Objective: compare the ecological merit of electric versus thermal vehicles.
- The calculator: https://pierreh.eu/ev-calc-app/
- Source code: https://github.com/pierre-haessig/ev-calc
Notice that the app is a work in progress. Please report any issues on GitHub or by email.
About the calculator
With this interactive calculator, you can compare the ecological merit (in terms of lifecycle CO2 emissions) of an electric vehicle (EV) with a thermal vehicle motored by an internal combustion engine (ICE).
The general idea is that, for its manufacturing, an EV requires more energy than an ICE car because of its battery. The EV has thus a “CO2 debt” that can be repaid after traveling some distance if, as one may expect, the EV indeed emits less CO2 during usage (CO2 per unit distance). The computation of this “distance to CO2 parity” is the objective of this calculator.
Distance to CO2 parity depends on several inputs which value is difficult to know precisely, so this calculator allows you to input lower and upper bounds in addition to nominal values. Then, it propagates this uncertainty intervals down to the final result. Playing a bit with the numbers, in particular using coal-based electricity for EV charging, the distance can get negative (EV loses to ICE)! Also, wide input uncertainty can lead to infinite uncertainty for parity distance.
My conclusion on this is clear: all vehicles should be light and small, and, if electric, should be recharged with green electricity. Indeed, with a small battery, EVs are definetely better than combustion-powered cars. My e-bike has only a 300 Wh (0.3 kWh) battery and consumes 6—11 Wh/km.
Sharing calculator results
All the input choices in the calculator are reflected in the address bar. This means that sharing the complete URL (including the
?bs=...&round=true part) does include all input values.
The inspiration for this calculator comes from the blog article by Damien Ernst “Electric car: 697,612 km to become green! True or false?”. Prof. Ernst got negative feedback for his huge value for CO2 parity distance (~700 000 km in his first article), including some disrespectful comments, but also more constructive responses. This is why I'm proposing a calculator, where people can put the input of their choice. Thus, responsibility for the output value is shifted to the user!
Second, I got feedback that Ernst's value had too many digits (“697,612 km” in the first version) which carries a false sense of a highly precise calculation despite the high input uncertainty. This is what triggered my idea to make a calculator which propagates uncertainty (using interval arithmetic). This enables performing a “meaningful rounding” of outputs based on their respective uncertainty.
Here is an implementation of Damien Ernst's numbers in the calculator: https://pierreh.eu/ev-calc-app/?bs=80&bmue_nom=538&bmue_lb=538&bmue_ub=538&mco2_nom=236&mco2_lb=236&mco2_ub=236&evc_nom=20&evc_lb=20&evc_ub=23&icec_nom=6&icec_lb=6&icec_ub=6&cco2_nom=550&cco2_lb=317&cco2_ub=550&gco2_nom=2.28&gco2_lb=2.28&gco2_ub=3.2&round=false
collection of a sound list of references is a work in progress
Production impact of Lithium-ion batteries
On the question of “how much does Li-ion batteries production consumes energy and generate greenhouse gases”, there are substantial differences in the sources.
Damien Ernst's figures
Damien Ernst used the following article in his blog post:
Yuan et al. “Manufacturing energy analysis of lithium ion battery pack for electric vehicles”. CIRP Annals, vol. 66, n. 1, 2017. doi:10.1016/j.cirp.2017.04.109. https://bit.ly/2VMa4hA
from it, he extracts two energy intensity values:
- orginal value: 3700 MJ i.e. 1027 kWh per kWh of battery
- final value: 1936 MJ i.e. 538 kWh per kWh of battery (after applying some process efficiency correction due to upscaling)
Second, he multiplies this energy by a carbon emission intensity. He chosed 236 gCO2/kWh, which yields 127 kgCO2 per kWh of battery.
Based on subsequent references I found, his ~2000 MJ/kWh value is on the high side of most estimates, but 236 gCO2/kWh is very weak (US electricity is around 500 gCO2/kWh, says Ernst) so that the product of the two, which is 127 kgCO2/kWh battery, is slightly lower than several other estimates.
IVL 2017 report
Romare and Dahllöf. “The Life Cycle Energy Consumption and Greenhouse Gas Emissions from Lithium-Ion Batteries”. Technical Report C 243, IVL Swedish Environmental Research Institute, May 2017. https://www.ivl.se/english/startpage/pages/publications/publication.html?id=5407
This 2017 report from the IVL Swedish Environmental Research Institute analyzes several recent reviews on the topic. The report summary states:
[...] Based on our review greenhouse gas emissions of 150-200 kgCO2-eq/kWh battery looks to correspond to the greenhouse gas burden of current battery production. Energy use for battery manufacturing with current technology is about 350 – 650 MJ/kWh battery.
350 – 650 MJ translates to 97 – 181 kWh (1 kWh = 3.6 MJ).
Interestingly enough, taking the ratio of the central values of the two manufacturing impact factors (500 MJ i.e. 139 kWg/kWh and 175 kgCO2/kWh) gives a CO2 intensity of 1260 g/kWh for the manufacturing energy, which is a quite high (coal : 1000 g/kWh).
Also, they report a wider uncertainty in the energy use than in the CO2 emission and this cannot fit in my calculator which propagates uncertainty since I use, like Ernst, the relation:
CO2 emissions = Manufacturing energy × CO2 intensity of manufacturing energy
Finally, I confess there is one aspect I didn't understand in IVL report: they cite several reviews concluding that manufacturing energy was “likely to be” around 1000 MJ/kWh (e.g. their “Peters (2017)” reference). From this, I missed how they converged on their 350 – 650 MJ range.
Default values in the calculator
Based on the IVL report, including the reviews they cite, I concluded that the formula “CO2 emissions = Manufacturing energy × CO2 intensity” can be misleading, so I decided to set the default values for both Manufacturing energy and CO2 intensity by a formula inversion to satisfy these two goals:
- CO2 emissions for battery production: in the range 150 – 250 kgCO2/kWh battery, with central value 200.
- Energy use battery production: central value 1000 MJ i.e. 278 kWh/kWh battery
Therefore, I set the CO2 intensity for manufacturing energy to 720 gCO2/kWh (200/278×1000, quite carbon intensive), with an artificial zero uncertainty. Also, I set the relative uncertainty of manufacturing energy to be my target of ±50/200, which gives 750 – 1250 MJ ie. 208 – 347 kWh/kWh battery. This interval is a bit narrow, but at least the central value is ok.
Now, as I said in the introduction, if you are not satified with my choice, the calculator is meant to accept alternatives!
CO2 content of fuels
For the Diesel and Gasoline preset, I've used data from the appendix of:
Sullivan, et al. “CO2 Emission Benefit of Diesel (versus Gasoline) Powered Vehicles”. Environmental Science & Technology, vol. 38, n. 12, 2004. ACS Publications, https://pubs.acs.org/doi/full/10.1021/es034928d
- Gasoline: 2.36 kgCO2/l [2.28 – 2.47]
- Diesel: 2.65 kgCO2/l [2.58 – 2.71]
- remark: the higher CO2 volumic content of Diesel fuel compared to Gasoline is more than compensated by the increased efficiency of Diesel motors
Uncertainty range comes from the uncertainty they report on the fuel densities.
These data accounts for the direct emission of CO2 only, not lifecycle emissions of greenhouse gases in general.
Other interesting sources:
left to be explored
Wikipedia FR: Émissions directes en CO2 des combustibles (emissions directes et ACV)
CO2 emissions of electricy generation
- my own 2019 bill: 13.4 gCO2/kWh
- Electricité Enercoop : quelles émissions de CO2 en 2016 ?