Comprehensive Diagram Charts Nation’s Energy Use and Waste

An updated energy flow chart released by the Lawrence Livermore National Laboratory (LLNL) that visually depicts the relative size of primary energy resources and end uses in the U.S., with fuels compared on a common energy unit basis, shows the nation consumed more natural gas and renewables but less coal in 2012.

Each year, the Department of Energy’s LLNL releases a Sankey diagram that tracks the nation’s consumption of energy resources. The 2012 Energy Flow Chart estimates, based on data from the Energy Department, that Americans used about 95.1 quadrillion (quads) British thermal units (Btu; 3,412 Btu are equivalent to about 1 kWh)—about 2.2 quads less than in 2011.

About 40% (38.1 quads) of that total was used for power generation, slightly lower than the 39.2 quads charted in 2011. The 2012 chart shows that wind power saw the highest gains, going from the 1.17 quads produced in 2011 up to 1.36 quads in 2012. Solar also soared from 0.158 quads in 2011 to 0.235 quads in 2012, driven by price declines in photovoltaic panels due to a global oversupply.

Energy produced from hydro dropped from 3.17 in 2011 to 2.69 quads in 2012. LLNL also noted that 2012 was the first year in at least a decade when there was a "measurable decrease in nuclear energy." Nuclear energy fell to 8.05 quads in 2012 from 8.26 quads in 2011. "It is likely to be a permanent cut as four nuclear reactors recently went offline (two units at San Onofre in California as well as the power stations at Kewaunee in Wisconsin and Crystal River in Florida)," said A.J. Simon, an LLNL energy systems analyst. "There are a couple of nuclear plants under construction, but they won’t come on for another few years."

Coal use, both for power generation and industrial use, fell from 19.7 quads in 2011 to 17.4 quads in 2012. In 2011, 18 quads were used in coal-fired power plants, but in 2012 only 15.9 quads were used to generate power.

Natural gas consumption increased to 26 quads in 2012, about 36% (9.31 quads) of which was used to generate power. In 2011, just 7.74 quads were used to generate power. A substantial 8.7 quads of natural gas were consumed by industrial entities, while 4.26 quads went to residential use and 2.96 quads went to commercial use.

Significantly, the 2012 chart shows that 61% (58.1 quads) of U.S. energy use was "rejected." That waste included 25.7 quads from energy used to generate power (comprising 67% of the 38.1 quads of energy used to generate power).

"In most power generation applications, between 50% and 70% of the input energy (heating value of the fuel) is not converted into electrical power that can be sold," Simon told POWERnews. "Instead, that energy is rejected to the environment as waste heat in the exhaust or cooling-water streams from the power plant. This is true of coal, oil, natural gas, biomass, geothermal, and nuclear-powered generation facilities. Calculating input and output energies can be a bit more complicated for hydro, solar, and wind power."

LLNL’s annual estimated energy use Sankey diagrams through 2008 can be found at: https://flowcharts.llnl.gov/#.

Sources: POWERnews, LLNL

Sonal Patel, Senior Writer (@POWERmagazine, @sonalcpatel)