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Batteries

Published on May 13th, 2016 | by Steve Hanley

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EV Battery Energy Density To Be At Parity With Gasoline By 2045, But That Misses The Point

May 13th, 2016 by  


Editor’s Note: Four great comments (well, even more than that) highlight why energy density parity with gasoline really misses some critical points. I’m highlighting them here before the article.

Adrian notes:

Yes, thanks to relative efficiency differences and much simpler support systems, batteries only need to be about 30% as energy-dense as gasoline to meet weight- and range-equivalance with ICE vehicles.

We might hit that in 2020-2025?

Bob Wallace notes:

“By 2045, BEV 300s will be comparable to conventional vehicles in terms of the energy spent at the wheel per kg of the powertrain mass.”

They are saying that it will take 30 years for batteries + electric motor to reach the same weight as an ICE + systems + fuel? Perhaps, but does it matter? Does it matter if your EV weighs a few hundred pounds more than the ICEV you left behind? Cost per mile and cost to purchase are the critical metrics.

arne-nl, in response to that comment from Bob, notes:

A point forgotten by many. Have you ever seen someone choosing a particular car, because “the engine was at 20% lighter than the competition”? People don’t analyse a car part for part. They look at the whole and ask themselves these three questions:
1. Can I afford it?
2. Does it suit me?
3. Do I want to be seen in it?

3x yes and it’s a sale. Simple as that.

arne-nl also notes:

“Right now the lab people say gasoline is 100 times more energy-dense than a battery. That means you would need 100 lbs of battery to go as far as 1 lb of gasoline can take you.”

Oh help. We have another one not accounting for the huge difference in efficiency between internal combustion engines and electric motors.

OK, now go enjoy the article….

Originally published on Gas2.

Argonne National Laboratory says the energy density of battery powered vehicles will not be the same as gasoline powered vehicles until some time in the far distant future. Right now the lab people say gasoline is 100 times more energy-dense than a battery. That means you would need 100 lbs of battery to go as far as 1 lb of gasoline can take you. If that’s true, how are we ever going to get to parity between electric and gas powered cars?

audi-r8-e-tron-batteryThere is one other critical factor to consider. Electric powertrains are far more efficient than powertrains powered by gasoline. In fact, in many cases, less than 20% of the energy contained in a gallon of gas actually gets converted to forward motion. The latest Toyota Prius has an internal combustion engine that is 40% efficient, but it stands at the top of the heap when it comes to engines.

Even assuming a gas engine is as efficient as the Toyota, it still has to transmit the power it makes through a complex set of gears in a transmission and a differential. By the time power gets to the wheels that do the actual driving, it has suffered significantly more mechanical losses. By contrast, an electric powertrain can be more than 90% efficient. That advantage tilts things in favor of electric cars.

Argonne Lab says in its latest report that just looking at the gas tank and battery is an “incomplete analysis,” which “ignores the impact of powertrain efficiency and mass of the powertrain itself. “When we compare the potential of battery electric vehicles (BEVs) as an alternative for conventional vehicles, it is important to include the energy in the fuel and their storage as well as the eventual conversion to mechanical energy.”

Weighing all the factors and adjusting for the differences between powertrain efficiency, Argonne Lab concludes that when it comes to driving a distance of 300 miles, gasoline and electric drivetrains will be equal to each other in about 30 years. “By 2045, BEV 300s will be comparable to conventional vehicles in terms of the energy spent at the wheel per kg of the powertrain mass.”

The Argonne Lab report does not consider price in its calculations. What it shows is that if we base the changeover from fossil fuels to electricity solely on energy density comparisons, it will come far too late for the environment. The key to keeping fossil fuels in the ground is to remove the enormous direct and indirect subsidies they enjoy and make their market price consistent with their total cost to society.

Source: AutoBlog, Photo credit: Audi

Reprinted with permission.


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About the Author

Steve writes about the interface between technology and sustainability from his home in Rhode Island and anywhere else the Singularity may take him. His muse is Charles Kuralt -- "I see the road ahead is turning. I wonder what's around the bend?" You can follow him on Google + and on Twitter.



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