of electric engines in terms of size and manoeuverability. Being able to have your thrusters turn 360 is critical for ocean going cranes, bow thrusters, and such, and is less complicated using an electric engine than would be required for a direct mechanical linkage.

In the cruise ship example, I kind of got the impression that so much electricity is required for the ship in general, that large generators were a given to start with, so powering the thrust of the ship from the same makes a lot of sense.

Very interesting to see this technology potentially cross over to the consumer. It will be interesting to see if the efficiency makes it feasible.

Re:Not trying to pick nits, but...

[ScrewMaster]

Not notpicking at all as they are two very different things: the term "electric engine" commonly refers to a reciprocating device with a crankshaft to convert linear to rotary motion. On the other hand, "electric motor" is generally reserved for purely rotary machines. Edison used to market a stationary electric engine for industrial use.

pros/cons

[thogard]

The energy savings comes from lack of friction in the drive shaft and the battery bank can store power so you need an engine big enough to supply the average power, not peak power which results in a smaller engine. This is good for larger vehicles like busses and some trucks. It also means more effecent engines can be used. A modern internal combustion engine as found in cars and trucks is designed to work over a wide range of speeds that aren't need if your just running an generator. Once an engine is running on a consistant load and output, efficiency can be improved even more.

This will not work so well for cars beause the high unsprung weight will make a car handle very poorly and the friction losses in a u-shaft would be better than extra weight in the wheels.

Re:Just an improvement of standard hybrid technolo

[Anonymous Coward]

The reasons it is so efficient:
- the diesel engine runs at it's optimal speed (that gives an easy 50-70% gain - engines usually run on sub-optimal speed)
- losses only occur in the electrical cirquits (the current regulaters and so), can cost like 10% of the energy
- and a significant energy gain is made by reversing the enige to generator when braking! (though I assume also a mechanical break for emergency stops). As it is a city bus, it will spend most time either accellerating or decellerating.

Wouter.

Re:electric engines

[Da Fokka]

To quote the Slashdot synopsis (not even TFA)
A diesel-powered generator which replaces the original engine on the vehicle charges the battery-pack continuously.

The electro motors are not used as an engine but just as a clever way of transmission. This system has been in diesl-electric trains for ages, since most diesel engines can operate quite efficiently if they always run at the same RPM.

Re:If I know something about batteries...

[Mr. Slippery]

Won't this create cleaner air AND dumps filled with highly toxic battery-waste?

Lead-acid batteries are highly recyclable. (Though, like computers, because of poor regulation such batteries are often just dumped on third-world nations.)

Re:A quiet bus in a busy city...

[Reziac]

Actually, MOST of the "indicator noise" (as distinguished from a vehicle's general noise level) you hear is not engine noise anyway, but from its tires contacting the pavement. And that's partly a function of the tire (heavier-grade tires tend to be noisier), partly of how smooth the pavement is (rough pavement makes for more noise). You don't need the roar of a diesel engine to tell you a bus is coming; the plentiful tire/pavement noise is sufficient. In fact, you're more likely to hear that *correctly* if it's not diluted by engine noise, plus tire noise gives you better auditory indication of speed and motion.

I'd wondered about using wheel revolutions as a charging source for onboard electric systems myself -- good to see engineers applying it. (IANAE :)

Re:This isn't anything new.

[blargorama]

Massive dump trucks used in mining and made by manufacturers like Euclid (http://www.hcmac.com/) have used this technology for as long as I can remember. At least the early 60's and maybe earlier.

I'm not convinced

[gvc]

I would be more impressed if the article were to concentrate on the novel aspects of wheel motors.

Diesel-electric technology has been used to power locomotives for 60 years. D-E locomotives have no mechanical transmission and the motors drive the axles directly. This electric transmission affords good efficiency, a very wide range of torque conversion, and allows the engine to operate within its optimal RPM range. Almost all of the efficiency benefits that this article attributes to the wheel motor can be had by this 60-year-old design.

There's also nothing new about regenerative braking, though it isn't practical for locomotives.

The real novelty here is that the motor turns with the wheel, rather than being stationary and transmitting its torque through a half-shaft. The benefit is the elimination of these half-shafts and a couple of CV joints. The cost is huge size and tremendous unsprung weight of the motors, plus significant engineering challenges of running high-current wires across a sprung connection, and the concern about competition with the brakes for the limited space and heat-dissipation capacity of the wheel area.

Have a look at the rear wheels of the bus in the photo. They're HUGE - the bus has obviously been modified to fit them.

In summary, the only novelty in this design is in transmitting the power the last 2 feet to the wheels. A conventional design would use half-shafts and CV joints while this design uses high-current electrical transmission. It may be that the engineering challenges of the latter can be overcome, but I remain to be convinced that there's any overall advantage. The company's interests would be better served by an article with more restrained hyperbole.

Cost of batteries

[Latent Heat]

The main issue I have with these hybrid drive systems is the cost of electricity extracted from a battery. Pulling some electric car numbers out of the air, a $3000 lead-acid battery pack stores 10 kWHr per charge times 300-500 charges or 60 cents to a dollar per kilowatt hour. Lets say a gasoline engine averages 1 lb fuel/hp-hour (it might peak at .45 lb fuel/hp-hour at peak load and optimum RPM). Lets say $2/gallon gas (yeah, yeah, I know people in the world pay more, but that is mainly tax policy -- the reason I ascribe dollars and cents costs is to keep track of all the hidden energy costs so we don't end up with the ethanol boondoggle that can use more fossil energy as input than it puts out). Then you are talking perhaps 40 cents per kWHr.

This means that even if increased the gas engine efficiency to 0 cents per kWHr (through smaller engine run at peak efficiency to only charge batteries) but ran all the power flows through the lead acid batteries, you costs would increase from 40 cents to 60 cents per kWHr delivered to the wheels.

Anyway, this argument is for series power flows. The traditional automatic transmission is a series power flow, at best 80 percent efficient. The automotive industry has latched on to parallel power flows as a way to boost efficiency. Modern automatic transmissions use split-torque direct drive and torque converter together with direct-drive clutches to boost this efficiency. The commercial hybrids today are parallel electric and gas engine drive. The Toyota Prius is gear shift free, but instead of the Diesel locomotive series drive of engine-generator-traction motor, the Prius has the gas engine, generator, and traction motor tied to a planetary gear set so there are parallel mechanical and electric torque paths, again to boost the efficiency.

If you have a parallel hybrid, obviously you need to use your 60 cents/kWHr battery electricity under circumstances where the gas engine electricity costs more than 60 cents/kWHr, or perhaps use it to resize the gas engine for greater efficiency while consuming the minimum of expensive 60 cents/kWHr juice. But given that batteries are 1) expensive, and 2) wear out (think laptop or cellphone or iPod battery), the hybrid vehicle is not a slam dunk.

unsprung weight problems completely ignored

[SuperBanana]

Why is this anything more than just a slightly more efficient way of doing a hybrid gas-electric system by putting the engine in the wheel. It's a good idea, but I can't say I hadn't thought of it too. If it's technically sound it's a natural progression

It's actually not technically sound at all. It drastically raises the unsprung weight at each wheel- the thing will ride like crap, and contact with the road will be extremely poor. It might be OK for slow moving busses, but certainly not passenger cars, SUVs, or light trucks.

The difference between a 15lb rim and a 30lb rim(rim= wheel minus tire, ie, the metal part) on your car is extremely noticeable, and racers/performance enthusiasts will go to all lengths to find lighter rims, and even braking systems made up of higher-tech, lighter materials(hence Porsche's ceramic brakes, for example.) Even suspension components themselves are usually made up of carefully designed aluminum components to be lightweight. Less unsprung weight means that it's easier for the suspension to keep the wheel firmly planted to the ground, to grossly simplify the situation.

This thing will eat tires like no tomorrow, too; it'll cause a lot of stress in the tire because the tire will need to flex a lot more than normal. Flexing takes energy, by the way- and that can add up fast. Improperly inflating your tires causes more flexing in the tire than usual, and can have a noticeable effect on your mileage.

Putting an electric motor inside the wheel is about the stupidest thing I've ever heard of- it should, if anything, be in the center of the car, with a traditional half-shaft and CV joints(slight loss)...or instead of using a standard automatic transmission, they should be using a CVT(constantly variable transmission) or something like Audi's DSG(Direct Shift Gearbox).

Two more words:

[osjedi]

Unsprung weight.

Making a wheel that is an electric motor would make such a heavy wheel thtat the vehicle would handle and drive like total crap. The huge weight of the wheels would require shock absorbers with huge dampening ability to keep the wheel planted on the road over uneven surfaces. It would ride like a dump-truck.

Re:Will it stand the test of time?

[sjames]

Interesting idea, but the real test will be with long term cost of operation.

While any new tech carries risks, this one has a lot going for it.

Diesel-electric is well proven as a technology. All diesel train engines use it. The difference is in the batteries. No battery pack could contribute much to storing the kinetic energy of a train. However, they do brake electrically. The big grid on the top of the engine is a simple resistance heater to dump the energy from the motors operating as generators.

Electric motors are simple things. The only moving part is a bering, a well understood part. Because of that, industrial motors tend to run for a very long time with minimal maintainance. These motors are not THAT different than other motors, so will likely have the same desirable characteristic.

Transmissions and differentials DO have a lot of moving parts subject to wear and tear. The generator/motor combo replaces all of that.

Engines running at constant RPM and load experiance less wear then on that runs at variable speeds and loads. The engine is smaller as well, so cheaper.

Because of th nature of the system, it doesn't need the latest and greatest cutting edge batteries. I don't know what they're using, but it probably isn't finniky expensive LiIon polymer.

A later generation could easily switch to composite flywheel once that's better proven and manufacturing costs come down. Because of the system design, it would likely be a drop-in replacement.

Even without the fuel savings and quiet operation, the new design might be worthwhile due to savings in maintainance and improved reliability.

But bumps "beat the daylights" out of the motor?

[Charles Kerr]

A Oct 2 article in the New York Times about e-Traction included a countering opinion:

But plenty of technological and economic hurdles must be overcome before such motors gain widespread use in transportation. "It is the future," said James Worden, founder and chief executive of Solectria, a company in Woburn, Mass., that has produced drivetrains for more than 100 hybrid electric buses. "Whether it is 10 years out, 20 years out or 30 years out."

Yet Mr. Worden of Solectria said that one drawback in the bus design was that the electronics in the motor were in direct contact with the road, not protected like the rest of the bus is by shock absorbers. If the tire hits a bump, he said, "it beats the living daylights out of any motor or electronics."

Re:this was done before by porshe

[f1rb]

Way before ... it was the Lohner -Porsche (N.B. The date at the top of this page is a typo).

May not be new but interesting nonetheless

[ajs318]

The fan on your processor is a spindleless, inside-out electric motor: the stator, with an electromagnet coil, is in the middle and the armature, with ceramic magnets, is on the outside. There is no commutator: the reversal of the current in the stator coil is done by means of a bridge of four transistors, and timed by one of the magnetic poles passing a sensor. So there is nothing particularly new in putting the armature on the outside of the stator.

Nor is there anything new in the way the control system would work. In Europe, most washing machines are front-loaders. The drum has to be able to revolve at a low speed in both directions for washing, and at a high speed for spin drying. Instead of using a gearbox, the motor's windings are split so they can be connected in various series and parallel combinations. Electronically there is no difference {a motor doing 300 watts of work is using 300 watts of electricity and just looks like a resistance dissipating 300 watts of heat} -- mechanically there may be an improvement {the speed-changer need only be a set of relay contacts, not a solenoid-operated or electro-hydraulic gearbox}.

Many trains in Britain {where not all railways are electrified} use a Diesel engine to spin a generator at constant RPM {everyone knows this is the most efficiengt way to run any sort of engine}, which then drives several small electric motors via an electronic control system which actually depends on the waveform of freshly-generated, as opposed to stored, electricity. I think this was invented by our baguette-munching neighbours at the SNCF {Societe/ Nationale de Cattle Freight by my own experience} but not sure so don't quote me on that.

So, all in all it's not much new. But hey, it's an interesting application anyway ..... and being a Diesel engine, it'll run quite happily on cooking fat, so the Dutch won't have to go to war with anybody when the oil wells run dry!

Batteries don't have to cost that much

[Tau Zero]

Lemme see if I can find that old link.... ah, here we go.

If you take a look at that graph, you'll see that even a lead-acid battery can last many thousands of cycles as long as they are shallow. The Yellow Tops in question are, I believe, rated at 55 AH (20-hour rate, don't ask me what discharge rate was used for the test) or about 660 WH nominal. The total throughput over 4500 cycles to 25% depth of discharge is over 600 KWH.

Let's make an assumption here. Let's assume that mass-production batteries like the Yellow Tops would cost about the same per AH as a deep-cycle trolling/starting battery does now. I bought a 105 AH unit for about $65 a couple years ago, assume $70 today or $0.66/AH or $55/KWH nominal. 4500 cycles to 25% depth would cost $(55/1125) or 4.9 cents per KWH. Depending where you're buying your juice, this is somewhere between one-third to one times the cost of your off-peak electricity.

Gasoline costs quite a bit more. At 6.67 lb/gallon and 0.4 lb/HP-hr, you'd get 16.7 HP-hr/gallon or 12.7 KWH/gallon; this is about 36.5% of the 119,000 BTU/gallon of energy that gasoline really carries. At $1.50/gallon you're already talking 19 cents per KWH. Hybrid propulsion using reclaimed (regenerated) energy appears to be quite a bit cheaper than making power from scratch, and charging from the grid when opportunity allows would be cheaper than buying fuel even at today's US prices. At typical European prices, it's a no-brainer.

That said, it makes you wonder why the in-wheel-motor hybrid scheme hasn't been done for the last 50 years. I recall seeing one of Ferdinand Porsche's early attempts to power a string of trailers using in-wheel electric motors... for World War One, to move war materiel. There is very little that's truly new under the sun.