HOW GREEN IS YOUR PLUG-IN ELECTRIC VEHICLE
By Larry L. Olson, PhD, PE.
INTRODUCTION:
For those of you who are not familiar with the all electric automobile called “TESLA”, manufactured in California and sold for a base purchase price of $109,000.00, refer to the internet site www.teslamotors.com. It is touted as the GREENEST automobile ever. It is supposed to go 240 miles on a charge, achieve some very high speeds and be the coolest auto available. Movie stars have plunked down their cash and will receive the first production cars, if they have not already done so.
The Tesla
However, if you drive the Tesla in Florida and recharge it from the utility line coming into your house, the Tesla has a carbon foot print that is larger than the Toyota Prius, the Honda Insight, and the Volkswagen Jetta, to name a few. If you calculate the Tesla’s carbon foot print from data in (www,caranddriver.com), you find that using their numbers the foot print is equivalent to an auto that gets slightly over 41 mpg. Incidentally, the recharge data yield an energy usage for recharging of 0.288 KwH per mile, but my electrical vehicle which weighs the same but is a DC system gets an equivalent energy usage of 0.45 KwH per mile. This yields an equivalent mileage of 27 mpg for my electric vehicle, based on carbon production, when it is charged in Florida.
The key phrase in this introduction is “when it is charged in Florida”. When the Tesla is charged in California, Colorado, or Washington state, its equivalent mileage, based on carbon foot print, is 85 mpg, 33 mpg and 191 mpg respectively. So you see, the electrical vehicle, which is touted as the salvation of our planet, is only as GREEN as the power plants in the location where the vehicle is being charged. A large portion of the power in the above named two west coast states comes from hydroelectric power, so their power is a lot greener than the power in Colorado. Most of the mid west power is derived from coal which has the highest carbon dioxide out put of any of the commonly used fuels (see Table 1 below).
My Plug In Conversion (done by me) In Front of Our Home With PV Panels on Roof .
I charge my EV from the solar panels and have zero carbon emissions.
CARBON DIOXIDE AND ELECTRICAL GENERATION
According to a 1999 study by the Department of Energy(reference: Carbon Dioxide Emissions from the Generation of Electric Power in the United States, October 15, 1999), the amount of carbon dioxide produced per kilowatt-hour of electrical energy is 1.37 for Florida and 5 other states, 0.38 for California, Oregon, and Washington and 1.54 for the eight state area including Colorado. These numbers are somewhat out of date. Using another report by the Department of Energy (reference: US Dept of Energy, EERE State Activities, 2007), we see that in 2007, Florida and three other selected states produced their power from the following energy sources:
From the 1999 report, the amount of carbon dioxide produced from these fuels is:
Table 1. Carbon Dioxide Production Per KwH of Energy Produced
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Fuel Carbon Dioxide Production (lbs/KwH)
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Coal 2.123
Oil 1.943
Gas 1.255
Nuclear 0
Hydroelectric 0
Solar 0
Renewables highly variable, but usually high
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Table 2. Fuels Used For Power Production and Calculated Carbon Dioxide Production Per KwH
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Percentage of Power Production for Each Fuel
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Fuel Florida Colorado California Washington
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Coal 26 76 1 11
Petroleum 31 0 3 0
Gas 27 19 36 7
Hydro 0 3 20 72
Nuclear 12 0 19 9
Renewables 3 2 20 2
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Weighted Av.* 1.51 1.85 0.72 0.32
Ave. + Losses** 1.70 2.09 0.82 0.36
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*Weighted average pounds of carbon dioxide per KwH at the power plant.
**Weighted average pounds of carbon dioxide per KwH + 13% losses.
Using a weighted average for the power production in Florida, I calculated an average carbon dioxide production of 1.508 pounds per kilowatt-hour. This is the figure, along with 20 pounds of carbon dioxide production for every gallon of gasoline that we burn to derive the equivalent mileage for the electric vehicle charged in the three chosen locations. Keep in mind that the 1.508 pounds of carbon dioxide per KwH does not take into account line losses, start up and shut down losses, transformer losses, etc. I do not know that figure, but based on a lot of reading, I will increase this number to 1.7 pounds of carbon dioxide per KwH. This is a 13% increase, which in my mind is not nearly enough, but it is the figure I use for all of my further calculations.
The equivalent carbon mileage for the Tesla electric vehicle recharged in Florida is calculated as follows:
0.288 KwH/mile x 1.7 lbs carbon dioxide /Kwh = 0.4986 lbs carbon dioxide per mile
The burning of one gallon of gas produces 20 pounds of carbon dioxide
20 lbs per gallon / 0.4986 lbs carbon dioxide per mile = 40.85 equivalent mpg
In a similar fashion, I calculated the equivalent mileage based on carbon dioxide production for the other three states and these data are shown in Table 3. Below:
Table 3. Equivalent Mileage for Electric “Tesla” for Four States
State Equivalent Carbon Dioxide Mileage*
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Colorado 33.2
Florida 40.8
California 85.1
Washington State 191.5
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*Calculated using 0.288 KwH per mile for Tesla & 20 pounds carbon dioxide per
Gallon of gasoline.
COMPARING THREE PLUG-IN EVS
 
The Nissan Leaf
Two other plug in electric vehicles will join the mass produced market in the near future. The LEAF manufactured by Nissan is already being marketed in selected cities in the USA as of this writing. Apparently the cities were selected based on their willingness to install emergency charging stations in their corporate entities. The VOLT manufactured by Chevrolet is supposed to come on the market “soon”. They have been saying that for several years. However, the Volt is supposed to be a plug in vehicle with an on-board charger in the event that you exceed the charged range. The data that is available for the Volt states that 8 Kilowatt-hours are required for a 40 mile drive. This comes out to 0.20 Kw-Hr per mile. I do not believe this figure, particularly when they are dragging along an engine and generator. Weight is the bane for electric vehicles. I will not use this “data“.
 
The Chevy Volt
Three vehicles will be compared in the table below. They are the Tesla, introduced above, the Leaf, from Nissan, and a 2003 Ford Ranger that the author converted from an internal combustion engine driven vehicle to an electric vehicle. Static and performance data are available on all three vehicles. The recharge data were measured for the Tesla and the Ranger, but the recharge data for the Leaf is from Nissan’s promotional data which is probably optimistic.
Table 4. Static and Performance Data for 3 Plug-in Electric Vehicles
PARAMETER TESLA LEAF RANGER
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Type 2 door sports 4 door sedan 2 door truck
Empty Weight(lbs) 3200
Battery Type Lithium-ion Lithium-ion Lead Acid
Battery Weight (lbs) 2400
Motor Type AC AC DC
Regen. Capability yes yes no
Base Price($) 109,000 17,000
Max. Speed (MPH) 200 64
Range (Miles) 240 100 50
Recharge (Kw/mile) .288 .25 .45
Calc. Carbon Mileage In:
Colorado 33.2 38.2 21.9
Florida 40.8 47.0 27
California 85.1 98.0 56.3
Washington St 191.5 220.6 126.7
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What does this all mean? It is obvious that the plug-in electric vehicle is not the panacea that most everyone sees it to be. There is lots of advertising hype, particularly by Chevrolet and the Tesla, that indicates that the vehicles get phenomenal mileage and has no adverse environmental impacts. These advertisements are not true.
More importantly, the way we produce electricity is very important to the future of these plug-in electric vehicles. Obviously, the most environmental friendly area of our country is the northwest because of the way they produce electricity (mostly from hydroelectric). However, the northwest is very cold in the winter and cold environments are not kind to electric vehicles. It is necessary to keep the batteries warm during the time they are not used, and of course, this requires energy. Consequently, the performance of a plug-in electrical vehicle in the winter is markedly degraded. Even hybrid vehicle performance is degraded in cold climates. A Prius owner in Iowa reported to me that his mileage degrades in the winter to about 38 MPG whereas in the summer his mileage is 51 MPG.
A common comment from people in the EV industry is that if you do not like the carbon mileage in Florida, you should install photo voltaic cells on your roof to provide for a zero carbon foot print. These people have probably not done this. I have and I find that the estimated cost of electricity generated by PV cells is 30 cents per kilowatt-hour. This compares to purchasing your power from a electric utility of about 12 cents per kilowatt hour. Because of this cost, the average owner of a plug-in electric vehicle will not install a photo voltaic system.
So, the question becomes: “Should we discourage EV’s in those areas where the electric industry uses dirty fuels or should we encourage our electric utilities to convert their electric power production to less polluting fuels. That is a “no brainer” except for financial considerations. For example, Florida Power and Light buys its electricity for approximately 3.8 cents per kilowatt hour and sells it for approximately 12 cents per kilowatt hour. They will not modify their system unless forced to. However, they are already doing this because they are under Federal edict to provide 20% of their power from green sources. It turns out that my photo voltaic cells, purchased by me, and installed on my roof, provides a portion of that 20 %. I guess that is the price for my connecting to the FPL grid.
Florida Power and Light is a good example of a company that generates lots of green power but does not import any of it to Florida. They have 62 wind farms in 16 different states providing 7441megawatts of generating capacity and not a single kilowatt hour of that energy comes to Florida. California and the New England states will pay five to ten times what the dirty energy costs in Florida, so it all goes to those locations.
As the number of plug-in electric vehicles increases, the amount of electricity that they require from the electric utilities increases. From the data in Table 4, it is obvious that Florida and Colorado are states where hybrid vehicles such as the Prius or the Incite have a lower carbon foot print than all of the plug-in electric vehicles. Something needs to be done in these states and all of the other states that have similar power generating facilities before the plug-in vehicle really catches on in the USA. It doesn’t make sense to promote a technology that, using the power from the electric utilities, is less green than the hybrid vehicles that we already have in the market place.
The only way it makes sense is that the plug electric vehicle is being powered by our coal reserves, which means that we are not importing foreign oil. Of course, this means that the plug in electric vehicle is in a real sense a coal powered vehicle.
CONCLUSIONS
There are only three significant conclusions. They are:
1. Your plug-in electric vehicle is only as green as the electricity from which it is charged. Because 50% of our total power capacity in this country comes from coal, that is not very green.
2. To keep personal transportation as green as our current hybrid vehicles make it, we need to limit where new plug-in electric vehicles should be sold, OR
3. We need to require that our electrical utilities produce more green power.
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