L. David Roper
United States Consumption of Energy by Source
The data for electricity production in the United States are available at http://www.eia.gov/electricity/monthly/xls/table_1_01.xlsx .
The following graph shows the major U.S. electricity sources versus time:
In this article I concentrate on the top three (coal, nuclear, natural gas) and renewables. The object of this study is to determine when in the future the exponential growth in renewable energy (renewables) as a source of electricity in the United States will pass the other three. (Here "renewables" represent the summation of wind, solar thermal, solar photovoltaic, wood, geothermal and other biomass. Note that hydroelectric is not included and that renewables have almost caught up with hydroelectric.
The top three can be approximately represented by straight lines, whereas renewables are growing exponentially:
The exponential curve is a fit to the 2008-2013 data.
The exponential rate is 5.426 years or a doubling time of 3.761 years..
Projecting straight-line fits to the top three and the exponential fit to renewables, one gets:
The linearly fit to coal electricity is only for years 2008-2013, the new era of coal decline.
Some salient points:
Of course, electricity from renewables cannot grow exponentially into the far future; at some time it has to level off, similar to a hyperbolic tangent curve.
Assuming the projection curves given above for U.S. electricity sources the total electricity projection is:
To counteract the fall in coal electricity and the upcoming fall in natural-gas electricity, the exponential-rise rate for renewables electricity needs to be increased as has been the case during the last decade.
One often hears the following two arguments against getting most of U.S. electricity from renewable sources:
Both of these issues would become moot if a smart national electricity grid were in place.
Renewable Energy Debate
L. David Roper interdisciplinary studies
L. David Roper, http://www.roperld.com/personal/roperldavid.htm
11 May, 2016