Posts Tagged ‘Chevy’

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More eye opening facts about the Chevy Volt

August 18, 2009

OK, so maybe the Chevy Volt doesn’t really get 230 miles per gallon.  Are such exaggerations justified because they serve a greater cause?  The Chevy Volt will help save the world, after all, by reducing  Co2 emissions, right?

Wrong!

In fact, in some cases the amount of CO2 generated per mile for the Chevy Volt is the same as a conventional automobile getting only 21 miles to the gallon.  Read on…

When running on gasoline (known as “charge sustaining operation”) the Volt will get 50 miles per gallon.   According to the EPA burning one gallon of gasoline yields 19.4 pounds of CO2.  That means the CO2 emitted per mile driven while running on gasoline will be 0.39 pounds.

 ( 19.4 lbs of CO2 / Gallon) / (50 miles / gallon) = 0.39 lbs of CO2 per mile

How much CO2 will be emitted per mile when the Volt is powered by energy from the electrical grid that has been stored in its battery?  That depends on how the energy on the grid is generated.  If you live in an area where the power on the grid is generated primarily with coal, then the amount of CO2 per kilowatt-hour generated is fairly high.  If you live in an area where the power on the grid is generated primarily from nuclear, then the amount is fairly low.  On the average, though, there are 1.34 pounds of CO2 pumped into the atmosphere for every kilowatt-hour of energy generated for the electric power grid in the United States, according to the Department of Energy (2000).

The fully charged lithium-ion batteries hold 16 kilowatt-hours of energy and will propel the Volt 40 miles.  That works out to 0.4 kilowatt-hours per mile.  So that means on the average, 0.54 pounds of CO2 will be put in the atomosphere for every mile that the Volt drives on energy drawn from the electrical grid, assuming perfect charging efficiency.

(1.34 lbs of CO2 per grid kWh) x (0.4 kWh per mile) = 0.54 lbs of CO2 per mile

But charging a lithium-ion battery off the grid is not 100% efficient.  There are grid transmission losses and grid to battery conversion losses which add up to about 10%.  So running your Volt  off of electric grid power will yield closer to 0.59 pounds of CO2 for every mile your drive.  That is 151% of the CO2 put in the atmosphere by the running the Volt off of gasoline.

How many miles per gallon must a conventional automobile get in order to put the same amount of CO2 into the atomsphere per mile as a Chevy Volt does when running off of grid power?  That’s easy- about 33 miles per gallon.  Here are some cars that will do better.

( 19.4 lbs of CO2 per Gallon) / (0.59 lbs of CO2 per mile) = 33 miles per gallon

If you drive in an area where the electric grid is primarily powered by coal, then the numbers are even worse.  Burning coal to power the electric grid yields about 2.1 pounds of CO2 for every kilowatt-hour generated.  Driving your Volt with grid generated power will yield about 0.92 pounds of CO2 for every mile driven (when 10% conversion inefficiencies are added in).

(2.1 lbs of CO2 per grid kWh) x (0.4 kWh per mile)  x 1.1 = 0.92 lbs of CO2 per mile

That is the same amount of CO2 per mile as a conventional automobile that gets only 21 miles per gallon!

( 19.4 lbs of CO2 per Gallon) / (0.92 lbs of CO2 per mile) = 21 miles per gallon

So don’t be fooled by astronomical claims of miles per gallon for the Chevy Volt.  And if you are worried about CO2 (I’m not), then don’t count of the Chevy Volt to save you – it won’t.

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BS from GM

August 15, 2009

You’ve heard the extraordinary numbers – 230 miles per gallon!!  This is the claim GM is making for its new Chevy Volt electric car.  Watch this video

If a voice in the back of your head is telling you this is too good to be true – listen to it.  This claim is one of the biggest whoppers in advertising history.  The folks making these claims are counting on the listeners to be complete innumerate fools.  And the news media seems to be playing along with total credulity.  You would think there would be some kind of government crack-down on GM’s fraudulent claims.  Oh, I forgot, the government is GM.

Here are some important facts about the Chevy Volt.  It will be powered by an electric motor which is run off a lithium-ion battery.  The battery will have an energy capacity of 16 kilowatt-hours and will propel the car for 40 miles.  That works out to 0.4 kilowatt-hours of energy per mile.  The battery will have to be replaced after about 150,000 mile.

When the battery’s charge runs down, a gasoline powered electric generator will kick in to recharge it.  Gasoline has an energy content of 1.3 x 108 Joules of energy per gallon. One kilowatt-hour is 3.6 x 106 Joules.  So one gallon of gasoline contains about 36 kilowatt-hours of energy per gallon (1.3 x 108 J0ules / 3.6 x 106 Joules/kilowatt-hour).

So, if you could manage to squeeze every single kilowatt-hour of energy out of one gallon of  gasoline and into your battery, then one gallon of gasoline would drive your Volt 90 miles (36 kilowatts / 0.4 kilowatts/mile).  But there are pesky complications – like the laws of physics – that insure not even 90 miles per gallon will be achieved.  Conversions are not 100% efficient.  If you read the fine print, you will see that the reality is that if you drive your Chevy Volt on gasoline it will get, at most 50 miles to the gallon. 

Fifty miles per gallon is still pretty good you might say.  But $40,000 is a lot to pay to be squeezed like a sardine.  Consider this: a 1987 Honda Civic Coupe HF got 57 miles to the gallon.  It cost about $7500 dollars (about $16,000 in 2009 dollars).  And, you didn’t have to spend $15,000 to replace the battery every 150,000 miles in the old Honda. 

I drove a 1988 Honda Civic Hatchback for over 250,000 miles, always tracked the mileage, and consistently got 47 miles to the gallon.  I comfortably took my family across the country multiple times. Man, I miss that car.  I am not impressed at all by the over-priced hybrids or electrics that we are seeing today. 

So how does GM justify the preposterous claim of 230 miles per gallon?  The way they figure it, for every gallon of gas that you put in the tank, you will re-charge the battery enough times by plugging it into the grid at home to power it for 180 miles.  So, 50 miles from a gallon of gas and 180 miles from multiple charges from the electric grid at home. Voila! 230 miles per gallon.  They could just as easily claimed 1000 miles per gallon by figuring that you would charge it off the grid for 950 miles worth of power for every gallon of gas you pumped into the tank.

I think GM has a problem.  Most people who are likely to spend $40,000 on a little car have been around long enough not to be innumerate fools.