

100 mpg Prius - kirubakaran
http://www.ecogeek.org/content/view/1582/

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jws
Stop this silliness now. Claiming a "miles per gallon" figure when you get
significant amount of your energy from another source is just silly. Its like
claiming 100mpg if you start at the top of Pike's Peak.

I propose we popularize "kilometers per megajoule", or kpm. A gallon of gas
has 130 megajoules, 33% efficient internal combustion engine, so a 60mpg car
would be something like 2.5kpm. This will nicely separate separate efficiency
of motion from energy source. People should be able to easily reason about a
2.5kpm vehicle with a 20 megajoule plugin chargeable battery. (I think, no one
has check these numbers. Notice I had to come back and edit for the engine
efficiency once already, so they should be scrutinized.)

The ugly part is how to think about the internal combustion engine. You may
have 1300 mega joules in the gas tank, but you will lose 60-70% of those in
your engine before they meet the drivetrain. I leave that part as an exercise
to the reader.

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brookr
But from an environmental perspective, perhaps people are more concerned about
the trade-off between carbon emissions and distance traveled. Efficiency
measures would be great way to evaluate drive sources, and would perhaps be
very revealing when internal combustion is exposed as being so inefficient.

But perhaps a rating of carbon "moles per kilometer" would be a better
indication of environmental impact of any motion source.

It would be interesting to compare even with walking, running, and biking (at
different speeds), as you exhale (significantly smaller) amounts of carbon
dioxide (and none of the worst carbon offender, CO, thankfully).

Here too, the energy source that you are plugging this module into could
greatly vary your MPK.

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dkokelley
I see that it's still more expensive to go green than to bite the gas-price
bullet.

Still, 100mpg is a good marketing angle for them.

Let's look at it this way:

Assume average person drives 1000 miles/month

Assume gas costs $4/gallon

Assume Prius gets 100mpg, and other cars get 20mpg

A Prius driver with the conversion kit spends $40/month on gas.

A typical car driver spends $200/month on gas.

A prius driver saves $160 per month for driving the prius.

It will take 5.2 years to re-earn the $10,000 upgrade. This does not include
the price for a prius, which I was surprised to find has come down quite a
bit. A 2008 prius base model costs $21,100.

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Alex3917
What if you factor in the cost of carbon?

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dkokelley
Please explain. Are you referring to the environmental, intangible "cost" of
carbon emissions, or maybe the cost of cleaning them from the environment?

What is the cost of carbon?

(To be clear, I was trying to evaluate the 2 cars economically, without the
consideration of carbon footprint or other moral duty to the environment to
get in the way of the calculations.)

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Alex3917
I meant the expected cost of carbon once a cap-and-trade system is
implemented. All three candidates favor putting such a system in place, so
there is something like a 90% chance of getting this legislation enacted
sometime within the next 24 months. McCain's bill actually is expected to go
up for a vote the week of June 2nd. The calculation should ideally take into
account the fact that most people would charge their cars at night when
electricity is cheaper and a greater percentage of the mix comes from
renewable sources (because of wind power).

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dkokelley
Ok I get it now.

I actually have no idea what a the cost of such a system will be, because I
hadn't heard much about the legislation you mentioned. I assume that once
something like that passes, it will help move more people to electric
vehicles. Personally, I'm saving for the Tesla Roadster
(<http://www.teslamotors.com/>).

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brookr
Problem is, most people's primary electricity source is coal-burning power
plants that do not provide significantly lower carbon emissions (depends on
the efficiency of the module, of course). However, more municipalities (like
here around seattle) are offering wind-sourced power to homes who "green-up".
There is a $12/month additional charge, but it is a great way to reduce
overall emissions.

~~~
ssharp
That's not a problem at all. If you compare the raw power usage, it's still
both cleaner and more efficient to use electricity than gas. Also, gas engines
aren't going to get that much cleaner, whereas the energy grid is only going
to get cleaner with cleaner coal, nuclear, and renewables.

I wouldn't be surprised if in 15 years from now, if half of all new cars sold
use electricity as their primary source. Energy independence should be a goal
for every country, but especially for a country like the U.S. that uses so
much oil.

