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Anything wrong with my CO2 emission calculation?

pigwet

Member
Jun 22, 2019
47
53
Albuquerque
I sat down and calculated my CO2 emissions given the electricity generation portfolio of my local power company.

First, here is New Mexico's PNM source distribution for electricity generation.

Source.JPG



The table below outlines the assumed amount of CO2 released per kwh of electricity generation for each source (nuclear, solar, etc. assumed no CO2 emissions). Trying to add in how much CO2 emission results from coal/oil/uranium extraction/transportation simply gets way too complicated. I assume 1 gallon of gasoline = 33.7 kWh of energy.

CO2.JPG


The CO2 emissions per mile driven for the PNM source mix is 0.476 kg/kWhr. Then I factored in transmission line losses based on distance of plants to Albuquerque which is only on the order of 5% per 1000km. Our Four Corners and San Juan coal plants are ~350km away, and the nuclear plant is ~700km away in Phoenix. So basically the losses are in the noise but they are included in the calculations/graph below.

PNM.JPG


The Model 3 is rated at an equivalent 138 MPGe or 0.242 kWh/mile (in terms of equivalent energy to a gallon of gas). In terms of CO2 emissions in ABQ, this equates to a gasoline vehicle with a 73 MPG rating.

Tesla.JPG



Sources

Energy Sources
AC Transmission Line Losses
What is the efficiency of different types of power plants? - FAQ - U.S. Energy Information Administration (EIA)
SAS Output
SAS Output
How much carbon dioxide is produced per kilowatthour of U.S. electricity generation? - FAQ - U.S. Energy Information Administration (EIA)
Environment - U.S. Energy Information Administration (EIA) - U.S. Energy Information Administration (EIA)
https://www.energy.gov/sites/prod/f... Gas Emissions from the U.S. Power Sector.pdf
 
  • Informative
Reactions: JBT66

SageBrush

REJECT Fascism
May 7, 2015
12,251
15,178
New Mexico
Hi neighbor,

Your calcs look about right to me within the constraints you impose. I say the latter because the PNM mix varies quite a bit through the day for one; and gasoline (petrol) sourced from the mountain region is quite a bit dirtier than the number you used.

By the way, lazy people like me go here for the same information.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
The Model 3 is rated at an equivalent 138 MPGe or 0.242 kWh/mile (in terms of equivalent energy to a gallon of gas)

It depends on which vehicle you have. The range for 2020 (after the efficiency improvements are rolled out) is 113MPGe (30kWh/100mi, Performance 20") to 141MPGe (24kWh/100mi, SR+).

I would use these numbers, then add a flat usage for vampire drain of about 300kWh/yr (3.1rmi/day*245Wh/rmi/0.93*365day/yr = 298kWh/yr). Also the efficiency numbers above may be 1-2% better if you use 48A charging (11.5kW), and considerably worse (20% worse) if you use 120V/12A charging (1.44kW). The vampire drain kWh per year is assuming closer to 11.5kW charging setup and would be subject to the 20% adder if you use 1.44kW charging.
 
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Reactions: Chisale

Chisale

Member
Sep 28, 2019
218
196
Ohio
That all looks pretty good to me too. Only quibble I would have is putting down nuclear as 0 emission. It most certainly does have emissions in the mining and enrichment of uranium. The best that I could find to put for it was somewhere around 0.05 lbs CO2/kWh or around 0. 023 kg as you're going with metric. Like I said, that is a very rough estimate that really doesn't take into account the long term storage aspects of spent fuel. Anyway, it is a fraction of coal and gas so it's not a big deal but I felt it was important to put it in. I guess you could argue the same with solar or wind as the panels and turbines have to be manufactured (most likely) using fossil fuels but frankly I still feel like it's okay to go 0 there since it's only an initial carbon expenditure.

So bottom line, our Tesla model 3s have 3-4 times less emission than my previous HEV which got a long term 47mpg and about 6-8 times less than the US average ICE car. Plus, as utility companies upgrade to more and more renewables and use less and less coal those numbers are going to climb even higher. We have tremendous more upside than ICE cars which could show marginal improvements but honestly very little as manufacturers have squeezed just about every bit of economy out of them.
 

Chisale

Member
Sep 28, 2019
218
196
Ohio
Not sure which one you're asking but I'll be glad to answer for my situation. On the best of days when getting close to the EPA range of the car then around 0.09 lbs CO2/mi. On the worst of days with the heater, windshield wipers and defrosters all going then closer to 0.15 lbs/mi. I live in the Midwest where the electrical generation is mostly an even mix of coal and natural gas with a smaller percentage of nuclear and a vanishing small amount of renewables.
Average HEV emits around 0.40-0.45 lbs/mi and national average ICE car emits 0.79 lbs/mi.
 

Paddy3101

Member
Mar 20, 2019
261
389
San Diego, US
Umm, you need to add in the CO2 cost of production of the Gas into the equation, not just the CO2 cost of production of Electric.

The CO2 emitted from the gas car is only half the story.
 

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