Don't judge a book by its cover: Getting to the bottom of EIA monthly data

July 18, 2011, 6:00AMANS Nuclear CafePaul Wilson

Earlier this month, a number of sources drew attention to the Energy Information Administration's report on energy (published in June), with headlines suggesting a landmark accomplishment: "Domestic Renewable Energy Production Surpasses Nuclear." Even Rep. Ed Markey (D., Mass.), ranking member of the House Natural Resources Committee, got in on the act, proclaiming that "The real energy renaissance happening in America is from the flourishing of renewable energy."

I should warn you that the EIA's spreadsheets are a real treat for people such as me who like numbers, and I offer many different views of these numbers below.

The EIA's  claim focused on the fact that in the first quarter of 2011, total renewable energy production-2.24 quads (quadrillion BTUs)-outpaced nuclear energy production (2.12 quads [See footnote on unit conversion]), which, on the surface, is an interesting change. But dig a little deeper and there are a couple of caveats that should be clarified.

First, it is important to recognize that the renewable energy here includes all hydro power and biomass combining to be more than 83 percent of this total production. Recognizing this, it should come as no suprise that it's not the first time that renewables have surpassed nuclear generation. In fact, until 1988, this was always the case (when assessed on an annual basis), when more than 98 percent of generation came from these sources. Since then, improved nuclear performance (and modest new construction) has kept nuclear ahead of total renewable generation, as hydro has fluctuated and wind energy has seen large growth rates.

Second, it is important to recognize that "total renewable energy production" includes non-electric applications. When we look at the the first quarter of 2011 in the electricity sector alone, we find that

  1. renewables produce only 13 percent of electricity, compared with 20 percent for nuclear,
  2. conventional hydro power is responsible for more than 63 percent of the generation, and
  3. conventional hydro power is responsible for more than 68 percent of the growth compared with last year.

Since there has not been a 28-percent growth in installed hydro capacity, this change can be attributed largely to the climate and a wet spring. The contribution of all renewable energy to the electricity sector is dominated by annual fluctations in hydro power more than any other factor. Total renewable electricity generation peaked in 1997 and is finally approaching those numbers again, while nuclear electricity generation has grown by more than 28 percent.

So, what is the real headline? Markey and others missed a chance to point out a large relative growth in wind energy production-40 percent-compared with the first quarter of 2010. While some may scoff at the small magnitude, these 0.083 quads represent more than 4 percent of the total nuclear generation in that same period. This is good news for the wind energy industry and consistent with its year-over-year growth rates between 30percent and 60 percent over the past few years. Nevertheless, wind energy is still less than 3 percent of total generation.

[unit conversion footnote] The EIA converts nuclear electricity to BTUs based on the average thermal efficiency of the nuclear fleet. This is clearly an appropriate converstion for fossil fuels, because all of their chemical potential energy is converted to heat and, in turn, to electricity. For nuclear energy, while this does measure how much heat is generated, it ignores the large quantities of remaining nuclear potential energy in the used fuel. For renewable energy sources that don't rely on thermal energy conversion, the EIA uses a simple unit conversion from kWh to BTU. Ultimately, this means comparing apples to oranges on a total energy production basis.



Paul P.H. Wilson is an associate professor of nuclear engineering at the University of Wisconsin-Madison, and the chair of the Energy Analysis and Policy graduate certificate program. Part of his research focuses on addressing policy-driven questions about the adoption of advanced nuclear fuel cycles.

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