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Published on December 23rd, 2010 | by Susan Kraemer


Compared Gram for Gram, Solar is Ten Times More Powerful than Nuclear

December 23rd, 2010 by  

An interestingly novel way of comparing solar power with nuclear power finds that solar easily bests nuclear. Ken Zweibel has an analysis at The Solar Review, that compares the two kinds of electrical energy, in terms of how much power is packed into each gram of its respective material: cadmium telluride, versus uranium.

He provides data showing that CdTe thin film solar power (using cadmium telluride) takes ten times less PV material to make 1 kilowatt hour of electricity, than nuclear uses of uranium, to make an identical 1 kilowatt hour of electricity.

This is even comparing the two as if solar “used up” each gram of cadmium telluride the way that nuclear power uses up its uranium fuel (pretty much – some can be recycled, theoretically). But of course, solar doesn’t burn up fuel. You can get electricity from the same grams of PV material for at least thirty years, and then the material can be recycled and still used again.

By contrast, the equivalent grams of nuclear uranium must be replaced with newly mined uranium once the first has yielded its energy.

Here’s his math. It takes 12 grams of CdTe to make a one square meter solar thin film module.

“In a year in an average US location, we harvest about 11% x 1750 kWh/m2-yr, or 154 kWh/yr (after accounting for another 20% in losses)” he notes.

So we need 0.08 of a gram per kilowatt hour for one year’s supply of electricity. But that assumes we’ve used up the gram by the end of the year.

“But wait!” he cries. “We don’t burn PV modules, and they don’t die after one year – warranties are about 30 years, so this is really one thirtieth of that, or 2.6 milligrams per kWh”.

So, compared with nuclear, solar packs a punch: using one-tenth as much material to make the same power.

But check out the comparison to coal. According to his calculations, even assuming just thirty years use, then tossing the solar, the thin film photovoltaic material uses just five millionths of the weight of coal needed to make the same kilowatt hour of electricity.

“Compared to coal, of course, the numbers are out of this world. These differences in resource needs bear on the ultimate sustainability of the PV in comparison to other more resource-intense energy technologies”.

Indeed. Solar looks to provide us with not just a cleaner, safer and healthier form of electricity, but also, one that is much more sustainably mined. It takes just a fraction of the stuff from the earth that coal or nuclear takes.

Image: Two Crabs
Susan Kraemer@Twitter

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About the Author

writes at CleanTechnica, CSP-Today, PV-Insider , SmartGridUpdate, and GreenProphet. She has also been published at Ecoseed, NRDC OnEarth, MatterNetwork, Celsius, EnergyNow, and Scientific American. As a former serial entrepreneur in product design, Susan brings an innovator's perspective on inventing a carbon-constrained civilization: If necessity is the mother of invention, solving climate change is the mother of all necessities! As a lover of history and sci-fi, she enjoys chronicling the strange future we are creating in these interesting times.    Follow Susan on Twitter @dotcommodity.

  • Snake Oil Baron

    Cadmium telluride? Why not do the comparison with silicon PV which is currently dominating the market? Is there enough of these raw materials to supply a good fraction of humanity’s future energy use while still supplying other uses for these substances? Solar might be useful in a lot of instances but I would be surprised if nuclear wasn’t the go-to power for certain contexts given that it can be used in places where vast tracts of land and/or unshaded roof space are not available.

    Uranium and coal mines look nasty at close range but are tiny areas of land compared to the whole. They can be reclaimed though it takes a while so enviros can always show early days of reclamation and claim it proves that reclamation is inadequate.

    As for nuclear waste, two types of radioactive elements are produced: short half-life ones which are economically and medically valuable and long half-life ones that are less dangerous and can be easilly stored until uses are found for them.

    • Susan Kraemer

      (Re Cadmium telluride?) As I remember, the author worked in the thinfilm biz, so he had the numbers at hand.

  • Pingback: Solar Compared (Gram for Gram) to Nuclear and Coal – climate change and environmental news()

  • Thomas Cheney

    I am wondering about the total amount of material like concrete and steel. Some fiqures show solar and nuclear similar in terms of life cycle GHG emissions. Also, what about storage for photovoltaics?

  • zafar

    good info about both solar and nuclear energy.

  • Bill Woods

    Of course this an apples-vs.-oranges comparison. For grins, I looked up how much fuel solar power actually takes: 6.2 e11 kilograms of hydrogen per second. That illuminates the Earth with 1.74 e17 W = 48 TW-h per second. Converted to electricity at 20%, that would be 10 TW-h/s. So solar power’s fuel consumption is about 60 kg/kW-h (60 million mg/kW-h).
    This could be improved enormously by building a Dyson sphere to capture the sunlight which doesn’t illuminate anything of consequence.

    On the other hand, fissioning uranium or thorium produces about 940 GW-days/tonne of heat. That works out to a fuel consumption of about 0.15 mg/kW-h of electricity. Current technology only uses about 1% of the energy in natural uranium; the flip side of that is that the ‘spent’ nuclear fuel and depleted uranium which have already been mined still hold a fantastic amount of energy.

  • Akhilesh Magal

    I don’t think this is a fair comparison. Remember in nuclear energy, the fuel is Uranium. In Solar the fuel is not CdTe, it is the conversion technology. So when we do such a comparison we need to compare fuel v/s fuel and conversion technology v/s conversion technology. Here we do a mix-match. Although it gives us numbers that we can admire, they convey a wrong picture (i.e Solar is much more efficient in material consumption than Nuclear).

    • Susan Kraemer

      Or you are restating the author’s point: uranium gets used up (fuel), while solar does not have to be fed a fuel that gets used up.

      • Akhilesh

        Exactly! That is why such a comparison is not very useful. It can lead an uninformed observer to the wrong conclusions.

    • Emily Wilson

      You’re right, Akhilesh, that this ‘comparison’ of Zweibel’s is more of a thought exercise than a fully-worked technical evaluation.

      A true comparison of current fuel efficiency between solar and nuclear systems would not use the parameters of the older, less-efficient thermal reactors.

      I would Zweibel’s post as a jumping off point for your own thinking. Do not use it as the basis for an honest technical argument with anyone qualified to argue the subject.

      When considered in that light, one hardly needs to go to the depth of calculating the comparative efficiency of power generative systems to know that solar has an obvious advantage in that its raw material is guaranteed to our planet for billions of years, while nuclear has an obvious advantage of continuous availability.

      These advantages cannot be directly compared. And any attempt to do so will raise honest questions such as yours.

    • WV Treehugger

      Uranium mining is just another way to destroy our Earth,blowing Mtn’s to heck. Just like good ole Mtr. Coal mining does. Solar energy leaves the Earth,Mtn’s and vital water sources untouched. Which in return leaves us with clean air,water and Mtn’s. The Sun will never get used up,to me there are no comparisons.

    • EL

      Uranium also has to be developed on the front end to be used as a fuel source: refining from naturally occurring ore into yellowcake, conversion (into uranium hexafluoride), enrichment, and fuel fabrication. These are very intensive energy processes at the front end, and sometimes result in high carbon emissions and pollution (which author includes via StormSmith). The crucial variable for solar is not conversion of materials, but variability of light source (latitude, cloud cover, etc.). Not sure of the author’s assumptions on this basis.

  • Chaitanya Patankar

    This is such an awesome thing to know

    Solar is very much preferred as compared to nuclear..
    Go Solar Goo!!

  • Jack Enright

    This is fantastic news. I would like to add that if you couple a passive solar design with active solar panels for a residential home or commercial office you could add to the efficiency of Solar energy with a similar lifetime of at least thirty years.

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