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Helen Maynard
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Helen writes about her favorite topics, science and money, at her blog, creatively named www.ScienceAndMoney.com. With a Ph.D. in Materials Science and fifteen years of experience in semiconductor research, development, and manufacturing, she turns a critical eye to financial planning and... More
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Affine Financial Services
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Science And Money
  • Sustainable Energy: Solar Cell Skeptic 6 comments
    Oct 17, 2009 11:28 PM | about stocks: ESLRQ, FSLR, CSUN, STP, SOL, TSL, YGE
    Polycrystalline Solar Cell
    Polycrystalline Solar Cell

    Back in July, I announced the start of a new series of posts on Sustainable Energy, but I haven't had a chance to actually write about the topic until today.  No time like the present, then, to launch into my favorite diatribe:  Solar Heresy.

    My concern about solar cells -- specifically silicon photovoltaic cells -- is that it takes a great deal of energy to make silicon.

    The starting material is sand (silicon dioxide, SiO2) which is a wondrously stable material.  It takes a lot of energy to reduce SiO2 to silicon.  It requires additional energy to purify the starting material into the superpure form of a true semiconductor.  To make the higher-efficiency single-crystal solar cells, one also needs to crystallize the material, requiring melting it at 2577 °F (1414  °C) and slowly pulling a crystal out of the melt.  Then there's the energy needed to create the solar cell including patterning, doping, and annealing.  The solar cell then needs to be packaged, mounted, shipped, and installed.

    Single crystal solar cell
    Single crystal solar cell (At least, I think it's single crystal.)

     

    How many years do I need to run a solar cell before I payback the energy consumed in making it?

    I'm not the first person to pose the question.  In fact it has been addressed by a number of studies, with widely varying conclusions.  Bankier and Gale reviewed a group of assessments that ranged from 0.7 to 25.5 years.  Each study had different assumptions -- mostly about the mounting frame and type of silicon (polycrystalline or single crystal).  It seems that none of the studies included the energy cost of the sand-to-silicon conversion.

    For many years it was acceptable to start the energy cost calculation from polysilicon.  After all, polysilicon is a waste product from the manufacturing of silicon wafers for the computer chip industry.  But this changed in 2008 when several plants were put on line to produce polysilicon just for solar cells (YGE).  China is now a leading producer of polysilicon.  Last time I checked, the main source of energy in China is coal, much of it with a high-sulfer content.

    The big picture is that we're burning high-sulfer coal in China at tremendous rates to make supposedly "green" silicon solar cells.

    Until someone can show me a conclusive study that solar cells are energy net positive, I remain a solar skeptic.

    Science is sexy

    So why all the fuss about solar?  Governments around the world are subsidizing solar production.

    Rich nations like to fund solar because it looks like they're creating high-tech jobs and advancing technology (ESLR, FSLR*).  Emerging nations fund it to try to jump-start their nascent technology infrastructure (CSUN, STP, SOL, TSL).

    I'm very much in favor of governmental funding of the science behind alternative energy solutions, but subsidizing the manufacturing and installation undermines the market forces that should select the best solution in a technological meritocracy.  I would rather use Uncle Sam's money to figure out which of the bazillion solar cell configurations currently under development (or on university sketchpads around the world) is the best solution, rather than burn our limited fossil fuels creating thousands (millions?) of metric tons of mediocre stuff right now.

    So what should we do instead?

    There are a hundred better ways to save and create energy today.  I'll write about some of them in future posts in this series.

    And now I'll climb down off my soapbox.  (For now.)

    *FSLR.  First Solar, Inc. makes CdTe photovoltaics, not silicon.  They do benefit from government support of solar programs.

    Full disclosure: No positions.

    Related Posts:

    • Sustainable Energy:  If Uncle Sam Went to a Financial Planner...

    Image credits: Clearly Ambiguous and toastforbrekkie at Flickr.


    Themes: solar energy, solar cells Stocks: ESLRQ, FSLR, CSUN, STP, SOL, TSL, YGE
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Comments (6)
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  • you burn fossil now to make it green for the next 30 years, so I believe it is a positive thing, you burn somewhere and you do not need to burn somewhere else where you usually burn much more(creating electricitY) than what you burn to make silicon......
    5 Nov 2009, 09:28 AM Reply Like
  • The reasoning for subsidies is the following: As the manufacturing process of silicon improves thanks to the industry larger scale due to a artificially larger demand , the money and energy used is less and less, so the thing will make sense at some point and no more subsidies will be needed.
    In your reasoning you take out of the picture that as solar production increases its share of the power grid the energy that is used to power silicon plants would be cleaner. Frankly your post is based on the idea that china's power grid is dependent on a highly polluting energy (carbon) which is what solar can help to solve!. In fact your reasoning can be applied to any clean energy produced there that needs subsidies. But its a fallacy, because the more clean energy facilities you put up the more energy used in the grid, (included the one used to produce silicon panels), is cleaner. Imagine for a second that you are able to substitute after a number of years all carbon based plants by solar power. Yes it might by uneconomical but... polluting? No way.
    6 Nov 2009, 02:34 AM Reply Like
  • Author’s reply » Thanks for your comments.

     

    If I have a barrel of oil, I can burn it today to make solar cells or I can burn it over the next thirty years. Either ways puts CO2 into the atmosphere.

     

    I see solar cells as a way to freeze (or store) energy that is then slowly released back over 20-30 years.
    18 Nov 2009, 10:00 PM Reply Like
  • Hello Helen, let me put up this quiz question. Without solar subsidies/incentives the oil/coal used in solar panel manufacturing will instead be : a)stored b) used in a more energy efficient cleaner way than solar panels c)used in some other manufacturing process that adds even more pollution and doesn’t change the energy grid carbon dependency problem.
    If the answer is c solar is very good business for the environment right now (my answer). If its a, then solar its neutral over 20-30 year period (taking you premise as truth) but could turn positive as solar tech efficiency improves. If it's b (dubious) then yes, its a bad business for the environment but given the highly uncertainty about future technological development wouldn’t be wise to explore all alternative energies? So even in this case it would be good move.

     

    7 Dec 2009, 05:50 AM Reply Like
  • Hello Helen, let me put up this quiz question. Without solar subsidies/incentives the oil/coal used in solar panel manufacturing will instead be : a)stored b) used in a more energy efficient cleaner way than solar panels c)used in some other manufacturing process that adds even more pollution and doesn’t change the energy grid carbon dependency problem.
    If the answer is c solar is very good business for the environment right now (my answer). If its a, then solar its neutral over 20-30 year period (taking you premise as truth) but could turn positive as solar tech efficiency improves. If it's b (dubious) then yes, its a bad business for the environment but given the highly uncertainty about future technological development wouldn’t be wise to explore all alternative energies? So even in this case it would be good move.

     

    7 Dec 2009, 05:53 AM Reply Like
  • Author’s reply » Seingalt:

     

    The way I see it, if we don't burn the oil today to make solar cells, then that oil is available for future use. I believe strongly in funding research today to improve our energy efficiency and alternative energy production. If we can hold off burning that barrel of oil for, say, five years, then when it is used, presumably we will have advanced our technology such that the barrel of oil will be used to produce a better technology.

     

    It doesn't make sense to me to spend oil today to make solar cells that perform poorly. We should wait until we improve our technology so that the energy payback is more favorable.

     

    In finance we have the concept of the "time value of money." Here I'm suggesting that we consider a "time value of energy."
    7 Jan 2010, 09:22 PM Reply Like
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