Serial / Series Hybrid Tracker
 

Here's a list of serial / series hybrid generators (aka range extender, aka EREV aka REEV):

Lotus: http://bioage.typepad.com/.a/6a00d83...3e21970b-800wi

GETRAG serial / parallel: http://bioage.typepad.com/.a/6a00d83...039c970c-800wi

FEV has two: Green Car Congress: FEV, Inc. Develops 40kW Range Extender Unit
http://www.blogcdn.com/green.autoblo...wankel-apu.jpg

FVT: http://futurevehicletechnologies.com...e-down-069.jpg
http://img.photobucket.com/albums/v7...tedtoFVTge.jpghttp://img.photobucket.com/albums/v7..._genset054.jpghttp://img.photobucket.com/albums/v7...Tgenerator.jpg

Capstone C30 turbine genset:

http://bioage.typepad.com/.a/6a00d83...4052970c-800wi

Chevrolet Volt (serial / part time parallel):

http://images.thecarconnection.com/l...00326238_l.jpg

Here's a different take on a serial hybrid:

Company Announces Diesel-Powered, Range Extending, Towable Trailer for Electric Cars | PluginCars.com

It has been done before, but this is company that intends to build 'em.

There are "obvious" losses in any drivetrain. But, EV's are by far better than ICE's in most driving situations. Only steady-state highway speeds are better in an ICE, and not coincidentally, a series/serial hybrid mimics an ICE on the highway; but it does so ALL THE TIME. So, the actual drive motor is electric which is much better in most situations, and when the ICE is needed, it runs in it's ideal conditions.

Series/serial hybrids have several big advantages over pure parallel-only hybrids:

The ICE *should* be run at a single RPM driving a fixed load. (Which is is not how the Volt uses it -- the Volt is not an ideal series/serial implimentation.) This makes several things possible:

This lets the engine be optimized for that one RPM, and we all know that this is ideal situation -- for parallel hybrids, too. (They run best at highway speeds when they don't need to use their transmission.) So, in the case of an Atkinson cycle ICE, this means it can always be at about 38% efficiency.

This reduces the required displacement and reduces the maximum torque, because the battery can be used as buffer, and only has to meet the average power level.

This reduces the weight of the engine, it's cooling system, the size of the fuel tank.

There is no multi-ratio transmission -- so less weight again. The need for a transmission is an engineering compromise -- the engine cannot meet the torque requirements, and it must be run at all sorts of off-peak conditions.

There is no idling the ICE; by definition, if it running it will be running at it peak efficiency actually doing work at all times when it is running. If you add a stop/start, then this is more complex.

You do not *need* to run the ICE when running at highway speeds, as you would in a true "Parallel-only" hybrid. So for short drives that under the range of the battery, the ICE never comes on.

If you are on a long drive with a lot of it at slow speeds, you cannot extend the range of electric-only mode. So, the ICE cannot contribute if the battery is depleted, and the driving needed is slower than where the engine can be used.

The ICE engine can be located in the car independent of the drivetrain; since there is no mechanical connections to the drive wheels.

Both series/serial hybrids have regenerative braking, and that's a good thing. Both types also run the ICE in it ideal mode, though on a parallel hybrid, the load is only constant on flat ground and no gusting winds. And the speed of the vehicle has to be linked to the ICE's RPM, in order for it to be peak efficiency, so this limits it's flexibility.

Parallel hybrids are more difficult to build: either they drive the rear wheels, while the electric motor drives the front (for better regen), or there needs to be a additional drive wheel. In a parallel hybrid, the ICE must be located to make the best connection the drive wheels, and this means it cannot necessarily be located for best cooling aerodynamics or weight distribution. The GM Precept is the only design I can think of that is a true parallel-only design, and they have a transmission on the ICE, and the ICE is in the back, making cooling more difficult and limiting the storage.

http://www.familycar.com/Future/Images/GM-Precept2.jpg

The "fifth" wheel type of parallel hybrid is even harder in many ways. It is aerodynamically and mechanically challenging. Lowering/Lifting the wheel needs to be figured out...

Both of these types of parallel-only setups require a second mechanical drivetrain, adding weight.

If the both the electric and the ICE motors drive the front wheels, then this adds a transmission and a clutch, and a more complex control system.

*******

In a nutshell, a series/serial hybrid has all the advantages of an EV, and uses the ICE at it's best RPM, and the ICE can be smaller, with all the related weight savings.

A true parallel-only hybrid is harder to implement, and is less flexible in the type of driving, and in it's physical set up. So, while it may have theoretical efficiency advantage (at a particular speed on flat ground and no gusting winds), I think if you cannot have the pure EV range (which is by far the best in most situations), then a range extending series/serial genset extends the advantage of the EV better.

The new NBM "Hummingbird" batteries might make the need for hybrids moot.

Edit: The X-Prize Knockout Round is important to consider.

The average of the 6 hybrids that used their ICE's during the contest (which did not including the FVT) was 61.26MPGe Please note, these are all parallel hybrids.

The average of the 5 internal combustion drive cars was 82.92MPGe.

The average of the 12 vehicles using electric drive MPGe (I'm including the FVT in this) was 134.7MPGe.

So the lowest MPGe of an electric drive; the AMP'd Sky was 86.7MPGe (Tango was 86.8), while the best of a car with an internal combustion is the Edison2 #97 at 101.4. (Actually, the FVT has a ICE powered generator onboard, but did not need it *at all* in the X-Prize. It would be great to see how the eVaro does for MPGe in charging mode!) The hybrids all were all below the 67MPGe -- except the WWU at 92.5 (and the FVT).

The FVT got 152.5MPGe while carrying the weight of the genset, and the genset would have to be pretty horrible to lower the average MPGe to below the WWU, which was by far the best hybrid -- and it (the WWU) was a EV drivetrain combined with an Insight drivetrain; so it was a parallel hybrid/parallel hybrid hybrid, so-to-speak.

Dude, do an accounting of the losses of a series drivetrain, just once, without the rose colored glasses. The "efficiency envelope" for an ICE is also much larger than steady state cruise. This seems like a very unbalanced viewpoint you have.

Yes all drivetrains have losses, but driving the wheels directly gives the volt a 15% boost in efficiency, so that should be a clue as to how sloppy series is.

Series/serial hybrids are essentially EV's, with a generator onboard. They beat parallel hybrids easily in efficiency -- look at the X-Prize data.

What have I said that is incorrect?

Hybrids did a big fail in the xprize.

"They beat parallel hybrids easily in efficiency" is completely unfounded. You have absolutely no data to back that up. I think it is irresponsible.

I think this comes down to if you are assuming stupid drivers or smart ones.

If I know I have to go 300 miles, and I have X battery charge and Y gallons of gas, and a few gears to choose from, I know for 100% certain that I can get to my destination with much less gas by using the engine to drive the wheels when it makes sense (i.e. when I can hold it within %85 of bsfc peak, which is almost 100% of the time), than I can by using the engine to drive a generator with a fixed 15% loss.

I also think it is a mistake to cater to stupid drivers, as you only breed more stupid drivers. Think of how many folks can't even drive a stick shift now.

The speed you can drive ultimately is determined by the roads you are driving on, the conditions (weather, etc.), traffic, etc., and if you are required to go slow at the beginning, and at the end of the drive, then a parallel hybrid won't help you go slow once the battery is depleted.

The FVT eVaro has a 22kWh battery and a 1100cc 20kW genset with a 2.2 gallon gasoline tank. It goes 125-150 miles in EV mode, and in charging mode it can go another 300-375 miles. So, if it uses ~20kWh of electricity and 2.2 gallons to go a total of ~425-525 miles, using the X-Prize spreadsheet, that is 152-188MPGe average.

The battery holds usable energy equivalent to 0.58 gallons of gasoline.

http://img.photobucket.com/albums/v7...o/VID01922.jpg

The electric only energy use is ~213-255MPGe. During the charging mode, that is 136-170MPGe. Those are the performance numbers; not theoretical mathematics.

So, the charging mode is 20-47% lower efficiency than in EV mode. That difference would be combination of the engine and generator efficiency; since the electric motor is in both sides of the equation.

++++++++

Do you have a real world example of a parallel hybrid performance?

The only one I can think of is the original Honda Insight.

Again, a smart driver can compensate for this quite adequately, especially if given some gears to choose from, by managing the different energy stores.

Say I am going on my 300 mile trip, I putter around on battery till I get to the hiway, then I stop using the battery excepting for keeping the lights on, and leave myself sufficient reserves to get to my destination charging station when I get off the hiway again. What I am assuming is that the driver has complete control over when to use electricity or gas or both and can make the appropriate decisions based on knowledge the car does not have.

the thing that makes the volt a good example is that it is still very much the same car, so it is far more an apples to apples comparison than fvt to ??? If series is better than why does the volt need a parallel mode to get better efficiency?

Also you are introducing mpge to the discussion, which is a contentious measure of efficiency.

The FVT is a two seat vehicle, so compare it to the Insight?

The Volt is not an ideal series/serial hybrid: it does NOT run in charging mode, but instead varies the RPM to provide power to the motor. It only goes into parallel mode when it needs more torque than the two electric motors can provide, and it weighs a lot more than it should. It is not an optimized EV -- and a good series/serial hybrid has to be an efficient EV.

The Volt uses 176-352wH/mile (8.8kWh / 25-50 miles range), while the eVaro uses 133-160wH/mile (~20kWh / 125-150 miles range). The Volt uses ~8-9 gallons to go 300 miles in charging mode, while the eVaro uses ~2.2 gallons to go 300-375 miles, so if we double that to move 4 people, it is still at least 2X better than the Volt.

Do you see a pattern here?

MPGe is not controversial -- it is repeatable and merely a conversion spreadsheet to compare energy use in various vehicles. We are not comparing carbon used (emissions), just energy used. Besides, the electrical use of the two can be compared, and the ICE mode can be compared separately if you want -- MPGe is just the simplest way to combine everything to a common denominator for an overall comparison.

Neil -

I love the concept of the series-hybrid because of the single-RPM BSFC sweet-spot argument. However, it seems like no one has made one for "normal" 4-wheeled cars. Do you think we could extrapolate the specs of an FVT eVaro into a 4-wheeled 4-passenger equivalent and see what MPGe it gets?

CarloSW2

I think 3 vs 4 wheels make virtually zero difference in efficiency. The aero shape (narrow at the back) matters, but the number of wheels is negligible.

that isn't what the video said. Not sure where you got that from. I do know it goes out of straight series mode when it wants to be 15% more efficient.


it absolutely is, at least around here. Separately listing the energy sources is the only sane way to make sense out of it. If you want to see the electric bias in mpge, look at the all electric wave II which basically was pegged at 190 mpge for the knockout efficiency hiway test. Given the fvt is largely an electric car, it is no suprise that it got good mpge marks. Not a function of series-ness.

The volt is the only apples to apples example out there that I know of. FVT to insight?!? That doesn't make any sense at all. You are saying to compare an xprize trike to a production car and say that this is the basis for saying how great series is? The only thing that changes in the volt is a couple clutches, otherwise it is the same vehicle, thus infinitely less variables than you are trying to introduce.


25% less rotating wheel mass and contact area has to be good for something.

Contact pressure/rolling drag is based on weight, not the number of wheels.

The Insight and the eVaro each carry two people and they are the best examples we have of parallel and series/serial hybrids, and this makes them the best concrete way to compare these types of hybrids.

Compare the Volt to what? Comparing it to itself is not a comparison.

Okay, I watched the videos again, and it is used in *reduced* torque demand situations. Look at video #2, especially from 4:00 to the end. The engine does not always engage physically to drive the wheels above 70MPH. This is reiterated in video 3.

I think the biggest improvement in the efficiency is the change in the reduction gear ratio, by driving the the ring gear with the ICE (transmitted through the generator/2nd electric motor), which lowers the RPM of the primary traction motor.

So, they are using the second electric motor, or the ICE to spin the ring gear to reduce the reduction gear ratio, which lowers the RPM of the traction motor -- so they are expending energy to save some energy overall. I would think that a 2-speed transmission or a variable ratio transmission (over a fairly narrow range) would have been a better way to go?

Instead of just changing gears, or adjusting the ratio of the reduction gears, they spin the outer ring gear, which uses power all the time, rather than momentarily.... Sheesh, that doesn't make much sense to this layman!

Old thread on series/serial hybrids:

http://ecomodder.com/forum/showthrea...ids-13213.html

http://www.blogcdn.com/www.autoblog....rain-630op.jpg
(click on image for link)

Here's a serial hybrid truck, that has been developed by a supermarket chain. They are concerned with efficiency, emissions in congested areas, and with noise.

http://www.colruytgroup.be/colruytgr...genontwerp.jpg

Here's a brief video (they turn down the music part way through, so you can hear the truck in motion):
http://www.colruytgroup.be/colruytgr...=400&width=500

http://bioage.typepad.com/.a/6a00d83...9b2c970c-800wi
(click on image for link)

An interesting use for a serial hybrid:

http://bioage.typepad.com/.a/6a00d83...1df6970d-800wi
(click on image for link)

[Emphasis is mine.]

Military turbines top out at 56% eff, single RPM dc generators top out at about 95% eff, dc charge controllers top out at 98% eff depending on load, battery charging tops out at 80% eff with power to the wheels not having this loss.

So lets see, EVEN IF we charge the battery instead of directly driving the electric motor you end up with a minimum 28.8% EFF charging batteries and a max EFF of 52.1% driving the electric motor.

Why don't I take the motor loss in account? Because all of the ICE BS never does either, ICES also run 0%-35% real world EFF depending on load

Cheers
Ryan

Had a little trouble believing that one, until I read this in the linked article: " The partners are presenting the two-seater motor glider..." So it has the motor running & recharging the battery when a normal motor-glider would be soaring with engine off.

I've also seen pure electric self-launching sailplanes.

not sure about motor glider here.


Cut consumption by 25%, in the same breath as "Wankel"? My BS alarm is going off.

Electric airplanes are also a bonehead move, that is the one application that would benefit most from liquid fuel, preferably of the renewable variety. Energy density/energy to weight of electric is atrocious by comparison, and size and weight are bad for airplane efficiency.

What? So you are going with %56 engine efficiency now? and %95 for generator efficiency, and %98 efficiency for the controller? And no mention of motor efficiency? Can you put your hands in your head?

Are you also assuming that you have to have a series electric hybrid to use a turbine? Turbines have been powering wheels for a long time, i.e. the hydrokinetic transmission in an M1 tank.

How does any of this apply to a "modder" anyway? You going to put a turbine on your citicar?

In hybrid electrics, I've found examples of:

• electric power <<< engine power - examples are GM's and other autostop, BAS, systems, ~5 hp EV vs. ~170 hp ICE. These are 'greenwash' systems such as the Chevy Malibu.
• electric power torque assist << engine power - examples are the Honda hybrids, ~15 hp EV vs. ~100 hp ICE. Because the engine torque provides the bottom end, a substantially smaller engine can still provide adequate driving experience.
• electric power drive < engine power - examples are the Toyota drive hybrids, 30 hp EV vs. ~70 hp ICE (NHW11.) The car has a non-trival amount of electric power, enough to handle slow speeds, ~25 mph, for distances up to a mile.
• electric power drive ~= engine power - examples are the Toyota plug-in hybrids. I don't have the EV vs. ICE power ratios (too lazy to lookup) but they extend the EV distances to 10 miles and speeds up to 50 mph.
• electric power > engine power - examples are the GM Volt and several concept cars including the Jaguar C-X75. Sometimes called extended range EV, the only production version is not so impressive on gas power.

That a hybrid electric can be built does not mean it should be. In the case of the Jaguar C-X75, this is an experiment investigating the limits. I support experimentation but there is a big gap between what can be built, a lab experiment, and a practical hybrid electric.

One serious flaw of the Volt is not so good gas assisted mileage. What this tells me is there is an efficiency problem in that design. Without a Volt to test, I can not diagnose the problem(s) but the gross mileage numbers indicate they are not able to equal the Toyota efficiency. It is not even close when the vehicle volume and non-electric, miles per gallon. But it is also GM's first production hybrid of merit ... the Precept was the unbuilt, GM prototype of the Volt, 10 years ago.

Bob Wilson

here is more info on that airframe and the stock 80hp engine
Diamond HK36 TC Super Dimona performance and specifications

I understand the concept, but a motor glider isn't the best example (especially since the prop can feather). I have little doubt that pulse and glide in this plane would simply blow away any cockamamie gizmo designed to automate away skill, and not bother anyone "behind" you.

And I have to think that a second engine (or extra cylinders anyway that can disengage) would solve the problem of right sizing the engine for best bsfc constant cruise and acceptable takeoff/climb power with less weight and size and cost penalty. That is what Rutan did with the voyager.

Not so bonehead for the self-launching sailplane application. You only need 10-15 minutes run time, and you don't have to mess with gas, starting, noise, vibration... It's basically all the advantages of my electric lawn mower over a gas one.

Might also look at how many electric RC airplanes (and helicopters) there are out there.

In my experience (a lot of long-distance drives in a Mazda RX-3, back in the '70s), the Wankel isn't at all bad at a constant, fairly high RPM. It would cruise down the interstate for hours at 70+, but the varying speed & load in city driving would kill the mpg.

That is what I do for a hobby actually, I prefer the non powered sailplanes personally (i.e. bungee launch). I have done fuel planes, and they ARE far superior in power to weight, as well as run time, and sometimes cost, but they are also toys, so spilling nitro in your back seat takes a lot of the fun out of it. And they also don't generally have a payload like real planes do. You are advocating convenience over efficiency here, and the larger scale of a commuter plane means greater losses to avoid something as routine as refuelling a car.

It makes sense for a 10 minute for fun RC flight to carry batteries, but it doesn't make sense if you are serious about efficiency on a larger scale.

This is the Siemens serial hybrid airplane:

http://www.wired.com/images_blogs/au...pi-660x476.jpg
(Click on image for link)

And that is why it won't reach production, because it is stupid. They have a plane and they are still talking in "future tense" about wanting to save 25% of the fuel. They haven't done it yet apparently.

“We want to cut fuel consumption and emissions by 25 percent,” Dr. Frank Anton of Siemens said in a statement.

Well I have already outlined a few ways to do that which have been done before. The series aspect doesn't fit the application, but will probably sucker in a few grants in the process.

But I don't think anyone is talking about commuter planes, they are talking about self-launching sailplanes & light sport airplane. Stuff you fly for fun, and expect to pay for that fun.

I don't know if you've ever flown either sailplanes or small planes, but with either you often fly from small fields where there's no fuel, so either you have to shlep in a bunch of 5-gallon cans, or fly to a larger airport whenever you need gas. With sailplanes, you've got the additional problems of waiting & paying for tows, which is both an expense and a waste of time if you have one towplane and several people wanting to launch.

"The technology, which is intended for later use also in large-scale aircraft, will cut fuel consumption and emissions by 25%, compared to today’s most efficient aircraft drives, according to Siemens."

I have not seen any scope limiting statements. And I don't believe this is all so you only have to schlep 6 gas cans out to the towplane instead of 8.

Tip, figure out how to add just enough fuel + safety margin between tows, quickly, to tow the next glider so you are not spending fuel lifting unneeded fuel into the air.

Tip: Understand what you're talking about before offering advice :-)

To elaborate, what I was talking about was the WAIT. You have two sailplanes wanting to fly, and one towplane. Obviously, one has to wait 10-15 minutes or so for the towplane to take the other to release point & return. If both are self-launching & electric, the second can depart as soon as the first has cleared the runway, plus you don't have to pay for that expensive towplane at all.

Tip, don't be a complete dumbass :)

Why are you so bent on not refueling? You are talking about a couple hours recharge time for your imaginary fleet anyway, sheesh! Then after 1000 launches you can go buy new batteries for all of them. Your specific example is just stupid. Escpecially since this is a hybrid thread and you are still going to have to refuel the stupid thing anyway.

If you want a sailplane that can self launch, and has ready fuel then buy a motor glider and go to an airport that has fuel. You make too many problems for yourself, but they are your problems. I don't really care about the nuances of your imaginary amusement park. There are people and cargo to move long distances.

And finally, if the death knell of series hybrid hasn't been heard loudly enough, here then is an actual example of an engine tuned for the task that cannot beat my 15 year old saturn for peak bsfc...

As well as these guys reporting best observed bsfc of a ~235g/kwh gasser which beats my saturn of < 250 by maybe 4% but doesn't come close to a tdi @~195g/kwh being about 20% away.
"I have seen 235 g/KWH on a 625cc per cylinder direct injection (piezo spray guided) Spark ignition engine running at Lambda=1 at best point. Injects at about 200 bar pressure. Engine also has twin cam phasing. 11.3:1 CR."
http://www.eng-tips.com/viewthread.c...185833&page=13

Tip 1: Don't display your complete ignorance of a subject in public.

Tip 1a: If you must do so, at least do it politely.

Or in other words, it's people who fly (and sell) sailplanes and light planes who're building the electric & hybrid planes. No doubt some are doing it just for the gee-whiz factor, but there's quite a bit of accumulated experience that thinks it's workable.

Err... This little thing about CO2, you know? Plus gas prices ($7/gal avgas), the inconvenience, etc.

And so? I fly for an hour or two, then it's parked for days.

Yeah, just like I had to replace the batteries in the Insight after a couple of years. (That's sarcasm - it's still on the original set, 11 years from new.)

Nobody cares about your imaginary problems and self imposed roadblocks. Before you were complaining about waiting for a tow and making money and whining about refueling, and seem to have forgotten that hybrids still need refueling.

Go buy one or shut up.

A small 56% eff turbine would never power anything at variable RPM without being a 30% eff turbine, not to mention it ramps up very slow.

That is the reason for a series/serial hybrid is to take advantage of the nearly double efficiency of single speed operation.

Also I didn't mention the motor because there are AC motors that can operate at above 95% at specific RPM and loads, using this as comparison is about as dumb as stating a prius is 38% eff when it really rarely is there except by people who do the extreme pulse and glide to 40ish MPH with prius.

So in other words I am admitting you aren't comparing apples to apples and the real world in both the prius and the situation I described varies from the absolute max in theory most of the time.

Unless of coarse the turbine is putting out exactly the amount required by the AC motor at its peak efficiency in which case battery losses go to zero.

I would if I could buy one small enough, the only ones I know of that were cut/crimped/dropped into passenger vehicles is when they were rather big vehicles, like the hummers, antique hobbiest cars and some racers.

Also the topic of this discussion was serial hybrids, the situation I described is the only situation that is described in scholarly papers on the advantage of the serial hybrid.

Any other situation is not usefull to persue.

In my round about way I was stating there is promise to serial hybrids but not by using a 5hp Kohlman gas generator to drive your pickup truck 20mph.

I think I know what you are saying, but I do want to draw a line in the sand. P&G is what sets the bar when comparing efficiency, it is entirely well know here and here is where the discussion be. You cannot replace a driver/pilot with a computer and not account for what that driver/pilot can do with mere training.

You have to assume that there will be an optimum technique for operating this hybrid configuration as well, then match up all the speeds/parameters/efficiencies (including charge and discharge losses if it is actually an advantageous strategy) and figure out what a thinking pilot can do before and after. At least then you will know the upper limits on efficiency rather than starting from complete fudge.