26 August 2010

U.S. Energy Flows

Lawrence Livermore National Laboratory has come out with its "Estimated U.S. Energy Use" flow chart covering the year 2009. These charts are always fascinating.

Chart by Lawrence Livermore National Laboratory from DOE/EIA data.
The full-size chart with annotations is available as PDF.

The most stunning thing about this picture, as in previous years, is how much of the energy that we mine or capture is wasted (the light grey parts of the diagram). The inefficiency of generators, motors and other devices, and losses during transmission, mean that of the 94.6 quadrillion BTUs the U.S. tapped in 2009, less than half provided useful heat or work. Fifty-eight percent was lost ("rejected", in EIA's terms).
  • 67% of the energy embodied in fuels used to generate electricity was lost, with only 33% of it being converted into electricity.
  • Of the energy embodied in fuels used for transportation, a stunning 75% didn't move any vehicles, but was lost.
  • By contrast use of energy in homes, businesses and factories was relatively efficient. The efficiency factor used by the LLNL analysts for these sectors is 80%.

Learning more

Here are some of the other things we can learn from this graph (and the accompanying LLNL press release):
  • Despite all the fuss about ethanol from corn, and the expenditure of billions every year subsidizing it, it only provided 3.4% of energy used for transportation (the thin green line leading from "biomass" to "transportation"). This was only a little more energy than the natural gas used for transport, though it is about 30 times as much as electricity used for transport.
  • Solar energy is a vanishingly small part of electricity supply--about three tenths of one percent.
  • Wind provided about 2% of energy used for electricity generation, up by about a third from 2008.
  • All the wind power in the chart is from large-scale wind farms. Distributed small-scale wind generation still isn't big enough to show on the chart.
  • Total energy use was down by about 5% from 2008 due to the weak economy, and also possibly some improvements in efficiency. Residential use was down about 2%, commercial use about 1%, industrial use about 9% and transportation about 3%.
  • Biomass is used to heat homes (4% of residential energy use), and to power cars as ethanol, and a minute amount to make electricity (1% of energy for generation), but more than half is used in industrial facilities. This is probably mostly waste being converted to power and process heat at paper mills, food processing plants, lumber mills, furniture manufacturers, waste processing plants and the like. 
  • Although one hears about the possibility of renewable energy powering plug-in battery-electric vehicles to help wean us off oil, even all the nation's renewably generated electricity (about 10% of electrical energy, one quad, not counting nuclear but including big hydro) would only satisfy about 4% of current transportation energy needs. This would be about 40 times more electricity than is currently used in transportation. And of course diversion of that amount of power to transportation would require a corresponding increase in energy resources to generate electricity for all its current uses.
  • To replace the 18 quads of coal used to generate electricity, output of utility-scale wind, solar and geothermal would have to increase nearly 20-fold.
  • 94.5 quads of energy consumption is 300 million BTU for every resident of the U.S., about 90,000 kW-h.
We should thank A.J. Simon, the LLNL energy systems analyst who develops the energy flow charts. His efforts provide real insight. (Compare the weak flow chart provided by EIA.) Here is a nice article on Lawrence Livermore's 25-year effort to chart U.S. energy use.

The data for the chart come from the EIA's Annual Energy Review 2009.

LLNL's news release is here. The PDF of the chart and notes from LLNL is here.

Credit is due to the Lawrence Livermore National Laboratory and the Department of Energy, under whose auspices the work was performed. Full source information is in the PDF of the chart here.

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