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 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.)
The top three can be approximately represented by straight lines, whereas renewables are growing exponentially:
Projecting straight-line fits to the top three and the exponential fit to renewables, one gets:
Actually, coal electricity is falling faster than linearly and nuclear electricity is essentially level.
Thus, if renewable sources of electricity continue to grow exponentially, they will surpass the current top three sources of electricity, changing linearly, before year 2020. This is an example of the efficacy of exponential growth.
If exponential growth of electricity from renewable energy can continue to grow in the current exponential way to year 2025, it will far surpass the current top three sources of electricity, changing linearly:
It appears that getting electricity from burning natural gas cannot grow as fast as linearly after 2020 because its extraction in the U.S. will peak between 2015 and 2020. After hydraulic fracturing (fracking) began for extraction of natural gas from shale deposits the price of natural gas fell rapidly. When power plants and vehicles rapidly began converting from coal to natural gas the price of natural gas rose rapidly, since the extraction cannot keep up with the demand.
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.
One often hears the following two arguments against getting most of U.S. electricity from renewable sources:
Renewable Energy Debate
L. David Roper interdisciplinary studies
L. David Roper, http://arts.bev.net/RoperLDavid/
1 December, 2012