Defining Terms : Parallel vs. Series Hybrid

[lakedude]

On the whole series thing it should be noted that the defination of a terms must take into accout the field in which it is used. The abbreviation RC can mean:

Road Construction
Royal Crown (cola)
Rosin Coated (photography paper)
Radio Controled
Reinforced Concrete
etc.

Parallel lines are one along side another in the same direction that never touch. Series can mean one thing after another or a bunch of ball games.

It really depends on what the writer or speaker intends. To me the Honda's are in series because the ICE and IMA are in a line one after another. If the industry standardizes on a different definition then my understanding would become incorrect.

[Foxpaw]

We could call the Honda hybrids "coaxial." That's much less ambiguous and it doesn't require likening to an electrical analogy that doesn't really apply in the same way anyway...

[b1shmu63]

Right! COAXIAL, duh, bonk, bonk, why didn't I suggest that!

Perhaps the Toyota should be called co-dependant as the gas motor will not start or run properly without the electric motor(s) and the electric motor will only drive an impractically short distance without the gas engine.

Then again, thud, the main motors on the Prius are coaxial too, though not not on the same shaft and bearings. Shucks, grumble grumble.

[Yves M.]

I see the confusion. The Insight engine and IMA motor are physically in series as they are bolted together. But that is besides the point here.

One needs to thing of the end result propulsion. The term series/parallel is tought to be like in the electrical term. The engine is a battery and the wheels (load) are a lamp. Each battery has an On*/Off switch.

With parrallel batteries connected to a lamp, any of the battery can separatly give current to the lamp.
With series batteries, each battery give to the next until the current reaches the lamp. If one battery is Off, no power can result.

So the Insight can not be a series. Each engine can drive the wheels separatly, meaning with the other engine to Off. If it was series, the gas engine could not be turning the wheels alone.
As for the IMA engine turning the wheels, one needs to have no gas left (one or two persons did experience the not efficient EV situation)

Like you guys wrote, more precices terms could be used. But in the parallel/series, there is no doupt for me.

[Foxpaw]

Hrmm, but the IMA and gas motor are not truly independant as they can affect the other's RPMs.

[Yves M.]

Here is what I found from Honda about parallel and series hybrid

http://www.md92raid.100freemb.com/pub/i ... ge102.html

It says "The Insight employs a parallel system"

[b1shmu63]

Thanks Yves. A Diesel-electric locomotive or a Diesel-electric ore truck would be an example of series hybrid system.

[clett]

Originally Posted by xcel

While towing this monstrosity, you can only expect ~ 30 - 35 mpg when on the trailer unfortunately. That is pretty pathetic actually.

Understandable though. The T-Zero can go about 6 miles per kWh (300 mile range from its 50kWh battery pack) in EV mode, so let's say 5 miles per kWh when running with a heavy, draggy trailer behind it (prob even less).

The next problem is the type of generator (it's gasoline). Spark ignition and a low (prob 10:1) expansion ratio mean an efficiency in converting chemical energy to electrical of only about 20%. One gallon of gasoline contains ~36kWh, so with an old-school generator like the one tacked onto the back of the T-zero, only 7.2 kWh will be converted to electricity for propulsion. Hence, 1 gallon of gasoline used in this way should give 7.2kWh and 36 miles travelled (ie 36 mpg in this mode).

BUT... imagine if we put in an engine designed specifically for the purpose of maximising series hybrid efficiency. We don't have to worry about torque, or idling or responsiveness at all - all of those constraints are abandoned, allowing us to design an engine purely for thermodynamic efficiency.

My calculations suggest that an atkinson cycle compression ignition engine should be capable of 60% efficiency - yes, significantly higher than the much touted 50% efficiency of the hydrogen fuel cell. As biodiesel contains ~39kWh per gallon, at 60% efficiency a series hybrid T-Zero (or Insight) could extract 23.4 kWh mechanical energy per gallon and with an efficient generator and motor, 22.5 kWh at the wheels, or 112 mpg when driving in this mode.

Series hybrid, it's the way forward!

[Yves M.]

I have read the "caculation" section. I find it very interesting.

Although I am no expert, I do dought that you could go higher than the 50% of a boat engine. Those already are large and turn at very low speed (basically Diesel turning at a Steam engine maybe 800 RPM max) that allows much of all the explosion to push the piston.

I found it strange that you spoke about series Hybrid while the person who responds talks about Parallel and the Prius. I see no relation to this. It is an EV thing or Series hybrid only.

You'll need an engine that is not too large but still gives a good enough KW output to drive on the highway. So a Miller is best output/weight ratio.

You wrote about 70 BHP but I think that such big horsepower for a high % efficiency engine will be too large. Less HP is needed to reduce engine size. You'll need the HP at a very low RPM, probably around 1000 rpm.