Yodrak
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MPG Equivalent ?

Tue Aug 24, 2010 10:17 am

Not quite a Gazillion.

Using some nice round numbers (double-check me on the math)
- if the Leaf requires 0.25 kWhr/mile (24 kWhr takes you 100 miles, add losses in the charging)
- generating electricity requires 10,000 Btu of fuel per kWhr (http://www.eia.doe.gov/cneaf/electricit ... at5p3.html)
- Leaf requires 2,500 Btu/mile of fuel
- gasoline has 125,000 Btu/gal (http://en.wikipedia.org/wiki/Fuel_effic ... nt_of_fuel)
- Leaf requires the equivalent of 50 gallons of gasoline per mile

SilverLeaf wrote:Going from about 20 MPG to about a Gazillion MPG (equivalent).
Khun Yodrak
2013 SL

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evnow
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Re: Poll : TradeIn or Gift ?

Tue Aug 24, 2010 10:22 am

Yodrak wrote:Not quite a Gazillion.

Using some nice round numbers (double-check me on the math)
...
- Leaf requires the equivalent of 50 gallons of gasoline per mile


Assume solar/wind power. So no fuel is consumed. So it is gazillion mpg ;-)

Other way to look at it is ... a gallon of gas has some 36 kwh of energy. With that amount of energy Leaf can travel 144 miles. So, 144 mpg (e).
1st Leaf : 2/28/2011 to 5/6/2013
2nd Leaf : 5/4/2013 to 3/21/2017
Volt : 3/25/2017 to 5/25/2018
Model 3 : 5/10/2018 to ?

Yodrak
Posts: 492
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Location: St Louis, MO

Re: Poll : TradeIn or Gift ?

Tue Aug 24, 2010 10:53 am

Nice try, but your assumption is wishful thinking. The sun doesn't shine at night (read all though posts by people who are looking at TOU rates for overnight charging) and even though the wind does it's not always there and it will be an insignificant source of electricity for years to come. At present wind and photovoltaic solar, along with wood, black liquor, other wood waste, biogenic municipal solid waste, landfill gas, sludge waste, agriculture byproducts, other biomass, geothermal and solar thermal account for less than 4% of the electricity produced in the USA. http://www.eia.doe.gov/cneaf/electricit ... le1_1.html

EV charging is going to come predominantly from fossil and nuclear power plants for quite a while yet, no matter how much wishful thinking people do.

So I'll give you 65 mpg equivalent if we don't count the <4% from 'renewables' and 20% from nuclear fuel in the generation of electricity.

I disagree with your 36 kWhr per gallon of gas. Show me your calculation. Mine is:
125,000 Btu in a gallon of gas (I gave the reference for this number),
10,000 Btu to produce a kWhr of electricity (I gave the reference for this number),
12.5 kWhr in a gallon of gas.
50 miles in a Leaf (recognizing that it takes ~25 kwHr of charging to get 24 kWhr into the battery)

evnow wrote:
Yodrak wrote:Not quite a Gazillion.

Using some nice round numbers (double-check me on the math)
...
- Leaf requires the equivalent of 50 gallons of gasoline per mile


Assume solar/wind power. So no fuel is consumed. So it is gazillion mpg ;-)

Other way to look at it is ... a gallon of gas has some 36 kwh of energy. With that amount of energy Leaf can travel 144 miles. So, 144 mpg (e).
Khun Yodrak
2013 SL

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evnow
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Re: Poll : TradeIn or Gift ?

Tue Aug 24, 2010 10:57 am

Yodrak wrote:Nice try, but your assumption is wishful thinking.


Offtopic for this thread. Let us move it somewhere else.
1st Leaf : 2/28/2011 to 5/6/2013
2nd Leaf : 5/4/2013 to 3/21/2017
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evnow
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Re: Poll : TradeIn or Gift ?

Tue Aug 24, 2010 11:06 am

Yodrak wrote:I disagree with your 36 kWhr per gallon of gas. Show me your calculation.


It is not a question of agreeing or disagreeing. A simple wiki search could have spared you all the typing.

http://en.wikipedia.org/wiki/Gasoline

Gasoline contains about 35 MJ/L (9.7 kW·h/L, 132 MJ/US gal, 36.6 kWh/US gal)


Yodrak wrote:The sun doesn't shine at night


I didn't say it does. Besides we get a lot of hydro here - and it does work at night.

Anyway, don't bring extraneous stuff here. We are just talking about mpge. Nothing new here - there are various ways to calculate this. Checkout what Automative X does, for eg.
1st Leaf : 2/28/2011 to 5/6/2013
2nd Leaf : 5/4/2013 to 3/21/2017
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wwhitney
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Re: MPG Equivalent ?

Tue Aug 24, 2010 11:25 am

Yodrak wrote:Using some nice round numbers (double-check me on the math)
- if the Leaf requires 0.25 kWhr/mile (24 kWhr takes you 100 miles, add losses in the charging)
- generating electricity requires 10,000 Btu of fuel per kWhr (http://www.eia.doe.gov/cneaf/electricit ... at5p3.html)
- Leaf requires 2,500 Btu/mile of fuel
- gasoline has 125,000 Btu/gal (http://en.wikipedia.org/wiki/Fuel_effic ... nt_of_fuel)
- Leaf requires the equivalent of 50 gallons of gasoline per mile

As others pointed out, there are ways of generating electricity that entail no fossil fuel consumption on an ongoing basis. But for the case of generating electricity from fossil fuels, you've neglected the energy costs to refine the gasoline. I'm not sure what is involved in the 10,000 Btu/kWhr figure for electricity generation, I didn't check your link. And of course, there are benefits to concentrated pollution sources rather than dispersed mobile pollution sources.

Anyway, I would think it would be best to convert to barrels of oil, there are oil burning power plants. So how many barrels of oil to generate electricity to move the Leaf one mile (include transmission losses), versus how much gasoline could be refined from those barrels of oil (include the oil necessary to generate any electricity needed to run the refinery).

Cheers, Wayne

jppandesv
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Location: OC, CA

Re: MPG Equivalent ?

Tue Aug 24, 2010 11:29 am

@Yodrak

Just "double-check(ing you on your) math", I think you flipped your units:

> - Leaf requires 2,500 Btu/mile of fuel
> - gasoline has 125,000 Btu/gal
> (http://en.wikipedia.org/wiki/Fuel_effic ... nt_of_fuel)
> - Leaf requires the equivalent of 50 gallons of gasoline per mile

Shouldn't this be 2,500 BTU/mi * gal/125,000 BTU
= 0.02 gal/mi , or
= 50 mi/gal ?? ... not 50 gal/mi.

BTW, not making a comment on the simplicity of the analysis, just the math (dimen analysis) ....
Last edited by jppandesv on Sat Sep 04, 2010 2:37 am, edited 1 time in total.

AndyH
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Re: Poll : TradeIn or Gift ?

Tue Aug 24, 2010 12:34 pm

evnow wrote:
Yodrak wrote:Not quite a Gazillion.

Using some nice round numbers (double-check me on the math)
...
- Leaf requires the equivalent of 50 gallons of gasoline per mile


Assume solar/wind power. So no fuel is consumed. So it is gazillion mpg ;-)

Other way to look at it is ... a gallon of gas has some 36 kwh of energy. With that amount of energy Leaf can travel 144 miles. So, 144 mpg (e).


Or at least 1/4 of a gazillion. :D

One point - a small quibble, actually, is that when we look at 'power generation' we tend to stay very macro. And that wide focus effectively trivializes wind and solar. Add to it simplistic statements possibly intended to further trivialize it (the sun doesn't shine at night; wind doesn't always blow) and it makes things look worse than necessary.

Fact is, it takes very simple technology to use solar power at night - and many thousands of off-grid folks have been using this technology for many, many years. This tech is called a 'battery'. ;)

edit..spelling's optional, right? :?
Last edited by AndyH on Tue Aug 24, 2010 1:28 pm, edited 1 time in total.

LEAFfan
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Re: MPG Equivalent ?

Tue Aug 24, 2010 12:57 pm

Yodrak wrote:Not quite a Gazillion.

Using some nice round numbers (double-check me on the math)
- if the Leaf requires 0.25 kWhr/mile (24 kWhr takes you 100 miles, add losses in the charging)
- generating electricity requires 10,000 Btu of fuel per kWhr (http://www.eia.doe.gov/cneaf/electricit ... at5p3.html)
- Leaf requires 2,500 Btu/mile of fuel
- gasoline has 125,000 Btu/gal (http://en.wikipedia.org/wiki/Fuel_effic ... nt_of_fuel)
- Leaf requires the equivalent of 50 gallons of gasoline per mile

SilverLeaf wrote:Going from about 20 MPG to about a Gazillion MPG (equivalent).


Respectfully Yodrak, but you have a major flaw in your formula. Most of us will be using pvs to charge our cars so you can throw out the 10K btus of fuel. Now recalculate and you may get the 367 mpge that Nissan is telling us. :D
2013 LEAF SV Del. 2/28/13
2013 LEAF World Record for Most Miles Driven On One Charge-188 miles/8.8 m/kW h
4.8 kW DC PV ($ .91/W fully installed)/ Dec., 2010

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LakeLeaf
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Re: Poll : TradeIn or Gift ?

Tue Aug 24, 2010 2:39 pm

Yodrak wrote:Nice try, but your assumption is wishful thinking......


One important environmental aspect not taken into account here. While it's true that for many, the electricity they use to charge their Leafs will come from the grid - and therefore mostly traditional fossil fuel sources, the charging will also take place primarily at night when the demand for power is lowest.

This means that (since electrical power generation is essentially a just-in-time function) that the plants used to produce the power will be those that run 24x7. These plants tend to be the newer power plants and therefore the most efficient at producing power and the least polluting. Oil refineries, on the other hand, tend to run 24*7 and whatever power they draw off the grid during the day time (peak hours) will be supplied partially by less efficient and higher polluting plants that are brought online during the day to meet that peak demand.

An energy supplier will run the most efficient plant (and therefore the most profitable) more then the less efficient plant - overcoming the cost of operating the less efficient plant by charging higher rates during peak periods.

So it is a little more subtle then just "EV's are still powered by fossil fuel". A lot will be, but they will be able to make use of the most efficiently generated power

As these things evolve, the battery packs will be able to hold more and more power. The DOE is projecting that EV's will be able to hold enough power in their battery packs within 10 years to be able to drive 500-1000 miles on a single charge (somewhat the mecca point for EV's as very few people will be driving more then 1000 miles in a day!). As some know - the belief is the highest energy storage density for batteries will come from something called Lithium-Air batteries which the DOE, IBM, GE, and others are investing billions in researching as we type.

However - most people will continue to drive in the 25-50 miles a day range. This means that your EVs will have far more juice in them then you need. As this evolves, so will the charging infrastructure. Your house (which typically has peak power demands at breakfast and dinner times) will at some point be able to draw power from you EVs battery packs instead of (or in addition to) drawing from the grid. This will help to increase efficiency even more - even less carbon emissions as the newest, most efficient power plants are supplying power to your vehicle overnight which you then use during the day.

Going on a trip that day and need a full charge? No problem - just pull your breakfast power from the grid instead of from your car. Stay at home mom with an EV full of juice parked in the garage? Even better! The power company will be looking to purchase some of that power from you to meet higher demand periods so that they don't have to power up another plant to fill the needs. Work at leading edge company? They might just install zero emission power generation capabilities at work and charge you all up for free - in exchange during first and last business hours when the generation capability is lower - your employer might draw power from your car to power of offices until the sun hits peak production hours, at which point you get paid back.

Some here are already way ahead of the curve - as self generation technologies come more and more mature and more and more affordable, many will be generating their own power during the day - storing it in their EV's and using it as needed. The power grid is still there for those times when your needs exceed your generating and storing ability.

A combination of environmentally friendly power generation technologies - many of which are time of day or weather dependent - along with generous storage capacities will allow us to meet most of our power needs with only the most energy efficient and least polluting plants - and the Leaf is step one along that path.

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