The Power to Charge Electric Vehicles comes from coal argument

The argument “The power to charge EVs comes from Coal” is thrown at EV enthusiast and early adapters of EV technology all the time. Although I am a big proponent of electric vehicles, I am not a blind supporter. I acknowledge the fact that emissions from coal fired power plants are major part of total emissions from EVs. So I decided to gather some basic data and crunch some numbers.

I will like to mention the assumptions made in this analysis

1. The emissions from the tailpipe are calculated using EPA formula.
2. Emissions from gasoline and hybrid vehicles are purely from burning the gasoline. Transport of crude oil, refining, transport of gasoline is not counted as I don’t have all the data.
3. MPG and kWh/mile are from EPA stickers and testing data.
4. All emissions shown are per mile.

With these assumptions in place, let us move towards actual math of it. Let us start with electric vehicles. There are various scenarios for emissions caused by electric vehicles. In real life there is zero tailpipe emission, but here “the power to charge EVs comes from coal” argument comes in. In today’s world, no power grid is using coal as a fuel for 100% of the electricity production. In US, Europe, India and China there is a good mix of natural gas, coal, nuclear, hydro power and renewable energy source. Considering this, I have created three different scenarios of grid power mix. 100% coal (for skeptics), 50% coal and 50% natural gas and 1/3^rd of each Coal, Natural Gas and renewable energy (Likely a 2020 scenario)

The information from eia.gov indicates the pounds of CO2 emitted per kWh of power generation. Let us assume all coal used for power generation is lignite coal (only 7% of this type is used in USA and this is the worst energy dense coal producing maximum green-house-gas emissions.  Please refer to the reference.  http://www.newcenturycoal.com/newscentre/coalinfo.php. Still to satisfy critics I am going to use highly polluting version of coal to calculate all emissions.)  So from the table below, it is shown that each kWh of electricity will emit 2.18 pounds of CO2.

Reference Link: http://www.eia.gov/tools/faqs/faq.cfm?id=74&t=11

Now let us take example of Nissan Leaf, the current largest selling electric car in the world. With EPA estimated range, Nissan leaf will consume 0.26kWh/ mile. Please consider that EPA estimated range is for 80% of battery usage so I am going to use that amount to calculate kWh/mile. So one mile operation of Nissan leaf will emit 0.57 pounds of CO2 when it is charged by electricity sourced 100% from coal fired power plant. I did similar calculations with Tesla and Chevy Volt, using the EPA estimated range numbers. All the calculations are available in the excel spreadsheet.  

Now let us take a look at emissions of conventional engines and hybrids. There are various types of vehicles with different MPG levels. To be fair, I used 15, 25, 35 and 45 MPG as standards. According to EPA, one gallon of gasoline produces 8887 grams (19.59 pounds) of CO2. Based on this data and formula mentioned below, I calculated CO2 emissions per mile using above mentioned MPG values. Again to be fair and non-biased, I added multiple MPG levels. I understand actual driving MPG can be lower but same can be said about EVs. Actual range of EVs also depends on driver behavior.

Reference: http://www.epa.gov/otaq/climate/documents/420f11041.pdf

So after crunching these numbers, I got very interesting results. The table below shows the numbers I got. The excel spreadsheet is available for download (Link: http://bit.ly/18bI2xV )

Emissions per gallon of gasoline	19.59	Lbs
Emissions	kWh/ Mile or MPG	Coal	Nat Gas	50-50	33-33-33
Emission per kWh based on grid mix		2.18	1.22	1.7	1.13
Leaf	0.26	0.57	0.32	0.45	0.30
Volt	0.35	0.76	0.43	0.60	0.40
Tesla	0.23	0.51	0.28	0.40	0.26
Gasoline	15.00	1.31	1.31	1.31	1.31
Gasoline	25.00	0.78	0.78	0.78	0.78
Gasoline	35.00	0.56	0.56	0.56	0.56
Hybrid	45.00	0.44	0.44	0.44	0.44
	Min Value	0.44	0.28	0.40	0.26
Diesel Bus	4.5	4.35	4.35	4.35	4.35
Electric Bus	1.9	4.14	2.32	3.23	2.15

The calculations were very close to my expectations. Only interesting fact that I observed is the fact that electric vehicle will reduce tremendous amount of emissions even if we just use natural gas instead of coal. I also calculated same emission calculation for heavy duty diesel buses. And surprisingly electric buses will emit less even if we use 100% electricity from the coal fired plants. So when we compare the results, we find with 100% coal power, hybrid vehicles with 45MPG fuel economy are the least emitting option. Overall emission from hybrid vehicles like Prius are lower than EVs when power is sourced 100% from Lignite (the worst quality coal available) based power plants.

Another major point is the fact that gasoline cars can never be made cleaner. Once you buy a new gasoline car, it can only get more polluting over time. But electric vehicle emissions can be reduced by improving the power mix of the grid. So as we move towards cleaner grid, automatically we will go towards cleaner EVs. We do not need to repair, install additional equipment or replace these vehicles to be cleaner.  

All this data crunching and efforts are to answer one argument, “The electricity to charge EVs comes from coal.” Of course this calculation is overly simplified version of the actual carbon footprint. But I will start adding data as and when I get access to it. There are transmission losses, charger to battery loses for an electric vehicle but similarly there are refining losses, leakages and spills in gasoline ecosystem. 

Signing Off

Nikhil Parchure

You can download the PDF copy of this analysis here: http://bit.ly/15seNED

The link for excel spreadsheet is : http://bit.ly/18bI2xV