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Power Science Technology

MIT Envisions DIY Solar Cells Made From Grass Clippings 126

Zothecula writes "Research scientist Andreas Mershin has a dream to bring inexpensive solar power to the masses, especially those in developing countries. After years of research, he and his team at MIT's Center for Bits and Atoms, along with University of Tennessee biochemist Barry Bruce, have worked out a process that extracts functional photosynthetic molecules from common yard and agricultural waste. If all goes well, in a few years it should be possible to gather up a pile of grass clippings, mix it with a blend of cheap chemicals, paint it on your roof and begin producing electricity. Talk about redefining green power plants!"
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MIT Envisions DIY Solar Cells Made From Grass Clippings

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  • Of course, at 0.01% efficiency, you won't be able to tell the difference. Unless, of course, you're into that "other" grass, in which case it's "Oh so kool man! Now I don't have to mow the roof AND get enough power to run a watch one day a year."

  • by ( 793321 ) on Monday February 06, 2012 @12:41PM (#38942971) Homepage Journal
    And yet another 10 years later they find that those "cheap chemicals" cause cancer...
  • Efficency (Score:5, Interesting)

    by vlm ( 69642 ) on Monday February 06, 2012 @12:47PM (#38943043)

    From the fine article they're getting 0.1% efficiency right now. In other words, about a thousandth. Conveniently, you get about a KW of light per sq meter. So, you get about one watt per square meter. So I could get about 40 watts at noon off my roof, well, other than that tree being in the way which shades me from the summer sun. That is somewhat more than the naysayers claim (barely enough to run a watch, etc) but is not enough to be useful.

    Its unlikely they'll exceed the best plants which have had hundreds of millions of years to optimize their design... so figure 5% or so would be quite an achievement. So in Star Trek miracle land, a KW or two is quite possible off a typical roof. Of course in Star Trek miracle land, you'd have 47% efficient cells thus generating about 40 KW. I donno what I'd do with 40 KW laying around, I guess air condition my entire open air backyard, replace my beer fridge with a supermarket open display case so I don't have to waste time opening the door?

    The crack about painting it on is laughable. conductive acid rain and bird poop will short it out. You're still going to need glass/plastic/etc and the cost of that will probably make high efficiency silicon more economical.

  • by tp1024 ( 2409684 ) on Monday February 06, 2012 @12:49PM (#38943071)
    If you need to blanket a whole country with solar cells and still don't have enough power for all people, you shouldn't talk about a drawback. You should talk about it being useless for this purpose.

    If you blanket all of Germany with cells of this type, you'll get 13.6 GW on average, assuming perfect and unlimited storage - Germany needs 70GW of electricity. And of course, you'd have to blanket *all* of the country, so you'd have to say goodbye to forests, mountains, lakes, rivers, fields ... or an unblocked view of the sky for that matter.
  • by timeOday ( 582209 ) on Monday February 06, 2012 @12:53PM (#38943117)
    I wonder if you wouldn't get a lot more bang from your compost heap by putting a tarp over it and collecting the gasses rising out of it to burn?
  • by vlm ( 69642 ) on Monday February 06, 2012 @12:55PM (#38943145)

    and will it last through the winter?

    If its made out of grass clippings, then by April or May at worst I'll have enough to make another cell-roof.

    One weird issue is if its pitifully 0.1% efficient, it might be more productive overall to simple TDP the collected grass clippings into gasoline and dump it into a generator. Or ferment into ethanol. Just simply burn as biomass?

    I think a solar powered electric self growing fence would be pretty cool, at least until it shorts out and starts itself on fire. Which brings up the other idea of a self growing survival tool, a mushroom grown in pitch blackness which when placed in sunlight eventually bursts into flame using self generated photosynthetic electricity.

  • Fraud - be careful (Score:5, Interesting)

    by Anonymous Coward on Monday February 06, 2012 @02:06PM (#38944069)

    A modified type of dye sensitized solar cell, nothing new. []

    You can easily make those at home: Take a piece of conductive glass, coat it with titanium dioxide (yes, exactly the pigment used for white paint, I tried the commercial pigments myself), dip it into a dye (yes, I tried chlorophyll, these things were known at least 15 years ago, this is when I did it), put on a second piece of glass and fill with electrolyte.

    I have made hundreds of those, you can do it at home it a toaster oven, google for "graetzel cell video".

    This type of cell has several very serious issues:

    1) The efficiency is very low

    2) The cell uses a liquid organic electrolyte. Of course there are tons of problems with leakage, toxic solvents etc.
    The electrolyte often breaks down from the light, you'll always have oxygen diffusion into the system and react with all the chemicals. It is extremely difficult to make anything organic that can withstand light. Have a look at your painted garden chairs after a few years in the sun.

    3) The dye breaks down quickly. Make a simple test. Take a few grass clippings and put them into the sun. You'll notice that they change color from green to brown.
    The reason is that the chlorophyll degrades very rapidly in the sun. Grass makes new chlorophyll all of the time.
    4) Titanium dioxide (and zinc oxide as well) are highly reactive materials under illumination. This is why you use them as white pigments. The sunlight creates free electrons, and those decompose a lot of the dirt in contact with the stuff. A white wall in the suns cleans itself to a large part.
    Of course, you'll have the same effect in the solar cell, the TiO2 will act as a catalyst and degrade dye and electrolyte.

    Make a simple test at home: Take a wall painted with titanium or zinc white. Dissolve some grass clippings in alcohol and spray the green stuff on the wall. Expose to sunlight and see how quickly it bleaches.

    As a scientist myself, I find it very sad and unprofessional, how MIT is lying to the public.
    A statement like
    "If all goes well, in a few years it should be possible to gather up a pile of grass clippings, mix it with a blend of cheap chemicals, paint it on your roof and begin producing electricity. Talk about redefining green power plants!"
    is very misleading, unethical and close to being a scientific fraud. Of course, you could never paint it on, how are you going to put on the electrodes?

Honesty is for the most part less profitable than dishonesty. -- Plato