Artificial Leaves Generate Power by Pumping Water

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Inspired by water transport in natural leaves (shown), researchers have created a synthetic, microfabricated "leaf" that can generate power from evaporative flow. Image credit: pdphoto.org

(PhysOrg.com) -- Natural leaves constantly lose water through evaporation, as the water in their veins is pumped up to the top of the tree. This process, called transpiration, could also create a mechanical water pump effect in synthetic leaves, and be used to generate power.

Researchers from the University of California, Berkeley, the University of Michigan, and MIT have constructed leaves out of glass wafers with tiny veins through which water can flow. The veins open at the tips of the glass "leaves," where evaporation draws water out of the veins at a rate of about 1.5 cm/sec.

Then, the researchers wired the leaves by adding metal plates to the walls of the central stems and connecting them to a circuit. By charging the metal plates, the researchers created a capacitor made from the two conducting plates separated by an insulating layer.

Next the researchers added air bubbles into the leaf veins to periodically interrupt the flow of water. Every time a bubble passed between the metal plates, it changed the capacitance and generated a small current. The current then passed to an external circuit where it increased the voltage on a storage capacitor.

Each bubble could create about 2-5 microvolts, or 2 microwatts per cubic centimeter. The researchers predict that they could easily improve this amount to a few hundred microwatts per cubic centimeter. This power density is still much less than that of batteries or fuel systems, and the power output is still modest compared to solar technology. Still, the researchers hope that, as an energy scavenging system, the synthetic leaves might serve as a complementary solar technology, with sunlight driving the transpiration process.

More information: Ruba T. Borno, Joseph D. Steinmeyer, and Michel M. Maharbiz. "Charge-pumping in a synthetic leaf for harvesting energy from evaporation-driven flows." Applied Physics Letters (DOI: 10.1063/1.3157144).

Via: New Scientist

© 2009 PhysOrg.com

   

• QubitTamer - Aug 03, 2009
  • Rank: 3 / 5 (2)
  every little bit helps, however with the ever increasing plethora of 'possible' technologies out there clamoring for funding, one wonders what the future of energy generation is going to be... my personal vote is that we build as many nuclear power plants as we can and in doing so learn many new important engineering lessons about affordability and sustainability...
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• acarrilho - Aug 03, 2009
  • Rank: 1 / 5 (1)
  I'm ashamed to say I didn't immediately pick up on the sarcasm.
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• docknowledge - Aug 04, 2009
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  acarrilho, if I hadn't read your comment first, I might have made the same mistake!
  
  Now. Why did I read yours first? Hmm. Yours was shorter. Your paragraph started with a capital letter.
  
  What lesson did I learn? Hmm. For mass appeal, keep your jokes short. For classy appeal, bury them.
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• NeilFarbstein - Aug 04, 2009
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  artifical leaves are pretty intertesting as an engineering topic
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• kcameron - Aug 04, 2009
  • Rank: 5 / 5 (2)
  The power output is modest in comparison yet "complementary" to conventional solar power?
  
  In that case, team Columbia should hire me on for the next Tour de France. After all, I'm perfectly capable of complementing the team since I know how to ride a bicycle.
  
  I'm all for scientific advancement and basic research. However, I don't think it's appropriate to tout your research as a viable and having practical applications unless it's better in some way. Just being based on a biological system isn't "better".
  
  Also note that the artificial leaves need to evaporate a continuous flow of water to operate. I.e., not practical at all.
  
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