Welcome to European Tribune. It's gone a bit quiet around here these days, but it's still going.
For a hybrid vehicle, all the energy comes from oil. Less is wasted (because the energy is saved when you brake), but the main advantage is in town, when you don't have to use your heat engine / thermal motor (?).

For a long trip, a hybrid vehicle has no advantage in terms of oil consumption.

But this is what I think : we should give up using heat engine. They are ineffective - but very practical. That is not what is implied by a 70 g/km recommendation : I think they imagine that the cars will still be using conventional motors.

Until now, only heat engine can transform oil into movement.

by Renard (scio at free point fr) on Thu Sep 13th, 2007 at 10:28:56 AM EST
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Note: "plug-in hybrid". Anyway, most journeys for most vehicles are short.
by Colman (colman at eurotrib.com) on Thu Sep 13th, 2007 at 10:34:56 AM EST
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Yep. I think fully electric (or plug-in) vehicle are likely, because, as you say, most of journeys are

There's a calculation which is seldom made :
only 3% of the solar energy is converted to chemical potential energy in a plant and then 2/3 of this energy is spilled in conventional motors so that a biofuel + heat engine line has a yield of 1% (and I'm considering that no energy has been necessary to obtain biofuel).

Solar panel convert 15% of the solar energy into electricity. 1/3 is lost when using batteries. Since the yield of an electrical motor is around 90%, then 9% of the solar energy is converted into movement. Ok, a lot of energy is required to make the solar panels (4 years of their production is necessary to fabricate the next panel).

So... I don't believe in conventional motors. Nowhere except for long journeys - because of the energetic density of fuel.

by Renard (scio at free point fr) on Thu Sep 13th, 2007 at 11:26:33 AM EST
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by Laurent GUERBY on Thu Sep 13th, 2007 at 02:34:02 PM EST
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Interesting enough, indeed.  Thanks for those links.

I guess that the speaker for tesla motors wasnt fully impartial. However, the figures are striking. Even if they are overestimated by one order of magnitude, electric motors are even more interesting than what I thought.

I think he has forgotten some phenomena (electricity transport, for instance) and that he underestimates the average cost of using batteries. Anyway, this is interesting. Partial, but interesting.

by Renard (scio at free point fr) on Thu Sep 13th, 2007 at 04:21:47 PM EST
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Yes of course Telsa Motors is not neutral, but they did cite their sources and the few numbers I went after on google were within reasonable bounds of what the paper said.

Electricity transport is not that costly (around 95% efficient IIRC) and also not mandatory (eg local production).

Batteries are of course the current hot topic (cost and storage capacity per mass/volume), but some EV models have in car fuel-burning generator that generate electricity to extend range.

by Laurent GUERBY on Fri Sep 14th, 2007 at 06:56:23 AM EST
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I do not disagree with the figures - I'm just saying they choose the "best ones", and not the more realistic ones.

From wikipedia :

The nickel cadmium and nickel metal-hydride designs have efficiencies of around 66%.[43] However, modern lithium designs have almost negated this wastage as they can have efficiencies of around 99%.[44]

But are the latter batteries really available ? It may be more reasonable to assume a 66% yield instead. This is what I usually do. :) With the idea that it is possible to have a much better yield using "modern" design.

by Renard (scio at free point fr) on Fri Sep 14th, 2007 at 07:47:34 AM EST
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Tesla (and many others) use Lithium-Ion batteries of course, expensive but best Wh/kg. The battery is usually the single most expensive component of EV, some vendor lease the battery.

The Modec van uses Zebra batteries with charge-discharge effiency above 90% (IIRC).


Even with NiMH AA batteries, 66% is near the absolute worst :).

by Laurent GUERBY on Fri Sep 14th, 2007 at 01:17:24 PM EST
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"For a long trip, a hybrid vehicle has no advantage in terms of oil consumption."

I don't think this is correct. The heat engine (gasoline or diesel) can be made to handle the average power requirement at some speed, and the electric motor/generator is used to balance uphill and downhill grades. In a conventional car, the heat engine must be sized to handle the largest instantaneous power requirement, which is typically a steep uphill segment on a high speed road.

My wife and I drove our Honda Insight hybrid round trip from Colorado Springs to Amarillo recently (360 miles each way, 580 km) and averaged 69 miles per gallon, which is about 3,4 l/100 km or about 78 gCO2/km. We maintained, at her insistence, the speed limit (mostly 70 mph, 113 kph) and ran the air conditioning--and it was about 90 degrees (32 C).

By reducing the speed we could have achieved 70 g/km in this 1999-technology car, with no loss of comfort.

by asdf on Sat Sep 15th, 2007 at 12:10:34 PM EST
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