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Old 05-04-2009, 08:22 PM   #131 (permalink)
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Quote:
Originally Posted by Jim Bullis View Post
What happened to the Ernie Rogers that argued for a 40% adjustment for the efficiency of the power plant that made the electricity?
Aw, jeez, I'm asleep at the wheel here. For every KJ of power that makes it to the grid, it takes an average of 2.5KJ of fuel.

Cost equivalence: 18.5KWh = 1 gal gasoline for me today. Wildly variable, changes daily, different everywhere.
Well to Wheels greenhouse gas equivalence: 15.2KWh = 1 gal gasoline
Energy equivalence of pure electricity: 34 KWh = 1 gal gasoline
Energy equivalence for grid average (guesstimated at 40% efficiency) plus 7.2% transmission losses: 12.6KWh = 1 gal.

I'm guesstimating 40% thermodynamic efficiency average, since most fossil-fueled plants get 36-40%, nuclear is slightly lower, and non-combustion methods could be said to be ~100% thermodynamically efficient for our purposes.

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Old 05-04-2009, 08:27 PM   #132 (permalink)
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There's an awesome table of WH/mi for various EVs on page two of http://web.mit.edu/evt/summary_mpgge.pdf . The team at MIT were less generous than I was, using 32.8% generation efficiency. The 39MPG Ranger is impressive, but the 69MPG EV1 is not.

How many WH/mi do EM EVers get?
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Old 05-04-2009, 08:42 PM   #133 (permalink)
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Let's just copy it here
Code:
Vehicle             Energy Use Battery-to-wheel fuel Full cycle equivalent fuel
                     (Wh/mi)    economy (mpgge)         economy (mpgge)
GM EV1                 179              188                      69
Tesla Roadster         240              140                      51
MIT Porsche 914 BEV    185              182                      67
Toyota RAV4 EV         235              143                      52
Ford Ranger EV         315              107                      39
Though the tesla wh/mi numbers don't jibe with the current site figures of 110 wh/mi (which I also arrived at by looking at the charger specifications) and claims it is tested per EPA specs, could be some improvements made since last year I suppose, but I don't know where the table figures are from.

Nonetheless consumer energy costs per mile are sick in favor of EV, considering similar performing cars to the tesla get like 15mpg or worse and based on historical average energy costs. (course below they are only comparing natural gas in the wtw figure)

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Old 05-05-2009, 12:45 AM   #134 (permalink)
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We see what we want to see

Quote:
Originally Posted by dcb View Post
Honestly I don't see that. Cost per mile the EV's wipe the floor with gas in the real world, by a factor of 2.8 by my reconing. It hasn't been accepted largely because gas is the incumbent. Lots of political machinery and pre-conceptions to keep gas in office, and there's no shortage of people who invest in oil stocks as well (whos judgement IS swayed).

Have you ever tried having a rational discussion with someone who has an addiction? It's kinda like that too.
Umm....
look around - there are no production EVs in the US - is it because they are so efficient?
- people are building them as hobbies (Like I hope to do) & keeping alive a few from the 70s
the conspiracy theories only go so far
in normal supply and demand curves you should start to see EVs in some niche if they are viable
some where they ought to make since for somebody
but like I said - they are even loosing as golf carts

does this happen because golfers like spending 2.8 as much on fuel?
No, it is because they don't make economic sense to the people that need transport
(and I pray we don't loose the EV start ups coming on line to 2$ gas)

Ernie is on the trail of part of the reason this happens
but if a simple conversion is not acceptable for all the fuel logs, better to spin EVs into there own kilowatt hour "fuel" log
because someone is sure to say"I buy carbon offsets, so all of the power I use off the grid comes straight from the organic windmills of Shagri La and therefore there are no coal burning thermodynamic losses charging my batteries!"
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Old 05-05-2009, 01:34 AM   #135 (permalink)
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Originally Posted by Concrete View Post
but like I said - they are even loosing as golf carts
If this is the basis for your position then please provide a source. And why you think it is more than a temporary phenomenon.

Also note the energy costs per mile are more like 30 times more expensive for gas (in 2007 terms) as I mentioned in a later post. 2.8 was just the btu for btu * average cost for electric vs gas. When you factor in the inefficiencies of the gas engine the cost per mile go much higher.

So maybe "cost" isn't the right term for the comparison you want to make. Sales? maybe, but that has as more to do with marketing and the state of the economy than anything else, and the good margin vehicles get the marketing dollars. And the good margin vehicles are the ones they already know how to make. No conspiracy, just business.

But lets keep our terms straight. Cost per mile there is no comparison with EV, Sales there is no comparison with Gas. They are not the same thing however, and nothing is written in stone.
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Old 05-05-2009, 03:54 AM   #136 (permalink)
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Quote:
Originally Posted by trebuchet03 View Post
This is why I keep posting that the problem isn't the method so much as it's the metric.

MPG is nowhere near total consumption. It is, however, an easily understood metric by non experts. If we want to consider total consumption - the site would need to change to a more appropriate metric which, I feel, would alienate potential newcomers.

I understand that if we wanted total consumption, we need well to wheels - but well to wheels is a bit off topic based on the OP (but a good topic either way)
That's what we get with the step we're at in terms of energy conversion, since converting gasoline to mechanical energy is almost always more efficient than converting energy from a battery into mechanical energy. What if, for instance, I get all the electricity for my EV from solar panels on my roof? Why should I have to deal with the limits of the Carnot cycle?

Anyway, in terms of site appeal, I think something that included the current energy mix of electricity sources would be the best for EV owners under an advanced tab or something. This thread reminds me of something out of the big bang theory.
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Old 05-05-2009, 01:55 PM   #137 (permalink)
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Quote:
Originally Posted by Concrete View Post
...but like I said - they are even loosing as golf carts...
Just think a bit, though: golf is supposed to be exercise, no? So we have the golfers who're supposedly out there to get exercise instead riding around in carts (whether gas or electric powered), thereby depriving themselves of the exercise - the "good walk spoiled" - they're out there to get. Hardly evidence that golfers are capable of rational economic decision-making, now is it?

But then, I've always regarded the desire to play golf as one of the more reliable early warning signs of Alzheimer's :-)
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Old 05-05-2009, 03:00 PM   #138 (permalink)
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Quote:
Originally Posted by roflwaffle View Post
That's what we get with the step we're at in terms of energy conversion, since converting gasoline to mechanical energy is almost always more efficient than converting energy from a battery into mechanical energy. What if, for instance, I get all the electricity for my EV from solar panels on my roof? Why should I have to deal with the limits of the Carnot cycle?

Anyway, in terms of site appeal, I think something that included the current energy mix of electricity sources would be the best for EV owners under an advanced tab or something. This thread reminds me of something out of the big bang theory.
I think you and I are on the same page... Except how do you figure gasoline energy->mechanical energy is more efficient than electrical energy to mechanical (I don't actually know, I'm just curious)?

Frankly, the best metric to publish to the world, in my opinion are the same metrics published elsewhere. Making figures on this site comparable elsewhere. I like the idea of advanced metrics, however
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Old 05-06-2009, 01:07 AM   #139 (permalink)
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The best peak efficiency I've seen for a SI engine (Prius) is 37% BTE, and for a CI engine is ~41% IIRC in the 3L Lupo, and given that cars still need to warm up, aren't operated at peak BTE all the time, and so on, average BTE tends to be much lower. The Prius for instance is at the high 20s over the ftp cycles IIRC, and I imagine the 3L Lupo is similar. Electric setups otoh, ike the AC150 from AC Propulsion, are in the 80s in terms of road load efficiency, and with charger efficiency in the high eighties low nineties, we're looking at ~60-70% road load efficiency from the plug. Even super big low speed diesel are only at ~50% peak BTE. If we were to look at the average efficiency of most vehicles compared to production EVs, the difference would be greater since throttling losses for conventional vehicles still kill efficiency, although I think manufacturers are gearing vehicles better and all that given the high gas prices we saw.

Anyway, the familiar metric is probably the best, although in that case it should be mpg for FF powered cars, wh/mile for EVs, and maybe even MPGge if we ever get a natural gas powered vehicle in the garage, w/ maybe a provision for the super eco geeks among us. A direct comparison is a total pain.
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Old 05-06-2009, 01:25 AM   #140 (permalink)
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How about we keep everything using a gallon

So a gallon of diesel is comparable to a gallon of gasoline and no conversion is typically done. So a gallon of electrons is 74,827,114,82,524,854,619.5Ah

Assuming a classical electron radius of 2.8179402894x10-15 m and they are packed tightly.

That is what I am going to use for my conversion and I'm sticking to it

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