I just had a conversation with a colleague who is somewhat mainstream in his/her thinking. The question came up as to why can’t we be energy independent.  What is taking so long with the electric cars and natural gas powered … everything? When can we break away from middle eastern petroleum?

In the public sphere, all I hear are the questioners seeking reassurance that there are energy forms out there that will allow us to maintain our current level of consumption. They rarely put it exactly that way, but that is the heart of the issue.

I think multiple generations of people have failed to appreciate the natural wonder of liquid hydrocarbons. The C7-C10 fractions of petroleum, whether directly from the ground or from a cat cracker or reformer, are the motive basis for most of our ground transportation. These liquid hydrocarbons are of a reasonably low vapor pressure and high enough boiling point to allow their use in everything from go-carts and lawn mowers to automobiles and caterpillars.  Teenagers and grandmothers can pump hydrocarbons into an inexpensive and simple tank for use at ambient pressure and temperature. This liquid has a melting point low enough to make it flowable under nearly all earthly conditions.

The high energy density and the liquid state of gasoline is what makes it nearly perfect for propulsion. The energy density of gasoline is 34.8 mega-Joules per liter (MJ/L), as opposed to 21.2 MJ/L for ethanol.

Yeah, gasoline is cheaper per liter than the bottled water inside the convenience store. That perversion is just a temporary historical aberration. This will change.

Cosmically, hydrocarbons in the C7-C10 range suitable for automotive use are quite scarce in the local stellar neighborhood.  Some small hydrocarbon molecules like methane have been spotted in the gas giant planets and on Titan. But for the most part, the only supply of hydrocarbons we have are found in porous deposits below the surface of the only place we can get to- Earth.

We should appreciate our hydrocarbon resources for the true natural wonder that it is and be a bit more reluctant to squander it.  I doubt we’ll ever find a source of energy that is as cheap and convenient to use with such a high energy density.  Battery technology may get close, but innovation there is a highly specialized art that is beyond the scope of most shade tree mechanics. Common lead acid batteries require material and energy inputs, like everything else, and have somewhat low energy density and a high weight penalty.

Lithium batteries, with their higher energy density require a variety of manufactured and relatively exotic substances. And, they require lithium which is fairly scarce, both cosmically and on earth. We really should be recycling lithium scrap.  Seriously, we need to have great respect and appreciation for lithium as well. There really isn’t enough lithium to support everyone’s high energy density lifestyle.

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