You've checked the usual suspects, I trust? Road and Track, Top Gear, those folks? Or do you require more specific data?

The only thing I have heard about hybrids that actually scares me a little bit is that there were cases where in california when they first came out that said in accidents, the battery damage had to be cleared up with a hazmat team which cost big bucks, that your insurance company did not cover. This may not be related to your query, but I felt I had to mention it.

I don't know how detailed your research needs to be, but Wikipedia has a good overview of the different types of hybrids. It might help you narrow the rest of your research to what is most relevant for you.

RJ

If you are looking for the good and the bad in your anaylsis, check out Diesel Power Magazine. They did a real life (L.A. version) driving comparison between the Toyota Prius and a diesel powered VW Jetta. They did city/freeway driving & found they both were getting between 46 to 49 mpg. Hybrids become more gas powered than electric on long drives.

Personally, I think Hybrids are a nice selling point, but a waste of effort. You have the disposal issues with the batteries, dangers to rescue personnel in accidents (power trunk lines) or HazMat cleanups as someone already pointed out, and you're still dependent on petroleum even with E85 (15% petroleum), whereas Diesels can get you the comparable mpg, more power, don't have to be dependent on petroleum (Bio), and don't have the dangers associated with Hybrids.

Trying to use batteries to power vehicles is still futile IMHO, secondary energy and all that. Hybrids conceived to use significant amounts of electrical energy have to be worse, you're carrying around two power plants for goodness sake.

Trying to recover the vehicle's kinetic energy instead of throwing it away into the atmoshpere on the other hand seems very worthwhile. I'm amazed we still allow friction braking! OK it depends very much on the type of journeys. This could have been realised long ago (electrically, compressed air...).

I still marvel, however, at the silent getaway achieved by, e.g, the Prius. Remind me of a steam car.

Batteries have come a long way, but not far enough, and you still end up with significant conversion losses.

Sorry but I've not addressed the question but there's masses of material on the web. Check out 'serial' and 'paralell' hybrids.

The Three Fundamental Efficiencies of Hybrid Technology - by Gavilan- March 12th 2006

In transportation based hybrid power production, how the power is produced takes a back seat to how the power is processed. The three fundamental efficiencies of refined wheeled vehicle hybrid power processes are "Prime Mover Power Averaging", "Regenerative Braking," and "Peaking Power."

Power Averaging:

"Power Averaging", also referred to as "load averaging or load leveling", allows maximum power output of the prime mover to be reduced to that slightly greater than that needed to cruise on level terrain at maximum sustained velocity. This reduces prime mover (engine) mass and volume; offsetting the mass and volume of the required temporary storage device.

Peak process demand in an automobile or other wheeled vehicle occurs during acceleration and grading (climbing hills). Existing hybrid systems translate this demand real time to the prime mover. In the next generation of hybrid automobiles the prime mover will operate at a near constant output from start up to shut down. The prime mover will feed near constant power into a temporary storage device (battery, capacitor, flywheel, or hydraulic accumulator) and the variable real time demand power will be pulled off that storage device. This will allow for a very significant reduction in maximum power requirements of the prime mover, optimize prime mover power production, and allow the introduction of prime movers not well suited to rapidly variable demand.

With Power Averaging as a primary efficiency of hybrid technology, the fueling algorithm of the next generation of hybrid automobiles will be a bit more complex than a simple iterative program. The coming generations of automotive control computers will "remember" power use based on both "routes" and "habits", calculate average demand, and de-couple operator control from prime mover demand with the ability to handle unanticipated variability of daily commuting. How that will be accomplished is beautiful in its simplicity.

The reciprocating engine dominates automotive technology because of its ability to respond rapidly through a broad power range. Power Averaging will allow the adaptation of prime movers that, although may not respond rapidly to power variation, operate at very high efficiently when operated at a near constant output. Given modern materials, the economics of scaled production, and the primary fundamental hybrid efficiency of Power Averaging, the choice of prime mover technology will be expanded to include Turbine and Sterling technology as well as existing Clean Diesel Combustion,conventional gasoline powered reciprocating engines, fuel cells, or any other primary power technology.

Regenerative Braking:

Regenerative Braking can be described as the recovery of kinetic energy (energy of the vehicle mass moving) to stored energy through numerous regenerative braking methods. Prior to regenerative capable hybrids, highway driving was more fuel-efficient than city driving even though aerodynamic losses of high speed highway driving far exceeded that of low speed driving in stop and go traffic.

In stop and go driving the energy conversion process can be described as the conversion of chemical potential energy of the fuel source by the prime mover, to kinetic energy of moving vehicle mass, to friction braking heat loss. The energy loss is directly proportional to the number of stop and go cycles. The multiple cycles of this conversion loss in stop and go driving can greatly exceed that of aerodynamic drag in constant state highway driving. Existing hybrid systems now regenerate significant amounts of energy lost during braking and this fundamental efficiency is expected to radically improve as the power and energy density of the temporary storage devices continue to improve.

Peaking Power:

"Peaking Power," when described as a fundamental efficiency of hybrid technology, refers to short term/ high power supply of energy to the power train from a temporary storage device during the peak demand periods of acceleration and grading (climbing hills.) This allows the drive train to be supplied power at rates much higher than the maximum power rating of the prime mover for short periods. The prime mover must still be capable of producing a sustained power slightly greater than the power required to cruise at maximum sustained velocity on level grade, but the cruising (or average) demand is much less than peak demand.

The coming generations of hybrid vehicles will have the operator controlled capability to rapidly accelerate to velocities significantly greater than maximum sustained velocity. This will be accomplished by summing the energy available in storage with prime mover output. As the storage device discharges, the sustained operating velocity will fall back to where prime mover power is balanced against drag and grade. The drive train will be the limiting factor in accelerative performance but the accelerative performance of yesterdays "muscle cars" may pale in comparison to the accelerative performance of a hybrid with a "muscled" drive train.

I am sure there will be more variations in storage and conversion methods but "Prime Mover Power Averaging", "Regenerative Braking," and "Peaking Power" will remain fundamental efficiencies in hybrid technologies whether it be wheeled vehicles, small unit electrical power production, or the myriad of other applications.

In closing I want to say the potential for significant enhancement of transportation efficiency still exists in both automotive and rail applications. Energy saving returns can come a lot quicker and cheaper than reinventing the technology. We have begun by sequencing traffic lights to traffic patterns and may soon expand that concept out to a 12,000-ton train that may never have to stop for a meet.

So you would argue that a hybrid can be both heavier and more fuel efficient than a conventional SI/CI powered car. It is the argument that brought hybrids into being.

I maintain that a serious attempt at reducing the mass of vehicles, incorporating regenerative braking and utilising the best powertrain technology available in its most compact form will yield a product far more envornmentally sound than a full-on hybrid with significant electrical storage. Mass = material consumption and energy in processing and the material in the batteries has significantly greater environmental impact than most of the other parts. What's important is not just the fuel usage during a vehicle's service lifetime, but the environmental impact of all the material and energy that went into making it, using it and disposing of it afterwards. I think we should include design, development and manufacture.

Hybrids are an interesting, sincere attempt at addressing one aspect of the environmental impact of passenger vehicles but cannot be seen as the solution to the need for sustainable transport.

As regeneration efficiency increases the mass variable becomes less important.

You forgot a very BIG part of the equation. Aerodynamic efficiency - ie: Aerodynamic cross-section and coefficient of drag.

Here is what you will be driving in the future. The Power/drive train. It will be a heat engine/generator but will operate at near constant output feeding in series with a storage device and regenerative capable - 4 wheel hub motors - with independent traction control in both acceleration and regenerative/emergency braking. Its acceleration will be limited only to the wheel road cohesion. Sustained cruising velocity will be where the drag and max horsepower of the prime mover balance with burst speeds probably double or more of that. Grade-ability based on storage capacity, but quite good.

I'm still a doubter. I'd prefer to see something a lot lighter. Now you're talking in terms of five motors and a generator and a storage device. Ouch! It's perfectly possible but the focus is IMHO in the wrong place.

I agree thee drag outweighs the rolling losses and, depending on usage, probably the energy lost in braking, but making the vehicle bigger - else how will all that equipment be housed - will not reduce its frontal area; and a very long & narrow vehicle will have undesireable stability issues.

First lets look at the reduction of prime mover maximum output requirements. Away from the most severe grade conditions, the prime mover will require about 1/3 or less the maximum power requirements of a real time demand power process. Why? Because the power output of the prime mover is AVERAGED over the entire operation cycle and approximates the power required to CRUISE at maximum sustained velocity. Because the power is averaged the prime mover will no longer have to have the capability of rapidly responding through a broad power range, which will allow us to move away from the heavy and bulky reciprocating engine. The radically reduced maximum power requirements of the Prime Mover combined with the introduction of micro-turbine or other technology will greatly reduce both the mass and volume of the prime mover. this will offset a good portion of the mass/volume needed for drive, storage, and electronics.

In the future ICE/Electric hybrid, the prime mover will be designed not just to produce electrical energy but also to act as a rotational storage device in which peak energy supply is stored. Through design the generator becomes integral with the turbine, as well as most of the the storage capacity needed for power averaging and peeking power requirements. By the way, this concept will carry over to point of use power production.

Since a transmission and related components are no longer needed, this offsets most if not all of the additional mass/volume required for the hub integral motors/regenerators. The storage device now only has to store the amount of energy equal to the regenerated brake energy of one braking cycle.

The same applies in a ICE/Hydraulic hybrid.

I have been waiting for this for nearly 30 years, the engineering inertia is beginning to wane and the economics of energy supply and the state of the technology is starting to reach critical mass.

Again, how the power is produced will take a back seat to how the power is processed.

There is some awesome technology coming down the pike. I just wish it wouldn't have taken so long to get here.

Gavilan

Yes, I do understand the principle. I haven't yet seen anything that could be a big enough step in development to give it a clear lead over other strategies for long term sustainability but you're clearly that much nearer the sharp end on this technology.

My view is that lifestyles are going to have to change big time if we are going to reduce our energy and raw material consumptions to a level that future generations can live by with global population as it currently is.