I think we are getting hung up on the semantics of the definition of a hybrid... as far as I'm concerned everything mentioned is a hybrid of sorts.

 

The other missing link, is the fact that a HSD CANNOT be driven witout the electric motors. If you remove the electric motors, the ICE will not move the tires, but the other shaft of the power split device where one of the motors should be located. if you were to remove the electric motor and weld the shaft it was attached to so it can not spin, then the car would be drivable.

But in the end, ALL cars sold to day with a HYBRID badge are true hybrids. Some just have greater efficiencies than others.

Also, it is still yet to be determined if the series hybrids are really better than the parrallel hybrids. There are additional conversion losses by generating electricity and then converting it back in to rotational energy that COULD be greater than the ICE losses alone in a less than ideal operating range.

 

Agreed. This seems petty, determining what is a TRUE hybrid. Isn't the efficiency (MPG, or range on electricity alone in the case of an EV) what we REALLY care about? Tell more about THOSE expectations, rather than slamming current technology and terminology technicalities. Believe me, if you got the goods (for a reasonable price) - you'll have a market!

I agree also that we DO NOT KNOW YET whether a series hybrid will be more efficient or not than the existing hybrids of today. I hope so, because they sound SO promising.

 

Using an ICE of any kind to generate power for electric motors is very inefficient. ICE's just aren't that good. You'd gain more efficiency just by connecting the ICE to the drive directly, as then there aren't adding additional electrical and thermal losses.

Basically, every time you transfer energy, there will be some loss. There isn't any such thing as a 100% efficient energy transfer in the real world.

If you are primarily going to power by electricty, then it is far more efficient to just plug it in. No ICE is even going to close to the efficiency of modern day power plants in energy production.

But, as everyone is well aware of, the energy density and charge time of batteries suck compared to the energy capacity of gasoline. So unless you have a flatbed full of batteries (and a fast way to charge them without exploding) you're not going to get the same range.

The upcoming offerings have it right for the current technology. Most people don't commute very far, relatively speaking. So if you pack in enough battery to carry for that range, plus the ability to plug in, then you get really high MPG. For longer distances, it switches to a hybrid mode where both the ICE and electric motors power the vehicle.

But using a ICE to generate electricity for powering electric motors really is not a good idea. At that point you need something like a reforming fuel cell to get close enough in efficiency to make sense.

~X~

 

If the question were 100% efficiency, Xyrus's point is well taken. Easy to take our eyes off the *actual* lived reality, though: even an imperfect ICE - electric hybrid is significantly more efficient than ICE alone. And a plug-in/ICE -electric hybrid will be even more efficient. We could wait a long time for the perfect system, or we could celebrate what we have right now while tweaking the hell out of it. Just don't want us to lose sight of how, with an HCH II for instance, we can make a nearly 3,000 lb car with a 1.3 l ICE reliably get 45-50 mpg. I'll take it -- and whatever's better next.

--doug

 

Geeze..true hybrid? I am an engineer and fully understand the various systems be it series, parallel or what have you. If the vehicle has two power sources then it is a true hybrid and even then that definition is limiting.

I have a diesel suburban to pull my boat on the weekends. It can and does run on petroleum diesel, biodiesel and straight recycled veg oil. With all the mods I've done to it I consider it a hybrid albeit a loose interpretation of the concept.

"True hybrid"? That hints of arrogance when they all are true hybrids. Others have stated a similar point so I'll stop. Good luck with developing a retrofit system just don't bash the rest of the hybrid technology.

 

Don't get me wrong, I'm not saying anything negative about hybrid technology.

My point was simply that using an ICE to generate electricity for electric motors is more wasteful than just using an ICE to power the wheels.

The most efficient ICEs in production right now are in the Prius (37% including mechanical losses). If you add in the additional transmission, thermal, and electric engine efficiency factors you degrade the efficiency even further (at least by another 5-10%, most likely more than that).

The models coming out in the next couple of years do it the "right way" for the time being. They'll have larger battery packs for completely electric driving, then kick over to two-mode hybrid when that drains. To recharge the main pack you can plug it in, which uses electricity produced by far more efficient means.

For extra points, the upward facing surfaces of the car could be covered with multi-crystalline PV arrays to trickle charge the batteries (an average car roof could probably produce a few hundred watt-hours of power during peak sun).

~X~

 

Hi,
This is factually in error because it ignores the inefficiency of an ICE at low power settings. The problem is ICE efficiency decreases by factors of 2-3 when a 100 hp engine is trying to generate the 20 or fewer HP needed at slow speeds. At low speeds, a hybrid runs the ICE in a fuel-efficient power level to charge the battery and then shuts off. So instead of an ICE running at 15% efficiency, it runs at 30% and 90% of the battery charging energy is later used to keep the car running at speed.

I know this is a difficult concept to master so let's do a compare and contrast of an ICE only system versus a hybrid system:

ICE ONLY AT 35 MPH FOR 10 MILES

• ICE runs for 10 miles with efficiency of 15%

HYBRID AT 35 MPH FOR 10 MILES

• ICE runs for 5 miles with efficiency of 30% (same fuel burn!)
• ICE off for 5 miles using stored energy

The true secret to hybrid efficiency is improved ICE efficiency. In the case of the Prius, the ICE is shutdown. In the case of the Honda IMA systems, the low-end torque, the low power inefficiencies are fixed. This is where the true savings occur.

Bob Wilson

 

It seems that there is a misunderstanding. I am not disputing that hybrid ICEs are efficient.

I'm aware of how hybrids work. I'm also aware the hybrid ICEs are more efficient than conventional engines.

Here is my point, with more detail. Gasoline has a certain amount of energy per gallon. Even the most efficient gasoline engine loses 60+% of that energy to various thermal and mechanical inefficiency even before it makes it to the wheels. Let's start with a 60% loss for simplicity.

That gives an us an energy, let's say E. We are discussing two paths to get this energy to the wheels.

1. Direct mechanical. The energy is transferred through the normal means. This adds loses in energy before making it to the wheels (depending on the the drive train).

2. Battery storage, then transferred to electric motors to drive the wheels. Since we aren't using superconductors, there are losses due to transmission (usually a few %). Then there are the losses from charging the battery itself (depends on the system for losses but usually around 15-20% loss for good systems), then finally there are the losses incurred by the electric motor (electric motors are not 100% efficient, usually in the 90+% range).

Of the two paths, using the same efficient ICE, starting off with the exact same energy, path one incurs the least amount of energy loss.

My argument against using an ICE to solely generate electricity for electric motors is not efficient, and you'd be better off just using the efficient ICE to power the vehicle.

The new plug-ins are the "right way" to go about this. You have a relatively short amount of all-electric miles, then a standard two-mode after that with all the perks. The electricity coming off-grid is generated far more efficiently than any ICE could ever hope to accomplish.

~X~

 

Actually the ICE energy loss varies from best case, ~60% to 90% or worse. The term we use is specific energy and can be measured. The following chart shows the relative fuel efficiency of the Prius ICE converting fuel into mechanical energy:

At low power settings, under 1,400 rpm, the Prius engine becomes pretty inefficient just like all ICE. But the hybrid transaxle plays a trick by forcing the ICE to not only move the car forward but also adds a load, charging the battery. This battery charging load moves the ICE rpm into an efficient ICE area. Once the battery is charged, the Prius will shutdown the ICE and use the stored energy, with at most a 10% loss, to sustain speed.

So let's put this in perspective:

• at the lowest power settings, typical ICE efficiency falls from 30% to 15% efficient
• by charging the battery and providing power, the ICE power output goes up and the efficiency to 30%
• by turning off the ICE, the battery returns 90% of the stored energy to sustain speed

The key is the Prius can and does keep the ICE in higher efficiency, power ranges and stores this efficient, excess power in the battery. This excess power is then used to sustain the speed. The generator->battery->motor losses are very much smaller than the energy losses from running the ICE at a low-power, inefficient range, less than 30% thermodynamic range.

Some utilities use a similar technique by pumping water up hill to a reservoir at night. This keeps their generators and turbines running at peak efficiency. Then during the day, they let the water run through generators to make power needed during the day. The pumping losses are a fraction of the energy that would be lost if they tried to throttle back the plant.

Bob Wilson