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Defining “Renewable Energy”

with 3 comments

NEI Nuclear Notes has recently posted a link to this blog entry from a member of the South Carolina legislature, pondering the question of nuclear energy and “renewable energy”.

“I concluded that the question yesterday was whether or not to keep “nuclear” in the definition of “renewable” and whether nuclear is renewable. The environmental community testified that they did not want nuclear energy included.”

If renewable energy is a meaningful factual term, then it needs to have a rigorous, meaningful, scientifically useful definition. The environmental community can’t just make up their own definition as they go along.

So, what is it?

The Oxford Advanced Learner’s Dictionary was the first good and credible English dictionary I could find that was searchable online.

re•new•able /r{I}'nju{shwa}bl; NAmE 'nu/ adj.
1 [usually before noun] (of energy and natural resources) that is replaced naturally or controlled carefully and can therefore be used without the risk of finishing it all: renewable sources of energy such as wind and solar power.

Nuclear energy can be used without the risk of “finishing it all” on a timescale relevant to our human civilisation on this planet into the future. There is sufficient uranium and thorium in the Earth to supply the energy needs of an advanced civilisation for every person on Earth for no less than one million years, assuming it is used sensibly and efficiently using Generation IV reactors and sensible fuel cycles.

So too can the energy from the sun, or the geothermal heat from radioactivity within the Earth. Based on this part of the definition, these systems, for example, are certainly renewable energy.

Are the nuclear fuels in the Earth being “replaced naturally”? Well, no, they are not. But the hydrogen in the sun is not being replaced naturally, either. The geothermal heat produced by the radioactive decay of uranium, thorium and potassium within the earth is not being replace naturally.

Clearly, if solar energy and geothermal energy are renewable energy, then this definition isn’t right, either. But the problem goes deeper.

The free energy of the universe is not being naturally replenished, now, is it?

It doesn’t matter what particular energy system you’re considering – if this is our definition of renewable energy, then renewable energy does not and cannot exist – that is the Second Law of Thermodynamics.


Written by Luke Weston

January 18, 2008 at 1:10 pm

Posted in renewable energy

3 Responses

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  1. Nuclear energy should not be classified as a renewable energy source. However, since the Second Law of Thermodynamics will not allow renewable energy sources, perhaps the term “Renewable Energy” should be viewed as definition of a particular industry, such as “The Renewable Energy Industry” as part of an effort to reduce reliance on petroleum.


    January 20, 2008 at 4:56 am

  2. Plutonium or Uranium-233 i breeder cycles would be renewed as fast or faster than consumed.

    In this case it would be renewed from the finite feedstock of Uranium-238 or Thorium-232.

    Status: Renewable

    Thermal Uranium reactors on the other hand directly uses Uranium-235 taken from the ground, producing less fissile material (plutonium 238-244) than consumed.

    Status: Not renewable

    Wind is renewed as fast or faster than consumed from the finite feedstock of Hydrogen-1 in the sun.

    Status: Renewable

    Solar PV is fed directly from the finite Hydrogen-1 feedstock of the sun.

    Status: Not renewable – “finite”

    Geothermal sources are sometimes renewed from deeper pockets of magma in which case it is renewable. In other cases the source is continuosly cooling an thus finite.

    Obviously cold logic hands out the “renewable” badge in a manner quite different from the so called “environmental groups”


    January 28, 2008 at 5:11 pm

  3. Sure, breeder reactors breed more fuel, but the U-238 or Th-232 is strictly speaking, finite, just like the hydrogen in the sun.

    It’s a really, really vast resource, but strictly speaking, finite.

    The same goes for the hot, deep geothermal magma.


    January 31, 2008 at 2:20 pm

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