Also it's a bit strange that the study quoted calculates a ESOI of 10 for Li-Ion, but JPetersen derives a ESOI of 1.1 for a 85 kWh battery and 3.3 for a 24 kWh battery (Leaf), using the assumption that they are used to drive the same amount of miles. (Whereas the cycle life of a 85 kWh battery would be more than 3x than that of a 24 kWh battery). I don't think using a fixed calendar life is a valid number to use.
Some points that come to mind regarding this discussion:
- Using JRP3's calculation, the energy density today (in Model S), by itself, already gives a 2x better number.
- An 85 kWh battery has a longer cycle life and calendar life than those numbers. The cycle life (in miles) grows proportionally with the battery's size.
- The battery has a value and use following the useful life for its original owner, for example it can be sold to someone who needs only a smaller battery (along with the car, or separately).
- Energy density has continuously improved, and will continue to do so, most likely at least 2x / 10 years and quite possibly even better.
- The corresponding values for an ICE are not zero.
- For a large part, J.Petersen uses the number to compare the EOIS of various battery types amongst each other, but that comparison is not the crucial one.
- The study referenced finds a ESOI of 10, even with lower energy density cells, but JP uses 1.1, a factor of 10x less. So his bottom line numbers are his own, and not really backed by the study.
- Studies which actually target EVs and calculate the environmental burden including production of batteries, give a different picture, such as the one stopcrazypp referenced:
Green Car Congress: Study Finds Environmental Impact of Li-ion Battery for BEVs is Relatively Small; The Operation Phase is the Dominant Contributor to Environmental Burden
Their study, published in the ACS journal Environmental Science & Technology, showed that the environmental burdens of mobility are dominated by the operation phase regardless of whether a gasoline-fueled ICEV or a European electricity-fueled BEV is used.
- Last but not least: For most practical purposes, including those of investors, the resulting cost considerations already go into the (well known) price comparisons of (EV + electricity) with (ICE + gasoline). (Which are of course expected to further improve, significantly, in the coming years, given that electric cars are now establishing themselves as a market).
And again, from an energy-use point of view, I consider the most significant factor today to be the acceleration of development of tomorrow's battery technology, contributing to renewable energy generation and use overall. The really "accurate" numbers are those we don't know yet, those from future battery technology in 5 years, in 10 years, in 20 years, in 50 years.
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Norbert, I thought I stated the difference between cell level and pack level fairly clearly, but maybe not. I can add a comment to expand on the topic more clearly.
If one reads it carefully and has some basic knowledge, it is very clear. However if one reads quickly, it seems easy to miss which numbers correspond to each other. The first impression is that 75 Wh/kg corresponds to 250 Wh/kg. Then in the next sentence it makes a step backwards. I'd think it is better to make steps forward, so to speak. I'm saying this more for future articles you might write (which I think you should, given your willingness to discuss these questions in the context of JP's articles, for example).
