Ernie, Yes it is appropriate to determine absolute efficiencies, not simply small scale comparisons. The corn-based ethanol band wagon is good analog of our desire to grasp for ostensible solutions without checking for the "man behind the curtain".
Of course the easy solution to the "hidden emissions" of electric transportation is renewable electricity generation, i.e. wind & solar . David On Apr 13, 2007, at 9:08 PM, [EMAIL PROTECTED] wrote: > > Hi, David, > > This is very good, the way you want to find out for sure. And, > your dismay > is understandable-- almost everybody has this false impression > that electric > cars save a lot of energy and CO2. The general concept is very > simple, > EFFICIENT cars save energy. And, the best place to improve > efficiency is not > necessarily in the power plant choice. > > I gave you a reference before, but I can be much more precise. > Here is a > direct link to a lot of data about cars and CO2. > > _http://auto.xprize.org/downloads/AXP- > EEWG_NRDC_100MPGE_veh_comparison.xls_ > (http://auto.xprize.org/downloads/AXP- > EEWG_NRDC_100MPGE_veh_comparison.xls) > > This Excel spreadsheet was designed to compare cars on the basis of > fuel > economy and CO2 emissions, with the objective that they all meet > the performance > qualifications for the Auto X Prize competition. That means they > have to > all nominally get 100 mpg and low CO2 emissions per mile. > > Here is the PDF file describing the spreadsheet, by its author. > > _http://auto.xprize.org/downloads/NRDC_AXP_Model_Description.pdf_ > (http://auto.xprize.org/downloads/NRDC_AXP_Model_Description.pdf) > > Now, a warning-- the mpg numbers only compare energy use from > tank to > wheels (or wall plug to wheels) so they don't include energy losses > in the > delivery system. However, the CO2 emissions are for the complete > energy delivery > cycle, from well (or coal mine) to wheels. The well-to-tank energy > efficiencies are given there in the supporting data, but let me > give you those > approximate numbers-- > > Electric car: > > Well /mine to wall plug: 38.1% (Average for US electrical grid) > Plug to wheels: 60% (Approximate, sometimes incorrectly given as > 70% or > more) > > Overall efficiency: 60% x 38.1% = 23% >> From the spreadsheet, a "135 mpg" car produces 194 grams CO2 per >> mile > > Gasoline car: > > Well to tank: 80.8% > Tank to wheels: 20% (Approximate) > > Overall efficiency: 20% x 80.8% = 16% >> From the spreadsheet, a 100 mpg car produces 118 grams CO2 per mile > > Diesel car: > > Well to tank: 82.6% > Tank to wheels: 27% (Approximate) > > > Overall efficiency: 27% x 82.6% = 22% >> From the spreadsheet, a 103 mpg car produces 111 grams CO2 per mile > > Another warning: For electric cars, it is widespread practice to > convert > electric energy input to the battery to gallons of gasoline > equivalent by > assuming the energy in the fuel is about 34 kWh per gallon. This > is grossly > incorrect, but everybody does it, ignoring the 38.1% efficiency > factor at the > powerplant. This means that the "136 mpg" electric car above is > grossly less > efficient than a 100 mpg gasoline car-- that's why it's CO2 > emissions are shown > as being higher than for the gas car. For cars of equally good > design, the > electric car will produce-- I'm calculating-- the electric car > produces about > 23% less CO2 than the gasoline car. > > By comparison, a diesel car running on biodiesel produces 55% LESS > CO2 than > the electric car, for the equivalent car design. > > In all of these calculations, I am ignoring the quality of the car > design. > THAT is where the biggest differences are made. > > Ernie Rogers > > In a message dated 4/13/2007 3:13:17 P.M. Mountain Daylight Time, > [EMAIL PROTECTED] writes: > > Ernie, > > Could you provide some data source for this claim? I understand > that electricity is produced with fossil fuels but I also believe > that electric cars are so much more efficient than internal > combustion heat engines at providing transportation. So how do the > efficiencies compare between CO2 emissions at the source (tailpipe vs > smokestack)? > > David > On Apr 13, 2007, at 2:03 PM, [EMAIL PROTECTED] wrote: > >> >> Electric cars and plug-in hybrids are only marginally better than >> ordinary >> hybrids in terms of energy consumption and CO2 emissions. They >> only appear to >> be better because most of the energy waste and CO2 happens "outside >> the box," >> back at the power plant. >> >> The best car today in terms of CO2 emissions is a diesel car using >> biodiesel >> fuel. You can find this documented in many places. The best >> current >> information will probably be found at _www.auto.xprize.org_ >> (http://www.auto.xprize.org) >> Or, search on Wang, Argonne National Laboratory. I can supply >> additional >> information to those that are interested. >> >> We should not be overly optimistic yet about saving the planet with >> better >> cars. Consumption of fossil energy is one of the top three >> environmental >> problems on earth, and cars are at its center. Most of the >> planet's organisms >> may be lost before we get this one under control. >> >> Ernie Rogers >> Driving for efficiency-- 65 mpg >> > > > > > > > > ************************************** See what's free at http:// > www.aol.com. David Bryant [EMAIL PROTECTED] 978-697-6123
