A friend of mine sent me this article a couple of weeks ago.  I admired its back of the envelope ingenuity and findings, until I looked at his assumptions.  Dowd could not have made them more obvious, but his use of the graph points out the potential of solar power.

It is much less wasteful in generation.

Dowd made great fanfare of the energy demand of the US: 70 quadrillion BTU (70 x 10^15 BTU).  From this fun flowchart, he could have derived 95, 38, 37, or even 12 “quads” as the total energy consumption, instead, but he simply chose those because they were four nice boxes that represent the American economy.  The problem  with these four boxes is they included used and rejected energy.  From 70 quads, only 37 quads of energy were used for useful work.

The differences are made up in rejected energy: mechanical or heat losses in energy in the conversion of fuel to usable energy.  Electricity is the biggest energy waster in America’s portfolio.  Burning coal or natural gas to boil water to make steam to turn a turbine to spin a dynamo has a to of places to lose energy to the process.  Of the 25 quads of coal and natural gas that we use to make electricity, less than 30% goes to make electricity that we use.  The second greatest waster of energy is in transportation.  Hundreds of millions of car and truck engines run lean, but are still only 30% efficient at moving the wheels on their vehicles.

Between electricity and transportation, we waste 47 quads of energy, almost half of the energy we consume.  Add to that the energy wasted at the consumer level (Residential, Commercial, and Industrial), and we waste almost two-thirds of  our energy.  Most of this energy is wasted in burning carbon (petroleum (35 quads),natural gas (26 quads, coal (17 quads)) to make energy.  What would it take to replace these with solar?

First, lets concern ourselves with the 8 quads of electricity it takes 25 quads of natural gas and coal to generate.  With the 50% contingency of the article (12 quads), and using their same math, this would call for 30,360 square miles of solar panel.  This is just a little bigger than Maine, and about 1% of the contiguous US.  I’d prescribe distributing the solar panels where the consumers are, on the roofs of buildings, first, this doesn’t account for 1% of the land area in the US.  Of course distributing the solar would mean that its not always going to be in the sunniest of states, but that’s what the contingency is for.  That’s well worth saving 25 quads of coal and natural gas though.

The first concern I had with Dowd’s article was with his use of 70 quads as his target.  His box of concern, clearly and helpfully labeled in red here, is helpfully divided into Residential, Commercial, Industrial and Transportation, but it does not show the amount of rejected energy from these bins.  For the 95 quads of energy we burn or collect, we really only use 37 quads, still less than 40% efficiency.  Of that 37 quads of useful energy, over half is in the industrial sector.  But America is de-industrializing, slowly, as we export processes and jobs to other countries.  This is abetted by economy of scale in transportation, which values delivery of volume over velocity of units.  I don’t have a figure for our de-industrialization, but I’ll find one for a later article.

US_historical_energy_consumption
http://energyfuture.wikidot.com/us-energy-use

Look further at the rejected and used energy for our four sectors.  Right now, transportation is assumed to be traffic and flight, because it pretty much is.  What could we regain from that 27 quads in transportation (and 21 quads rejected energy) if we had transportation choice in the US?  If the 50% of trips that were under 3 miles were taken by bike, we would cut those numbers down significantly.  More on biking, walking and transit as appropriate alternatives to traffic as I get the data.

USENERGY
Animation of our energy flows 2007-2013

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