Fact #1: the energy and power density of automotive batteries are constantly increasing. Fact #2: they still have a long, long way to go to match the energy density of gasoline. Fact #3: according to Argonne National Lab, once you correct for the efficiency of the powertrain, we're only 40 years away from a time when gas and electric powertrains will offer the same energy density.

The problem, from a plug-in vehicle perspective, is that gasoline is about 100 times as energy dense as today's lithium-ion battery. As a brief refresher, energy density refers to the amount of energy you can put into a given amount of stuff. So, say, you've got 10 pounds of gasoline and 10 pounds of li-ion battery. One will take you X miles and the other a fraction of that. And so, given that 100x factor mentioned above, you'd need 100 pounds of battery to go as far as those 10 pounds of gasoline would take you, if all other factors were the same. That's the problem.

Just looking at the gas tank and battery is an "incomplete analysis."

But Argonne looked at things a little different, mainly because all those other factors are not the same. An all-electric powertrain loses nowhere near as much energy as a gasoline engine does as it converts fuel into motion. So, you don't need as much energy to go a set distance in the EV compared to the gas car. Just looking at the gas tank and battery is an "incomplete analysis," the Argonne authors say, that, "ignores the impact of powertrain efficiency and mass of the powertrain itself." The paper doesn't address charging vs. refueling time, but who knows where that technology will be in 2045. The abstract continues:

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. For instance, useful work expected out of a conventional vehicle as well as a BEV is the same (to drive 300 miles with a payload of about 300 lb). However, the test weight of a Conventional vehicle and BEV will differ on the basis of what is needed to convert their respective stored energy to mechanical energy.

When you look at the complete picture, that's when the 2045 date comes into view. The paper says, "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." You can read more here.

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