Spinach Can Give Silicon a Power Boost

Researchers at Vanderbilt University said they have found a way to build biohybrid solar cells using photosynthetic protein that converts light into electrochemical energy in spinach with silicon. Apparently the use of spinach increases current and voltage levels.

"This combination produces current levels almost 1,000 times higher than we were able to achieve by depositing the protein on various types of metals. It also produces a modest increase in voltage," said David Cliffel, associate professor of chemistry, at Vanderbilt. "If we can continue on our current trajectory of increasing voltage and current levels, we could reach the range of mature solar conversion technologies in three years."

The use of biomaterials is attractive for scientists since they mar much more efficient than our artificial materials. While nature can convert sunlight into electrical energy with nearly 100-percent efficiency, the best man-made systems today are still below 50-percent. Of course, the wide availability of biomaterials is another factor that is promoting this kind of research. However, there is a long way to go until the technology will make it into production devices.

First, the researchers said that size matters -- they need a two-foot panel to generate "at least 100 milliamps at one volt." Their area size required to generate a certain power output may not be feasible enough when compared to traditional solar cells. The Vanderbilt researchers report that their PS1/silicon combination produces 850 microamps of current per square centimeter at 0.3 volts.

Also, the hybrid cells deteriorate rather fast. The scientists said that some early test cells deteriorated after only a few weeks. However, there have been scenarios in which the cells lasted for nine months. In nature, a PS1 cell in evergreens survives for years.

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  • SuckRaven
    As a technology enthusiast and a biologist, I find it awesome and somewhat humbling, that many of our great insights and advances into increasing the efficiency and energy density of our man-made gadgets seems to prove time and time again, that nature has solved many of the same problems through the continual adaptation and evolution of "molecular" machines like various proteins and enzymes. There is a beauty in this that one can really appreciate and simply stand in awe. We're getting there...but slowly. It will be interesting to see where we are in terms of energy output vs. efficiency in another 50 years.
  • sixdegree
    This gives the whole new meaning to the word "Green Power".
  • iceman1992
    Popeye's silicon!
  • CaedenV
    More like Silicon provides spinach a power boost, and spinach hurt's silicon's efficiency.
    I don't mean to sound jaded, but there are a few very obvious issues with this that are going to have a hard time competing with current PV cells.

    1) space used is a premium. At best, a roof of a traditional home is going to have 50% of southern exposure, and with many houses there is much less southern surface area. Getting into urban areas it is much worse; you have a flat roof which gives you 100% square footage to work with, but there are often many more families to provide for in that same area. These voltages with this kind of surface areas are not useful for mass application.

    2) In nature you do get near 100% efficiency, as in use of power received, but that power is not stored or transferred in the form of electrical energy like the article states; It is stored in the form of proteins which are used very directly as fuel for the rest of the plant. When we have to convert to electricity, store it in batteries, and then convert to AC electricity, we loose a ton of that potential energy, but then again what else are we going to do? I mean, my heater/AC/lights/computer run on electricity, not proteins. If plants had to convert to and use electrical energy like we use for power they would not be anywhere near 100% either.

    3) I am not going purchase new cells, and go on my roof, or hire someone to go on my roof every few years, much less months or weeks. Current PV cells last about 15 years, and from what I am reading some of the ones coming down the pipe will be good for 20-25 years (which is awesome because you can replace both the roof and cells on the same time table). Current cells pay themselves off in ~5-7 years, which means that soon you could be getting ~18-20 years of 'free' power from them, with very little maintenance on the cells (the batteries are obviously another matter). These organic cells would have to be extremely cheap and easily replaceable to justify frequent replacement costs. The lower up-front costs would be appealing, but roof work is scary, and dangerous, and priced appropriately.
  • bluekoala
    I think you fail to realize that this is just a prototype.

    And plant photosynthesis produces sugar, not proteins.
    I'd also like to add that most of the electricity produced is from hydrocarbon, which probably used to be proteins.

    We'll see what this project holds in the future. Any discovery is a good contribution to human knowledge, so long as it doesn't make the earth explode.
  • master_chen
  • doive1231
    As power output = voltage x current you need improvements in both voltage and current to see benefits in power output. Sounds like a "modest" increase in voltages may not be enough for impressive gains at the moment.
  • so the efficiency was really bad last month when they used a metal substrate for the protein

    They are using silicon this month and get a x1000 increase in efficiency.

    If they continue to get a 1000x increase in efficiency every month for the next 3 years ('continue trajectory') they 'could' approach the efficiency of conventional silicon cells.

    But the protein will still photobleach in 3 weeks and be rendered useless, because unlike actual spinnach it doesn't continuously produce new photosensitive proteins.

    Not too excited by this one right now...

  • freggo
    stuart72...If they continue to get a 1000x increase in efficiency every month for the next 3 years ('continue trajectory') they 'could' approach the efficiency of conventional silicon cells....
    I think you are a bit generous with your math here :-)
    10^3^36 = 10^39 fold efficiency increase. If that only puts them to a level where Silicone is now than the current efficiency would have to be so low it would be virtually impossible to measure; or at least tell a researcher that he is on the wrong path to start with.

  • _Cosmin_
    The Matrix is near.... next stop humans used as battery