Energy Matters Forums

[jamessteward]

Did you read the last bit of that autospeed.com article?

Well-to-Wheels versus Cradle-to-Grave

A well-to-wheels study considers only energy inputs/emissions outputs used for driving. But what about the energy used (and the emissions created) when the car is being manufactured? And what about the emissions and energy for development of the fuel creation infrastructure (whether that’s a power station or an oil rig)? These latter factors are taken into account only in a ‘cradle-to-grave’ analysis.

Andrew Simpson says: “I did not include the ‘embodied energy/emissions’ (as they’re known) in my study.

“Ideally, you should include everything, but as a practical matter, you have to set the system boundary somewhere. A rule-of-thumb that I have seen is that the embodied energy in making a car is ~10% of the energy it consumes via driving over its life. This of course varies by technology, and doesn’t mean you can ignore the embodied factors, but I think my comparison was informative nonetheless.”

This is what the CNW report I cited (regardless of how correct/incorrect the data) attempts to do, and while perhaps Andrew Simpson has uncovered some truths, by his own admission it is not the whole story.

According to http://www.green-car-guide.com/news/are ... -green.htm

Example 3: The CNW study states that hybrids require more lifetime energy than even large SUVs. Toyota’s internal analysis does conclude that there is more energy required in the materials production stage for a hybrid, but that this is overwhelmingly made up for in the driving stage (the 80-85% stage), causing the hybrid to have a significantly lower lifetime energy use.

So manufacture of a hybrid is 15 - 20% of the total cost of ownership. A bit more than Andrew's assumed ~10%.

Who do you believe? Someone always foots the bill for a report or study.

To recycle a battery it must be shipped and energy is used to move it and recycle it. How much? Who knows? Toyota?

Comparing a Prius to a Barina and a 107 is like comparing a postie bike to a goldenwing.

I thought I made it pretty clear when I did compare apples with oranges, that it was because the Toyota Prius advert I heard was down right misleading. No it wasn't a Camry ad. The point is there are several other more fuel efficient vehicles to chose from.

Yes I drive the Jeep because I use every ounce of it's capability. Not every day, but often enough. Interestingly, I used to have a Suzuki Sierra 1.3L. The Jeep only uses about 1 L/100km more, despite it being 1/2 a tonne heavier and sporting a 4L engine!

Which brings me back to the title, "Horses for courses". The fuel efficiency we get from fossil fueled vehicles and hybrid alike, is largely due to improved aerodynamics and computer controlled engines. The hybrid isn't worth having on the highway. The horse isn't for that course.

Oh don't get me wrong, if I could travel at hwy speeds, refill a battery every 4-500kms in a few minutes and tow a trailer over Mt Hotham and into the wilderness in my Jeep, I would. Don't see it happening any time soon though. Battery technology might have improved, but it's still so far from that reality.

I'd also love to see more wind generators, but so often we hear that the "view conservationists" object!

[munter]

OK - I can't really comment on the ad you heard and whether it was misleading or not. I highly doubt that Toyota would falsely claim that the Prius was Australian made when it isn't - that would be far too easy for their competitors to ping them for. Given that Ford have made such a big deal out of their better diesel fuel economy I also highly doubt that Toyota would be trying to mis-inform people about the Prius being the most fuel efficient but again - with hearing the ad or seeing a reference I can't really say any more. I've tried to help out with a plausible alternative but you seem confident of what you heard.

I find the Prius advertising pretty un-appealing (toyota - are you listenting?). The whole "Prius type of person" angle that they use in the current ads is a alienating and self-righteous. The advertising almost encourages a type of smugness which detracts from the appeal. This is completely unrelated to the value of the engineering in the car though.

I agree that there are probably cars which use less fuel than the Prius in production somewhere in the world. I don't think you can use this fact to discredit hybrid drive trains and the Prius though. That is what you seem to be doing and that is why I keep pointing out that you are comparing different vehicles. Why not include a solar car and laugh at the pathetic fuel efficiency of the small diesels? Without a comparison to an equivalent vehicle you can't really make an assessment of the worth of the technology.

Re embodied energy - I don't have a solid reference on this one but if we assume that manufacture takes 20% of the lifetime energy of a car and that a hybrid has 150% the embodied energy of a standard car then we've still only increased the lifetime energy due to manufacture 10% to make the car a hybrid and will achieve a saving of say 30% on the lifetime energy associated with fuel. Nett - it seems likely that the hybrid will have lower lifetime energy. These numbers are only roughly based on the links posted above but the methodology seems like an OK starting point.

Your Jeep results sound good. Is the difference in specific fuel consumption coming from the use of fuel injection vs carby? I'm all for pursuing improvements in efficiency in IC motors and there is some very clever engineering being done around the world to push the technology as far as it can go but as noted before - it seems to be at a relative plateau compared to the rapid development in electric drive trains and batteries.

You say that a hybrid isn't worth having on the highway. I agree that the effectiveness of the drivetrain is reduced and that aerodynamics become more important but what if you can have both? The hybrid doesn't return poorer results than a standard car on the freeway (where weight isn't so important) so why not prepare for both city and country driving? Would you buy a car without headlights because you never planned to drive at night? Sure - some cars might only drive in the country but I think the majority will find themselves operating in a mix of conditions. I agree that good aerodynamics are a very important part to highway fuel economy. It's quite revealing to see the fuel economy drop accelerate at speeds over 60 km/hr.

You've probably worked out that I drive a Prius by now. That doesn't really mean anything in the context of this discussion (except for the potential for me to be biased to "validate" my purchase I suppose) but it does give me the ability to report first hand experience in how effective the car is in the real world. Here's an example - this weekend I drove 500 kilometers for a family event. It was a mix of traffic from 110 km/hr to standstill traffic jams. We had the air con on all the way because my son was asleep in the back and can overheat inside the claustraphobic child's seat. The average fuel economy for the trip on the onboard computer was 4.3L/100km. This is approximately half what a corolla would have used (real world consumption - not published fuel rating). The car was fully loaded with camping equipment, food & drink. There are few cars that could achieve that mileage with that carrying capacity. This, to me, is a good demonstration of the effectiveness of hybrid technology.

Re: An electric car for you - I agree that it doesn't sound like they currently match your requriements. Then again, your requirements are quite demanding and probably not indicative of the performance typically required for an electric car. Thats ok - nobody is going to force you to buy one. You might not be ready for an electric car and vice versa but there are quite a few other applications where an electric car with reasonable (say 80km) range would be perfectly fine. Inner city commuters seem like a common target market for manufacturers. The first electric only car will not be a direct replacement for existing petrol cars. They will have limitations and these will gradually be addressed. I think this will all happen faster than people currently think. For sure there are issues that need to be resolved to make sure that any new technology pitched as being environmental actually delivers on that promise but I don't think the Prius has any outstanding environmental failings which (particularly for a breakthrough product) is very impressive.

[jamessteward]

I didn't think I was discrediting hybrid drive trains. I purposely compared apples with oranges because the advert I heard was sweeping and made no such distinction. It is obvious that if you add a device that can store and reuse some braking energy especially on the city cycle too what is already a fuel efficient vehicle it will become more efficient. I can't say I share your optimism regarding the battery production or recycling though. I've read some nasty stuff about the whole manufacturing process. Trouble is it's so difficult to know what to believe.

(Boy, I wish I'd recorded the advert.)

There is probably little improvement to be made to the IC engine as you note. Carby V EFI is a tough comparison. Provided the carby is well tuned to the engine and provides the stoichiometric air/fuel ratio, there will be no real difference I suppose. After all EFI simply uses a closed loop feedback system to do the same. If the EFI system components are working well it has the potential to keep the system at peak performance longer (as parts wear), because of the continual measurement and adjustment. But there are more parts in the EFI system to go wrong, and because it's a closed loop identifying the root cause of a problem can be difficult.

I like the idea of ceramic components, particularly in the combustion chamber. Improved performance is one benefit, and wear characteristics. But if the vehicle lasted longer the manufacturers wouldn't make as much money selling new cars, so I doubt it will take off. This, like most possible improvements, are costly and provide relatively small improvements, so the end users are less likely to pay for them.

I guess the Jeep and Suzi fuel consumption is comparable because the wind resistance is probably comparable. The Jeep is a little larger and heavier with a much bigger engine, yet still the same basic shape, hence it uses a little more fuel but not much more.

You took a family camping in the Prius? Bravo. I guess it was just an overnight trip? How would it go towing a trailer? Could you collect 1 tonne of railway sleepers from half way across town without making several trips?

I'm sure the Prius delivers great fuel economy, especially around town. And if you can afford to sacrifice a little luggage space there are even more fuel efficient vehicles available. It's just not practical for many of us. Roll on the electric Jeep. (Or compressed air, or weetbix fuel cell

I really like the compressed air idea. Imagine a petrol station becomes a compressor station and air conditioning costs nothing...